Tracerestrict: Create slot/group inside selected slot group

[openttd-jgr.git] / src / viewport.cpp

/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */

/**
 * @file viewport.cpp Handling of all viewports.
 *
 * \verbatim
 * The in-game coordinate system looks like this *
 *                                               *
 *                    ^ Z                        *
 *                    |                          *
 *                    |                          *
 *                    |                          *
 *                    |                          *
 *                 /     \                       *
 *              /           \                    *
 *           /                 \                 *
 *        /                       \              *
 *   X <                             > Y         *
 * \endverbatim
 */

/**
 * @defgroup vp_column_row Rows and columns in the viewport
 *
 * Columns are vertical sections of the viewport that are half a tile wide.
 * The origin, i.e. column 0, is through the northern and southern most tile.
 * This means that the column of e.g. Tile(0, 0) and Tile(100, 100) are in
 * column number 0. The negative columns are towards the left of the screen,
 * or towards the west, whereas the positive ones are towards respectively
 * the right and east.
 * With half a tile wide is meant that the next column of tiles directly west
 * or east of the centre line are respectively column -1 and 1. Their tile
 * centers are only half a tile from the center of their adjoining tile when
 * looking only at the X-coordinate.
 *
 * \verbatim
 *        ╳        *
 *       ╱ ╲       *
 *      ╳ 0 ╳      *
 *     ╱ ╲ ╱ ╲     *
 *    ╳-1 ╳ 1 ╳    *
 *   ╱ ╲ ╱ ╲ ╱ ╲   *
 *  ╳-2 ╳ 0 ╳ 2 ╳  *
 *   ╲ ╱ ╲ ╱ ╲ ╱   *
 *    ╳-1 ╳ 1 ╳    *
 *     ╲ ╱ ╲ ╱     *
 *      ╳ 0 ╳      *
 *       ╲ ╱       *
 *        ╳        *
 * \endverbatim
 *
 *
 * Rows are horizontal sections of the viewport, also half a tile wide.
 * This time the northern most tile on the map defines 0 and
 * everything south of that has a positive number.
 */

#include "stdafx.h"
#include "clear_map.h"
#include "tree_map.h"
#include "industry.h"
#include "smallmap_gui.h"
#include "smallmap_colours.h"
#include "table/tree_land.h"
#include "blitter/32bpp_base.hpp"
#include "blitter/8bpp_simple.hpp"
#include "blitter/null.hpp"
#include "core/math_func.hpp"
#include "landscape.h"
#include "viewport_func.h"
#include "station_base.h"
#include "waypoint_base.h"
#include "town.h"
#include "signs_base.h"
#include "signs_func.h"
#include "plans_base.h"
#include "plans_func.h"
#include "vehicle_base.h"
#include "vehicle_gui.h"
#include "blitter/factory.hpp"
#include "strings_func.h"
#include "zoom_func.h"
#include "vehicle_func.h"
#include "company_func.h"
#include "waypoint_func.h"
#include "window_func.h"
#include "tilehighlight_func.h"
#include "zoning.h"
#include "window_gui.h"
#include "linkgraph/linkgraph_gui.h"
#include "viewport_kdtree.h"
#include "town_kdtree.h"
#include "viewport_sprite_sorter.h"
#include "bridge_map.h"
#include "company_base.h"
#include "command_func.h"
#include "network/network_func.h"
#include "framerate_type.h"
#include "depot_base.h"
#include "tunnelbridge_map.h"
#include "gui.h"
#include "core/container_func.hpp"
#include "tunnelbridge_map.h"
#include "video/video_driver.hpp"
#include "scope_info.h"
#include "scope.h"
#include "blitter/32bpp_base.hpp"
#include "object_map.h"
#include "newgrf_object.h"
#include "infrastructure_func.h"
#include "tracerestrict.h"
#include "worker_thread.h"
#include "vehiclelist.h"
#include "core/backup_type.hpp"
#include "3rdparty/robin_hood/robin_hood.h"

#include <bit>
#include <map>
#include <vector>
#include <math.h>
#include <algorithm>
#include <tuple>
#include <atomic>
#include <cmath>

#include <mutex>
#include <condition_variable>

#include "table/strings.h"
#include "table/string_colours.h"

#include "safeguards.h"

Point _tile_fract_coords;

#if defined(DEDICATED)
using Blitter_8bppDrawing = Blitter_Null;
#else
using Blitter_8bppDrawing = Blitter_8bppSimple;
#endif

ViewportSignKdtree _viewport_sign_kdtree{};
bool _viewport_sign_kdtree_valid = false;
static int _viewport_sign_maxwidth = 0;


//static const int MAX_TILE_EXTENT_LEFT   = ZOOM_BASE * TILE_PIXELS;                     ///< Maximum left   extent of tile relative to north corner.
//static const int MAX_TILE_EXTENT_RIGHT  = ZOOM_BASE * TILE_PIXELS;                     ///< Maximum right  extent of tile relative to north corner.
static const int MAX_TILE_EXTENT_TOP    = ZOOM_BASE * MAX_BUILDING_PIXELS;             ///< Maximum top    extent of tile relative to north corner (not considering bridges).
static const int MAX_TILE_EXTENT_BOTTOM = ZOOM_BASE * (TILE_PIXELS + 2 * TILE_HEIGHT); ///< Maximum bottom extent of tile relative to north corner (worst case: #SLOPE_STEEP_N).

struct StringSpriteToDraw {
        StringID string;
        Colours colour;
        int32_t x;
        int32_t y;
        uint64_t params[2];
        uint16_t width;
};

struct TileSpriteToDraw {
        SpriteID image;
        PaletteID pal;
        const SubSprite *sub;           ///< only draw a rectangular part of the sprite
        int32_t x;                      ///< screen X coordinate of sprite
        int32_t y;                      ///< screen Y coordinate of sprite
};

struct ChildScreenSpriteToDraw {
        SpriteID image;
        PaletteID pal;
        const SubSprite *sub;           ///< only draw a rectangular part of the sprite
        int32_t x;
        int32_t y;
        ChildScreenSpritePositionMode position_mode;
        int next;                       ///< next child to draw (-1 at the end)
};

/**
 * Mode of "sprite combining"
 * @see StartSpriteCombine
 */
enum SpriteCombineMode {
        SPRITE_COMBINE_NONE,     ///< Every #AddSortableSpriteToDraw start its own bounding box
        SPRITE_COMBINE_PENDING,  ///< %Sprite combining will start with the next unclipped sprite.
        SPRITE_COMBINE_ACTIVE,   ///< %Sprite combining is active. #AddSortableSpriteToDraw outputs child sprites.
};

typedef std::vector<TileSpriteToDraw> TileSpriteToDrawVector;
typedef std::vector<StringSpriteToDraw> StringSpriteToDrawVector;
typedef std::vector<ParentSpriteToDraw> ParentSpriteToDrawVector;
typedef std::vector<ChildScreenSpriteToDraw> ChildScreenSpriteToDrawVector;

enum RouteStepOrderType : uint8_t {
        RSOT_INVALID,
        RSOT_GOTO_STATION,
        RSOT_VIA_STATION,
        RSOT_IMPLICIT,
        RSOT_WAYPOINT,
        RSOT_DEPOT,
};

typedef std::vector<std::pair<uint16_t, RouteStepOrderType>> RankOrderTypeList;
typedef std::map<TileIndex, RankOrderTypeList> RouteStepsMap;

const uint max_rank_order_type_count = 10;

enum RailSnapMode {
        RSM_NO_SNAP,
        RSM_SNAP_TO_TILE,
        RSM_SNAP_TO_RAIL,
};

/**
 * Snapping point for a track.
 *
 * Point where a track (rail/road/other) can be snapped to while selecting tracks with polyline
 * tool (HT_POLY). Besides of x/y coordinates expressed in tile "units" it contains a set of
 * allowed line directions.
 */
struct LineSnapPoint : Point {
        uint8_t dirs; ///< Allowed line directions, set of #Direction bits.
};

typedef std::vector<LineSnapPoint> LineSnapPoints; ///< Set of snapping points

/** Coordinates of a polyline track made of 2 connected line segments. */
struct PolylineInfo {
        Point start;           ///< The point where the first segment starts (as given in LineSnapPoint).
        Direction first_dir;   ///< Direction of the first line segment.
        uint first_len;        ///< size of the first segment - number of track pieces.
        Direction second_dir;  ///< Direction of the second line segment.
        uint second_len;       ///< size of the second segment - number of track pieces.
};

struct TunnelToMap {
        TunnelBridgeToMap tb;
        int y_intercept;
        uint8_t tunnel_z;
};
struct TunnelToMapStorage {
        std::vector<TunnelToMap> tunnels;
};

struct BridgeSetXComparator {
        bool operator() (const TileIndex a, const TileIndex b) const
        {
                return std::make_tuple(TileX(a), TileY(a)) < std::make_tuple(TileX(b), TileY(b));
        }
};

struct BridgeSetYComparator {
        bool operator() (const TileIndex a, const TileIndex b) const
        {
                return a < b;
        }
};

using ChildStoreID = uint32_t;
static constexpr ChildStoreID NO_CHILD_STORE = UINT32_MAX;
static constexpr ChildStoreID CHILD_SPRITE_STORE_TAG = 1 << 31;

/** Data structure storing rendering information */
struct ViewportDrawer {
        TunnelToMapStorage tunnel_to_map_x;
        TunnelToMapStorage tunnel_to_map_y;

        ChildStoreID last_child;

        SpriteCombineMode combine_sprites;               ///< Current mode of "sprite combining". @see StartSpriteCombine
        uint combine_psd_index;
        int combine_left;
        int combine_right;
        int combine_top;
        int combine_bottom;

        int foundation[FOUNDATION_PART_END];             ///< Foundation sprites (index into parent_sprites_to_draw).
        FoundationPart foundation_part;                  ///< Currently active foundation for ground sprite drawing.
        ChildStoreID last_foundation_child[FOUNDATION_PART_END]; ///< Tail of ChildSprite list of the foundations. (index into child_screen_sprites_to_draw)
        Point foundation_offset[FOUNDATION_PART_END];    ///< Pixel offset for ground sprites on the foundations.
};
static ViewportDrawer _vd;

struct ViewportProcessParentSpritesData {
        DrawPixelInfo dpi;
        ParentSpriteToSortVector psts;
};

/** Data structure storing rendering information */
struct ViewportDrawerDynamic {
        DrawPixelInfo dpi;
        int offset_x;
        int offset_y;

        StringSpriteToDrawVector string_sprites_to_draw;
        TileSpriteToDrawVector tile_sprites_to_draw;
        ParentSpriteToDrawVector parent_sprites_to_draw;
        std::vector<ViewportProcessParentSpritesData> parent_sprite_sets;
        ParentSpriteToDrawSubSpriteHolder parent_sprite_subsprites;
        ChildScreenSpriteToDrawVector child_screen_sprites_to_draw;
        btree::btree_map<TileIndex, TileIndex, BridgeSetXComparator> bridge_to_map_x;
        btree::btree_map<TileIndex, TileIndex, BridgeSetYComparator> bridge_to_map_y;

        uint8_t display_flags;

        std::atomic<uint> draw_jobs_active;

        TransparencyOptionBits transparency_opt;
        TransparencyOptionBits invisibility_opt;

        const uint8_t *pal2trsp_remap_ptr = nullptr;

        SpritePointerHolder sprite_data;

        inline bool IsTransparencySet(TransparencyOption to)
        {
                return (HasBit(this->transparency_opt, to) && _game_mode != GM_MENU);
        }

        inline bool IsInvisibilitySet(TransparencyOption to)
        {
                return (HasBit(this->transparency_opt & this->invisibility_opt, to) && _game_mode != GM_MENU);
        }

        inline DrawPixelInfo MakeDPIForText() const
        {
                DrawPixelInfo dpi_for_text = this->dpi;
                dpi_for_text.left   = UnScaleByZoom(this->dpi.left,   this->dpi.zoom);
                dpi_for_text.top    = UnScaleByZoom(this->dpi.top,    this->dpi.zoom);
                dpi_for_text.width  = UnScaleByZoom(this->dpi.width,  this->dpi.zoom);
                dpi_for_text.height = UnScaleByZoom(this->dpi.height, this->dpi.zoom);
                dpi_for_text.zoom   = ZOOM_LVL_MIN;
                return dpi_for_text;
        }

        inline void SetChild(ChildStoreID store_index, int child)
        {
                if ((store_index & CHILD_SPRITE_STORE_TAG) != 0) {
                        this->child_screen_sprites_to_draw[store_index & ~CHILD_SPRITE_STORE_TAG].next = child;
                } else {
                        this->parent_sprites_to_draw[store_index].first_child = child;
                }
        }
};

static void MarkRouteStepDirty(RouteStepsMap::const_iterator cit);
static void MarkRouteStepDirty(const TileIndex tile, uint order_nr);
static void HideMeasurementTooltips();
static void ViewportDrawPlans(const Viewport *vp, Blitter *blitter, DrawPixelInfo *plan_dpi);

static std::unique_ptr<ViewportDrawerDynamic> _vdd;
std::vector<std::unique_ptr<ViewportDrawerDynamic>> _spare_viewport_drawers;

struct ViewportDrawerReturn {
        Viewport *vp;
        std::unique_ptr<ViewportDrawerDynamic> vdd;
};
static std::mutex _viewport_drawer_return_lock;
static std::vector<ViewportDrawerReturn> _viewport_drawer_returns;
static std::condition_variable _viewport_drawer_empty_cv;
static uint _viewport_drawer_jobs = 0;

static std::vector<Viewport *> _viewport_window_cache;
static std::vector<Rect> _viewport_coverage_rects;
std::vector<Rect> _viewport_vehicle_normal_redraw_rects;
std::vector<Rect> _viewport_vehicle_map_redraw_rects;

uint _vp_route_step_sprite_width = 0;
uint _vp_route_step_base_width = 0;
uint _vp_route_step_height_top = 0;
uint _vp_route_step_height_bottom = 0;
uint _vp_route_step_string_width[4] = {};

struct DrawnPathRouteTileLine {
        TileIndex from_tile;
        TileIndex to_tile;
        bool order_conditional;

        bool operator==(const DrawnPathRouteTileLine &other) const
        {
                return std::tie(this->from_tile, this->to_tile, this->order_conditional) == std::tie(other.from_tile, other.to_tile, other.order_conditional);
        }

        bool operator!=(const DrawnPathRouteTileLine &other) const
        {
                return !(*this == other);
        }

        bool operator<(const DrawnPathRouteTileLine &other) const
        {
                return std::tie(this->from_tile, this->to_tile, this->order_conditional) < std::tie(other.from_tile, other.to_tile, other.order_conditional);
        }
};

struct ViewportRouteOverlay {
private:
        RouteStepsMap route_steps;
        RouteStepsMap route_steps_last_mark_dirty;
        std::vector<DrawnPathRouteTileLine> route_paths;
        std::vector<DrawnPathRouteTileLine> route_paths_last_mark_dirty;

        struct PrepareRouteStepState {
                robin_hood::unordered_flat_set<const Order *> visited;
                uint lines_added;
                TileIndex from_tile;

                inline void reset(TileIndex from_tile)
                {
                        this->visited.clear();
                        this->lines_added = 0;
                        this->from_tile = from_tile;
                }
        };

        void PrepareRoutePathsConditionalOrder(const Vehicle *veh, const Order *order, PrepareRouteStepState &state, bool conditional, uint depth);
        void PrepareRouteSteps(const Vehicle *veh);
        void PrepareRoutePaths(const Vehicle *veh);
        void PrepareRouteStepsAndMarkDirtyIfChanged(const Vehicle *veh);
        void PrepareRoutePathsAndMarkDirtyIfChanged(const Vehicle *veh);

public:
        void PrepareRouteAndMarkDirtyIfChanged(const Vehicle *veh);
        void DrawVehicleRouteSteps(const Viewport *vp);
        void DrawVehicleRoutePath(const Viewport *vp, ViewportDrawerDynamic *vdd);

        inline bool HasVehicleRouteSteps() const { return !this->route_steps.empty(); }
};
static ViewportRouteOverlay _vp_focused_window_route_overlay;

struct FixedVehicleViewportRouteOverlay : public ViewportRouteOverlay {
        VehicleID veh;
        bool enabled = false;
};
static std::vector<FixedVehicleViewportRouteOverlay> _vp_fixed_route_overlays;

static void MarkRoutePathsDirty(const std::vector<DrawnPathRouteTileLine> &lines);

TileHighlightData _thd;
static TileInfo _cur_ti;
bool _draw_bounding_boxes = false;
bool _draw_dirty_blocks = false;
std::atomic<uint> _dirty_block_colour;
static VpSpriteSorter _vp_sprite_sorter = nullptr;

const uint8_t *_pal2trsp_remap_ptr = nullptr;

static RailSnapMode _rail_snap_mode = RSM_NO_SNAP; ///< Type of rail track snapping (polyline tool).
static LineSnapPoints _tile_snap_points; ///< Tile to which a rail track will be snapped to (polyline tool).
static LineSnapPoints _rail_snap_points; ///< Set of points where a rail track will be snapped to (polyline tool).
static LineSnapPoint _current_snap_lock; ///< Start point and direction at which selected track is locked on currently (while dragging in polyline mode).

static RailSnapMode GetRailSnapMode();
static void SetRailSnapMode(RailSnapMode mode);
static TileIndex GetRailSnapTile();
static void SetRailSnapTile(TileIndex tile);

enum ViewportDebugFlags {
        VDF_DIRTY_BLOCK_PER_DRAW,
        VDF_DIRTY_WHOLE_VIEWPORT,
        VDF_DIRTY_BLOCK_PER_SPLIT,
        VDF_DISABLE_DRAW_SPLIT,
        VDF_SHOW_NO_LANDSCAPE_MAP_DRAW,
        VDF_DISABLE_LANDSCAPE_CACHE,
        VDF_DISABLE_THREAD,
};
uint32_t _viewport_debug_flags;

static Point MapXYZToViewport(const Viewport *vp, int x, int y, int z)
{
        Point p = RemapCoords(x, y, z);
        p.x -= vp->virtual_width / 2;
        p.y -= vp->virtual_height / 2;
        return p;
}

static void FillViewportCoverageRect()
{
        _viewport_coverage_rects.resize(_viewport_window_cache.size());
        _viewport_vehicle_normal_redraw_rects.clear();
        _viewport_vehicle_map_redraw_rects.clear();

        for (uint i = 0; i < _viewport_window_cache.size(); i++) {
                const Viewport *vp = _viewport_window_cache[i];
                Rect &r = _viewport_coverage_rects[i];
                r.left = vp->virtual_left;
                r.top = vp->virtual_top;
                r.right = vp->virtual_left + vp->virtual_width + (1 << vp->zoom) - 1;
                r.bottom = vp->virtual_top + vp->virtual_height + (1 << vp->zoom) - 1;

                if (vp->zoom >= ZOOM_LVL_DRAW_MAP) {
                        _viewport_vehicle_map_redraw_rects.push_back(r);
                } else {
                        _viewport_vehicle_normal_redraw_rects.push_back({
                                r.left - (MAX_VEHICLE_PIXEL_X * ZOOM_BASE),
                                r.top - (MAX_VEHICLE_PIXEL_Y * ZOOM_BASE),
                                r.right + (MAX_VEHICLE_PIXEL_X * ZOOM_BASE),
                                r.bottom + (MAX_VEHICLE_PIXEL_Y * ZOOM_BASE),
                        });
                }
        }
}

using ScrollViewportPixelCacheGenericFillRegion = void (*)(Viewport *vp, int x, int y, int width, int height);

static bool ScrollViewportPixelCacheGeneric(Viewport *vp, std::vector<uint8_t> &cache, int offset_x, int offset_y, uint pixel_width, ScrollViewportPixelCacheGenericFillRegion fill_region)
{
        if (cache.empty()) return false;
        if (abs(offset_x) >= vp->width || abs(offset_y) >= vp->height) return true;

        int width = vp->width * pixel_width;
        offset_x *= pixel_width;

        int height = vp->height;

        /* Blitter_8bppDrawing::ScrollBuffer can be used on 32 bit buffers if widths and offsets are suitably adjusted */
        const int pitch = width;
        Blitter_8bppDrawing blitter(&pitch);
        blitter.ScrollBuffer(cache.data(), 0, 0, width, height, offset_x, offset_y);

        auto fill_rect = [&](int x, int y, int w, int h) {
                blitter.DrawRectAt(cache.data(), x, y, w, h, 0xD7);
                if (fill_region != nullptr) fill_region(vp, x, y, w, h);
        };

        int x = 0;
        if (offset_x < 0) {
                /* scrolling right, moving pixels left, fill in on right */
                width += offset_x;
                fill_rect(width, 0, -offset_x, height);
        } else if (offset_x > 0) {
                /* scrolling left, moving pixels right, fill in on left */
                fill_rect(0, 0, offset_x, height);
                width -= offset_x;
                x += offset_x;
        }
        if (offset_y < 0) {
                /* scrolling down, moving pixels up, fill in at bottom */
                height += offset_y;
                fill_rect(x, height, width, -offset_y);
        } else if (offset_y > 0) {
                /* scrolling up, moving pixels down, fill in at top */
                fill_rect(x, 0, width, offset_y);
        }
        return false;
}

void ClearViewportLandPixelCache(Viewport *vp)
{
        vp->land_pixel_cache.assign(vp->land_pixel_cache.size(), 0xD7);
}

static void ScrollViewportLandPixelCache(Viewport *vp, int offset_x, int offset_y)
{
        bool clear = ScrollViewportPixelCacheGeneric(vp, vp->land_pixel_cache, offset_x, offset_y, BlitterFactory::GetCurrentBlitter()->GetScreenDepth() / 8, nullptr);
        if (clear) ClearViewportLandPixelCache(vp);
}

static void ClearViewportPlanPixelCache(Viewport *vp)
{
        vp->plan_pixel_cache.clear();
        vp->last_plan_update_number = 0;
}

static void ScrollPlanPixelCache(Viewport *vp, int offset_x, int offset_y)
{
        if (vp->last_plan_update_number != _plan_update_counter) {
                ClearViewportPlanPixelCache(vp);
                return;
        }
        bool clear = ScrollViewportPixelCacheGeneric(vp, vp->plan_pixel_cache, offset_x, offset_y, 1, [](Viewport *vp, int x, int y, int width, int height) {
                DrawPixelInfo plan_dpi;
                plan_dpi.dst_ptr = vp->plan_pixel_cache.data() + x + (y * vp->width);
                plan_dpi.height = height;
                plan_dpi.width = width;
                plan_dpi.pitch = vp->width;
                plan_dpi.zoom = ZOOM_LVL_MIN;
                plan_dpi.left = UnScaleByZoomLower(vp->virtual_left, vp->zoom) + x;
                plan_dpi.top = UnScaleByZoomLower(vp->virtual_top, vp->zoom) + y;

                const int pitch = vp->width;
                Blitter_8bppDrawing blitter(&pitch);
                ViewportDrawPlans(vp, &blitter, &plan_dpi);
        });
        if (clear) ClearViewportPlanPixelCache(vp);
}

static void ScrollOrInvalidateOverlayPixelCache(Viewport *vp, int offset_x, int offset_y)
{
        if (vp->overlay_pixel_cache.empty()) return;

        if (vp->zoom < ZOOM_LVL_DRAW_MAP || vp->last_overlay_rebuild_counter != vp->overlay->GetRebuildCounter()) {
                vp->overlay_pixel_cache.clear();
                return;
        }

        bool clear = ScrollViewportPixelCacheGeneric(vp, vp->overlay_pixel_cache, offset_x, offset_y, 1, [](Viewport *vp, int x, int y, int width, int height) {
                DrawPixelInfo overlay_dpi;
                overlay_dpi.dst_ptr = vp->overlay_pixel_cache.data() + x + (y * vp->width);
                overlay_dpi.height = height;
                overlay_dpi.width = width;
                overlay_dpi.pitch = vp->width;
                overlay_dpi.zoom = ZOOM_LVL_MIN;
                overlay_dpi.left = UnScaleByZoomLower(vp->virtual_left, vp->zoom) + x;
                overlay_dpi.top = UnScaleByZoomLower(vp->virtual_top, vp->zoom) + y;

                const int pitch = vp->width;
                Blitter_8bppDrawing blitter(&pitch);
                vp->overlay->Draw(&blitter, &overlay_dpi);
        });
        if (clear) vp->overlay_pixel_cache.clear();
}

void ClearViewportCache(Viewport *vp)
{
        if (vp->zoom >= ZOOM_LVL_DRAW_MAP) {
                memset(vp->map_draw_vehicles_cache.done_hash_bits, 0, sizeof(vp->map_draw_vehicles_cache.done_hash_bits));
                if (!vp->map_draw_vehicles_cache.vehicle_pixels.empty()) {
                        MemSetT(vp->map_draw_vehicles_cache.vehicle_pixels.data(), 0, vp->map_draw_vehicles_cache.vehicle_pixels.size());
                }
        }
}

void ClearViewportCaches()
{
        for (Viewport *vp : _viewport_window_cache) {
                ClearViewportCache(vp);
        }
        if (unlikely(HasBit(_viewport_debug_flags, VDF_DISABLE_LANDSCAPE_CACHE))) {
                for (Viewport *vp : _viewport_window_cache) {
                        ClearViewportLandPixelCache(vp);
                }
        }
}

void DeleteWindowViewport(Window *w)
{
        if (w->viewport == nullptr) return;

        container_unordered_remove(_viewport_window_cache, w->viewport);
        delete w->viewport->overlay;
        delete w->viewport;
        w->viewport = nullptr;
        FillViewportCoverageRect();
}

/**
 * Initialize viewport of the window for use.
 * @param w Window to use/display the viewport in
 * @param x Offset of left edge of viewport with respect to left edge window \a w
 * @param y Offset of top edge of viewport with respect to top edge window \a w
 * @param width Width of the viewport
 * @param height Height of the viewport
 * @param follow_flags Flags controlling the viewport.
 *        - If bit 31 is set, the lower 20 bits are the vehicle that the viewport should follow.
 *        - If bit 31 is clear, it is a #TileIndex.
 * @param zoom Zoomlevel to display
 */
void InitializeWindowViewport(Window *w, int x, int y,
        int width, int height, uint32_t follow_flags, ZoomLevel zoom)
{
        assert(w->viewport == nullptr);

        ViewportData *vp = new ViewportData();

        vp->overlay = nullptr;
        vp->left = x + w->left;
        vp->top = y + w->top;
        vp->width = width;
        vp->height = height;

        vp->zoom = static_cast<ZoomLevel>(Clamp(zoom, _settings_client.gui.zoom_min, _settings_client.gui.zoom_max));

        vp->virtual_left = 0;
        vp->virtual_top = 0;
        vp->virtual_width = ScaleByZoom(width, vp->zoom);
        vp->virtual_height = ScaleByZoom(height, vp->zoom);

        vp->map_type = VPMT_BEGIN;

        UpdateViewportSizeZoom(vp);

        Point pt;

        if (follow_flags & 0x80000000) {
                const Vehicle *veh;

                vp->follow_vehicle = (VehicleID)(follow_flags & 0xFFFFF);
                veh = Vehicle::Get(vp->follow_vehicle);
                pt = MapXYZToViewport(vp, veh->x_pos, veh->y_pos, veh->z_pos);
        } else {
                x = TileX(follow_flags) * TILE_SIZE;
                y = TileY(follow_flags) * TILE_SIZE;

                vp->follow_vehicle = INVALID_VEHICLE;
                pt = MapXYZToViewport(vp, x, y, GetSlopePixelZ(x, y));
        }

        vp->scrollpos_x = pt.x;
        vp->scrollpos_y = pt.y;
        vp->dest_scrollpos_x = pt.x;
        vp->dest_scrollpos_y = pt.y;

        w->viewport = vp;
        _viewport_window_cache.push_back(vp);
        FillViewportCoverageRect();
}

struct ViewportRedrawRegion {
        Rect coords;
};

static std::vector<ViewportRedrawRegion> _vp_redraw_regions;

static void DoViewportRedrawRegions(const Window *w_start, int left, int top, int width, int height)
{
        if (width <= 0 || height <= 0) return;

        for (const Window *w : Window::IterateFromBack<const Window>(w_start)) {
                if (left + width > w->left &&
                                w->left + w->width > left &&
                                top + height > w->top &&
                                w->top + w->height > top) {

                        if (left < w->left) {
                                DoViewportRedrawRegions(w, left, top, w->left - left, height);
                                DoViewportRedrawRegions(w, left + (w->left - left), top, width - (w->left - left), height);
                                return;
                        }

                        if (left + width > w->left + w->width) {
                                DoViewportRedrawRegions(w, left, top, (w->left + w->width - left), height);
                                DoViewportRedrawRegions(w, left + (w->left + w->width - left), top, width - (w->left + w->width - left), height);
                                return;
                        }

                        if (top < w->top) {
                                DoViewportRedrawRegions(w, left, top, width, (w->top - top));
                                DoViewportRedrawRegions(w, left, top + (w->top - top), width, height - (w->top - top));
                                return;
                        }

                        if (top + height > w->top + w->height) {
                                DoViewportRedrawRegions(w, left, top, width, (w->top + w->height - top));
                                DoViewportRedrawRegions(w, left, top + (w->top + w->height - top), width, height - (w->top + w->height - top));
                                return;
                        }

                        return;
                }
        }

        _vp_redraw_regions.push_back({ { left, top, left + width, top + height } });
}

static void DoSetViewportPositionFillRegion(int left, int top, int width, int height, int xo, int yo) {
        int src_left = left - xo;
        int src_top = top - yo;
        int src_right = src_left + width;
        int src_bottom = src_top + height;
        for (const auto &region : _vp_redraw_regions) {
                if (region.coords.left < src_right &&
                                region.coords.right > src_left &&
                                region.coords.top < src_bottom &&
                                region.coords.bottom > src_top) {
                        /* can use this region as a source */
                        if (src_left < region.coords.left) {
                                DoSetViewportPositionFillRegion(src_left + xo, src_top + yo, region.coords.left - src_left, height, xo, yo);
                                src_left = region.coords.left;
                                width = src_right - src_left;
                        }
                        if (src_top < region.coords.top) {
                                DoSetViewportPositionFillRegion(src_left + xo, src_top + yo, width, region.coords.top - src_top, xo, yo);
                                src_top = region.coords.top;
                                height = src_bottom - src_top;
                        }
                        if (src_right > region.coords.right) {
                                DoSetViewportPositionFillRegion(region.coords.right + xo, src_top + yo, src_right - region.coords.right, height, xo, yo);
                                src_right = region.coords.right;
                                width = src_right - src_left;
                        }
                        if (src_bottom > region.coords.bottom) {
                                DoSetViewportPositionFillRegion(src_left + xo, region.coords.bottom + yo, width, src_bottom - region.coords.bottom, xo, yo);
                                src_bottom = region.coords.bottom;
                                height = src_bottom - src_top;
                        }

                        if (xo >= 0) {
                                /* scrolling left, moving pixels right */
                                width += xo;
                        } else {
                                /* scrolling right, moving pixels left */
                                src_left += xo;
                                width -= xo;
                        }
                        if (yo >= 0) {
                                /* scrolling down, moving pixels up */
                                height += yo;
                        } else {
                                /* scrolling up, moving pixels down */
                                src_top += yo;
                                height -= yo;
                        }
                        BlitterFactory::GetCurrentBlitter()->ScrollBuffer(_screen.dst_ptr, src_left, src_top, width, height, xo, yo);

                        return;
                }
        }
        DrawOverlappedWindowForAll(left, top, left + width, top + height);
};

static void DoSetViewportPosition(Window *w, const Point move_offset, const int vp_left, const int vp_top, const int vp_width, const int vp_height)
{
        const int xo = move_offset.x;
        const int yo = move_offset.y;

        IncrementWindowUpdateNumber();

        _vp_redraw_regions.clear();
        DoViewportRedrawRegions(w, vp_left, vp_top, vp_width, vp_height);

        if (abs(xo) >= vp_width || abs(yo) >= vp_height) {
                /* fully outside */
                for (ViewportRedrawRegion &vrr : _vp_redraw_regions) {
                        RedrawScreenRect(vrr.coords.left, vrr.coords.top, vrr.coords.right, vrr.coords.bottom);
                }
                return;
        }

        Blitter *blitter = BlitterFactory::GetCurrentBlitter();

        if (_cursor.visible) UndrawMouseCursor();

        if (_networking) NetworkUndrawChatMessage();

        if (xo != 0) {
                std::sort(_vp_redraw_regions.begin(), _vp_redraw_regions.end(), [&](const ViewportRedrawRegion &a, const ViewportRedrawRegion &b) {
                        if (a.coords.right <= b.coords.left && xo > 0) return true;
                        if (a.coords.left >= b.coords.right && xo < 0) return true;
                        return false;
                });
                if (yo != 0) {
                        std::stable_sort(_vp_redraw_regions.begin(), _vp_redraw_regions.end(), [&](const ViewportRedrawRegion &a, const ViewportRedrawRegion &b) {
                                if (a.coords.bottom <= b.coords.top && yo > 0) return true;
                                if (a.coords.top >= b.coords.bottom && yo < 0) return true;
                                return false;
                        });
                }
        } else {
                std::sort(_vp_redraw_regions.begin(), _vp_redraw_regions.end(), [&](const ViewportRedrawRegion &a, const ViewportRedrawRegion &b) {
                        if (a.coords.bottom <= b.coords.top && yo > 0) return true;
                        if (a.coords.top >= b.coords.bottom && yo < 0) return true;
                        return false;
                });
        }

        while (!_vp_redraw_regions.empty()) {
                const Rect &rect = _vp_redraw_regions.back().coords;
                int left = rect.left;
                int top = rect.top;
                int width = rect.right - rect.left;
                int height = rect.bottom - rect.top;
                _vp_redraw_regions.pop_back();
                VideoDriver::GetInstance()->MakeDirty(left, top, width, height);
                int fill_width = abs(xo);
                int fill_height = abs(yo);
                if (fill_width < width && fill_height < height) {
                        blitter->ScrollBuffer(_screen.dst_ptr, left, top, width, height, xo, yo);
                } else {
                        if (width < fill_width) fill_width = width;
                        if (height < fill_height) fill_height = height;
                }
                if (xo < 0) {
                        /* scrolling right, moving pixels left, fill in on right */
                        width -= fill_width;
                        DoSetViewportPositionFillRegion(left + width, top, fill_width, height, xo, yo);
                } else if (xo > 0) {
                        /* scrolling left, moving pixels right, fill in on left */
                        DoSetViewportPositionFillRegion(left, top, fill_width, height, xo, yo);
                        width -= fill_width;
                        left += fill_width;
                }
                if (yo < 0 && width > 0) {
                        /* scrolling down, moving pixels up, fill in at bottom */
                        height -= fill_height;
                        DoSetViewportPositionFillRegion(left, top + height, width, fill_height, xo, yo);
                } else if (yo > 0 && width > 0) {
                        /* scrolling up, moving pixels down, fill in at top */
                        DoSetViewportPositionFillRegion(left, top, width, fill_height, xo, yo);
                }
        }
}

inline void UpdateViewportDirtyBlockLeftMargin(Viewport *vp)
{
        if (vp->zoom >= ZOOM_LVL_DRAW_MAP) {
                vp->dirty_block_left_margin = 0;
        } else {
                vp->dirty_block_left_margin = UnScaleByZoomLower((-vp->virtual_left) & 127, vp->zoom);
        }
}

static void SetViewportPosition(Window *w, int x, int y, bool force_update_overlay)
{
        if (unlikely(HasBit(_viewport_debug_flags, VDF_DIRTY_WHOLE_VIEWPORT))) {
                w->flags |= WF_DIRTY;
        }

        Viewport *vp = w->viewport;
        int old_left = vp->virtual_left;
        int old_top = vp->virtual_top;
        int i;
        int left, top, width, height;

        vp->virtual_left = x;
        vp->virtual_top = y;
        UpdateViewportDirtyBlockLeftMargin(vp);

        bool have_overlay = w->viewport->overlay != nullptr &&
                        w->viewport->overlay->GetCompanyMask() != 0 &&
                        w->viewport->overlay->GetCargoMask() != 0;

        if (have_overlay && (force_update_overlay || !w->viewport->overlay->CacheStillValid())) RebuildViewportOverlay(w, true);

        /* Viewport is bound to its left top corner, so it must be rounded down (UnScaleByZoomLower)
         * else glitch described in FS#1412 will happen (offset by 1 pixel with zoom level > NORMAL)
         */
        old_left = UnScaleByZoomLower(old_left, vp->zoom);
        old_top = UnScaleByZoomLower(old_top, vp->zoom);
        x = UnScaleByZoomLower(x, vp->zoom);
        y = UnScaleByZoomLower(y, vp->zoom);

        old_left -= x;
        old_top -= y;

        if (old_top == 0 && old_left == 0) return;

        Point move_offset = { old_left, old_top };

        left = vp->left;
        top = vp->top;
        width = vp->width;
        height = vp->height;

        if (left < 0) {
                width += left;
                left = 0;
        }

        i = left + width - _screen.width;
        if (i >= 0) width -= i;

        if (width > 0) {
                if (top < 0) {
                        height += top;
                        top = 0;
                }

                i = top + height - _screen.height;
                if (i >= 0) height -= i;

                if (height > 0 && (move_offset.x != 0 || move_offset.y != 0)) {
                        SCOPE_INFO_FMT([&], "DoSetViewportPosition: {}, {}, {}, {}, {}, {}, {}", left, top, width, height, move_offset.x, move_offset.y, WindowInfoDumper(w));
                        ScrollViewportLandPixelCache(vp, move_offset.x, move_offset.y);
                        ScrollPlanPixelCache(vp, move_offset.x, move_offset.y);
                        if (have_overlay) ScrollOrInvalidateOverlayPixelCache(vp, move_offset.x, move_offset.y);
                        w->viewport->update_vehicles = true;
                        DoSetViewportPosition((Window *) w->z_front, move_offset, left, top, width, height);
                        ClearViewportCache(w->viewport);
                        FillViewportCoverageRect();
                }
        }
}

/**
 * Is a xy position inside the viewport of the window?
 * @param w Window to examine its viewport
 * @param x X coordinate of the xy position
 * @param y Y coordinate of the xy position
 * @return Pointer to the viewport if the xy position is in the viewport of the window,
 *         otherwise \c nullptr is returned.
 */
Viewport *IsPtInWindowViewport(const Window *w, int x, int y)
{
        Viewport *vp = w->viewport;

        if (vp != nullptr &&
                        IsInsideMM(x, vp->left, vp->left + vp->width) &&
                        IsInsideMM(y, vp->top, vp->top + vp->height))
                return vp;

        return nullptr;
}

/**
 * Translate screen coordinate in a viewport to underlying tile coordinate.
 *
 * Returns exact point of the map that is visible in the given place
 * of the viewport (3D perspective), height of tiles and foundations matter.
 *
 * @param vp  Viewport that contains the (\a x, \a y) screen coordinate
 * @param x   Screen x coordinate, distance in pixels from the left edge of viewport frame
 * @param y   Screen y coordinate, distance in pixels from the top edge of viewport frame
 * @param clamp_to_map Clamp the coordinate outside of the map to the closest, non-void tile within the map
 * @return Tile coordinate or (-1, -1) if given x or y is not within viewport frame
 */
Point TranslateXYToTileCoord(const Viewport *vp, int x, int y, bool clamp_to_map)
{
        if (!IsInsideBS(x, vp->left, vp->width) || !IsInsideBS(y, vp->top, vp->height)) {
                Point pt = { -1, -1 };
                return pt;
        }

        return InverseRemapCoords2(
                        ScaleByZoom(x - vp->left, vp->zoom) + vp->virtual_left,
                        ScaleByZoom(y - vp->top, vp->zoom) + vp->virtual_top, clamp_to_map);
}

/* When used for zooming, check area below current coordinates (x,y)
 * and return the tile of the zoomed out/in position (zoom_x, zoom_y)
 * when you just want the tile, make x = zoom_x and y = zoom_y */
static Point GetTileFromScreenXY(int x, int y, int zoom_x, int zoom_y)
{
        Window *w = FindWindowFromPt(x, y);
        if (w != nullptr) {
                Viewport *vp = IsPtInWindowViewport(w, x, y);
                if (vp != nullptr) {
                        return TranslateXYToTileCoord(vp, zoom_x, zoom_y);
                }
        }

        return { -1, -1 };
}

Point GetTileBelowCursor()
{
        return GetTileFromScreenXY(_cursor.pos.x, _cursor.pos.y, _cursor.pos.x, _cursor.pos.y);
}


Point GetTileZoomCenterWindow(bool in, Window * w)
{
        int x, y;
        Viewport *vp = w->viewport;

        if (in) {
                x = ((_cursor.pos.x - vp->left) >> 1) + (vp->width >> 2);
                y = ((_cursor.pos.y - vp->top) >> 1) + (vp->height >> 2);
        } else {
                x = vp->width - (_cursor.pos.x - vp->left);
                y = vp->height - (_cursor.pos.y - vp->top);
        }
        /* Get the tile below the cursor and center on the zoomed-out center */
        return GetTileFromScreenXY(_cursor.pos.x, _cursor.pos.y, x + vp->left, y + vp->top);
}

/**
 * Update the status of the zoom-buttons according to the zoom-level
 * of the viewport. This will update their status and invalidate accordingly
 * @param w Window pointer to the window that has the zoom buttons
 * @param vp pointer to the viewport whose zoom-level the buttons represent
 * @param widget_zoom_in widget index for window with zoom-in button
 * @param widget_zoom_out widget index for window with zoom-out button
 */
void HandleZoomMessage(Window *w, const Viewport *vp, WidgetID widget_zoom_in, WidgetID widget_zoom_out)
{
        w->SetWidgetDisabledState(widget_zoom_in, vp->zoom <= _settings_client.gui.zoom_min);
        w->SetWidgetDirty(widget_zoom_in);

        w->SetWidgetDisabledState(widget_zoom_out, vp->zoom >= _settings_client.gui.zoom_max);
        w->SetWidgetDirty(widget_zoom_out);
}

/**
 * Schedules a tile sprite for drawing.
 *
 * @param image the image to draw.
 * @param pal the provided palette.
 * @param x position x (world coordinates) of the sprite.
 * @param y position y (world coordinates) of the sprite.
 * @param z position z (world coordinates) of the sprite.
 * @param sub Only draw a part of the sprite.
 * @param extra_offs_x Pixel X offset for the sprite position.
 * @param extra_offs_y Pixel Y offset for the sprite position.
 */
static void AddTileSpriteToDraw(SpriteID image, PaletteID pal, int32_t x, int32_t y, int z, const SubSprite *sub = nullptr, int extra_offs_x = 0, int extra_offs_y = 0)
{
        dbg_assert((image & SPRITE_MASK) < MAX_SPRITES);

        TileSpriteToDraw &ts = _vdd->tile_sprites_to_draw.emplace_back();
        ts.image = image;
        ts.pal = pal;
        ts.sub = sub;
        Point pt = RemapCoords(x, y, z);
        ts.x = pt.x + extra_offs_x;
        ts.y = pt.y + extra_offs_y;
}

/**
 * Adds a child sprite to the active foundation.
 *
 * The pixel offset of the sprite relative to the ParentSprite is the sum of the offset passed to OffsetGroundSprite() and extra_offs_?.
 *
 * @param image the image to draw.
 * @param pal the provided palette.
 * @param sub Only draw a part of the sprite.
 * @param foundation_part Foundation part.
 * @param extra_offs_x Pixel X offset for the sprite position.
 * @param extra_offs_y Pixel Y offset for the sprite position.
 */
static void AddChildSpriteToFoundation(SpriteID image, PaletteID pal, const SubSprite *sub, FoundationPart foundation_part, int extra_offs_x, int extra_offs_y)
{
        dbg_assert(IsInsideMM(foundation_part, 0, FOUNDATION_PART_END));
        dbg_assert(_vd.foundation[foundation_part] != -1);
        Point offs = _vd.foundation_offset[foundation_part];

        /* Change the active ChildSprite list to the one of the foundation */
        ChildStoreID old_child = _vd.last_child;
        _vd.last_child = _vd.last_foundation_child[foundation_part];

        AddChildSpriteScreen(image, pal, offs.x + extra_offs_x, offs.y + extra_offs_y, false, sub, false, ChildScreenSpritePositionMode::NonRelative);

        /* Switch back to last ChildSprite list */
        _vd.last_child = old_child;
}

/**
 * Draws a ground sprite at a specific world-coordinate relative to the current tile.
 * If the current tile is drawn on top of a foundation the sprite is added as child sprite to the "foundation"-ParentSprite.
 *
 * @param image the image to draw.
 * @param pal the provided palette.
 * @param x position x (world coordinates) of the sprite relative to current tile.
 * @param y position y (world coordinates) of the sprite relative to current tile.
 * @param z position z (world coordinates) of the sprite relative to current tile.
 * @param sub Only draw a part of the sprite.
 * @param extra_offs_x Pixel X offset for the sprite position.
 * @param extra_offs_y Pixel Y offset for the sprite position.
 */
void DrawGroundSpriteAt(SpriteID image, PaletteID pal, int32_t x, int32_t y, int z, const SubSprite *sub, int extra_offs_x, int extra_offs_y)
{
        /* Switch to first foundation part, if no foundation was drawn */
        if (_vd.foundation_part == FOUNDATION_PART_NONE) _vd.foundation_part = FOUNDATION_PART_NORMAL;

        if (_vd.foundation[_vd.foundation_part] != -1) {
                Point pt = RemapCoords(x, y, z);
                AddChildSpriteToFoundation(image, pal, sub, _vd.foundation_part, pt.x + extra_offs_x * ZOOM_BASE, pt.y + extra_offs_y * ZOOM_BASE);
        } else {
                AddTileSpriteToDraw(image, pal, _cur_ti.x + x, _cur_ti.y + y, _cur_ti.z + z, sub, extra_offs_x * ZOOM_BASE, extra_offs_y * ZOOM_BASE);
        }
}

/**
 * Draws a ground sprite for the current tile.
 * If the current tile is drawn on top of a foundation the sprite is added as child sprite to the "foundation"-ParentSprite.
 *
 * @param image the image to draw.
 * @param pal the provided palette.
 * @param sub Only draw a part of the sprite.
 * @param extra_offs_x Pixel X offset for the sprite position.
 * @param extra_offs_y Pixel Y offset for the sprite position.
 */
void DrawGroundSprite(SpriteID image, PaletteID pal, const SubSprite *sub, int extra_offs_x, int extra_offs_y)
{
        DrawGroundSpriteAt(image, pal, 0, 0, 0, sub, extra_offs_x, extra_offs_y);
}

/**
 * Called when a foundation has been drawn for the current tile.
 * Successive ground sprites for the current tile will be drawn as child sprites of the "foundation"-ParentSprite, not as TileSprites.
 *
 * @param x sprite x-offset (screen coordinates) of ground sprites relative to the "foundation"-ParentSprite.
 * @param y sprite y-offset (screen coordinates) of ground sprites relative to the "foundation"-ParentSprite.
 */
void OffsetGroundSprite(int x, int y)
{
        /* Switch to next foundation part */
        switch (_vd.foundation_part) {
                case FOUNDATION_PART_NONE:
                        _vd.foundation_part = FOUNDATION_PART_NORMAL;
                        break;
                case FOUNDATION_PART_NORMAL:
                        _vd.foundation_part = FOUNDATION_PART_HALFTILE;
                        break;
                default: NOT_REACHED();
        }

        /* _vd.last_child == NO_CHILD_STORE if foundation sprite was clipped by the viewport bounds */
        if (_vd.last_child != NO_CHILD_STORE) _vd.foundation[_vd.foundation_part] = (uint)_vdd->parent_sprites_to_draw.size() - 1;

        _vd.foundation_offset[_vd.foundation_part].x = x * ZOOM_BASE;
        _vd.foundation_offset[_vd.foundation_part].y = y * ZOOM_BASE;
        _vd.last_foundation_child[_vd.foundation_part] = _vd.last_child;
}

/**
 * Adds a child sprite to a parent sprite.
 * In contrast to "AddChildSpriteScreen()" the sprite position is in world coordinates
 *
 * @param image the image to draw.
 * @param pal the provided palette.
 * @param x position x of the sprite.
 * @param y position y of the sprite.
 * @param z position z of the sprite.
 * @param sub Only draw a part of the sprite.
 */
static void AddCombinedSprite(SpriteID image, PaletteID pal, int x, int y, int z, const SubSprite *sub)
{
        Point pt = RemapCoords(x, y, z);
        const Sprite *spr = GetSprite(image & SPRITE_MASK, SpriteType::Normal, ZoomMask(_vdd->dpi.zoom));

        int left = pt.x + spr->x_offs;
        int right = pt.x + spr->x_offs + spr->width;
        int top = pt.y + spr->y_offs;
        int bottom = pt.y + spr->y_offs + spr->height;
        if (left >= _vdd->dpi.left + _vdd->dpi.width ||
                        right <= _vdd->dpi.left ||
                        top >= _vdd->dpi.top + _vdd->dpi.height ||
                        bottom <= _vdd->dpi.top) {
                return;
        }

        AddChildSpriteScreen(image, pal, pt.x, pt.y, false, sub, false, ChildScreenSpritePositionMode::Absolute);
        if (left < _vd.combine_left) _vd.combine_left = left;
        if (right > _vd.combine_right) _vd.combine_right = right;
        if (top < _vd.combine_top) _vd.combine_top = top;
        if (bottom > _vd.combine_bottom) _vd.combine_bottom = bottom;
}

/**
 * Draw a (transparent) sprite at given coordinates with a given bounding box.
 * The bounding box extends from (x + bb_offset_x, y + bb_offset_y, z + bb_offset_z) to (x + w - 1, y + h - 1, z + dz - 1), both corners included.
 * Bounding boxes with bb_offset_x == w or bb_offset_y == h or bb_offset_z == dz are allowed and produce thin slices.
 *
 * @note Bounding boxes are normally specified with bb_offset_x = bb_offset_y = bb_offset_z = 0. The extent of the bounding box in negative direction is
 *       defined by the sprite offset in the grf file.
 *       However if modifying the sprite offsets is not suitable (e.g. when using existing graphics), the bounding box can be tuned by bb_offset.
 *
 * @pre w >= bb_offset_x, h >= bb_offset_y, dz >= bb_offset_z. Else w, h or dz are ignored.
 *
 * @param image the image to combine and draw,
 * @param pal the provided palette,
 * @param x position X (world) of the sprite,
 * @param y position Y (world) of the sprite,
 * @param w bounding box extent towards positive X (world),
 * @param h bounding box extent towards positive Y (world),
 * @param dz bounding box extent towards positive Z (world),
 * @param z position Z (world) of the sprite,
 * @param transparent if true, switch the palette between the provided palette and the transparent palette,
 * @param bb_offset_x bounding box extent towards negative X (world),
 * @param bb_offset_y bounding box extent towards negative Y (world),
 * @param bb_offset_z bounding box extent towards negative Z (world)
 * @param sub Only draw a part of the sprite.
 * @param special_flags Special flags (special sorting, etc).
 */
void AddSortableSpriteToDraw(SpriteID image, PaletteID pal, int x, int y, int w, int h, int dz, int z, bool transparent, int bb_offset_x, int bb_offset_y, int bb_offset_z, const SubSprite *sub, ViewportSortableSpriteSpecialFlags special_flags)
{
        int32_t left, right, top, bottom;

        dbg_assert((image & SPRITE_MASK) < MAX_SPRITES);

        /* make the sprites transparent with the right palette */
        if (transparent) {
                SetBit(image, PALETTE_MODIFIER_TRANSPARENT);
                pal = PALETTE_TO_TRANSPARENT;
        }

        if (_vd.combine_sprites == SPRITE_COMBINE_ACTIVE) {
                AddCombinedSprite(image, pal, x, y, z, sub);
                return;
        }

        _vd.last_child = NO_CHILD_STORE;

        Point pt = RemapCoords(x, y, z);
        int tmp_left, tmp_top, tmp_x = pt.x, tmp_y = pt.y;
        uint16_t tmp_width, tmp_height;

        /* Compute screen extents of sprite */
        if (unlikely(image == SPR_EMPTY_BOUNDING_BOX)) {
                left = tmp_left = RemapCoords(x + w          , y + bb_offset_y, z + bb_offset_z).x;
                right           = RemapCoords(x + bb_offset_x, y + h          , z + bb_offset_z).x + 1;
                top  = tmp_top  = RemapCoords(x + bb_offset_x, y + bb_offset_y, z + dz         ).y;
                bottom          = RemapCoords(x + w          , y + h          , z + bb_offset_z).y + 1;
                tmp_width = right - left;
                tmp_height = bottom - top;
        } else {
                const Sprite *spr = GetSprite(image & SPRITE_MASK, SpriteType::Normal, ZoomMask(_vdd->dpi.zoom));
                left = tmp_left = (pt.x += spr->x_offs);
                right           = (pt.x +  spr->width );
                top  = tmp_top  = (pt.y += spr->y_offs);
                bottom          = (pt.y +  spr->height);
                tmp_width = spr->width;
                tmp_height = spr->height;
        }

        if (unlikely(_draw_bounding_boxes && (image != SPR_EMPTY_BOUNDING_BOX))) {
                /* Compute maximal extents of sprite and its bounding box */
                left   = std::min(left  , RemapCoords(x + w          , y + bb_offset_y, z + bb_offset_z).x);
                right  = std::max(right , RemapCoords(x + bb_offset_x, y + h          , z + bb_offset_z).x + 1);
                top    = std::min(top   , RemapCoords(x + bb_offset_x, y + bb_offset_y, z + dz         ).y);
                bottom = std::max(bottom, RemapCoords(x + w          , y + h          , z + bb_offset_z).y + 1);
        }

        /* Do not add the sprite to the viewport, if it is outside */
        if (left   >= _vdd->dpi.left + _vdd->dpi.width  ||
                right  <= _vdd->dpi.left                   ||
                top    >= _vdd->dpi.top  + _vdd->dpi.height ||
                bottom <= _vdd->dpi.top) {
                return;
        }

        _vd.last_child = static_cast<ChildStoreID>(_vdd->parent_sprites_to_draw.size());

        ParentSpriteToDraw &ps = _vdd->parent_sprites_to_draw.emplace_back();
        ps.x = tmp_x;
        ps.y = tmp_y;

        ps.left = tmp_left;
        ps.top  = tmp_top;

        ps.image = image;
        ps.pal = pal;
        _vdd->parent_sprite_subsprites.Set(&ps, sub);
        ps.special_flags = special_flags;

        ps.xmin = x + bb_offset_x;
        ps.xmax = x + std::max(bb_offset_x, w) - 1;

        ps.ymin = y + bb_offset_y;
        ps.ymax = y + std::max(bb_offset_y, h) - 1;

        ps.zmin = z + bb_offset_z;
        ps.zmax = z + std::max(bb_offset_z, dz) - 1;

        ps.first_child = -1;
        ps.width = tmp_width;
        ps.height = tmp_height;

        /* bit 15 of ps.height */
        // ps.comparison_done = false;

        if (_vd.combine_sprites == SPRITE_COMBINE_PENDING) {
                _vd.combine_sprites = SPRITE_COMBINE_ACTIVE;
                _vd.combine_psd_index = (uint)_vdd->parent_sprites_to_draw.size() - 1;
                _vd.combine_left = tmp_left;
                _vd.combine_right = right;
                _vd.combine_top = tmp_top;
                _vd.combine_bottom = bottom;
        }
}

void SetLastSortableSpriteToDrawSpecialFlags(ViewportSortableSpriteSpecialFlags flags)
{
        _vdd->parent_sprites_to_draw.back().special_flags = flags;
}

/**
 * Starts a block of sprites, which are "combined" into a single bounding box.
 *
 * Subsequent calls to #AddSortableSpriteToDraw will be drawn into the same bounding box.
 * That is: The first sprite that is not clipped by the viewport defines the bounding box, and
 * the following sprites will be child sprites to that one.
 *
 * That implies:
 *  - The drawing order is definite. No other sprites will be sorted between those of the block.
 *  - You have to provide a valid bounding box for all sprites,
 *    as you won't know which one is the first non-clipped one.
 *    Preferable you use the same bounding box for all.
 *  - You cannot use #AddChildSpriteScreen inside the block, as its result will be indefinite.
 *
 * The block is terminated by #EndSpriteCombine.
 *
 * You cannot nest "combined" blocks.
 */
void StartSpriteCombine()
{
        dbg_assert(_vd.combine_sprites == SPRITE_COMBINE_NONE);
        _vd.combine_sprites = SPRITE_COMBINE_PENDING;
}

/**
 * Terminates a block of sprites started by #StartSpriteCombine.
 * Take a look there for details.
 */
void EndSpriteCombine()
{
        dbg_assert(_vd.combine_sprites != SPRITE_COMBINE_NONE);
        if (_vd.combine_sprites == SPRITE_COMBINE_ACTIVE) {
                ParentSpriteToDraw &ps = _vdd->parent_sprites_to_draw[_vd.combine_psd_index];
                ps.left = _vd.combine_left;
                ps.top = _vd.combine_top;
                ps.width = _vd.combine_right - _vd.combine_left;
                ps.height = _vd.combine_bottom - _vd.combine_top;
        }
        _vd.combine_sprites = SPRITE_COMBINE_NONE;
}

/**
 * Check if the parameter "check" is inside the interval between
 * begin and end, including both begin and end.
 * @note Whether \c begin or \c end is the biggest does not matter.
 *       This method will account for that.
 * @param begin The begin of the interval.
 * @param end   The end of the interval.
 * @param check The value to check.
 */
static bool IsInRangeInclusive(int begin, int end, int check)
{
        if (begin > end) Swap(begin, end);
        return begin <= check && check <= end;
}

/**
 * Checks whether a point is inside the selected rectangle given by _thd.size, _thd.pos and _thd.diagonal
 * @param x The x coordinate of the point to be checked.
 * @param y The y coordinate of the point to be checked.
 * @return True if the point is inside the rectangle, else false.
 */
static bool IsInsideSelectedRectangle(int x, int y)
{
        if (!_thd.diagonal) {
                return IsInsideBS(x, _thd.pos.x, _thd.size.x) && IsInsideBS(y, _thd.pos.y, _thd.size.y);
        }

        int dist_a = (_thd.size.x + _thd.size.y);      // Rotated coordinate system for selected rectangle.
        int dist_b = (_thd.size.x - _thd.size.y);      // We don't have to divide by 2. It's all relative!
        int a = ((x - _thd.pos.x) + (y - _thd.pos.y)); // Rotated coordinate system for the point under scrutiny.
        int b = ((x - _thd.pos.x) - (y - _thd.pos.y));

        /* Check if a and b are between 0 and dist_a or dist_b respectively. */
        return IsInRangeInclusive(dist_a, 0, a) && IsInRangeInclusive(dist_b, 0, b);
}

/**
 * Add a child sprite to a parent sprite.
 *
 * @param image the image to draw.
 * @param pal the provided palette.
 * @param x sprite x-offset (screen coordinates), optionally relative to parent sprite.
 * @param y sprite y-offset (screen coordinates), optionally relative to parent sprite.
 * @param transparent if true, switch the palette between the provided palette and the transparent palette,
 * @param sub Only draw a part of the sprite.
 * @param scale if true, scale offsets to base zoom level.
 * @param position_mode position mode.
 */
void AddChildSpriteScreen(SpriteID image, PaletteID pal, int x, int y, bool transparent, const SubSprite *sub, bool scale, ChildScreenSpritePositionMode position_mode)
{
        dbg_assert((image & SPRITE_MASK) < MAX_SPRITES);

        /* If the ParentSprite was clipped by the viewport bounds, do not draw the ChildSprites either */
        if (_vd.last_child == NO_CHILD_STORE) return;

        /* make the sprites transparent with the right palette */
        if (transparent) {
                SetBit(image, PALETTE_MODIFIER_TRANSPARENT);
                pal = PALETTE_TO_TRANSPARENT;
        }

        _vdd->SetChild(_vd.last_child, (uint)_vdd->child_screen_sprites_to_draw.size());
        const ChildStoreID child_store = static_cast<ChildStoreID>(_vdd->child_screen_sprites_to_draw.size()) | CHILD_SPRITE_STORE_TAG;

        ChildScreenSpriteToDraw &cs = _vdd->child_screen_sprites_to_draw.emplace_back();
        cs.image = image;
        cs.pal = pal;
        cs.sub = sub;
        cs.x = scale ? x * ZOOM_BASE : x;
        cs.y = scale ? y * ZOOM_BASE : y;
        cs.position_mode = position_mode;
        cs.next = -1;

        /* Append the sprite to the active ChildSprite list.
         * If the active ParentSprite is a foundation, update last_foundation_child as well.
         * Note: ChildSprites of foundations are NOT sequential in the vector, as selection sprites are added at last. */
        if (_vd.last_foundation_child[0] == _vd.last_child) _vd.last_foundation_child[0] = child_store;
        if (_vd.last_foundation_child[1] == _vd.last_child) _vd.last_foundation_child[1] = child_store;
        _vd.last_child = child_store;
}

static void AddStringToDraw(ViewportDrawerDynamic *vdd, int x, int y, StringID string, uint64_t params_1, uint64_t params_2, Colours colour, uint16_t width)
{
        dbg_assert(width != 0);
        StringSpriteToDraw &ss = vdd->string_sprites_to_draw.emplace_back();
        ss.string = string;
        ss.x = x;
        ss.y = y;
        ss.params[0] = params_1;
        ss.params[1] = params_2;
        ss.width = width;
        ss.colour = colour;
}


/**
 * Draws sprites between ground sprite and everything above.
 *
 * The sprite is either drawn as TileSprite or as ChildSprite of the active foundation.
 *
 * @param image the image to draw.
 * @param pal the provided palette.
 * @param ti TileInfo Tile that is being drawn
 * @param z_offset Z offset relative to the groundsprite. Only used for the sprite position, not for sprite sorting.
 * @param foundation_part Foundation part the sprite belongs to.
 * @param extra_offs_x Pixel X offset for the sprite position.
 * @param extra_offs_y Pixel Y offset for the sprite position.
 * @param sub Sub-section of sprite to draw.
 */
void DrawSelectionSprite(SpriteID image, PaletteID pal, const TileInfo *ti, int z_offset, FoundationPart foundation_part, int extra_offs_x, int extra_offs_y, const SubSprite *sub)
{
        /* FIXME: This is not totally valid for some autorail highlights that extend over the edges of the tile. */
        if (_vd.foundation[foundation_part] == -1) {
                /* draw on real ground */
                AddTileSpriteToDraw(image, pal, ti->x, ti->y, ti->z + z_offset, sub, extra_offs_x, extra_offs_y);
        } else {
                /* draw on top of foundation */
                AddChildSpriteToFoundation(image, pal, sub, foundation_part, extra_offs_x, extra_offs_y - z_offset * ZOOM_BASE);
        }
}

/**
 * Draws a selection rectangle on a tile.
 *
 * @param ti TileInfo Tile that is being drawn
 * @param pal Palette to apply.
 */
void DrawTileSelectionRect(const TileInfo *ti, PaletteID pal)
{
        if (!IsValidTile(ti->tile)) return;

        SpriteID sel;
        if (IsHalftileSlope(ti->tileh)) {
                Corner halftile_corner = GetHalftileSlopeCorner(ti->tileh);
                SpriteID sel2 = SPR_HALFTILE_SELECTION_FLAT + halftile_corner;
                DrawSelectionSprite(sel2, pal, ti, 7 + TILE_HEIGHT, FOUNDATION_PART_HALFTILE);

                Corner opposite_corner = OppositeCorner(halftile_corner);
                if (IsSteepSlope(ti->tileh)) {
                        sel = SPR_HALFTILE_SELECTION_DOWN;
                } else {
                        sel = ((ti->tileh & SlopeWithOneCornerRaised(opposite_corner)) != 0 ? SPR_HALFTILE_SELECTION_UP : SPR_HALFTILE_SELECTION_FLAT);
                }
                sel += opposite_corner;
        } else {
                sel = SPR_SELECT_TILE + SlopeToSpriteOffset(ti->tileh);
        }
        DrawSelectionSprite(sel, pal, ti, 7, FOUNDATION_PART_NORMAL);
}

static HighLightStyle GetPartOfAutoLine(int px, int py, const Point &selstart, const Point &selend, HighLightStyle dir)
{
        if (!IsInRangeInclusive(selstart.x & ~TILE_UNIT_MASK, selend.x & ~TILE_UNIT_MASK, px)) return HT_DIR_END;
        if (!IsInRangeInclusive(selstart.y & ~TILE_UNIT_MASK, selend.y & ~TILE_UNIT_MASK, py)) return HT_DIR_END;

        px -= selstart.x & ~TILE_UNIT_MASK;
        py -= selstart.y & ~TILE_UNIT_MASK;

        switch (dir) {
                case HT_DIR_X: return (py == 0) ? HT_DIR_X : HT_DIR_END;
                case HT_DIR_Y: return (px == 0) ? HT_DIR_Y : HT_DIR_END;
                case HT_DIR_HU: return (px == -py) ? HT_DIR_HU : (px == -py - (int)TILE_SIZE) ? HT_DIR_HL : HT_DIR_END;
                case HT_DIR_HL: return (px == -py) ? HT_DIR_HL : (px == -py + (int)TILE_SIZE) ? HT_DIR_HU : HT_DIR_END;
                case HT_DIR_VL: return (px ==  py) ? HT_DIR_VL : (px ==  py + (int)TILE_SIZE) ? HT_DIR_VR : HT_DIR_END;
                case HT_DIR_VR: return (px ==  py) ? HT_DIR_VR : (px ==  py - (int)TILE_SIZE) ? HT_DIR_VL : HT_DIR_END;
                default: NOT_REACHED(); break;
        }

        return HT_DIR_END;
}

#include "table/autorail.h"

/**
 * Draws autorail highlights.
 *
 * @param *ti TileInfo Tile that is being drawn
 * @param autorail_type \c HT_DIR_XXX, offset into _AutorailTilehSprite[][]
 * @param pal Palette to use, -1 to autodetect
 */
static void DrawAutorailSelection(const TileInfo *ti, HighLightStyle autorail_type, PaletteID pal = -1)
{
        SpriteID image;
        FoundationPart foundation_part = FOUNDATION_PART_NORMAL;
        int offset;
        bool bridge_head_mode = false;

        if (IsFlatRailBridgeHeadTile(ti->tile)) {
                extern bool IsValidFlatRailBridgeHeadTrackBits(Slope normalised_slope, DiagDirection bridge_direction, TrackBits tracks);

                offset = _AutorailTilehSprite[SLOPE_FLAT][autorail_type];
                const Slope real_tileh = GetTileSlope(ti->tile);
                const Slope normalised_tileh = IsSteepSlope(real_tileh) ? SlopeWithOneCornerRaised(GetHighestSlopeCorner(real_tileh)) : real_tileh;
                if (!IsValidFlatRailBridgeHeadTrackBits(normalised_tileh, GetTunnelBridgeDirection(ti->tile), TrackToTrackBits((Track) autorail_type))) {
                        offset = -offset;
                }
                if (!IsRailCustomBridgeHead(ti->tile)) {
                        bridge_head_mode = true;
                }
        } else {
                Slope autorail_tileh = RemoveHalftileSlope(ti->tileh);
                if (IsHalftileSlope(ti->tileh)) {
                        static const HighLightStyle _lower_rail[CORNER_END] = { HT_DIR_VR, HT_DIR_HU, HT_DIR_VL, HT_DIR_HL }; // CORNER_W, CORNER_S, CORNER_E, CORNER_N
                        Corner halftile_corner = GetHalftileSlopeCorner(ti->tileh);
                        if (autorail_type != _lower_rail[halftile_corner]) {
                                foundation_part = FOUNDATION_PART_HALFTILE;
                                /* Here we draw the highlights of the "three-corners-raised"-slope. That looks ok to me. */
                                autorail_tileh = SlopeWithThreeCornersRaised(OppositeCorner(halftile_corner));
                        }
                }
                assert(autorail_type < HT_DIR_END);
                offset = _AutorailTilehSprite[autorail_tileh][autorail_type];
        }

        if (offset >= 0) {
                image = SPR_AUTORAIL_BASE + offset;
                if (pal == (PaletteID)-1) pal = _thd.square_palette;
        } else {
                image = SPR_AUTORAIL_BASE - offset;
                if (pal == (PaletteID)-1) pal = PALETTE_SEL_TILE_RED;
        }

        if (bridge_head_mode) {
                AddSortableSpriteToDraw(image, pal, ti->x, ti->y, 16, 16, 0, ti->z + 15);
        } else {
                DrawSelectionSprite(image, pal, ti, 7, foundation_part);
        }
}

enum TileHighlightType {
        THT_NONE,
        THT_WHITE,
        THT_BLUE,
        THT_RED,
        THT_LIGHT_BLUE,
};

const Station *_viewport_highlight_station;   ///< Currently selected station for coverage area highlight
const Waypoint *_viewport_highlight_waypoint; ///< Currently selected waypoint for coverage area highlight
const Town *_viewport_highlight_town;         ///< Currently selected town for coverage area highlight
const TraceRestrictProgram *_viewport_highlight_tracerestrict_program; ///< Currently selected tracerestrict program for highlight

/**
 * Get tile highlight type of coverage area for a given tile.
 * @param t Tile that is being drawn
 * @return Tile highlight type to draw
 */
static TileHighlightType GetTileHighlightType(TileIndex t)
{
        if (_viewport_highlight_station != nullptr) {
                if (IsTileType(t, MP_STATION) && GetStationIndex(t) == _viewport_highlight_station->index) return THT_LIGHT_BLUE;
                if (_viewport_highlight_station->TileIsInCatchment(t)) return THT_BLUE;
        }
        if (_viewport_highlight_waypoint != nullptr) {
                if (IsTileType(t, MP_STATION) && GetStationIndex(t) == _viewport_highlight_waypoint->index) return THT_LIGHT_BLUE;
        }

        if (_viewport_highlight_town != nullptr) {
                if (IsTileType(t, MP_HOUSE)) {
                        if (GetTownIndex(t) == _viewport_highlight_town->index) {
                                TileHighlightType type = THT_RED;
                                for (const Station *st : _viewport_highlight_town->stations_near) {
                                        if (st->owner != _current_company) continue;
                                        if (st->TileIsInCatchment(t)) return THT_BLUE;
                                }
                                return type;
                        }
                } else if (IsTileType(t, MP_STATION)) {
                        for (const Station *st : _viewport_highlight_town->stations_near) {
                                if (st->owner != _current_company) continue;
                                if (GetStationIndex(t) == st->index) return THT_WHITE;
                        }
                }
        }

        if (_viewport_highlight_tracerestrict_program != nullptr) {
                const TraceRestrictRefId *refs = _viewport_highlight_tracerestrict_program->GetRefIdsPtr();
                for (uint i = 0; i < _viewport_highlight_tracerestrict_program->refcount; i++) {
                        if (GetTraceRestrictRefIdTileIndex(refs[i]) == t) return THT_LIGHT_BLUE;
                }
        }

        return THT_NONE;
}

/**
 * Draw tile highlight for coverage area highlight.
 * @param *ti TileInfo Tile that is being drawn
 * @param tht Highlight type to draw.
 */
static void DrawTileHighlightType(const TileInfo *ti, TileHighlightType tht)
{
        switch (tht) {
                default:
                case THT_NONE: break;
                case THT_WHITE: DrawTileSelectionRect(ti, PAL_NONE); break;
                case THT_BLUE:  DrawTileSelectionRect(ti, PALETTE_SEL_TILE_BLUE); break;
                case THT_RED:   DrawTileSelectionRect(ti, PALETTE_SEL_TILE_RED); break;
                case THT_LIGHT_BLUE: DrawTileSelectionRect(ti, SPR_ZONING_INNER_HIGHLIGHT_LIGHT_BLUE); break;
        }
}

/**
 * Highlights tiles insede local authority of selected towns.
 * @param *ti TileInfo Tile that is being drawn
 */
static void HighlightTownLocalAuthorityTiles(const TileInfo *ti)
{
        /* Going through cases in order of computational time. */

        if (_town_local_authority_kdtree.Count() == 0) return;

        /* Tile belongs to town regardless of distance from town. */
        if (GetTileType(ti->tile) == MP_HOUSE) {
                if (!Town::GetByTile(ti->tile)->show_zone) return;

                DrawTileSelectionRect(ti, PALETTE_CRASH);
                return;
        }

        /* If the closest town in the highlighted list is far, we can stop searching. */
        TownID tid = _town_local_authority_kdtree.FindNearest(TileX(ti->tile), TileY(ti->tile));
        Town *closest_highlighted_town = Town::Get(tid);

        if (DistanceManhattan(ti->tile, closest_highlighted_town->xy) >= _settings_game.economy.dist_local_authority) return;

        /* Tile is inside of the local autrhority distance of a highlighted town,
           but it is possible that a non-highlighted town is even closer. */
        Town *closest_town = ClosestTownFromTile(ti->tile, _settings_game.economy.dist_local_authority);

        if (closest_town->show_zone) {
                DrawTileSelectionRect(ti, PALETTE_CRASH);
        }

}

/**
 * Checks if the specified tile is selected and if so draws selection using correct selectionstyle.
 * @param *ti TileInfo Tile that is being drawn
 */
static void DrawTileSelection(const TileInfo *ti)
{
        /* Highlight tiles insede local authority of selected towns. */
        HighlightTownLocalAuthorityTiles(ti);

        /* Draw a red error square? */
        bool is_redsq = _thd.redsq == ti->tile;
        if (is_redsq) DrawTileSelectionRect(ti, PALETTE_TILE_RED_PULSATING);

        TileHighlightType tht = GetTileHighlightType(ti->tile);
        DrawTileHighlightType(ti, tht);

        switch (_thd.drawstyle & HT_DRAG_MASK) {
                default: break; // No tile selection active?

                case HT_RECT:
                        if (!is_redsq) {
                                if (IsInsideSelectedRectangle(ti->x, ti->y)) {
                                        DrawTileSelectionRect(ti, _thd.square_palette);
                                } else if (_thd.outersize.x > 0 && (tht == THT_NONE || tht == THT_RED) &&
                                                /* Check if it's inside the outer area? */
                                                IsInsideBS(ti->x, _thd.pos.x + _thd.offs.x, _thd.size.x + _thd.outersize.x) &&
                                                IsInsideBS(ti->y, _thd.pos.y + _thd.offs.y, _thd.size.y + _thd.outersize.y)) {
                                        /* Draw a blue rect. */
                                        DrawTileSelectionRect(ti, PALETTE_SEL_TILE_BLUE);
                                }
                        }
                        break;

                case HT_POINT:
                        if (IsInsideSelectedRectangle(ti->x, ti->y)) {
                                /* Figure out the Z coordinate for the single dot. */
                                int z = 0;
                                FoundationPart foundation_part = FOUNDATION_PART_NORMAL;
                                if (ti->tileh & SLOPE_N) {
                                        z += TILE_HEIGHT;
                                        if (RemoveHalftileSlope(ti->tileh) == SLOPE_STEEP_N) z += TILE_HEIGHT;
                                }
                                if (IsHalftileSlope(ti->tileh)) {
                                        Corner halftile_corner = GetHalftileSlopeCorner(ti->tileh);
                                        if ((halftile_corner == CORNER_W) || (halftile_corner == CORNER_E)) z += TILE_HEIGHT;
                                        if (halftile_corner != CORNER_S) {
                                                foundation_part = FOUNDATION_PART_HALFTILE;
                                                if (IsSteepSlope(ti->tileh)) z -= TILE_HEIGHT;
                                        }
                                }
                                DrawSelectionSprite(SPR_DOT, PAL_NONE, ti, z, foundation_part);
                        }
                        break;

                case HT_RAIL:
                        if (ti->tile == TileVirtXY(_thd.pos.x, _thd.pos.y)) {
                                assert((_thd.drawstyle & HT_DIR_MASK) < HT_DIR_END);
                                DrawAutorailSelection(ti, _thd.drawstyle & HT_DIR_MASK);
                        }
                        break;

                case HT_LINE: {
                        HighLightStyle type = GetPartOfAutoLine(ti->x, ti->y, _thd.selstart, _thd.selend, _thd.drawstyle & HT_DIR_MASK);
                        if (type < HT_DIR_END) {
                                DrawAutorailSelection(ti, type);
                        } else if (_thd.dir2 < HT_DIR_END) {
                                type = GetPartOfAutoLine(ti->x, ti->y, _thd.selstart2, _thd.selend2, _thd.dir2);
                                if (type < HT_DIR_END) DrawAutorailSelection(ti, type, PALETTE_SEL_TILE_BLUE);
                        }
                        break;
                }
        }
}

/**
 * Returns the y coordinate in the viewport coordinate system where the given
 * tile is painted.
 * @param tile Any tile.
 * @return The viewport y coordinate where the tile is painted.
 */
static int GetViewportY(Point tile)
{
        /* Each increment in X or Y direction moves down by half a tile, i.e. TILE_PIXELS / 2. */
        return (tile.y * (int)(TILE_PIXELS / 2) + tile.x * (int)(TILE_PIXELS / 2) - TilePixelHeightOutsideMap(tile.x, tile.y)) << ZOOM_BASE_SHIFT;
}

/**
 * Add the landscape to the viewport, i.e. all ground tiles and buildings.
 */
static void ViewportAddLandscape()
{
        dbg_assert(_vdd->dpi.top <= _vdd->dpi.top + _vdd->dpi.height);
        dbg_assert(_vdd->dpi.left <= _vdd->dpi.left + _vdd->dpi.width);

        Point upper_left = InverseRemapCoords(_vdd->dpi.left, _vdd->dpi.top);
        Point upper_right = InverseRemapCoords(_vdd->dpi.left + _vdd->dpi.width, _vdd->dpi.top);

        /* Transformations between tile coordinates and viewport rows/columns: See vp_column_row
         *   column = y - x
         *   row    = x + y
         *   x      = (row - column) / 2
         *   y      = (row + column) / 2
         * Note: (row, columns) pairs are only valid, if they are both even or both odd.
         */

        /* Columns overlap with neighbouring columns by a half tile.
         *  - Left column is column of upper_left (rounded down) and one column to the left.
         *  - Right column is column of upper_right (rounded up) and one column to the right.
         * Note: Integer-division does not round down for negative numbers, so ensure rounding with another increment/decrement.
         */
        int left_column = DivTowardsNegativeInf(upper_left.y - upper_left.x, (int)TILE_SIZE) - 1;
        int right_column = DivTowardsPositiveInf(upper_right.y - upper_right.x, (int)TILE_SIZE) + 1;

        int potential_bridge_height = ZOOM_BASE * TILE_HEIGHT * _settings_game.construction.max_bridge_height;

        /* Rows overlap with neighbouring rows by a half tile.
         * The first row that could possibly be visible is the row above upper_left (if it is at height 0).
         * Due to integer-division not rounding down for negative numbers, we need another decrement.
         */
        int row = DivTowardsNegativeInf(upper_left.y + upper_left.x, (int)TILE_SIZE) - 1;
        bool last_row = false;
        for (; !last_row; row++) {
                last_row = true;
                for (int column = left_column; column <= right_column; column++) {
                        /* Valid row/column? */
                        if ((row + column) % 2 != 0) continue;

                        Point tilecoord;
                        tilecoord.x = (row - column) / 2;
                        tilecoord.y = (row + column) / 2;
                        dbg_assert(column == tilecoord.y - tilecoord.x);
                        dbg_assert(row == tilecoord.y + tilecoord.x);

                        TileType tile_type;
                        _cur_ti.x = tilecoord.x * TILE_SIZE;
                        _cur_ti.y = tilecoord.y * TILE_SIZE;

                        if (IsInsideBS(tilecoord.x, 0, MapSizeX()) && IsInsideBS(tilecoord.y, 0, MapSizeY())) {
                                /* This includes the south border at MapMaxX / MapMaxY. When terraforming we still draw tile selections there. */
                                _cur_ti.tile = TileXY(tilecoord.x, tilecoord.y);
                                tile_type = GetTileType(_cur_ti.tile);
                        } else {
                                _cur_ti.tile = INVALID_TILE;
                                tile_type = MP_VOID;
                        }

                        if (tile_type != MP_VOID) {
                                /* We are inside the map => paint landscape. */
                                std::tie(_cur_ti.tileh, _cur_ti.z) = GetTilePixelSlope(_cur_ti.tile);
                        } else {
                                /* We are outside the map => paint black. */
                                std::tie(_cur_ti.tileh, _cur_ti.z) = GetTilePixelSlopeOutsideMap(tilecoord.x, tilecoord.y);
                        }

                        int viewport_y = GetViewportY(tilecoord);

                        if (viewport_y + MAX_TILE_EXTENT_BOTTOM < _vdd->dpi.top) {
                                /* The tile in this column is not visible yet.
                                 * Tiles in other columns may be visible, but we need more rows in any case. */
                                last_row = false;
                                continue;
                        }

                        int min_visible_height = viewport_y - (_vdd->dpi.top + _vdd->dpi.height);
                        bool tile_visible = min_visible_height <= 0;

                        if (tile_type != MP_VOID) {
                                /* Is tile with buildings visible? */
                                if (min_visible_height < MAX_TILE_EXTENT_TOP) tile_visible = true;

                                if (IsBridgeAbove(_cur_ti.tile)) {
                                        /* Is the bridge visible? */
                                        TileIndex bridge_tile = GetNorthernBridgeEnd(_cur_ti.tile);
                                        int bridge_height = ZOOM_BASE * (GetBridgePixelHeight(bridge_tile) - TilePixelHeight(_cur_ti.tile));
                                        if (min_visible_height < bridge_height + MAX_TILE_EXTENT_TOP) tile_visible = true;
                                }

                                /* Would a higher bridge on a more southern tile be visible?
                                 * If yes, we need to loop over more rows to possibly find one. */
                                if (min_visible_height < potential_bridge_height + MAX_TILE_EXTENT_TOP) last_row = false;
                        } else {
                                /* Outside of map. If we are on the north border of the map, there may still be a bridge visible,
                                 * so we need to loop over more rows to possibly find one. */
                                if ((tilecoord.x <= 0 || tilecoord.y <= 0) && min_visible_height < potential_bridge_height + MAX_TILE_EXTENT_TOP) last_row = false;

                                if (_settings_game.construction.map_edge_mode == 2 && _cur_ti.tileh == SLOPE_FLAT && _cur_ti.z == 0 && min_visible_height <= 0) {
                                        last_row = false;
                                        AddTileSpriteToDraw(SPR_FLAT_WATER_TILE, PAL_NONE, _cur_ti.x, _cur_ti.y, _cur_ti.z);
                                        continue;
                                }
                        }

                        if (tile_visible) {
                                last_row = false;
                                _vd.foundation_part = FOUNDATION_PART_NONE;
                                _vd.foundation[0] = -1;
                                _vd.foundation[1] = -1;
                                _vd.last_foundation_child[0] = NO_CHILD_STORE;
                                _vd.last_foundation_child[1] = NO_CHILD_STORE;

                                bool no_ground_tiles = min_visible_height > 0;
                                _tile_type_procs[tile_type]->draw_tile_proc(&_cur_ti, { min_visible_height, no_ground_tiles });
                                if (_cur_ti.tile != INVALID_TILE && min_visible_height <= 0) {
                                        DrawTileSelection(&_cur_ti);
                                        DrawTileZoning(&_cur_ti);
                                }
                        }
                }
        }
}

/**
 * Add a string to draw in the viewport
 * @param vdd viewport drawer
 * @param dpi current viewport area
 * @param small_from Zoomlevel from when the small font should be used
 * @param sign sign position and dimension
 * @param string_normal String for normal and 2x zoom level
 * @param string_small String for 4x and 8x zoom level
 * @param string_small_shadow Shadow string for 4x and 8x zoom level; or #STR_NULL if no shadow
 * @param colour colour of the sign background; or INVALID_COLOUR if transparent
 */
void ViewportAddString(ViewportDrawerDynamic *vdd, const DrawPixelInfo *dpi, ZoomLevel small_from, const ViewportSign *sign, StringID string_normal, StringID string_small, StringID string_small_shadow, uint64_t params_1, uint64_t params_2, Colours colour)
{
        bool small = dpi->zoom >= small_from;

        int left   = dpi->left;
        int top    = dpi->top;
        int right  = left + dpi->width;
        int bottom = top + dpi->height;

        int sign_height     = ScaleByZoom(WidgetDimensions::scaled.fullbevel.top + GetCharacterHeight(small ? FS_SMALL : FS_NORMAL) + WidgetDimensions::scaled.fullbevel.bottom, dpi->zoom);
        int sign_half_width = ScaleByZoom((small ? sign->width_small : sign->width_normal) / 2, dpi->zoom);

        if (bottom < sign->top ||
                        top   > sign->top + sign_height ||
                        right < sign->center - sign_half_width ||
                        left  > sign->center + sign_half_width) {
                return;
        }

        if (!small) {
                AddStringToDraw(vdd, sign->center - sign_half_width, sign->top, string_normal, params_1, params_2, colour, sign->width_normal);
        } else {
                int shadow_offset = 0;
                if (string_small_shadow != STR_NULL) {
                        shadow_offset = 4;
                        AddStringToDraw(vdd, sign->center - sign_half_width + shadow_offset, sign->top, string_small_shadow, params_1, params_2, INVALID_COLOUR, sign->width_small | 0x8000);
                }
                AddStringToDraw(vdd, sign->center - sign_half_width, sign->top - shadow_offset, string_small, params_1, params_2,
                                colour, sign->width_small | 0x8000);
        }
}

static Rect ExpandRectWithViewportSignMargins(Rect r, ZoomLevel zoom)
{
        const int fh = std::max(GetCharacterHeight(FS_NORMAL), GetCharacterHeight(FS_SMALL));
        const int max_tw = _viewport_sign_maxwidth / 2 + 1;
        const int expand_y = ScaleByZoom(WidgetDimensions::scaled.fullbevel.top + fh + WidgetDimensions::scaled.fullbevel.bottom, zoom);
        const int expand_x = ScaleByZoom(WidgetDimensions::scaled.fullbevel.left + max_tw + WidgetDimensions::scaled.fullbevel.right, zoom);

        r.left -= expand_x;
        r.right += expand_x;
        r.top -= expand_y;
        r.bottom += expand_y;

        return r;
}

static void ViewportAddKdtreeSigns(ViewportDrawerDynamic *vdd, DrawPixelInfo *dpi, bool towns_only)
{
        Rect search_rect{ dpi->left, dpi->top, dpi->left + dpi->width, dpi->top + dpi->height };
        search_rect = ExpandRectWithViewportSignMargins(search_rect, dpi->zoom);

        bool show_stations = HasBit(_display_opt, DO_SHOW_STATION_NAMES) && _game_mode != GM_MENU && !towns_only;
        bool show_waypoints = HasBit(_display_opt, DO_SHOW_WAYPOINT_NAMES) && _game_mode != GM_MENU && !towns_only;
        bool show_towns = HasBit(_display_opt, DO_SHOW_TOWN_NAMES) && _game_mode != GM_MENU;
        bool show_signs = HasBit(_display_opt, DO_SHOW_SIGNS) && !vdd->IsInvisibilitySet(TO_SIGNS) && !towns_only;
        bool show_competitors = HasBit(_display_opt, DO_SHOW_COMPETITOR_SIGNS) && !towns_only;
        bool hide_hidden_waypoints = _settings_client.gui.allow_hiding_waypoint_labels && !HasBit(_extra_display_opt, XDO_SHOW_HIDDEN_SIGNS);

        /* Collect all the items first and draw afterwards, to ensure layering */
        std::vector<const BaseStation *> stations;
        std::vector<const Town *> towns;
        std::vector<const Sign *> signs;

        _viewport_sign_kdtree.FindContained(search_rect.left, search_rect.top, search_rect.right, search_rect.bottom, [&](const ViewportSignKdtreeItem & item) {
                switch (item.type) {
                        case ViewportSignKdtreeItem::VKI_STATION: {
                                if (!show_stations) break;
                                const BaseStation *st = BaseStation::Get(item.id.station);

                                /* Don't draw if station is owned by another company and competitor station names are hidden. Stations owned by none are never ignored. */
                                if (!show_competitors && _local_company != st->owner && st->owner != OWNER_NONE) break;

                                stations.push_back(st);
                                break;
                        }

                        case ViewportSignKdtreeItem::VKI_WAYPOINT: {
                                if (!show_waypoints) break;
                                const BaseStation *st = BaseStation::Get(item.id.station);

                                /* Don't draw if station is owned by another company and competitor station names are hidden. Stations owned by none are never ignored. */
                                if (!show_competitors && _local_company != st->owner && st->owner != OWNER_NONE) break;
                                if (hide_hidden_waypoints && HasBit(Waypoint::From(st)->waypoint_flags, WPF_HIDE_LABEL)) break;

                                stations.push_back(st);
                                break;
                        }

                        case ViewportSignKdtreeItem::VKI_TOWN:
                                if (!show_towns) break;
                                towns.push_back(Town::Get(item.id.town));
                                break;

                        case ViewportSignKdtreeItem::VKI_SIGN: {
                                if (!show_signs) break;
                                const Sign *si = Sign::Get(item.id.sign);

                                /* Don't draw if sign is owned by another company and competitor signs should be hidden.
                                 * Note: It is intentional that also signs owned by OWNER_NONE are hidden. Bankrupt
                                 * companies can leave OWNER_NONE signs after them. */
                                if (!show_competitors && si->IsCompetitorOwned()) break;

                                signs.push_back(si);
                                break;
                        }

                        default:
                                NOT_REACHED();
                }
        });

        /* Layering order (bottom to top): Town names, signs, stations */

        for (const auto *t : towns) {
                ViewportAddString(vdd, dpi, ZOOM_LVL_OUT_4X, &t->cache.sign,
                        STR_VIEWPORT_TOWN_LABEL, STR_VIEWPORT_TOWN_LABEL_TINY, STR_VIEWPORT_TOWN_TINY_BLACK,
                        t->index, t->LabelParam2());
        }

        /* Do not draw signs nor station names if they are set invisible */
        if (vdd->IsInvisibilitySet(TO_SIGNS)) return;

        for (const auto *si : signs) {
                ViewportAddString(vdd, dpi, ZOOM_LVL_OUT_4X, &si->sign,
                        STR_WHITE_SIGN,
                        (vdd->IsTransparencySet(TO_SIGNS) || si->owner == OWNER_DEITY) ? STR_VIEWPORT_SIGN_SMALL_WHITE : STR_VIEWPORT_SIGN_SMALL_BLACK, STR_NULL,
                        si->index, 0, (si->owner == OWNER_NONE) ? COLOUR_GREY : (si->owner == OWNER_DEITY ? INVALID_COLOUR : _company_colours[si->owner]));
        }

        for (const auto *st : stations) {
                if (Station::IsExpected(st)) {
                        /* Station */
                        ViewportAddString(vdd, dpi, ZOOM_LVL_OUT_4X, &st->sign,
                                STR_VIEWPORT_STATION, STR_VIEWPORT_STATION_TINY, STR_NULL,
                                st->index, st->facilities, (st->owner == OWNER_NONE || !st->IsInUse()) ? COLOUR_GREY : _company_colours[st->owner]);
                } else {
                        /* Waypoint */
                        ViewportAddString(vdd, dpi, ZOOM_LVL_OUT_4X, &st->sign,
                                STR_VIEWPORT_WAYPOINT, STR_VIEWPORT_WAYPOINT_TINY, STR_NULL,
                                st->index, st->facilities, (st->owner == OWNER_NONE || !st->IsInUse()) ? COLOUR_GREY : _company_colours[st->owner]);
                }
        }
}


/**
 * Update the position of the viewport sign.
 * @param center the (preferred) center of the viewport sign
 * @param top    the new top of the sign
 * @param str    the string to show in the sign
 * @param str_small the string to show when zoomed out. STR_NULL means same as \a str
 */
void ViewportSign::UpdatePosition(ZoomLevel maxzoom, int center, int top, StringID str, StringID str_small)
{
        if (this->width_normal != 0) this->MarkDirty(maxzoom);

        this->top = top;

        format_buffer buffer;

        AppendStringInPlace(buffer, str);
        this->width_normal = WidgetDimensions::scaled.fullbevel.left + Align(GetStringBoundingBox(buffer).width, 2) + WidgetDimensions::scaled.fullbevel.right;
        this->center = center;

        /* zoomed out version */
        if (str_small != STR_NULL) {
                buffer.clear();
                AppendStringInPlace(buffer, str_small);
        }
        this->width_small = WidgetDimensions::scaled.fullbevel.left + Align(GetStringBoundingBox(buffer, FS_SMALL).width, 2) + WidgetDimensions::scaled.fullbevel.right;

        this->MarkDirty(maxzoom);
}

/**
 * Mark the sign dirty in all viewports.
 * @param maxzoom Maximum %ZoomLevel at which the text is visible.
 *
 * @ingroup dirty
 */
void ViewportSign::MarkDirty(ZoomLevel maxzoom) const
{
        if (maxzoom == ZOOM_LVL_END) return;

        Rect zoomlevels[ZOOM_LVL_END];

        const uint small_height = WidgetDimensions::scaled.fullbevel.top + GetCharacterHeight(FS_SMALL) + WidgetDimensions::scaled.fullbevel.bottom + 1;
        const uint normal_height = WidgetDimensions::scaled.fullbevel.top + GetCharacterHeight(FS_NORMAL) + WidgetDimensions::scaled.fullbevel.bottom + 1;

        for (ZoomLevel zoom = ZOOM_LVL_BEGIN; zoom != ZOOM_LVL_END; zoom++) {
                const ZoomLevel small_from = (maxzoom == ZOOM_LVL_OUT_2X) ? ZOOM_LVL_OUT_2X : ZOOM_LVL_OUT_4X;
                const int width = (zoom >= small_from) ? this->width_small : this->width_normal;
                zoomlevels[zoom].left   = this->center - ScaleByZoom(width / 2 + 1, zoom);
                zoomlevels[zoom].top    = this->top    - ScaleByZoom(1, zoom);
                zoomlevels[zoom].right  = this->center + ScaleByZoom(width / 2 + 1, zoom);
                zoomlevels[zoom].bottom = this->top    + ScaleByZoom((zoom >= small_from) ? small_height : normal_height, zoom);
        }

        for (Viewport *vp : _viewport_window_cache) {
                if (vp->zoom <= maxzoom) {
                        Rect &zl = zoomlevels[vp->zoom];
                        MarkViewportDirty(vp, zl.left, zl.top, zl.right, zl.bottom, VMDF_NONE);
                }
        }
}

static void ViewportDrawTileSprites(const ViewportDrawerDynamic *vdd)
{
        for (const TileSpriteToDraw &ts : vdd->tile_sprites_to_draw) {
                DrawSpriteViewport(vdd->sprite_data, &vdd->dpi, ts.image, ts.pal, ts.x, ts.y, ts.sub);
        }
}

/** This fallback sprite checker always exists. */
static bool ViewportSortParentSpritesChecker()
{
        return true;
}

static void ViewportSortParentSpritesSingleComparison(ParentSpriteToDraw *ps, ParentSpriteToDraw *ps2, ParentSpriteToDraw *ps_to_move, ParentSpriteToDraw **psd, ParentSpriteToDraw **psd2)
{
        /* Decide which comparator to use, based on whether the bounding
         * boxes overlap
         */
        if (ps->xmax >= ps2->xmin && ps->xmin <= ps2->xmax && // overlap in X?
                        ps->ymax >= ps2->ymin && ps->ymin <= ps2->ymax && // overlap in Y?
                        ps->zmax >= ps2->zmin && ps->zmin <= ps2->zmax) { // overlap in Z?
                /* Use X+Y+Z as the sorting order, so sprites closer to the bottom of
                 * the screen and with higher Z elevation, are drawn in front.
                 * Here X,Y,Z are the coordinates of the "center of mass" of the sprite,
                 * i.e. X=(left+right)/2, etc.
                 * However, since we only care about order, don't actually divide / 2
                 */
                if (ps->xmin + ps->xmax + ps->ymin + ps->ymax + ps->zmin + ps->zmax <=
                                ps2->xmin + ps2->xmax + ps2->ymin + ps2->ymax + ps2->zmin + ps2->zmax) {
                        return;
                }
        } else {
                /* We only change the order, if it is definite.
                 * I.e. every single order of X, Y, Z says ps2 is behind ps or they overlap.
                 * That is: If one partial order says ps behind ps2, do not change the order.
                 */
                if (ps->xmax < ps2->xmin ||
                                ps->ymax < ps2->ymin ||
                                ps->zmax < ps2->zmin) {
                        return;
                }
        }

        /* Move ps_to_move (ps2) in front of ps */
        ParentSpriteToDraw *temp = ps_to_move;
        for (auto psd3 = psd2; psd3 > psd; psd3--) {
                *psd3 = *(psd3 - 1);
        }
        *psd = temp;
}

bool ViewportSortParentSpritesSpecial(ParentSpriteToDraw *ps, ParentSpriteToDraw *ps2, ParentSpriteToDraw **psd, ParentSpriteToDraw **psd2)
{
        ParentSpriteToDraw temp;

        auto is_bridge_diag_veh_comparison = [&](ParentSpriteToDraw *a, ParentSpriteToDraw *b) -> bool {
                if ((a->special_flags & VSSSF_SORT_SPECIAL_TYPE_MASK) == VSSSF_SORT_SORT_BRIDGE_BB && (b->special_flags & VSSSF_SORT_SPECIAL_TYPE_MASK) == VSSSF_SORT_DIAG_VEH && a->zmin > b->zmax) {
                        temp = *a;
                        temp.xmax += 4;
                        temp.ymax += 4;
                        return true;
                }
                return false;
        };

        if (is_bridge_diag_veh_comparison(ps, ps2)) {
                ViewportSortParentSpritesSingleComparison(&temp, ps2, ps2, psd, psd2);
                return true;
        }
        if (is_bridge_diag_veh_comparison(ps2, ps)) {
                ViewportSortParentSpritesSingleComparison(ps, &temp, ps2, psd, psd2);
                return true;
        }

        return false;
}

/** Sort parent sprites pointer array */
static void ViewportSortParentSprites(ParentSpriteToSortVector *psdv)
{
        ParentSpriteToDraw ** const psdvend = psdv->data() + psdv->size();
        ParentSpriteToDraw **psd = psdv->data();
        while (psd != psdvend) {
                ParentSpriteToDraw *ps = *psd;

                if (ps->IsComparisonDone()) {
                        psd++;
                        continue;
                }

                ps->SetComparisonDone(true);
                const bool is_special = (ps->special_flags & VSSSF_SORT_SPECIAL) != 0;

                for (auto psd2 = psd + 1; psd2 != psdvend; psd2++) {
                        ParentSpriteToDraw *ps2 = *psd2;

                        if (ps2->IsComparisonDone()) continue;

                        if (is_special && (ps2->special_flags & VSSSF_SORT_SPECIAL) != 0) {
                                if (ViewportSortParentSpritesSpecial(ps, ps2, psd, psd2)) continue;
                        }

                        ViewportSortParentSpritesSingleComparison(ps, ps2, ps2, psd, psd2);
                }
        }
}

static void ViewportDrawParentSprites(const ViewportDrawerDynamic *vdd, const DrawPixelInfo *dpi, const ParentSpriteToSortVector *psd, const ChildScreenSpriteToDrawVector *csstdv)
{
        for (const ParentSpriteToDraw *ps : *psd) {
                if (ps->image != SPR_EMPTY_BOUNDING_BOX) DrawSpriteViewport(vdd->sprite_data, dpi, ps->image, ps->pal, ps->x, ps->y, vdd->parent_sprite_subsprites.Get(ps));

                int child_idx = ps->first_child;
                while (child_idx >= 0) {
                        const ChildScreenSpriteToDraw *cs = csstdv->data() + child_idx;
                        child_idx = cs->next;
                        int x = cs->x;
                        int y = cs->y;
                        switch (cs->position_mode) {
                                case ChildScreenSpritePositionMode::Relative:
                                        x += ps->left;
                                        y += ps->top;
                                        break;
                                case ChildScreenSpritePositionMode::NonRelative:
                                        x += ps->x;
                                        y += ps->y;
                                        break;
                                case ChildScreenSpritePositionMode::Absolute:
                                        /* No adjustment */
                                        break;
                        }
                        DrawSpriteViewport(vdd->sprite_data, dpi, cs->image, cs->pal, x, y, cs->sub);
                }
        }
}

/**
 * Draws the bounding boxes of all ParentSprites
 * @param psd Array of ParentSprites
 */
static void ViewportDrawBoundingBoxes(const DrawPixelInfo *dpi, const ParentSpriteToDrawVector &psd)
{
        for (const ParentSpriteToDraw &ps : psd) {
                Point pt1 = RemapCoords(ps.xmax + 1, ps.ymax + 1, ps.zmax + 1); // top front corner
                Point pt2 = RemapCoords(ps.xmin    , ps.ymax + 1, ps.zmax + 1); // top left corner
                Point pt3 = RemapCoords(ps.xmax + 1, ps.ymin    , ps.zmax + 1); // top right corner
                Point pt4 = RemapCoords(ps.xmax + 1, ps.ymax + 1, ps.zmin    ); // bottom front corner

                DrawBox(dpi,
                                pt1.x,         pt1.y,
                        pt2.x - pt1.x, pt2.y - pt1.y,
                        pt3.x - pt1.x, pt3.y - pt1.y,
                        pt4.x - pt1.x, pt4.y - pt1.y);
        }
}

static void ViewportMapStoreBridge(const Viewport * const vp, const TileIndex tile)
{
        extern LegendAndColour _legend_land_owners[NUM_NO_COMPANY_ENTRIES + MAX_COMPANIES + 1];
        extern uint _company_to_list_pos[MAX_COMPANIES];

        /* No need to bother for hidden things */
        if (!_settings_client.gui.show_bridges_on_map) return;
        const Owner o = GetTileOwner(tile);
        if (o < MAX_COMPANIES && !_legend_land_owners[_company_to_list_pos[o]].show_on_map) return;

        switch (GetTunnelBridgeDirection(tile)) {
                case DIAGDIR_NE: {
                        /* X axis: tile at higher coordinate, facing towards lower coordinate */
                        auto iter = _vdd->bridge_to_map_x.lower_bound(tile);
                        if (iter != _vdd->bridge_to_map_x.begin()) {
                                auto prev = iter;
                                --prev;
                                if (prev->second == tile) return;
                        }
                        _vdd->bridge_to_map_x.insert(iter, std::make_pair(GetOtherTunnelBridgeEnd(tile), tile));
                        break;
                }

                case DIAGDIR_NW: {
                        /* Y axis: tile at higher coordinate, facing towards lower coordinate */
                        auto iter = _vdd->bridge_to_map_y.lower_bound(tile);
                        if (iter != _vdd->bridge_to_map_y.begin()) {
                                auto prev = iter;
                                --prev;
                                if (prev->second == tile) return;
                        }
                        _vdd->bridge_to_map_y.insert(iter, std::make_pair(GetOtherTunnelBridgeEnd(tile), tile));
                        break;
                }

                case DIAGDIR_SW: {
                        /* X axis: tile at lower coordinate, facing towards higher coordinate */
                        auto iter = _vdd->bridge_to_map_x.lower_bound(tile);
                        if (iter != _vdd->bridge_to_map_x.end() && iter->first == tile) return;
                        _vdd->bridge_to_map_x.insert(iter, std::make_pair(tile, GetOtherTunnelBridgeEnd(tile)));
                        break;
                }

                case DIAGDIR_SE: {
                        /* Y axis: tile at lower coordinate, facing towards higher coordinate */
                        auto iter = _vdd->bridge_to_map_y.lower_bound(tile);
                        if (iter != _vdd->bridge_to_map_y.end() && iter->first == tile) return;
                        _vdd->bridge_to_map_y.insert(iter, std::make_pair(tile, GetOtherTunnelBridgeEnd(tile)));
                        break;
                }

                default:
                        NOT_REACHED();
        }
}

void ViewportMapStoreTunnel(const TileIndex tile, const TileIndex tile_south, const int tunnel_z, const bool insert_sorted)
{
        extern LegendAndColour _legend_land_owners[NUM_NO_COMPANY_ENTRIES + MAX_COMPANIES + 1];
        extern uint _company_to_list_pos[MAX_COMPANIES];

        /* No need to bother for hidden things */
        if (!_settings_client.gui.show_tunnels_on_map) return;
        const Owner o = GetTileOwner(tile);
        if (o < MAX_COMPANIES && !_legend_land_owners[_company_to_list_pos[o]].show_on_map) return;

        const Axis axis = (TileX(tile) == TileX(tile_south)) ? AXIS_Y : AXIS_X;
        const Point viewport_pt = RemapCoords(TileX(tile) * TILE_SIZE, TileY(tile) * TILE_SIZE, tunnel_z);
        int y_intercept;
        if (axis == AXIS_X) {
                /* NE to SW */
                y_intercept = viewport_pt.y + (viewport_pt.x / 2);
        } else {
                /* NW to SE */
                y_intercept = viewport_pt.y - (viewport_pt.x / 2);
        }
        TunnelToMapStorage &storage = (axis == AXIS_X) ? _vd.tunnel_to_map_x : _vd.tunnel_to_map_y;
        TunnelToMap *tbtm;
        if (insert_sorted) {
                auto iter = std::upper_bound(storage.tunnels.begin(), storage.tunnels.end(), y_intercept, [](int a, const TunnelToMap &b) -> bool {
                        return a < b.y_intercept;
                });
                tbtm = &(*(storage.tunnels.emplace(iter)));
        } else {
                storage.tunnels.emplace_back();
                tbtm = &(storage.tunnels.back());
        }

        /* ensure deterministic ordering, to avoid render flicker */
        tbtm->tb.from_tile = tile;
        tbtm->tb.to_tile = tile_south;
        tbtm->y_intercept = y_intercept;
        tbtm->tunnel_z = tunnel_z;
}

void ViewportMapClearTunnelCache()
{
        _vd.tunnel_to_map_x.tunnels.clear();
        _vd.tunnel_to_map_y.tunnels.clear();
}

void ViewportMapInvalidateTunnelCacheByTile(const TileIndex tile, const Axis axis)
{
        if (!_settings_client.gui.show_tunnels_on_map) return;
        std::vector<TunnelToMap> &tbtmv = (axis == AXIS_X) ? _vd.tunnel_to_map_x.tunnels : _vd.tunnel_to_map_y.tunnels;
        for (auto tbtm = tbtmv.begin(); tbtm != tbtmv.end(); tbtm++) {
                if (tbtm->tb.from_tile == tile) {
                        tbtmv.erase(tbtm);
                        return;
                }
        }
}

void ViewportMapBuildTunnelCache()
{
        ViewportMapClearTunnelCache();
        if (_settings_client.gui.show_tunnels_on_map) {
                for (Tunnel *tunnel : Tunnel::Iterate()) {
                        ViewportMapStoreTunnel(tunnel->tile_n, tunnel->tile_s, tunnel->height, false);
                }
                auto sorter = [](const TunnelToMap &a, const TunnelToMap &b) -> bool {
                        return a.y_intercept < b.y_intercept;
                };
                std::sort(_vd.tunnel_to_map_x.tunnels.begin(), _vd.tunnel_to_map_x.tunnels.end(), sorter);
                std::sort(_vd.tunnel_to_map_y.tunnels.begin(), _vd.tunnel_to_map_y.tunnels.end(), sorter);
        }
}

/**
 * Draw/colour the blocks that have been redrawn.
 */
void ViewportDrawDirtyBlocks(const DrawPixelInfo *dpi, bool increment_colour)
{
        Blitter *blitter = BlitterFactory::GetCurrentBlitter();
        void *dst;
        int right =  UnScaleByZoom(dpi->width,  dpi->zoom);
        int bottom = UnScaleByZoom(dpi->height, dpi->zoom);

        const uint dirty_block_colour = increment_colour ? _dirty_block_colour.fetch_add(1, std::memory_order_relaxed) : _dirty_block_colour.load(std::memory_order_relaxed);
        int colour = _string_colourmap[dirty_block_colour & 0xF];

        dst = dpi->dst_ptr;

        uint8_t bo = UnScaleByZoom(dpi->left + dpi->top, dpi->zoom) & 1;
        do {
                for (int i = (bo ^= 1); i < right; i += 2) blitter->SetPixel(dst, i, 0, (uint8_t)colour);
                dst = blitter->MoveTo(dst, 0, 1);
        } while (--bottom > 0);
}

static void ViewportDrawStrings(ViewportDrawerDynamic *vdd, ZoomLevel zoom, const StringSpriteToDrawVector *sstdv)
{
        for (const StringSpriteToDraw &ss : *sstdv) {
                TextColour colour = TC_BLACK;
                bool small = HasBit(ss.width, 15);
                int w = GB(ss.width, 0, 15);
                int x = UnScaleByZoom(ss.x, zoom);
                int y = UnScaleByZoom(ss.y, zoom);
                int h = WidgetDimensions::scaled.fullbevel.Vertical() + GetCharacterHeight(small ? FS_SMALL : FS_NORMAL);

                SetDParam(0, ss.params[0]);
                SetDParam(1, ss.params[1]);

                if (ss.colour != INVALID_COLOUR) {
                        if (vdd->IsTransparencySet(TO_SIGNS) && ss.string != STR_WHITE_SIGN) {
                                /* Don't draw the rectangle.
                                 * Real colours need the TC_IS_PALETTE_COLOUR flag.
                                 * Otherwise colours from _string_colourmap are assumed. */
                                colour = (TextColour)GetColourGradient(ss.colour, SHADE_LIGHTER) | TC_IS_PALETTE_COLOUR;
                        } else {
                                /* Draw the rectangle if 'transparent station signs' is off,
                                 * or if we are drawing a general text sign (STR_WHITE_SIGN). */
                                DrawFrameRect(
                                        x, y, x + w, y + h, ss.colour,
                                        vdd->IsTransparencySet(TO_SIGNS) ? FR_TRANSPARENT : FR_NONE
                                );
                        }
                }

                DrawString(x + WidgetDimensions::scaled.fullbevel.left, x + w - 1 - WidgetDimensions::scaled.fullbevel.right, y + WidgetDimensions::scaled.fullbevel.top, ss.string, colour, SA_HOR_CENTER, false, small ? FS_SMALL : FS_NORMAL);
        }
}

static inline Vehicle *GetVehicleFromWindow(const Window *w)
{
        if (w != nullptr) {
                WindowClass wc = w->window_class;
                WindowNumber wn = w->window_number;

                if (wc == WC_DROPDOWN_MENU) GetDropDownParentWindowInfo(w, wc, wn);

                switch (wc) {
                        case WC_VEHICLE_VIEW:
                        case WC_VEHICLE_ORDERS:
                        case WC_VEHICLE_TIMETABLE:
                        case WC_VEHICLE_DETAILS:
                        case WC_VEHICLE_REFIT:
                        case WC_VEHICLE_CARGO_TYPE_LOAD_ORDERS:
                        case WC_VEHICLE_CARGO_TYPE_UNLOAD_ORDERS:
                        case WC_SCHDISPATCH_SLOTS:
                                if (wn != INVALID_VEHICLE) return Vehicle::GetIfValid(wn);
                                break;
                        case WC_TRAINS_LIST:
                        case WC_ROADVEH_LIST:
                        case WC_SHIPS_LIST:
                        case WC_AIRCRAFT_LIST: {
                                VehicleListIdentifier vli = VehicleListIdentifier::UnPack(wn);
                                if (vli.type == VL_SHARED_ORDERS) {
                                        return Vehicle::GetIfValid(vli.index);
                                }
                                break;
                        }
                        default:
                                break;
                }
        }
        return nullptr;
}

static bool ViewportVehicleRouteShouldSkipOrder(const Order *order)
{
        if (_settings_client.gui.show_vehicle_route_mode != 2) return false;

        switch (order->GetType()) {
                case OT_GOTO_STATION:
                case OT_IMPLICIT:
                        return (order->GetNonStopType() & ONSF_NO_STOP_AT_DESTINATION_STATION) != 0;

                default:
                        return true;
        }
}

void ViewportRouteOverlay::PrepareRoutePathsConditionalOrder(const Vehicle *veh, const Order *order, PrepareRouteStepState &state, bool conditional, uint depth)
{
        /* Prevent excessive recursion */
        if (depth >= 10) return;

        for (; order != nullptr && state.lines_added < 16; order = veh->orders->GetNext(order)) {
                if (!state.visited.insert(order).second) {
                        /* Already visited this order */
                        return;
                }

                if (ViewportVehicleRouteShouldSkipOrder(order)) continue;

                if (order->IsType(OT_CONDITIONAL)) {
                        this->PrepareRoutePathsConditionalOrder(veh, veh->GetOrder(order->GetConditionSkipToOrder()), state,
                                        conditional || order->GetConditionVariable() != OCV_UNCONDITIONALLY, depth + 1);
                        if (order->GetConditionVariable() == OCV_UNCONDITIONALLY) return;

                        continue;
                }

                const TileIndex to_tile = order->GetLocation(veh, veh->type == VEH_AIRCRAFT);
                if (to_tile == INVALID_TILE) continue;

                DrawnPathRouteTileLine path = { state.from_tile, to_tile, conditional };
                if (path.from_tile > path.to_tile) std::swap(path.from_tile, path.to_tile);
                this->route_paths.push_back(path);
                state.lines_added++;
                return;
        }
}

void ViewportRouteOverlay::PrepareRoutePaths(const Vehicle *veh)
{
        this->route_paths.clear();

        if (veh == nullptr || !_settings_client.gui.show_vehicle_route) return;

        PrepareRouteStepState state;

        TileIndex from_tile = INVALID_TILE;
        bool conditional = false;
        auto handle_order = [&](const Order *order) -> bool {
                if (ViewportVehicleRouteShouldSkipOrder(order)) return false;

                if (order->IsType(OT_CONDITIONAL) && from_tile != INVALID_TILE) {
                        state.reset(from_tile);
                        this->PrepareRoutePathsConditionalOrder(veh, order, state,
                                        conditional || order->GetConditionVariable() != OCV_UNCONDITIONALLY, 0);
                        if (order->GetConditionVariable() == OCV_UNCONDITIONALLY) {
                                from_tile = INVALID_TILE;
                                return true;
                        }
                        conditional = true;
                        return false;
                }

                const TileIndex to_tile = order->GetLocation(veh, veh->type == VEH_AIRCRAFT);
                if (to_tile == INVALID_TILE) return false;

                if (from_tile != INVALID_TILE) {
                        DrawnPathRouteTileLine path = { from_tile, to_tile, conditional };
                        if (path.from_tile > path.to_tile) std::swap(path.from_tile, path.to_tile);
                        this->route_paths.push_back(path);
                }

                from_tile = to_tile;
                conditional = false;

                return true;
        };
        for (const Order *order : veh->Orders()) {
                handle_order(order);
        }
        if (from_tile != INVALID_TILE) {
                /* Handle wrap around from last order back to first */
                for (const Order *order : veh->Orders()) {
                        if (handle_order(order)) break;
                }
        }

        /* Remove duplicate lines */
        std::sort(this->route_paths.begin(), this->route_paths.end());
        auto unique_end = std::unique(this->route_paths.begin(), this->route_paths.end(), [](const DrawnPathRouteTileLine &a, const DrawnPathRouteTileLine &b) {
                /* Consider elements with the same tile values but different order_conditional values as equal */
                return a.from_tile == b.from_tile && a.to_tile == b.to_tile;
        });
        this->route_paths.erase(unique_end, this->route_paths.end());
}

/** Draw the route of a vehicle. */
void ViewportRouteOverlay::DrawVehicleRoutePath(const Viewport *vp, ViewportDrawerDynamic *vdd)
{
        if (this->route_paths.empty()) return;

        DrawPixelInfo dpi_for_text = vdd->MakeDPIForText();

        for (const auto &iter : this->route_paths) {
                const int from_tile_x = TileX(iter.from_tile) * TILE_SIZE + TILE_SIZE / 2;
                const int from_tile_y = TileY(iter.from_tile) * TILE_SIZE + TILE_SIZE / 2;
                Point from_pt = RemapCoords(from_tile_x, from_tile_y, 0);
                const int from_x = UnScaleByZoom(from_pt.x, vp->zoom);

                const int to_tile_x = TileX(iter.to_tile) * TILE_SIZE + TILE_SIZE / 2;
                const int to_tile_y = TileY(iter.to_tile) * TILE_SIZE + TILE_SIZE / 2;
                Point to_pt = RemapCoords(to_tile_x, to_tile_y, 0);
                const int to_x = UnScaleByZoom(to_pt.x, vp->zoom);

                if (from_x < dpi_for_text.left - 1 && to_x < dpi_for_text.left - 1) continue;
                if (from_x > dpi_for_text.left + dpi_for_text.width + 1 && to_x > dpi_for_text.left + dpi_for_text.width + 1) continue;

                from_pt.y -= GetSlopePixelZ(from_tile_x, from_tile_y) * ZOOM_BASE;
                to_pt.y -= GetSlopePixelZ(to_tile_x, to_tile_y) * ZOOM_BASE;
                const int from_y = UnScaleByZoom(from_pt.y, vp->zoom);
                const int to_y = UnScaleByZoom(to_pt.y, vp->zoom);

                int line_width = 3;
                if (_settings_client.gui.dash_level_of_route_lines == 0) {
                        GfxDrawLine(BlitterFactory::GetCurrentBlitter(), &dpi_for_text, from_x, from_y, to_x, to_y, PC_BLACK, 3, _settings_client.gui.dash_level_of_route_lines);
                        line_width = 1;
                }
                GfxDrawLine(BlitterFactory::GetCurrentBlitter(), &dpi_for_text, from_x, from_y, to_x, to_y, iter.order_conditional ? PC_YELLOW : PC_WHITE, line_width, _settings_client.gui.dash_level_of_route_lines);
        }
}

static void ViewportDrawVehicleRoutePath(const Viewport *vp, ViewportDrawerDynamic *vdd)
{
        _vp_focused_window_route_overlay.DrawVehicleRoutePath(vp, vdd);
        for (auto &it : _vp_fixed_route_overlays) {
                if (it.enabled) it.DrawVehicleRoutePath(vp, vdd);
        }
}

static inline void DrawRouteStep(const Viewport * const vp, const TileIndex tile, const RankOrderTypeList list)
{
        if (tile == INVALID_TILE) return;
        const int x_pos = TileX(tile) * TILE_SIZE + TILE_SIZE / 2;
        const int y_pos = TileY(tile) * TILE_SIZE + TILE_SIZE / 2;
        Point pt = RemapCoords(x_pos, y_pos, 0);
        uint width_bucket = 0;
        if (list.size() <= max_rank_order_type_count) {
                for (RankOrderTypeList::const_iterator cit = list.begin(); cit != list.end(); cit++) {
                        if (cit->first >= 10000) {
                                width_bucket = std::max<uint>(width_bucket, 3);
                        } else if (cit->first >= 1000) {
                                width_bucket = std::max<uint>(width_bucket, 2);
                        } else if (cit->first >= 100) {
                                width_bucket = std::max<uint>(width_bucket, 1);
                        }
                }
        }
        const uint str_width = _vp_route_step_string_width[width_bucket];
        const uint total_width = str_width + _vp_route_step_base_width;
        const int x_centre = UnScaleByZoomLower(pt.x - _vdd->dpi.left, _vdd->dpi.zoom);
        const int x = x_centre - (total_width / 2);
        if (x >= _cur_dpi->width || (x + total_width) <= 0) return;
        const uint step_count = list.size() > max_rank_order_type_count ? 1 : (uint)list.size();
        pt.y -= GetSlopePixelZ(x_pos, y_pos) * ZOOM_BASE;
        const int char_height = GetCharacterHeight(FS_SMALL) + 1;
        const int rsth = _vp_route_step_height_top + (int) step_count * char_height + _vp_route_step_height_bottom;
        const int y = UnScaleByZoomLower(pt.y - _vdd->dpi.top,  _vdd->dpi.zoom) - rsth;
        if (y >= _cur_dpi->height || (y + rsth) <= 0) return;

        /* Draw the background. */
        GfxFillRect(_cur_dpi->left + x, _cur_dpi->top + y, _cur_dpi->left + x + total_width - 1, _cur_dpi->top + y + _vp_route_step_height_top - 1, PC_BLACK);
        int y2 = y + _vp_route_step_height_top + (char_height * step_count);

        GfxFillRect(_cur_dpi->left + x, _cur_dpi->top + y + _vp_route_step_height_top, _cur_dpi->left + x + total_width - 1, _cur_dpi->top + y2 - 1, PC_WHITE);
        GfxFillRect(_cur_dpi->left + x, _cur_dpi->top + y + _vp_route_step_height_top, _cur_dpi->left + x + _vp_route_step_height_top - 1, _cur_dpi->top + y2 - 1, PC_BLACK);
        GfxFillRect(_cur_dpi->left + x + total_width - _vp_route_step_height_top, _cur_dpi->top + y + _vp_route_step_height_top, _cur_dpi->left + x + total_width - 1, _cur_dpi->top + y2 - 1, PC_BLACK);

        if (total_width > _vp_route_step_sprite_width) {
                GfxFillRect(_cur_dpi->left + x, _cur_dpi->top + y2, _cur_dpi->left + x + total_width - 1, _cur_dpi->top + y2 + _vp_route_step_height_top - 1, PC_BLACK);
        }

        const int x_bottom_spr = x_centre - (_vp_route_step_sprite_width / 2);
        DrawSprite(SPR_ROUTE_STEP_BOTTOM, PAL_NONE, _cur_dpi->left + x_bottom_spr, _cur_dpi->top + y2);
        SpriteID s = SPR_ROUTE_STEP_BOTTOM_SHADOW;
        DrawSprite(SetBit(s, PALETTE_MODIFIER_TRANSPARENT), PALETTE_TO_TRANSPARENT, _cur_dpi->left + x_bottom_spr, _cur_dpi->top + y2);

        /* Fill with the data. */
        y2 = y + _vp_route_step_height_top;
        DrawPixelInfo dpi_for_text = _vdd->MakeDPIForText();
        AutoRestoreBackup dpi_backup(_cur_dpi, &dpi_for_text);

        const int x_str = x_centre - (str_width / 2);
        if (list.size() > max_rank_order_type_count) {
                /* Write order overflow item */
                SetDParam(0, list.size());
                DrawString(dpi_for_text.left + x_str, dpi_for_text.left + x_str + str_width - 1, dpi_for_text.top + y2,
                                STR_VIEWPORT_SHOW_VEHICLE_ROUTE_STEP_OVERFLOW, TC_FROMSTRING, SA_CENTER, false, FS_SMALL);
        } else {
                for (RankOrderTypeList::const_iterator cit = list.begin(); cit != list.end(); cit++, y2 += char_height) {
                        bool ok = true;
                        switch (cit->second) {
                                case RSOT_GOTO_STATION:
                                        SetDParam(1, STR_VIEWPORT_SHOW_VEHICLE_ROUTE_STEP_STATION);
                                        break;
                                case RSOT_VIA_STATION:
                                        SetDParam(1, STR_VIEWPORT_SHOW_VEHICLE_ROUTE_STEP_VIA_STATION);
                                        break;
                                case RSOT_DEPOT:
                                        SetDParam(1, STR_VIEWPORT_SHOW_VEHICLE_ROUTE_STEP_DEPOT);
                                        break;
                                case RSOT_WAYPOINT:
                                        SetDParam(1, STR_VIEWPORT_SHOW_VEHICLE_ROUTE_STEP_WAYPOINT);
                                        break;
                                case RSOT_IMPLICIT:
                                        SetDParam(1, STR_VIEWPORT_SHOW_VEHICLE_ROUTE_STEP_IMPLICIT);
                                        break;
                                default:
                                        ok = false;
                                        break;
                        }
                        if (ok) {
                                /* Write order info */
                                SetDParam(0, cit->first);
                                DrawString(dpi_for_text.left + x_str, dpi_for_text.left + x_str + str_width - 1, dpi_for_text.top + y2,
                                                STR_VIEWPORT_SHOW_VEHICLE_ROUTE_STEP, TC_FROMSTRING, SA_CENTER, false, FS_SMALL);
                        }
                }
        }
}

void ViewportRouteOverlay::PrepareRouteSteps(const Vehicle *veh)
{
        this->route_steps.clear();

        if (veh == nullptr || !_settings_client.gui.show_vehicle_route_steps) return;

        /* Prepare data. */
        uint16_t order_rank = 0;
        for (const Order *order : veh->Orders()) {
                order_rank++;
                if (ViewportVehicleRouteShouldSkipOrder(order)) continue;
                const TileIndex tile = order->GetLocation(veh, veh->type == VEH_AIRCRAFT);
                if (tile == INVALID_TILE) continue;
                RouteStepOrderType type = RSOT_INVALID;
                switch (order->GetType()) {
                        case OT_GOTO_STATION:
                                type = (order->GetNonStopType() & ONSF_NO_STOP_AT_DESTINATION_STATION) != 0 ? RSOT_VIA_STATION : RSOT_GOTO_STATION;
                                break;

                        case OT_IMPLICIT:
                                type = RSOT_IMPLICIT;
                                break;

                        case OT_GOTO_WAYPOINT:
                                type = RSOT_WAYPOINT;
                                break;

                        case OT_GOTO_DEPOT:
                                type = RSOT_DEPOT;
                                break;

                        default:
                                break;
                }
                if (type != RSOT_INVALID) {
                        this->route_steps[tile].push_back(std::pair<uint16_t, RouteStepOrderType>(order_rank, type));
                }
        }
}

void ViewportPrepareVehicleRoute()
{
        if (_settings_client.gui.show_vehicle_route_mode == 0) return;
        if (!_settings_client.gui.show_vehicle_route_steps && !_settings_client.gui.show_vehicle_route) return;

        const Vehicle *focused_veh = GetVehicleFromWindow(_focused_window);
        _vp_focused_window_route_overlay.PrepareRouteAndMarkDirtyIfChanged(focused_veh);
        for (auto &it : _vp_fixed_route_overlays) {
                const Vehicle *v = Vehicle::GetIfValid(it.veh);
                it.PrepareRouteAndMarkDirtyIfChanged(v);
                it.enabled = !(v != nullptr && focused_veh != nullptr && v->FirstShared() == focused_veh->FirstShared());
        }
}

void ViewportRouteOverlay::DrawVehicleRouteSteps(const Viewport *vp)
{
        for (RouteStepsMap::const_iterator cit = this->route_steps.begin(); cit != this->route_steps.end(); cit++) {
                DrawRouteStep(vp, cit->first, cit->second);
        }
}

static bool ViewportDrawHasVehicleRouteSteps()
{
        return _vp_focused_window_route_overlay.HasVehicleRouteSteps() || !_vp_fixed_route_overlays.empty();
}

/** Draw the route steps of a vehicle. */
static void ViewportDrawVehicleRouteSteps(const Viewport * const vp)
{
        _vp_focused_window_route_overlay.DrawVehicleRouteSteps(vp);
        for (auto &it : _vp_fixed_route_overlays) {
                if (it.enabled) it.DrawVehicleRouteSteps(vp);
        }
}

static void ViewportDrawPlans(const Viewport *vp, Blitter *blitter, DrawPixelInfo *plan_dpi)
{
        const Rect bounds = {
                ScaleByZoom(plan_dpi->left - 2, vp->zoom),
                ScaleByZoom(plan_dpi->top - 2, vp->zoom),
                ScaleByZoom(plan_dpi->left + plan_dpi->width + 2, vp->zoom),
                ScaleByZoom(plan_dpi->top + plan_dpi->height + 2, vp->zoom) + (int)(ZOOM_BASE * TILE_HEIGHT * _settings_game.construction.map_height_limit)
        };

        const int min_coord_delta = bounds.left / (int)(2 * ZOOM_BASE * TILE_SIZE);
        const int max_coord_delta = (bounds.right / (int)(2 * ZOOM_BASE * TILE_SIZE)) + 1;

        for (const Plan *p : Plan::Iterate()) {
                if (!p->IsVisible()) continue;
                for (const PlanLine &pl : p->lines) {
                        if (
                                bounds.left   > pl.viewport_extents.right ||
                                bounds.right  < pl.viewport_extents.left ||
                                bounds.top    > pl.viewport_extents.bottom ||
                                bounds.bottom < pl.viewport_extents.top
                        ) {
                                continue;
                        }

                        TileIndex to_tile = pl.tiles[0];
                        int to_coord_delta = (int)TileY(to_tile) - (int)TileX(to_tile);
                        for (uint i = 1; i < pl.tiles.size(); i++) {
                                const TileIndex from_tile = to_tile;
                                const int from_coord_delta = to_coord_delta;
                                to_tile = pl.tiles[i];
                                to_coord_delta = (int)TileY(to_tile) - (int)TileX(to_tile);

                                if (to_coord_delta < min_coord_delta && from_coord_delta < min_coord_delta) continue;
                                if (to_coord_delta > max_coord_delta && from_coord_delta > max_coord_delta) continue;

                                const Point from_pt = RemapCoords2(TileX(from_tile) * TILE_SIZE + TILE_SIZE / 2, TileY(from_tile) * TILE_SIZE + TILE_SIZE / 2);
                                const int from_x = UnScaleByZoom(from_pt.x, vp->zoom);
                                const int from_y = UnScaleByZoom(from_pt.y, vp->zoom);

                                const Point to_pt = RemapCoords2(TileX(to_tile) * TILE_SIZE + TILE_SIZE / 2, TileY(to_tile) * TILE_SIZE + TILE_SIZE / 2);
                                const int to_x = UnScaleByZoom(to_pt.x, vp->zoom);
                                const int to_y = UnScaleByZoom(to_pt.y, vp->zoom);

                                GfxDrawLine(blitter, plan_dpi, from_x, from_y, to_x, to_y, PC_BLACK, 3);
                                if (pl.focused) {
                                        GfxDrawLine(blitter, plan_dpi, from_x, from_y, to_x, to_y, PC_RED, 1);
                                } else {
                                        GfxDrawLine(blitter, plan_dpi, from_x, from_y, to_x, to_y, _colour_value[p->colour], 1);
                                }
                        }
                }
        }

        if (_current_plan && _current_plan->temp_line.tiles.size() > 1) {
                const BasePlanLine &pl = _current_plan->temp_line;
                TileIndex to_tile = pl.tiles[0];
                int to_coord_delta = (int)TileY(to_tile) - (int)TileX(to_tile);
                for (uint i = 1; i < pl.tiles.size(); i++) {
                        const TileIndex from_tile = to_tile;
                        const int from_coord_delta = to_coord_delta;
                        to_tile = pl.tiles[i];
                        to_coord_delta = (int)TileY(to_tile) - (int)TileX(to_tile);

                        if (to_coord_delta < min_coord_delta && from_coord_delta < min_coord_delta) continue;
                        if (to_coord_delta > max_coord_delta && from_coord_delta > max_coord_delta) continue;

                        const Point from_pt = RemapCoords2(TileX(from_tile) * TILE_SIZE + TILE_SIZE / 2, TileY(from_tile) * TILE_SIZE + TILE_SIZE / 2);
                        const int from_x = UnScaleByZoom(from_pt.x, vp->zoom);
                        const int from_y = UnScaleByZoom(from_pt.y, vp->zoom);

                        const Point to_pt = RemapCoords2(TileX(to_tile) * TILE_SIZE + TILE_SIZE / 2, TileY(to_tile) * TILE_SIZE + TILE_SIZE / 2);
                        const int to_x = UnScaleByZoom(to_pt.x, vp->zoom);
                        const int to_y = UnScaleByZoom(to_pt.y, vp->zoom);

                        GfxDrawLine(blitter, plan_dpi, from_x, from_y, to_x, to_y, _colour_value[_current_plan->colour], 3, 1);
                }
        }
}

#define SLOPIFY_COLOUR(tile, vF, vW, vS, vE, vN, action) { \
        if (show_slope) { \
                const Slope slope = GetTileSlope((tile)); \
                switch (slope) { \
                        case SLOPE_FLAT: \
                        case SLOPE_ELEVATED: \
                                action (vF); break; \
                        default: { \
                                switch (slope & SLOPE_EW) { \
                                        case SLOPE_W: action (vW); break; \
                                        case SLOPE_E: action (vE); break; \
                                        default:      action (slope & SLOPE_S) ? (vS) : (vN); break; \
                                } \
                                break; \
                        } \
                } \
        } else { \
                action (vF); \
        } \
}
#define RETURN_SLOPIFIED_COLOUR(tile, colour, colour_light, colour_dark) SLOPIFY_COLOUR(tile, colour, colour_light, colour_dark, colour_dark, colour_light, return)
#define ASSIGN_SLOPIFIED_COLOUR(tile, colour, colour_light, colour_dark, to_var) SLOPIFY_COLOUR(tile, colour, colour_light, colour_dark, colour_dark, colour_light, to_var =)
#define GET_SLOPE_INDEX(slope_index) SLOPIFY_COLOUR(tile, 0, 1, 2, 3, 4, slope_index =)

#define COL8TO32(x) _cur_palette.palette[x].data
#define COLOUR_FROM_INDEX(x) ((const uint8_t *)&(x))[colour_index]
#define IS32(x) (is_32bpp ? COL8TO32(x) : (x))

/* Variables containing Colour if 32bpp or palette index if 8bpp. */
uint32_t _vp_map_vegetation_clear_colours[16][6][8]; ///< [Slope][ClearGround][Multi (see LoadClearGroundMainColours())]
uint32_t _vp_map_vegetation_tree_colours[16][5][MAX_TREE_COUNT_BY_LANDSCAPE]; ///< [Slope][TreeGround][max of _tree_count_by_landscape]
uint32_t _vp_map_water_colour[5]; ///< [Slope]

static inline uint ViewportMapGetColourIndexMulti(const TileIndex tile, const ClearGround cg)
{
        switch (cg) {
                case CLEAR_GRASS:
                case CLEAR_SNOW:
                case CLEAR_DESERT:
                        return GetClearDensity(tile);
                case CLEAR_ROUGH:
                        return GB(TileX(tile) ^ TileY(tile), 4, 3);
                case CLEAR_ROCKS:
                        return TileHash(TileX(tile), TileY(tile)) & 1;
                case CLEAR_FIELDS:
                        return GetFieldType(tile) & 7;
                default: NOT_REACHED();
        }
}

static const ClearGround _treeground_to_clearground[5] = {
        CLEAR_GRASS, // TREE_GROUND_GRASS
        CLEAR_ROUGH, // TREE_GROUND_ROUGH
        CLEAR_SNOW,  // TREE_GROUND_SNOW_DESERT, make it +1 if _settings_game.game_creation.landscape == LT_TROPIC
        CLEAR_GRASS, // TREE_GROUND_SHORE
        CLEAR_SNOW,  // TREE_GROUND_ROUGH_SNOW, make it +1 if _settings_game.game_creation.landscape == LT_TROPIC
};

template <bool is_32bpp>
static inline uint32_t ViewportMapGetColourVegetationTree(const TileIndex tile, const TreeGround tg, const uint td, const uint tc, const uint colour_index, Slope slope)
{
        if (IsTransparencySet(TO_TREES)) {
                ClearGround cg = _treeground_to_clearground[tg];
                if (cg == CLEAR_SNOW && _settings_game.game_creation.landscape == LT_TROPIC) cg = CLEAR_DESERT;
                uint32_t ground_colour = _vp_map_vegetation_clear_colours[slope][cg][td];

                if (IsInvisibilitySet(TO_TREES)) {
                        /* Like ground. */
                        return ground_colour;
                }

                /* Take ground and make it darker. */
                if (is_32bpp) {
                        return Blitter_32bppBase::MakeTransparent(ground_colour, 192, 256).data;
                } else {
                        /* 8bpp transparent snow trees give blue. Definitely don't want that. Prefer grey. */
                        if (cg == CLEAR_SNOW && td > 1) return GREY_SCALE(13 - tc);
                        return _pal2trsp_remap_ptr[ground_colour];
                }
        } else {
                if (tg == TREE_GROUND_SNOW_DESERT || tg == TREE_GROUND_ROUGH_SNOW) {
                        return _vp_map_vegetation_clear_colours[colour_index ^ slope][_settings_game.game_creation.landscape == LT_TROPIC ? CLEAR_DESERT : CLEAR_SNOW][td];
                } else {
                        const uint rnd = std::min<uint>(tc ^ (((tile & 3) ^ (TileY(tile) & 3)) * td), MAX_TREE_COUNT_BY_LANDSCAPE - 1);
                        return _vp_map_vegetation_tree_colours[slope][tg][rnd];
                }
        }
}

static bool ViewportMapGetColourVegetationCustomObject(uint32_t &colour, const TileIndex tile, const uint colour_index, bool is_32bpp, bool show_slope)
{
        ObjectViewportMapType vmtype = OVMT_DEFAULT;
        const ObjectSpec *spec = ObjectSpec::GetByTile(tile);
        if (spec->ctrl_flags & OBJECT_CTRL_FLAG_VPORT_MAP_TYPE) vmtype = spec->vport_map_type;

        auto do_clear_ground = [&](ClearGround cg, uint multi) -> bool {
                Slope slope = SLOPE_FLAT;
                if (show_slope) {
                        slope = GetTileSlope(tile);
                        extern Foundation GetFoundation_Object(TileIndex tile, Slope tileh);
                        ApplyFoundationToSlope(GetFoundation_Object(tile, slope), slope);
                        slope &= SLOPE_ELEVATED;
                }
                colour = _vp_map_vegetation_clear_colours[slope][cg][multi];
                return true;
        };

        auto do_water = [&](bool coast) -> bool {
                if (is_32bpp) {
                        uint slope_index = 0;
                        if (!coast) GET_SLOPE_INDEX(slope_index);
                        colour = _vp_map_water_colour[slope_index];
                        return true;
                }
                colour = ApplyMask(MKCOLOUR_XXXX(GREY_SCALE(3)), &_smallmap_vehicles_andor[MP_WATER]);
                colour = COLOUR_FROM_INDEX(colour);
                return false;
        };

        switch (vmtype) {
                case OVMT_CLEAR:
                        if (spec->ctrl_flags & OBJECT_CTRL_FLAG_USE_LAND_GROUND) {
                                if (IsTileOnWater(tile) && GetObjectGroundType(tile) != OBJECT_GROUND_SHORE) {
                                        return do_water(false);
                                } else {
                                        switch (GetObjectGroundType(tile)) {
                                                case OBJECT_GROUND_GRASS:
                                                        return do_clear_ground(CLEAR_GRASS, GetObjectGroundDensity(tile));

                                                case OBJECT_GROUND_SNOW_DESERT:
                                                        return do_clear_ground(_settings_game.game_creation.landscape == LT_TROPIC ? CLEAR_DESERT : CLEAR_SNOW, GetObjectGroundDensity(tile));

                                                case OBJECT_GROUND_SHORE:
                                                        return do_water(true);

                                                default:
                                                        /* This should never be reached, just draw as clear as a fallback */
                                                        return do_clear_ground(CLEAR_GRASS, 0);
                                        }
                                }
                        }
                        return do_clear_ground(CLEAR_GRASS, 0);
                case OVMT_GRASS:
                        return do_clear_ground(CLEAR_GRASS, 3);
                case OVMT_ROUGH:
                        return do_clear_ground(CLEAR_ROUGH, GB(TileX(tile) ^ TileY(tile), 4, 3));
                case OVMT_ROCKS:
                        return do_clear_ground(CLEAR_ROCKS, TileHash(TileX(tile), TileY(tile)) & 1);
                case OVMT_FIELDS:
                        return (colour_index & 1) ? do_clear_ground(CLEAR_GRASS, 1) : do_clear_ground(CLEAR_FIELDS, spec->vport_map_subtype & 7);
                case OVMT_SNOW:
                        return do_clear_ground(CLEAR_SNOW, 3);
                case OVMT_DESERT:
                        return do_clear_ground(CLEAR_DESERT, 3);
                case OVMT_TREES: {
                        Slope slope = SLOPE_FLAT;
                        if (show_slope) {
                                slope = GetTileSlope(tile);
                                extern Foundation GetFoundation_Object(TileIndex tile, Slope tileh);
                                ApplyFoundationToSlope(GetFoundation_Object(tile, slope), slope);
                                slope &= SLOPE_ELEVATED;
                        }
                        TreeGround tg = (TreeGround)GB(spec->vport_map_subtype, 0, 4);
                        if (tg > TREE_GROUND_ROUGH_SNOW) tg = TREE_GROUND_GRASS;
                        const uint td = std::min<uint>(GB(spec->vport_map_subtype, 4, 4), 3);
                        const uint tc = Clamp<uint>(GB(spec->vport_map_subtype, 8, 4), 1, 4);
                        if (is_32bpp) {
                                colour = ViewportMapGetColourVegetationTree<true>(tile, tg, td, tc, colour_index, slope);
                        } else {
                                colour = ViewportMapGetColourVegetationTree<false>(tile, tg, td, tc, colour_index, slope);
                        }
                        return true;
                }
                case OVMT_HOUSE:
                        colour = ApplyMask(MKCOLOUR_XXXX(GREY_SCALE(3)), &_smallmap_vehicles_andor[MP_HOUSE]);
                        colour = COLOUR_FROM_INDEX(colour);
                        return false;
                case OVMT_WATER:
                        return do_water(false);

                default:
                        return false;
        }
}

template <bool is_32bpp, bool show_slope>
static inline uint32_t ViewportMapGetColourVegetation(const TileIndex tile, TileType t, const uint colour_index)
{
        uint32_t colour;

        auto set_default_colour = [&](TileType ttype) {
                colour = ApplyMask(MKCOLOUR_XXXX(GREY_SCALE(3)), &_smallmap_vehicles_andor[ttype]);
                colour = COLOUR_FROM_INDEX(colour);
        };

        switch (t) {
                case MP_CLEAR: {
                        Slope slope = show_slope ? (Slope) (GetTileSlope(tile) & 15) : SLOPE_FLAT;
                        uint multi;
                        ClearGround cg = GetClearGround(tile);
                        if (cg == CLEAR_FIELDS && colour_index & 1) {
                                cg = CLEAR_GRASS;
                                multi = 1;
                        } else multi = ViewportMapGetColourIndexMulti(tile, cg);
                        return _vp_map_vegetation_clear_colours[slope][cg][multi];
                }

                case MP_INDUSTRY:
                        colour = IsTileForestIndustry(tile) ? (colour_index & 1 ? PC_GREEN : 0x7B) : GREY_SCALE(3);
                        break;

                case MP_TREES: {
                        const TreeGround tg = GetTreeGround(tile);
                        const uint td = GetTreeDensity(tile);
                        const uint tc = GetTreeCount(tile);
                        Slope slope = show_slope ? (Slope) (GetTileSlope(tile) & 15) : SLOPE_FLAT;
                        return ViewportMapGetColourVegetationTree<is_32bpp>(tile, tg, td, tc, colour_index, slope);
                }

                case MP_OBJECT: {
                        set_default_colour(MP_OBJECT);
                        if (GetObjectHasViewportMapViewOverride(tile)) {
                                if (ViewportMapGetColourVegetationCustomObject(colour, tile, colour_index, is_32bpp, show_slope)) return colour;
                        }
                        break;
                }

                case MP_WATER:
                        if (is_32bpp) {
                                uint slope_index = 0;
                                if (IsTileType(tile, MP_WATER) && GetWaterTileType(tile) != WATER_TILE_COAST) GET_SLOPE_INDEX(slope_index);
                                return _vp_map_water_colour[slope_index];
                        }
                        set_default_colour(t);
                        break;

                default:
                        colour = ApplyMask(MKCOLOUR_XXXX(GREY_SCALE(3)), &_smallmap_vehicles_andor[t]);
                        colour = COLOUR_FROM_INDEX(colour);
                        set_default_colour(t);
                        break;
        }

        if (is_32bpp) {
                return COL8TO32(colour);
        } else {
                if (show_slope) ASSIGN_SLOPIFIED_COLOUR(tile, colour, _lighten_colour[colour], _darken_colour[colour], colour);
                return colour;
        }
}

template <bool is_32bpp, bool show_slope>
static inline uint32_t ViewportMapGetColourIndustries(const TileIndex tile, const TileType t, const uint colour_index)
{
        extern LegendAndColour _legend_from_industries[NUM_INDUSTRYTYPES + 1];
        extern uint _industry_to_list_pos[NUM_INDUSTRYTYPES];

        TileType t2 = t;
        if (t == MP_INDUSTRY) {
                /* If industry is allowed to be seen, use its colour on the map. */
                const IndustryType it = Industry::GetByTile(tile)->type;
                if (_legend_from_industries[_industry_to_list_pos[it]].show_on_map)
                        return IS32(GetIndustrySpec(it)->map_colour);
                /* Otherwise, return the colour which will make it disappear. */
                t2 = IsTileOnWater(tile) ? MP_WATER : MP_CLEAR;
        }

        if (t == MP_OBJECT && GetObjectHasViewportMapViewOverride(tile)) {
                ObjectViewportMapType vmtype = OVMT_DEFAULT;
                const ObjectSpec *spec = ObjectSpec::GetByTile(tile);
                if (spec->ctrl_flags & OBJECT_CTRL_FLAG_VPORT_MAP_TYPE) vmtype = spec->vport_map_type;
                if (vmtype == OVMT_CLEAR && spec->ctrl_flags & OBJECT_CTRL_FLAG_USE_LAND_GROUND) {
                        if (IsTileOnWater(tile) && GetObjectGroundType(tile) != OBJECT_GROUND_SHORE) {
                                vmtype = OVMT_WATER;
                        }
                }
                switch (vmtype) {
                        case OVMT_DEFAULT:
                                break;

                        case OVMT_TREES:
                                t2 = MP_TREES;
                                break;

                        case OVMT_HOUSE:
                                t2 = MP_HOUSE;
                                break;

                        case OVMT_WATER:
                                t2 = MP_WATER;
                                break;

                        default:
                                t2 = MP_CLEAR;
                                break;
                }
        }

        if (is_32bpp && t2 == MP_WATER) {
                uint slope_index = 0;
                if (t != MP_INDUSTRY && IsTileType(tile, MP_WATER) && GetWaterTileType(tile) != WATER_TILE_COAST) GET_SLOPE_INDEX(slope_index); ///< Ignore industry on water not shown on map.
                return _vp_map_water_colour[slope_index];
        }

        const int h = TileHeight(tile);
        const SmallMapColourScheme * const cs = &_heightmap_schemes[_settings_client.gui.smallmap_land_colour];
        const uint32_t colours = ApplyMask(_settings_client.gui.show_height_on_viewport_map ? cs->height_colours[h] : cs->default_colour, &_smallmap_vehicles_andor[t2]);
        uint32_t colour = COLOUR_FROM_INDEX(colours);

        if (show_slope) ASSIGN_SLOPIFIED_COLOUR(tile, colour, _lighten_colour[colour], _darken_colour[colour], colour);

        return IS32(colour);
}

template <bool is_32bpp, bool show_slope>
static inline uint32_t ViewportMapGetColourOwner(const TileIndex tile, TileType t, const uint colour_index)
{
        extern LegendAndColour _legend_land_owners[NUM_NO_COMPANY_ENTRIES + MAX_COMPANIES + 1];
        extern uint _company_to_list_pos[MAX_COMPANIES];

        switch (t) {
                case MP_INDUSTRY: return IS32(PC_DARK_GREY);
                case MP_HOUSE:    return IS32(colour_index & 1 ? PC_DARK_RED : GREY_SCALE(3));
                default:          break;
        }

        const Owner o = GetTileOwner(tile);
        if (o == OWNER_NONE && t == MP_ROAD) {
                return IS32(colour_index & 1 ? PC_BLACK : GREY_SCALE(3));
        } else if ((o < MAX_COMPANIES && !_legend_land_owners[_company_to_list_pos[o]].show_on_map) || o == OWNER_NONE || o == OWNER_WATER) {
                if (t == MP_WATER) {
                        if (is_32bpp) {
                                uint slope_index = 0;
                                if (IsTileType(tile, MP_WATER) && GetWaterTileType(tile) != WATER_TILE_COAST) GET_SLOPE_INDEX(slope_index);
                                return _vp_map_water_colour[slope_index];
                        } else {
                                return PC_WATER;
                        }
                }

                const SmallMapColourScheme * const cs = &_heightmap_schemes[_settings_client.gui.smallmap_land_colour];
                uint32_t colour = COLOUR_FROM_INDEX(_settings_client.gui.show_height_on_viewport_map ? cs->height_colours[TileHeight(tile)] : cs->default_colour);
                if (show_slope) ASSIGN_SLOPIFIED_COLOUR(tile, colour, _lighten_colour[colour], _darken_colour[colour], colour);
                return IS32(colour);

        } else if (o == OWNER_TOWN) {
                return IS32(t == MP_ROAD ? (colour_index & 1 ? PC_BLACK : GREY_SCALE(3)) : PC_DARK_RED);
        }

        /* Train stations are sometimes hard to spot.
         * So we give the player a hint by mixing his colour with black. */
        uint32_t colour = _legend_land_owners[_company_to_list_pos[o]].colour;
        if (t != MP_STATION) {
                if (show_slope) ASSIGN_SLOPIFIED_COLOUR(tile, colour, _lighten_colour[colour], _darken_colour[colour], colour);
        } else {
                if (GetStationType(tile) == STATION_RAIL) colour = colour_index & 1 ? colour : PC_BLACK;
        }
        if (is_32bpp) return COL8TO32(colour);
        return colour;
}

template <bool is_32bpp, bool show_slope>
static inline uint32_t ViewportMapGetColourRoutes(const TileIndex tile, TileType t, const uint colour_index)
{
        uint32_t colour;

        switch (t) {
                case MP_WATER:
                        if (is_32bpp) {
                                uint slope_index = 0;
                                if (IsTileType(tile, MP_WATER) && GetWaterTileType(tile) != WATER_TILE_COAST) GET_SLOPE_INDEX(slope_index);
                                return _vp_map_water_colour[slope_index];
                        } else {
                                return PC_WATER;
                        }

                case MP_INDUSTRY:
                        return IS32(PC_DARK_GREY);

                case MP_HOUSE:
                        return IS32(colour_index & 1 ? PC_DARK_RED : GREY_SCALE(3));

                case MP_OBJECT: {
                        ObjectViewportMapType vmtype = OVMT_DEFAULT;
                        if (GetObjectHasViewportMapViewOverride(tile)) {
                                const ObjectSpec *spec = ObjectSpec::GetByTile(tile);
                                if (spec->ctrl_flags & OBJECT_CTRL_FLAG_VPORT_MAP_TYPE) vmtype = spec->vport_map_type;
                                if (vmtype == OVMT_CLEAR && spec->ctrl_flags & OBJECT_CTRL_FLAG_USE_LAND_GROUND) {
                                        if (IsTileOnWater(tile) && GetObjectGroundType(tile) != OBJECT_GROUND_SHORE) {
                                                vmtype = OVMT_WATER;
                                        }
                                }
                        }
                        switch (vmtype) {
                                case OVMT_DEFAULT:
                                case OVMT_HOUSE:
                                        return IS32(colour_index & 1 ? PC_DARK_RED : GREY_SCALE(3));

                                case OVMT_WATER:
                                        if (is_32bpp) {
                                                return _vp_map_water_colour[0];
                                        } else {
                                                return PC_WATER;
                                        }

                                default: {
                                        const SmallMapColourScheme * const cs = &_heightmap_schemes[_settings_client.gui.smallmap_land_colour];
                                        colour = COLOUR_FROM_INDEX(_settings_client.gui.show_height_on_viewport_map ? cs->height_colours[TileHeight(tile)] : cs->default_colour);
                                        break;
                                }
                        }
                        break;
                }

                case MP_STATION:
                        switch (GetStationType(tile)) {
                                case STATION_RAIL:    return IS32(PC_VERY_DARK_BROWN);
                                case STATION_AIRPORT: return IS32(PC_RED);
                                case STATION_TRUCK:   return IS32(PC_ORANGE);
                                case STATION_BUS:     return IS32(PC_YELLOW);
                                case STATION_DOCK:    return IS32(PC_LIGHT_BLUE);
                                default:              return IS32(0xFF);
                        }

                case MP_RAILWAY: {
                        colour = GetRailTypeInfo(GetRailType(tile))->map_colour;
                        break;
                }

                case MP_ROAD: {
                        const RoadTypeInfo *rti = nullptr;
                        if (GetRoadTypeRoad(tile) != INVALID_ROADTYPE) {
                                rti = GetRoadTypeInfo(GetRoadTypeRoad(tile));
                        } else {
                                rti = GetRoadTypeInfo(GetRoadTypeTram(tile));
                        }
                        if (rti != nullptr) {
                                colour = rti->map_colour;
                                break;
                        }
                        [[fallthrough]];
                }

                default: {
                        const SmallMapColourScheme * const cs = &_heightmap_schemes[_settings_client.gui.smallmap_land_colour];
                        colour = COLOUR_FROM_INDEX(_settings_client.gui.show_height_on_viewport_map ? cs->height_colours[TileHeight(tile)] : cs->default_colour);
                        break;
                }
        }

        if (show_slope) ASSIGN_SLOPIFIED_COLOUR(tile, colour, _lighten_colour[colour], _darken_colour[colour], colour);
        return IS32(colour);
}

static inline void ViewportMapStoreBridgeAboveTile(const Viewport * const vp, const TileIndex tile)
{
        /* No need to bother for hidden things */
        if (!_settings_client.gui.show_bridges_on_map) return;

        if (GetBridgeAxis(tile) == AXIS_X) {
                auto iter = _vdd->bridge_to_map_x.lower_bound(tile);
                if (iter != _vdd->bridge_to_map_x.end() && iter->first < tile && iter->second > tile) return; /* already covered */
                _vdd->bridge_to_map_x.insert(iter, std::make_pair(GetNorthernBridgeEnd(tile), GetSouthernBridgeEnd(tile)));
        } else {
                auto iter = _vdd->bridge_to_map_y.lower_bound(tile);
                if (iter != _vdd->bridge_to_map_y.end() && iter->first < tile && iter->second > tile) return; /* already covered */
                _vdd->bridge_to_map_y.insert(iter, std::make_pair(GetNorthernBridgeEnd(tile), GetSouthernBridgeEnd(tile)));
        }
}

static inline TileIndex ViewportMapGetMostSignificantTileType(const Viewport * const vp, const TileIndex from_tile, TileType * const tile_type)
{
        if (vp->zoom <= ZOOM_LVL_OUT_32X) {
                const TileType ttype = GetTileType(from_tile);
                /* Store bridges and tunnels. */
                if (ttype != MP_TUNNELBRIDGE) {
                        *tile_type = ttype;
                        if (IsBridgeAbove(from_tile)) ViewportMapStoreBridgeAboveTile(vp, from_tile);
                } else {
                        if (IsBridge(from_tile)) {
                                ViewportMapStoreBridge(vp, from_tile);
                        }
                        switch (GetTunnelBridgeTransportType(from_tile)) {
                                case TRANSPORT_RAIL:  *tile_type = MP_RAILWAY; break;
                                case TRANSPORT_ROAD:  *tile_type = MP_ROAD;    break;
                                case TRANSPORT_WATER: *tile_type = MP_WATER;   break;
                                default:              NOT_REACHED();           break;
                        }
                }
                return from_tile;
        }

        const uint8_t length = (vp->zoom - ZOOM_LVL_OUT_32X) * 2;
        TileArea tile_area = TileArea(from_tile, length, length);
        tile_area.ClampToMap();

        /* Find the most important tile of the area. */
        TileIndex result = from_tile;
        uint importance = 0;
        for (OrthogonalPrefetchTileIterator tile(tile_area); tile != INVALID_TILE; ++tile) {
                const TileType ttype = GetTileType(tile);
                const uint tile_importance = _tiletype_importance[ttype];
                if (tile_importance > importance) {
                        importance = tile_importance;
                        result = tile;
                }
                if (ttype != MP_TUNNELBRIDGE && IsBridgeAbove(tile)) {
                        ViewportMapStoreBridgeAboveTile(vp, tile);
                }
        }

        /* Store bridges and tunnels. */
        *tile_type = GetTileType(result);
        if (*tile_type == MP_TUNNELBRIDGE) {
                if (IsBridge(result)) {
                        ViewportMapStoreBridge(vp, result);
                }
                switch (GetTunnelBridgeTransportType(result)) {
                        case TRANSPORT_RAIL: *tile_type = MP_RAILWAY; break;
                        case TRANSPORT_ROAD: *tile_type = MP_ROAD;    break;
                        default:             *tile_type = MP_WATER;   break;
                }
        }

        return result;
}

static uint32_t ViewportMapVoidColour()
{
        return (_settings_game.construction.map_edge_mode == 2) ? _vp_map_water_colour[SLOPE_FLAT] : 0;
}

/** Get the colour of a tile, can be 32bpp RGB or 8bpp palette index. */
template <bool is_32bpp, bool show_slope>
uint32_t ViewportMapGetColour(const Viewport * const vp, int x, int y, const uint colour_index)
{
        if (x >= static_cast<int>(MapMaxX() * TILE_SIZE) || y >= static_cast<int>(MapMaxY() * TILE_SIZE)) return ViewportMapVoidColour();

        /* Very approximative but fast way to get the tile when taking Z into account. */
        const TileIndex tile_tmp = TileVirtXY(std::max(0, x), std::max(0, y));
        const int z = TileHeight(tile_tmp) * 4;
        if (x + z < 0 || y + z < 0 || static_cast<uint>(x + z) >= MapSizeX() << 4) {
                /* Wrapping of tile X coordinate causes a graphic glitch below south west border. */
                return ViewportMapVoidColour();
        }
        TileIndex tile = TileVirtXY(x + z, y + z);
        if (tile >= MapSize()) return ViewportMapVoidColour();
        const int z2 = TileHeight(tile) * 4;
        if (unlikely(z2 != z)) {
                const int approx_z = (z + z2) / 2;
                if (x + approx_z < 0 || y + approx_z < 0 || static_cast<uint>(x + approx_z) >= MapSizeX() << 4) {
                        /* Wrapping of tile X coordinate causes a graphic glitch below south west border. */
                        return ViewportMapVoidColour();
                }
                tile = TileVirtXY(x + approx_z, y + approx_z);
                if (tile >= MapSize()) return ViewportMapVoidColour();
        }
        TileType tile_type = MP_VOID;
        tile = ViewportMapGetMostSignificantTileType(vp, tile, &tile_type);
        if (tile_type == MP_VOID) return ViewportMapVoidColour();

        /* Return the colours. */
        switch (vp->map_type) {
                default:              return ViewportMapGetColourOwner<is_32bpp, show_slope>(tile, tile_type, colour_index);
                case VPMT_INDUSTRY:   return ViewportMapGetColourIndustries<is_32bpp, show_slope>(tile, tile_type, colour_index);
                case VPMT_VEGETATION: return ViewportMapGetColourVegetation<is_32bpp, show_slope>(tile, tile_type, colour_index);
                case VPMT_ROUTES:     return ViewportMapGetColourRoutes<is_32bpp, show_slope>(tile, tile_type, colour_index);
        }
}

/* Taken from http://stereopsis.com/doubleblend.html, PixelBlend() is faster than ComposeColourRGBANoCheck() */
static inline void PixelBlend(uint32_t * const d, const uint32_t s)
{
#if defined(__EMSCRIPTEN__)
        *d = Blitter_32bppBase::ComposeColourRGBANoCheck(s & 0xFF, (s >> 8) & 0xFF, (s >> 16) & 0xFF, (s >> 24) & 0xFF, Colour(*d)).data;
        return;
#endif
        const uint32_t a     = (s >> 24) + 1;
        const uint32_t dstrb = *d & 0xFF00FF;
        const uint32_t dstg  = *d & 0xFF00;
        const uint32_t srcrb = s & 0xFF00FF;
        const uint32_t srcg  = s & 0xFF00;
        uint32_t drb = srcrb - dstrb;
        uint32_t dg  =  srcg - dstg;
        drb *= a;
        dg  *= a;
        drb >>= 8;
        dg  >>= 8;
        uint32_t rb = (drb + dstrb) & 0xFF00FF;
        uint32_t g  = (dg  + dstg) & 0xFF00;
        *d = rb | g;
}

/** Draw the bounding boxes of the scrolling viewport (right-clicked and dragged) */
static void ViewportMapDrawScrollingViewportBox(const Viewport * const vp)
{
        if (_scrolling_viewport && _scrolling_viewport->viewport) {
                const ViewportData * const vp_scrolling = _scrolling_viewport->viewport;
                if (vp_scrolling->zoom < ZOOM_LVL_DRAW_MAP) {
                        const int w = UnScaleByZoom(_vdd->dpi.width, vp->zoom);
                        const int l = UnScaleByZoomLower(vp_scrolling->next_scrollpos_x - _vdd->dpi.left, _vdd->dpi.zoom);
                        const int r = UnScaleByZoomLower(vp_scrolling->next_scrollpos_x + vp_scrolling->virtual_width - _vdd->dpi.left, _vdd->dpi.zoom);
                        /* Check intersection of dpi and vp_scrolling */
                        if (l < w && r >= 0) {
                                const int h = UnScaleByZoom(_vdd->dpi.height, vp->zoom);
                                const int t = UnScaleByZoomLower(vp_scrolling->next_scrollpos_y - _vdd->dpi.top, _vdd->dpi.zoom);
                                const int b = UnScaleByZoomLower(vp_scrolling->next_scrollpos_y + vp_scrolling->virtual_height - _vdd->dpi.top, _vdd->dpi.zoom);
                                if (t < h && b >= 0) {
                                        /* OK, so we can draw something that tells where the scrolling viewport is */
                                        Blitter * const blitter = BlitterFactory::GetCurrentBlitter();
                                        const int l_inter = std::max(l, 0);
                                        const int r_inter = std::min(r, w);
                                        const int t_inter = std::max(t, 0);
                                        const int b_inter = std::min(b, h);

                                        /* If asked, with 32bpp we can do some blending */
                                        if (_settings_client.gui.show_scrolling_viewport_on_map >= 2 && blitter->GetScreenDepth() == 32) {
                                                for (int j = t_inter; j < b_inter; j++) {
                                                        uint32_t *buf = (uint32_t*) blitter->MoveTo(_vdd->dpi.dst_ptr, 0, j);
                                                        for (int i = l_inter; i < r_inter; i++) {
                                                                PixelBlend(buf + i, 0x40FCFCFC);
                                                        }
                                                }
                                        }

                                        /* Draw area contour */
                                        if (_settings_client.gui.show_scrolling_viewport_on_map != 2) {
                                                if (t >= 0) {
                                                        for (int i = l_inter; i < r_inter; i += 2) {
                                                                blitter->SetPixel(_vdd->dpi.dst_ptr, i, t, PC_WHITE);
                                                        }
                                                }
                                                if (b < h) {
                                                        for (int i = l_inter; i < r_inter; i += 2) {
                                                                blitter->SetPixel(_vdd->dpi.dst_ptr, i, b, PC_WHITE);
                                                        }
                                                }
                                                if (l >= 0) {
                                                        for (int j = t_inter; j < b_inter; j += 2) {
                                                                blitter->SetPixel(_vdd->dpi.dst_ptr, l, j, PC_WHITE);
                                                        }
                                                }
                                                if (r < w) {
                                                        for (int j = t_inter; j < b_inter; j += 2) {
                                                                blitter->SetPixel(_vdd->dpi.dst_ptr, r, j, PC_WHITE);
                                                        }
                                                }
                                        }
                                }
                        }
                }
        }
}

static void ViewportMapDrawSelection(const Viewport * const vp)
{
        DrawPixelInfo dpi_for_text = _vdd->MakeDPIForText();
        AutoRestoreBackup dpi_backup(_cur_dpi, &dpi_for_text);

        auto draw_line = [&](Point from_pt, Point to_pt) {
                GfxDrawLine(from_pt.x, from_pt.y, to_pt.x, to_pt.y, PC_WHITE, 2, 0);
        };

        Point start_coord = RemapCoords2(_thd.selstart.x, _thd.selstart.y);
        Point end_coord = RemapCoords2(_thd.selend.x, _thd.selend.y);

        Point start_effective = InverseRemapCoords(start_coord.x, start_coord.y);
        Point end_effective = InverseRemapCoords(end_coord.x, end_coord.y);

        auto get_corner = [&](int pos_x, int pos_y) -> Point {
                Point pt = RemapCoords(pos_x, pos_y, 0);
                return { UnScaleByZoom(pt.x, vp->zoom), UnScaleByZoom(pt.y, vp->zoom) };
        };
        Point start_pt = get_corner(start_effective.x, start_effective.y);
        Point end_pt = get_corner(end_effective.x, end_effective.y);
        Point mid1_pt = get_corner(start_effective.x, end_effective.y);
        Point mid2_pt = get_corner(end_effective.x, start_effective.y);

        draw_line(start_pt, mid1_pt);
        draw_line(mid1_pt, end_pt);
        draw_line(end_pt, mid2_pt);
        draw_line(mid2_pt, start_pt);

        if (BlitterFactory::GetCurrentBlitter()->GetScreenDepth() == 32) {
                static std::vector<Point> points(4);
                points[0] = start_pt;
                points[1] = mid1_pt;
                points[2] = end_pt;
                points[3] = mid2_pt;
                GfxFillPolygon(points, 0, FILLRECT_FUNCTOR, [](void *dst, int count) {
                        uint32_t *buf = reinterpret_cast<uint32_t *>(dst);
                        for (int i = 0; i < count; i++) {
                                PixelBlend(buf + i, 0x40FCFCFC);
                        }
                });
        } else {
                draw_line(start_pt, end_pt);
        }
}

template <bool is_32bpp>
static void ViewportMapDrawBridgeTunnel(Viewport * const vp, const TunnelBridgeToMap * const tbtm, const int z,
                const bool is_tunnel, const int w, const int h, Blitter * const blitter)
{
        extern LegendAndColour _legend_land_owners[NUM_NO_COMPANY_ENTRIES + MAX_COMPANIES + 1];
        extern uint _company_to_list_pos[MAX_COMPANIES];

        TileIndex tile = tbtm->from_tile;
        const Owner o = GetTileOwner(tile);
        if (o < MAX_COMPANIES && !_legend_land_owners[_company_to_list_pos[o]].show_on_map) return;

        uint8_t colour;
        if (vp->map_type == VPMT_OWNER && _settings_client.gui.use_owner_colour_for_tunnelbridge && o < MAX_COMPANIES) {
                colour = _legend_land_owners[_company_to_list_pos[o]].colour;
                colour = is_tunnel ? _darken_colour[colour] : _lighten_colour[colour];
        } else if (vp->map_type == VPMT_ROUTES && IsTileType(tile, MP_TUNNELBRIDGE)) {
                switch (GetTunnelBridgeTransportType(tile)) {
                        case TRANSPORT_WATER:
                                colour = PC_WATER;
                                break;

                        case TRANSPORT_RAIL:
                                colour = GetRailTypeInfo(GetRailType(tile))->map_colour;
                                break;

                        case TRANSPORT_ROAD: {
                                const RoadTypeInfo *rti = nullptr;
                                if (GetRoadTypeRoad(tile) != INVALID_ROADTYPE) {
                                        rti = GetRoadTypeInfo(GetRoadTypeRoad(tile));
                                } else {
                                        rti = GetRoadTypeInfo(GetRoadTypeTram(tile));
                                }
                                if (rti != nullptr) {
                                        colour = rti->map_colour;
                                        break;
                                }
                                [[fallthrough]];
                        }

                        default:
                                colour = PC_BLACK;
                                break;
                }

        } else {
                colour = is_tunnel ? PC_BLACK : PC_VERY_LIGHT_YELLOW;
        }

        TileIndexDiff delta = TileOffsByDiagDir(GetTunnelBridgeDirection(tile));
        uint zoom_mask = (1 << (vp->zoom - ZOOM_LVL_DRAW_MAP)) - 1;
        for (tile += delta; tile != tbtm->to_tile; tile += delta) { // For each tile
                if (zoom_mask != 0 && ((TileX(tile) ^ TileY(tile)) & zoom_mask)) continue;
                const Point pt = RemapCoords(TileX(tile) * TILE_SIZE, TileY(tile) * TILE_SIZE, z);
                const int x = UnScaleByZoomLower(pt.x - _vdd->dpi.left, _vdd->dpi.zoom);
                if (IsInsideMM(x, 0, w)) {
                        const int y = UnScaleByZoomLower(pt.y - _vdd->dpi.top, _vdd->dpi.zoom);
                        if (IsInsideMM(y, 0, h)) {
                                uint idx = (x + _vdd->offset_x) + ((y + _vdd->offset_y) * vp->width);
                                if (is_32bpp) {
                                        reinterpret_cast<uint32_t *>(vp->land_pixel_cache.data())[idx] = COL8TO32(colour);
                                } else {
                                        reinterpret_cast<uint8_t *>(vp->land_pixel_cache.data())[idx] = colour;
                                }
                        }
                }
        }
}

/** Draw the map on a viewport. */
template <bool is_32bpp, bool show_slope>
void ViewportMapDraw(Viewport * const vp)
{
        dbg_assert(vp != nullptr);
        Blitter * const blitter = BlitterFactory::GetCurrentBlitter();

        SmallMapWindow::RebuildColourIndexIfNecessary();

        /* Index of colour: _green_map_heights[] contains blocks of 4 colours, say ABCD
         * For a XXXY colour block to render nicely, follow the model:
         *   line 1: ABCDABCDABCD
         *   line 2: CDABCDABCDAB
         *   line 3: ABCDABCDABCD
         * => colour_index_base's second bit is changed every new line.
         */
        const  int sx = UnScaleByZoomLower(_vdd->dpi.left, _vdd->dpi.zoom);
        const  int sy = UnScaleByZoomLower(_vdd->dpi.top, _vdd->dpi.zoom);
        const uint line_padding = 2 * (sy & 1);
        uint       colour_index_base = (sx + line_padding) & 3;

        const  int incr_a = (1 << (vp->zoom - 2)) / ZOOM_BASE;
        const  int incr_b = (1 << (vp->zoom - 1)) / ZOOM_BASE;
        const  int a = (_vdd->dpi.left >> 2) / ZOOM_BASE;
        int        b = (_vdd->dpi.top >> 1) / ZOOM_BASE;
        const  int w = UnScaleByZoom(_vdd->dpi.width, vp->zoom);
        const  int h = UnScaleByZoom(_vdd->dpi.height, vp->zoom);
        int        j = 0;

        const int land_cache_start = _vdd->offset_x + (_vdd->offset_y * vp->width);
        uint32_t *land_cache_ptr32 = reinterpret_cast<uint32_t *>(vp->land_pixel_cache.data()) + land_cache_start;
        uint8_t *land_cache_ptr8 = reinterpret_cast<uint8_t *>(vp->land_pixel_cache.data()) + land_cache_start;

        bool cache_updated = false;

        /* Render base map. */
        do { // For each line
                int i = w;
                uint colour_index = colour_index_base;
                colour_index_base ^= 2;
                int c = b - a;
                int d = b + a;
                do { // For each pixel of a line
                        if (is_32bpp) {
                                if (*land_cache_ptr32 == 0xD7D7D7D7) {
                                        *land_cache_ptr32 = ViewportMapGetColour<is_32bpp, show_slope>(vp, c, d, colour_index);
                                        cache_updated = true;
                                }
                                land_cache_ptr32++;
                        } else {
                                if (*land_cache_ptr8 == 0xD7) {
                                        *land_cache_ptr8 = (uint8_t) ViewportMapGetColour<is_32bpp, show_slope>(vp, c, d, colour_index);
                                        cache_updated = true;
                                }
                                land_cache_ptr8++;
                        }
                        colour_index = (colour_index + 1) & 3;
                        c -= incr_a;
                        d += incr_a;
                } while (--i);
                if (is_32bpp) {
                        land_cache_ptr32 += (vp->width - w);
                } else {
                        land_cache_ptr8 += (vp->width - w);
                }
                b += incr_b;
        } while (++j < h);

        auto draw_tunnels = [&](const int y_intercept_min, const int y_intercept_max, const TunnelToMapStorage &storage) {
                auto iter = std::lower_bound(storage.tunnels.begin(), storage.tunnels.end(), y_intercept_min, [](const TunnelToMap &a, int b) -> bool {
                        return a.y_intercept < b;
                });
                for (; iter != storage.tunnels.end() && iter->y_intercept <= y_intercept_max; ++iter) {
                        const TunnelToMap &ttm = *iter;
                        const int tunnel_z = (ttm.tunnel_z - 1) * TILE_HEIGHT;
                        const Point pt_from = RemapCoords(TileX(ttm.tb.from_tile) * TILE_SIZE, TileY(ttm.tb.from_tile) * TILE_SIZE, tunnel_z);
                        const Point pt_to = RemapCoords(TileX(ttm.tb.to_tile) * TILE_SIZE, TileY(ttm.tb.to_tile) * TILE_SIZE, tunnel_z);

                        /* check if tunnel is wholly outside redrawing area */
                        const int x_from = UnScaleByZoomLower(pt_from.x - _vdd->dpi.left, _vdd->dpi.zoom);
                        const int x_to = UnScaleByZoomLower(pt_to.x - _vdd->dpi.left, _vdd->dpi.zoom);
                        if ((x_from < 0 && x_to < 0) || (x_from > w && x_to > w)) continue;
                        const int y_from = UnScaleByZoomLower(pt_from.y - _vdd->dpi.top, _vdd->dpi.zoom);
                        const int y_to = UnScaleByZoomLower(pt_to.y - _vdd->dpi.top, _vdd->dpi.zoom);
                        if ((y_from < 0 && y_to < 0) || (y_from > h && y_to > h)) continue;

                        ViewportMapDrawBridgeTunnel<is_32bpp>(vp, &ttm.tb, tunnel_z, true, w, h, blitter);
                }
        };

        if (cache_updated) {
                /* Render tunnels */
                if (_settings_client.gui.show_tunnels_on_map && _vd.tunnel_to_map_x.tunnels.size() != 0) {
                        const int y_intercept_min = _vdd->dpi.top + (_vdd->dpi.left / 2);
                        const int y_intercept_max = _vdd->dpi.top + _vdd->dpi.height + ((_vdd->dpi.left + _vdd->dpi.width) / 2);
                        draw_tunnels(y_intercept_min, y_intercept_max, _vd.tunnel_to_map_x);
                }
                if (_settings_client.gui.show_tunnels_on_map && _vd.tunnel_to_map_y.tunnels.size() != 0) {
                        const int y_intercept_min = _vdd->dpi.top - ((_vdd->dpi.left + _vdd->dpi.width) / 2);
                        const int y_intercept_max = _vdd->dpi.top + _vdd->dpi.height - (_vdd->dpi.left / 2);
                        draw_tunnels(y_intercept_min, y_intercept_max, _vd.tunnel_to_map_y);
                }

                /* Render bridges */
                if (_settings_client.gui.show_bridges_on_map && _vdd->bridge_to_map_x.size() != 0) {
                        for (const auto &it : _vdd->bridge_to_map_x) { // For each bridge
                                TunnelBridgeToMap tbtm { it.first, it.second };
                                ViewportMapDrawBridgeTunnel<is_32bpp>(vp, &tbtm, (GetBridgeHeight(tbtm.from_tile) - 1) * TILE_HEIGHT, false, w, h, blitter);
                        }
                }
                if (_settings_client.gui.show_bridges_on_map && _vdd->bridge_to_map_y.size() != 0) {
                        for (const auto &it : _vdd->bridge_to_map_y) { // For each bridge
                                TunnelBridgeToMap tbtm { it.first, it.second };
                                ViewportMapDrawBridgeTunnel<is_32bpp>(vp, &tbtm, (GetBridgeHeight(tbtm.from_tile) - 1) * TILE_HEIGHT, false, w, h, blitter);
                        }
                }
        }

        if (is_32bpp) {
                blitter->SetRect32(_vdd->dpi.dst_ptr, 0, 0, reinterpret_cast<uint32_t *>(vp->land_pixel_cache.data()) + land_cache_start, h, w, vp->width);
        } else {
                blitter->SetRect(_vdd->dpi.dst_ptr, 0, 0, reinterpret_cast<uint8_t *>(vp->land_pixel_cache.data()) + land_cache_start, h, w, vp->width);
        }

        if (unlikely(HasBit(_viewport_debug_flags, VDF_SHOW_NO_LANDSCAPE_MAP_DRAW)) && !cache_updated) {
                ViewportDrawDirtyBlocks(_cur_dpi, true);
        }
}

static void ViewportProcessParentSprites(ViewportDrawerDynamic *vdd, uint data_index)
{
        ViewportProcessParentSpritesData *data = &vdd->parent_sprite_sets[data_index];
        if (data->psts.size() > 80 && (UnScaleByZoomLower(data->dpi.width, data->dpi.zoom) >= 64 || UnScaleByZoomLower(data->dpi.height, data->dpi.zoom) >= 64) && !HasBit(_viewport_debug_flags, VDF_DISABLE_DRAW_SPLIT)) {
                /* split drawing region */

                uint data_index_2 = (uint)vdd->parent_sprite_sets.size();
                vdd->parent_sprite_sets.emplace_back();
                data = &vdd->parent_sprite_sets[data_index];
                ViewportProcessParentSpritesData *data2 = &vdd->parent_sprite_sets[data_index_2];
                data2->dpi = data->dpi;

                if (data->dpi.height > data->dpi.width) {
                        /* vertical split: upper half */
                        const int upper_height = (data->dpi.height / 2) & ScaleByZoom(-1, data->dpi.zoom);
                        const int split = data2->dpi.top + upper_height;
                        data2->dpi.height = upper_height;
                        for (ParentSpriteToDraw *psd : data->psts) {
                                if (psd->top < split) data2->psts.push_back(psd);
                        }

                        ViewportProcessParentSprites(vdd, data_index_2);
                        data = &vdd->parent_sprite_sets[data_index];

                        /* vertical split: lower half */
                        data->dpi.dst_ptr = BlitterFactory::GetCurrentBlitter()->MoveTo(data->dpi.dst_ptr, 0, UnScaleByZoom(upper_height, data->dpi.zoom));
                        data->dpi.top = split;
                        data->dpi.height = data->dpi.height - upper_height;

                        ParentSpriteToSortVector psts;
                        for (ParentSpriteToDraw *psd : data->psts) {
                                psd->SetComparisonDone(false);
                                if (psd->top + psd->height > data->dpi.top) {
                                        psts.push_back(psd);
                                }
                        }
                        data->psts = std::move(psts);

                        ViewportProcessParentSprites(vdd, data_index);
                } else {
                        /* horizontal split: left half */
                        const int left_width = (data->dpi.width / 2) & ScaleByZoom(-1, data->dpi.zoom);
                        const int margin = UnScaleByZoom(128, data->dpi.zoom); // Half tile (1 column) margin either side of split
                        const int split = data2->dpi.left + left_width;
                        data2->dpi.width = left_width;
                        for (ParentSpriteToDraw *psd : data->psts) {
                                if (psd->left < split + margin) data2->psts.push_back(psd);
                        }

                        ViewportProcessParentSprites(vdd, data_index_2);
                        data = &vdd->parent_sprite_sets[data_index];

                        /* horizontal split: right half */
                        data->dpi.dst_ptr = BlitterFactory::GetCurrentBlitter()->MoveTo(data->dpi.dst_ptr, UnScaleByZoom(left_width, data->dpi.zoom), 0);
                        data->dpi.left = split;
                        data->dpi.width = data->dpi.width - left_width;

                        ParentSpriteToSortVector psts;
                        for (ParentSpriteToDraw *psd : data->psts) {
                                psd->SetComparisonDone(false);
                                if (psd->left + psd->width > data->dpi.left - margin) {
                                        psts.push_back(psd);
                                }
                        }
                        data->psts = std::move(psts);

                        ViewportProcessParentSprites(vdd, data_index);
                }
        } else {
                _vp_sprite_sorter(&data->psts);
        }
}

static void ViewportDoDrawPhase2(Viewport *vp, ViewportDrawerDynamic *vdd);
static void ViewportDoDrawPhase3(Viewport *vp);
static void ViewportDoDrawRenderJob(Viewport *vp, ViewportDrawerDynamic *vdd);

/* This is run in the main thread */
void ViewportDoDraw(Viewport *vp, int left, int top, int right, int bottom, uint8_t display_flags)
{
        if (_spare_viewport_drawers.empty()) {
                _vdd.reset(new ViewportDrawerDynamic());
        } else {
                _vdd = std::move(_spare_viewport_drawers.back());
                _spare_viewport_drawers.pop_back();
        }

        _vdd->display_flags = display_flags;
        _vdd->transparency_opt = _transparency_opt;
        _vdd->invisibility_opt = _invisibility_opt;

        _vdd->dpi.zoom = vp->zoom;
        int mask = ScaleByZoom(-1, vp->zoom);

        _vd.combine_sprites = SPRITE_COMBINE_NONE;

        _vdd->dpi.width = (right - left) & mask;
        _vdd->dpi.height = (bottom - top) & mask;
        _vdd->dpi.left = left & mask;
        _vdd->dpi.top = top & mask;
        _vdd->dpi.pitch = _cur_dpi->pitch;
        _vd.last_child = NO_CHILD_STORE;

        _vdd->offset_x = UnScaleByZoomLower(_vdd->dpi.left - (vp->virtual_left & mask), vp->zoom);
        _vdd->offset_y = UnScaleByZoomLower(_vdd->dpi.top - (vp->virtual_top & mask), vp->zoom);
        int x = _vdd->offset_x + vp->left;
        int y = _vdd->offset_y + vp->top;

        _vdd->dpi.dst_ptr = BlitterFactory::GetCurrentBlitter()->MoveTo(_cur_dpi->dst_ptr, x - _cur_dpi->left, y - _cur_dpi->top);

        AutoRestoreBackup dpi_backup(_cur_dpi, &_vdd->dpi);

        if (vp->overlay != nullptr && vp->overlay->GetCargoMask() != 0 && vp->overlay->GetCompanyMask() != 0) {
                vp->overlay->PrepareDraw();

                if (vp->zoom >= ZOOM_LVL_DRAW_MAP && (vp->overlay_pixel_cache.empty() || vp->last_overlay_rebuild_counter != vp->overlay->GetRebuildCounter())) {
                        vp->last_overlay_rebuild_counter = vp->overlay->GetRebuildCounter();

                        vp->overlay_pixel_cache.assign(vp->ScreenArea(), 0xD7);

                        DrawPixelInfo overlay_dpi;
                        overlay_dpi.dst_ptr = vp->overlay_pixel_cache.data();
                        overlay_dpi.height = vp->height;
                        overlay_dpi.width = vp->width;
                        overlay_dpi.pitch = vp->width;
                        overlay_dpi.zoom = ZOOM_LVL_MIN;
                        overlay_dpi.left = UnScaleByZoomLower(vp->virtual_left, vp->zoom);
                        overlay_dpi.top = UnScaleByZoomLower(vp->virtual_top, vp->zoom);

                        const int pitch = vp->width;
                        Blitter_8bppDrawing blitter(&pitch);
                        vp->overlay->Draw(&blitter, &overlay_dpi);
                }
        }

        if (vp->zoom >= ZOOM_LVL_DRAW_MAP) {
                /* Here the rendering is like smallmap. */
                if (BlitterFactory::GetCurrentBlitter()->GetScreenDepth() == 32) {
                        if (_settings_client.gui.show_slopes_on_viewport_map) {
                                ViewportMapDraw<true, true>(vp);
                        } else {
                                ViewportMapDraw<true, false>(vp);
                        }
                } else {
                        _pal2trsp_remap_ptr = IsTransparencySet(TO_TREES) ? GetNonSprite(GB(PALETTE_TO_TRANSPARENT, 0, PALETTE_WIDTH), SpriteType::Recolour) : nullptr;
                        if (_settings_client.gui.show_slopes_on_viewport_map) {
                                ViewportMapDraw<false, true>(vp);
                        } else {
                                ViewportMapDraw<false, false>(vp);
                        }
                }
                ViewportMapDrawVehicles(&_vdd->dpi, vp);
                if (_scrolling_viewport && _settings_client.gui.show_scrolling_viewport_on_map) ViewportMapDrawScrollingViewportBox(vp);
                if (unlikely(_thd.place_mode == (HT_SPECIAL | HT_MAP) && (_thd.drawstyle & HT_DRAG_MASK) == HT_RECT && _thd.select_proc == DDSP_MEASURE)) ViewportMapDrawSelection(vp);
                if (vp->zoom < ZOOM_LVL_OUT_64X) ViewportAddKdtreeSigns(_vdd.get(), &_vdd->dpi, true);

                if (AreAnyPlansVisible()) {
                        if (vp->last_plan_update_number != _plan_update_counter) {
                                vp->last_plan_update_number = _plan_update_counter;

                                vp->plan_pixel_cache.assign(vp->ScreenArea(), 0xD7);

                                DrawPixelInfo plan_dpi;
                                plan_dpi.dst_ptr = vp->plan_pixel_cache.data();
                                plan_dpi.height = vp->height;
                                plan_dpi.width = vp->width;
                                plan_dpi.pitch = vp->width;
                                plan_dpi.zoom = ZOOM_LVL_MIN;
                                plan_dpi.left = UnScaleByZoomLower(vp->virtual_left, vp->zoom);
                                plan_dpi.top = UnScaleByZoomLower(vp->virtual_top, vp->zoom);

                                const int pitch = vp->width;
                                Blitter_8bppDrawing blitter(&pitch);
                                ViewportDrawPlans(vp, &blitter, &plan_dpi);
                        }
                } else {
                        vp->plan_pixel_cache.clear();
                }

                ViewportDoDrawPhase2(vp, _vdd.get());
                ViewportDoDrawPhase3(vp);
        } else {
                /* Classic rendering. */
                ViewportAddLandscape();
                ViewportAddVehicles(&_vdd->dpi, vp->update_vehicles);

                for (const TileSpriteToDraw &ts : _vdd->tile_sprites_to_draw) {
                        PrepareDrawSpriteViewportSpriteStore(_vdd->sprite_data, &_vdd->dpi, ts.image, ts.pal);
                }
                for (const ParentSpriteToDraw &ps : _vdd->parent_sprites_to_draw) {
                        if (ps.image != SPR_EMPTY_BOUNDING_BOX) PrepareDrawSpriteViewportSpriteStore(_vdd->sprite_data, &_vdd->dpi, ps.image, ps.pal);
                }
                for (const ChildScreenSpriteToDraw &cs : _vdd->child_screen_sprites_to_draw) {
                        PrepareDrawSpriteViewportSpriteStore(_vdd->sprite_data, &_vdd->dpi, cs.image, cs.pal);
                }

                _viewport_drawer_jobs++;
                extern bool _draw_widget_outlines;
                if (unlikely(_draw_widget_outlines || HasBit(_viewport_debug_flags, VDF_DISABLE_THREAD))) {
                        ViewportDoDrawRenderJob(vp, _vdd.release());
                } else {
                        _general_worker_pool.EnqueueJob<ViewportDoDrawRenderJob>(vp, _vdd.release());
                }
        }
}

/* This is run in a worker thread */
static void ViewportDoDrawRenderSubJob(Viewport *vp, ViewportDrawerDynamic *vdd, uint data_index) {
        ViewportDrawParentSprites(vdd, &vdd->parent_sprite_sets[data_index].dpi, &vdd->parent_sprite_sets[data_index].psts, &vdd->child_screen_sprites_to_draw);

        if (_draw_dirty_blocks && HasBit(_viewport_debug_flags, VDF_DIRTY_BLOCK_PER_SPLIT)) {
                ViewportDrawDirtyBlocks(&vdd->parent_sprite_sets[data_index].dpi, true);
        }

        if (vdd->draw_jobs_active.fetch_sub(1) != 1) return;

        if (_draw_bounding_boxes) ViewportDrawBoundingBoxes(&vdd->dpi, vdd->parent_sprites_to_draw);

        ViewportDoDrawPhase2(vp, vdd);

        std::unique_lock<std::mutex> lk(_viewport_drawer_return_lock);
        bool notify = _viewport_drawer_returns.empty();
        ViewportDrawerReturn &ret = _viewport_drawer_returns.emplace_back();
        ret.vp = vp;
        ret.vdd.reset(vdd);
        lk.unlock();
        if (notify) _viewport_drawer_empty_cv.notify_one();
}

/* This is run in a worker thread */
static void ViewportDoDrawRenderJob(Viewport *vp, ViewportDrawerDynamic *vdd)
{
        ViewportAddKdtreeSigns(vdd, &vdd->dpi, false);

        DrawTextEffects(vdd, &vdd->dpi, vdd->IsTransparencySet(TO_LOADING));

        if (vdd->tile_sprites_to_draw.size() != 0) {
                ViewportDrawTileSprites(vdd);
        }

        vdd->parent_sprite_sets.resize(1);
        vdd->parent_sprite_sets[0].psts.reserve(vdd->parent_sprites_to_draw.size());
        for (auto &psd : vdd->parent_sprites_to_draw) {
                vdd->parent_sprite_sets[0].psts.push_back(&psd);
        }
        vdd->parent_sprite_sets[0].dpi = vdd->dpi;

        ViewportProcessParentSprites(vdd, 0);

        vdd->draw_jobs_active.store((uint)vdd->parent_sprite_sets.size(), std::memory_order_relaxed);

        for (uint i = 1; i < (uint)vdd->parent_sprite_sets.size(); i++) {
                extern bool _draw_widget_outlines;
                if (unlikely(_draw_widget_outlines || HasBit(_viewport_debug_flags, VDF_DISABLE_THREAD))) {
                        ViewportDoDrawRenderSubJob(vp, vdd, i);
                } else {
                        _general_worker_pool.EnqueueJob<ViewportDoDrawRenderSubJob>(vp, vdd, i);
                }
        }

        ViewportDoDrawRenderSubJob(vp, vdd, 0);
}

void ViewportDoDrawProcessAllPending()
{
        if (_viewport_drawer_jobs == 0) return;

        PerformanceAccumulator framerate(PFE_DRAWWORLD);

        std::unique_lock<std::mutex> lk(_viewport_drawer_return_lock);
        while (true) {
                if (_viewport_drawer_returns.empty()) {
                        _viewport_drawer_empty_cv.wait(lk);
                } else {
                        Viewport *vp = _viewport_drawer_returns.back().vp;
                        _vdd = std::move(_viewport_drawer_returns.back().vdd);
                        _viewport_drawer_returns.pop_back();
                        lk.unlock();

                        {
                                AutoRestoreBackup dpi_backup(_cur_dpi, AutoRestoreBackupNoNewValueTag{});
                                ViewportDoDrawPhase3(vp);
                        }

                        _viewport_drawer_jobs--;
                        if (_viewport_drawer_jobs == 0) return;
                        lk.lock();
                }
        }
}

/* This may be run either in a worker thread, or in the main thead */
static void ViewportDoDrawPhase2(Viewport *vp, ViewportDrawerDynamic *vdd)
{
        if (_draw_dirty_blocks && !(HasBit(_viewport_debug_flags, VDF_DIRTY_BLOCK_PER_SPLIT) && vp->zoom < ZOOM_LVL_DRAW_MAP)) {
                ViewportDrawDirtyBlocks(&vdd->dpi, HasBit(_viewport_debug_flags, VDF_DIRTY_BLOCK_PER_DRAW));
        }

        if (vp->overlay != nullptr && vp->overlay->GetCargoMask() != 0 && vp->overlay->GetCompanyMask() != 0) {
                if (vp->zoom < ZOOM_LVL_DRAW_MAP) {
                        /* translate to window coordinates */
                        DrawPixelInfo dp = vdd->dpi;
                        ZoomLevel zoom = vdd->dpi.zoom;
                        dp.zoom = ZOOM_LVL_MIN;
                        dp.width = UnScaleByZoom(dp.width, zoom);
                        dp.height = UnScaleByZoom(dp.height, zoom);
                        dp.left = vdd->offset_x + vp->left;
                        dp.top = vdd->offset_y + vp->top;
                        vp->overlay->Draw(BlitterFactory::GetCurrentBlitter(), &dp);
                } else {
                        const int pixel_cache_start = vdd->offset_x + (vdd->offset_y * vp->width);
                        BlitterFactory::GetCurrentBlitter()->SetRectNoD7(vdd->dpi.dst_ptr, 0, 0, vp->overlay_pixel_cache.data() + pixel_cache_start,
                                        UnScaleByZoom(vdd->dpi.height, vdd->dpi.zoom), UnScaleByZoom(vdd->dpi.width, vdd->dpi.zoom), vp->width);
                }
        }

        if (_settings_client.gui.show_vehicle_route_mode != 0 && _settings_client.gui.show_vehicle_route) ViewportDrawVehicleRoutePath(vp, vdd);
}

/* This is run in the main thread */
static void ViewportDoDrawPhase3(Viewport *vp)
{
        DrawPixelInfo dp = _vdd->dpi;
        ZoomLevel zoom = _vdd->dpi.zoom;
        dp.zoom = ZOOM_LVL_MIN;
        dp.width = UnScaleByZoom(dp.width, zoom);
        dp.height = UnScaleByZoom(dp.height, zoom);
        _cur_dpi = &dp;
        if (_vdd->string_sprites_to_draw.size() != 0) {
                /* translate to world coordinates */
                dp.left = UnScaleByZoom(_vdd->dpi.left, zoom);
                dp.top = UnScaleByZoom(_vdd->dpi.top, zoom);
                ViewportDrawStrings(_vdd.get(), zoom, &_vdd->string_sprites_to_draw);
        }
        if (_settings_client.gui.show_vehicle_route_mode != 0 && _settings_client.gui.show_vehicle_route_steps && ViewportDrawHasVehicleRouteSteps()) {
                dp.left = _vdd->offset_x + vp->left;
                dp.top = _vdd->offset_y + vp->top;
                ViewportDrawVehicleRouteSteps(vp);
        }
        _cur_dpi = nullptr;

        if (vp->zoom < ZOOM_LVL_DRAW_MAP && AreAnyPlansVisible()) {
                DrawPixelInfo plan_dpi = _vdd->MakeDPIForText();
                ViewportDrawPlans(vp, BlitterFactory::GetCurrentBlitter(), &plan_dpi);
        } else if (vp->zoom >= ZOOM_LVL_DRAW_MAP && !vp->plan_pixel_cache.empty()) {
                const int pixel_cache_start = _vdd->offset_x + (_vdd->offset_y * vp->width);
                BlitterFactory::GetCurrentBlitter()->SetRectNoD7(_vdd->dpi.dst_ptr, 0, 0, vp->plan_pixel_cache.data() + pixel_cache_start,
                                dp.height, dp.width, vp->width);
        }

        if (_vdd->display_flags & (ND_SHADE_GREY | ND_SHADE_DIMMED)) {
                DrawPixelInfo dp = _vdd->MakeDPIForText();
                GfxFillRect(BlitterFactory::GetCurrentBlitter(), &dp, dp.left, dp.top, dp.left + dp.width, dp.top + dp.height,
                                (_vdd->display_flags & ND_SHADE_DIMMED) ? PALETTE_TO_TRANSPARENT : PALETTE_NEWSPAPER, FILLRECT_RECOLOUR);
        }

        _vdd->bridge_to_map_x.clear();
        _vdd->bridge_to_map_y.clear();
        _vdd->string_sprites_to_draw.clear();
        _vdd->tile_sprites_to_draw.clear();
        _vdd->parent_sprites_to_draw.clear();
        _vdd->parent_sprite_sets.clear();
        _vdd->parent_sprite_subsprites.Clear();
        _vdd->child_screen_sprites_to_draw.clear();
        _vdd->sprite_data.Clear();

        _spare_viewport_drawers.emplace_back(std::move(_vdd));
}

/**
 * Make sure we don't draw a too big area at a time.
 * If we do, the sprite sorter will run into major performance problems and the sprite memory may overflow.
 */
void ViewportDrawChk(Viewport *vp, int left, int top, int right, int bottom, uint8_t display_flags)
{
        if ((vp->zoom < ZOOM_LVL_DRAW_MAP) && ((int64_t)ScaleByZoom(bottom - top, vp->zoom) * (int64_t)ScaleByZoom(right - left, vp->zoom) > (int64_t)(1000000 * ZOOM_BASE * ZOOM_BASE))) {
                if ((bottom - top) > (right - left)) {
                        int t = (top + bottom) >> 1;
                        ViewportDrawChk(vp, left, top, right, t, display_flags);
                        ViewportDrawChk(vp, left, t, right, bottom, display_flags);
                } else {
                        int t = (left + right) >> 1;
                        ViewportDrawChk(vp, left, top, t, bottom, display_flags);
                        ViewportDrawChk(vp, t, top, right, bottom, display_flags);
                }
        } else {
                ViewportDoDraw(vp,
                        ScaleByZoom(left - vp->left, vp->zoom) + vp->virtual_left,
                        ScaleByZoom(top - vp->top, vp->zoom) + vp->virtual_top,
                        ScaleByZoom(right - vp->left, vp->zoom) + vp->virtual_left,
                        ScaleByZoom(bottom - vp->top, vp->zoom) + vp->virtual_top,
                        display_flags
                );
        }
}

static inline void ViewportDraw(Viewport *vp, int left, int top, int right, int bottom, uint8_t display_flags)
{
        if (right <= vp->left || bottom <= vp->top) return;

        if (left >= vp->left + vp->width) return;

        if (left < vp->left) left = vp->left;
        if (right > vp->left + vp->width) right = vp->left + vp->width;

        if (top >= vp->top + vp->height) return;

        if (top < vp->top) top = vp->top;
        if (bottom > vp->top + vp->height) bottom = vp->top + vp->height;

        vp->is_drawn = true;

        ViewportDrawChk(vp, left, top, right, bottom, display_flags);
}

/**
 * Draw the viewport of this window.
 */
void Window::DrawViewport(uint8_t display_flags) const
{
        PerformanceAccumulator framerate(PFE_DRAWWORLD);

        DrawPixelInfo *dpi = _cur_dpi;

        dpi->left += this->left;
        dpi->top += this->top;

        ViewportDraw(this->viewport, dpi->left, dpi->top, dpi->left + dpi->width, dpi->top + dpi->height, display_flags);

        dpi->left -= this->left;
        dpi->top -= this->top;
}

/**
 * Ensure that a given viewport has a valid scroll position.
 *
 * There must be a visible piece of the map in the center of the viewport.
 * If there isn't, the viewport will be scrolled to nearest such location.
 *
 * @param vp The viewport.
 * @param[in,out] scroll_x Viewport X scroll.
 * @param[in,out] scroll_y Viewport Y scroll.
 */
static inline void ClampViewportToMap(const Viewport *vp, int *scroll_x, int *scroll_y)
{
        /* Centre of the viewport is hot spot. */
        Point pt = {
                *scroll_x + vp->virtual_width / 2,
                *scroll_y + vp->virtual_height / 2
        };

        /* Find nearest tile that is within borders of the map. */
        bool clamped;
        pt = InverseRemapCoords2(pt.x, pt.y, true, &clamped);

        if (clamped) {
                /* Convert back to viewport coordinates and remove centering. */
                pt = RemapCoords2(pt.x, pt.y);
                *scroll_x = pt.x - vp->virtual_width / 2;
                *scroll_y = pt.y - vp->virtual_height / 2;
        }
}


/**
 * Clamp the smooth scroll to a maxmimum speed and distance based on time elapsed.
 *
 * Every 30ms, we move 1/4th of the distance, to give a smooth movement experience.
 * But we never go over the max_scroll speed.
 *
 * @param delta_ms Time elapsed since last update.
 * @param delta_hi The distance to move in highest dimension (can't be zero).
 * @param delta_lo The distance to move in lowest dimension.
 * @param[out] delta_hi_clamped The clamped distance to move in highest dimension.
 * @param[out] delta_lo_clamped The clamped distance to move in lowest dimension.
 */
static void ClampSmoothScroll(uint32_t delta_ms, int64_t delta_hi, int64_t delta_lo, int &delta_hi_clamped, int &delta_lo_clamped)
{
        /** A tile is 64 pixels in width at 1x zoom; viewport coordinates are in 4x zoom. */
        constexpr int PIXELS_PER_TILE = TILE_PIXELS * 2 * ZOOM_BASE;

        assert(delta_hi != 0);

        /* Move at most 75% of the distance every 30ms, for a smooth experience */
        int64_t delta_left = delta_hi * std::pow(0.75, delta_ms / 30.0);
        /* Move never more than 16 tiles per 30ms. */
        int max_scroll = ScaleByMapSize1D(16 * PIXELS_PER_TILE * delta_ms / 30);

        /* We never go over the max_scroll speed. */
        delta_hi_clamped = Clamp(delta_hi - delta_left, -max_scroll, max_scroll);
        /* The lower delta is in ratio of the higher delta, so we keep going straight at the destination. */
        delta_lo_clamped = delta_lo * delta_hi_clamped / delta_hi;

        /* Ensure we always move (delta_hi can't be zero). */
        if (delta_hi_clamped == 0) {
                delta_hi_clamped = delta_hi > 0 ? 1 : -1;
        }
}

/**
 * Update the next viewport position being displayed.
 * @param w %Window owning the viewport.
 */
void UpdateNextViewportPosition(Window *w, uint32_t delta_ms)
{
        const Viewport *vp = w->viewport;

        if (w->viewport->follow_vehicle != INVALID_VEHICLE) {
                const Vehicle *veh = Vehicle::Get(w->viewport->follow_vehicle);
                Point pt = MapXYZToViewport(vp, veh->x_pos, veh->y_pos, veh->z_pos);

                w->viewport->next_scrollpos_x = pt.x;
                w->viewport->next_scrollpos_y = pt.y;
                w->viewport->force_update_overlay_pending = false;
        } else {
                /* Ensure the destination location is within the map */
                ClampViewportToMap(vp, &w->viewport->dest_scrollpos_x, &w->viewport->dest_scrollpos_y);

                int delta_x = w->viewport->dest_scrollpos_x - w->viewport->scrollpos_x;
                int delta_y = w->viewport->dest_scrollpos_y - w->viewport->scrollpos_y;

                int current_x = w->viewport->scrollpos_x;
                int current_y = w->viewport->scrollpos_y;

                w->viewport->next_scrollpos_x = w->viewport->scrollpos_x;
                w->viewport->next_scrollpos_y = w->viewport->scrollpos_y;

                bool update_overlay = false;
                if (delta_x != 0 || delta_y != 0) {
                        if (_settings_client.gui.smooth_scroll) {
                                int delta_x_clamped;
                                int delta_y_clamped;

                                if (abs(delta_x) > abs(delta_y)) {
                                        ClampSmoothScroll(delta_ms, delta_x, delta_y, delta_x_clamped, delta_y_clamped);
                                } else {
                                        ClampSmoothScroll(delta_ms, delta_y, delta_x, delta_y_clamped, delta_x_clamped);
                                }

                                w->viewport->next_scrollpos_x += delta_x_clamped;
                                w->viewport->next_scrollpos_y += delta_y_clamped;
                        } else {
                                w->viewport->next_scrollpos_x = w->viewport->dest_scrollpos_x;
                                w->viewport->next_scrollpos_y = w->viewport->dest_scrollpos_y;
                        }
                        update_overlay = (w->viewport->next_scrollpos_x == w->viewport->dest_scrollpos_x &&
                                                                w->viewport->next_scrollpos_y == w->viewport->dest_scrollpos_y);
                }
                w->viewport->force_update_overlay_pending = update_overlay;

                ClampViewportToMap(vp, &w->viewport->next_scrollpos_x, &w->viewport->next_scrollpos_y);

                /* When moving small amounts around the border we can get stuck, and
                 * not actually move. In those cases, teleport to the destination. */
                if ((delta_x != 0 || delta_y != 0) && current_x == w->viewport->next_scrollpos_x && current_y == w->viewport->next_scrollpos_y) {
                        w->viewport->next_scrollpos_x = w->viewport->dest_scrollpos_x;
                        w->viewport->next_scrollpos_y = w->viewport->dest_scrollpos_y;
                }

                if (_scrolling_viewport == w) UpdateActiveScrollingViewport(w);
        }
}

/**
 * Apply the next viewport position being displayed.
 * @param w %Window owning the viewport.
 */
void ApplyNextViewportPosition(Window *w)
{
        w->viewport->scrollpos_x = w->viewport->next_scrollpos_x;
        w->viewport->scrollpos_y = w->viewport->next_scrollpos_y;
        SetViewportPosition(w, w->viewport->next_scrollpos_x, w->viewport->next_scrollpos_y, w->viewport->force_update_overlay_pending);
}

void UpdateViewportSizeZoom(Viewport *vp)
{
        vp->dirty_blocks_per_column = CeilDiv(vp->height, vp->GetDirtyBlockHeight());
        vp->dirty_blocks_per_row = CeilDiv(vp->width, vp->GetDirtyBlockWidth());
        vp->dirty_blocks_column_pitch = CeilDivT(vp->dirty_blocks_per_column, VP_BLOCK_BITS);
        vp->dirty_blocks.assign(vp->dirty_blocks_column_pitch * vp->dirty_blocks_per_row, 0);
        UpdateViewportDirtyBlockLeftMargin(vp);
        if (vp->zoom >= ZOOM_LVL_DRAW_MAP) {
                memset(vp->map_draw_vehicles_cache.done_hash_bits, 0, sizeof(vp->map_draw_vehicles_cache.done_hash_bits));
                vp->map_draw_vehicles_cache.vehicle_pixels.assign(CeilDivT<size_t>(vp->ScreenArea(), VP_BLOCK_BITS), 0);

                if (BlitterFactory::GetCurrentBlitter()->GetScreenDepth() == 32) {
                        vp->land_pixel_cache.assign(vp->ScreenArea() * 4, 0xD7);
                } else {
                        vp->land_pixel_cache.assign(vp->ScreenArea(), 0xD7);
                }
                vp->overlay_pixel_cache.clear();
                vp->plan_pixel_cache.clear();
        } else {
                vp->map_draw_vehicles_cache.vehicle_pixels.clear();
                vp->land_pixel_cache.clear();
                vp->land_pixel_cache.shrink_to_fit();
                vp->overlay_pixel_cache.clear();
                vp->overlay_pixel_cache.shrink_to_fit();
                vp->plan_pixel_cache.clear();
                vp->plan_pixel_cache.shrink_to_fit();
        }
        vp->last_plan_update_number = 0;
        vp->update_vehicles = true;
        FillViewportCoverageRect();
}

void UpdateActiveScrollingViewport(Window *w)
{
        if (w != nullptr && (!_settings_client.gui.show_scrolling_viewport_on_map || w->viewport->zoom >= ZOOM_LVL_DRAW_MAP)) w = nullptr;

        const bool bound_valid = (_scrolling_viewport_bound.left != _scrolling_viewport_bound.right);

        if (w == nullptr && !bound_valid) return;

        const int gap = ScaleByZoom(1, ZOOM_LVL_MAX);

        auto get_bounds = [](const ViewportData *vp) -> Rect {
                return { vp->next_scrollpos_x, vp->next_scrollpos_y, vp->next_scrollpos_x + vp->virtual_width + 1, vp->next_scrollpos_y + vp->virtual_height + 1 };
        };

        if (w != nullptr  && !bound_valid) {
                const Rect bounds = get_bounds(w->viewport);
                MarkAllViewportMapsDirty(bounds.left, bounds.top, bounds.right, bounds.bottom);
                _scrolling_viewport_bound = bounds;
        } else if (w == nullptr && bound_valid) {
                const Rect &bounds = _scrolling_viewport_bound;
                MarkAllViewportMapsDirty(bounds.left, bounds.top, bounds.right, bounds.bottom);
                _scrolling_viewport_bound = { 0, 0, 0, 0 };
        } else {
                /* Calculate symmetric difference of two rectangles */
                const Rect a = get_bounds(w->viewport);
                const Rect &b = _scrolling_viewport_bound;
                if (a.left != b.left) MarkAllViewportMapsDirty(std::min(a.left, b.left) - gap, std::min(a.top, b.top) - gap, std::max(a.left, b.left) + gap, std::max(a.bottom, b.bottom) + gap);
                if (a.top != b.top) MarkAllViewportMapsDirty(std::min(a.left, b.left) - gap, std::min(a.top, b.top) - gap, std::max(a.right, b.right) + gap, std::max(a.top, b.top) + gap);
                if (a.right != b.right) MarkAllViewportMapsDirty(std::min(a.right, b.right) - gap, std::min(a.top, b.top) - gap, std::max(a.right, b.right) + gap, std::max(a.bottom, b.bottom) + gap);
                if (a.bottom != b.bottom) MarkAllViewportMapsDirty(std::min(a.left, b.left) - gap, std::min(a.bottom, b.bottom) - gap, std::max(a.right, b.right) + gap, std::max(a.bottom, b.bottom) + gap);
                _scrolling_viewport_bound = a;
        }
}

/**
 * Marks a viewport as dirty for repaint if it displays (a part of) the area the needs to be repainted.
 * @param vp     The viewport to mark as dirty
 * @param left   Left edge of area to repaint
 * @param top    Top edge of area to repaint
 * @param right  Right edge of area to repaint
 * @param bottom Bottom edge of area to repaint
 * @ingroup dirty
 */
void MarkViewportDirty(Viewport * const vp, int left, int top, int right, int bottom, ViewportMarkDirtyFlags flags)
{
        /* Rounding wrt. zoom-out level */
        right  += (1 << vp->zoom) - 1;
        bottom += (1 << vp->zoom) - 1;

        right -= vp->virtual_left;
        if (right <= 0) return;
        right = std::min(right, vp->virtual_width);

        bottom -= vp->virtual_top;
        if (bottom <= 0) return;
        bottom = std::min(bottom, vp->virtual_height);

        left = std::max(0, left - vp->virtual_left);

        if (left >= vp->virtual_width) return;

        top = std::max(0, top - vp->virtual_top);

        if (top >= vp->virtual_height) return;

        uint x = std::max<int>(0, UnScaleByZoomLower(left, vp->zoom) - vp->dirty_block_left_margin) >> vp->GetDirtyBlockWidthShift();
        uint y = UnScaleByZoomLower(top, vp->zoom) >> vp->GetDirtyBlockHeightShift();
        uint w = (std::max<int>(0, UnScaleByZoom(right, vp->zoom) - 1 - vp->dirty_block_left_margin) >> vp->GetDirtyBlockWidthShift()) + 1 - x;
        uint h = ((UnScaleByZoom(bottom, vp->zoom) - 1) >> vp->GetDirtyBlockHeightShift()) + 1 - y;

        if (w == 0 || h == 0) return;

        uint col_start = (x * vp->dirty_blocks_column_pitch) + (y / VP_BLOCK_BITS);
        uint y_end = y + h;
        if ((y_end - 1) / VP_BLOCK_BITS == y / VP_BLOCK_BITS) {
                /* Only dirtying a single block row */
                const ViewPortBlockT mask = GetBitMaskSC<ViewPortBlockT>(y % VP_BLOCK_BITS, h);
                for (uint i = 0; i < w; i++, col_start += vp->dirty_blocks_column_pitch) {
                        vp->dirty_blocks[col_start] |= mask;
                }
        } else {
                /* Dirtying multiple block rows */
                const uint h_non_first = y_end - Align(y + 1, VP_BLOCK_BITS); // Height, excluding the first block
                for (uint i = 0; i < w; i++, col_start += vp->dirty_blocks_column_pitch) {
                        uint pos = col_start;

                        /* Set only high bits for first block in column */
                        vp->dirty_blocks[pos] |= (~static_cast<ViewPortBlockT>(0)) << (y % VP_BLOCK_BITS);

                        uint left = h_non_first;
                        while (left > 0) {
                                pos++;
                                if (left < VP_BLOCK_BITS) {
                                        /* Set only low bits for last block in column */
                                        vp->dirty_blocks[pos] |= GetBitMaskSC<ViewPortBlockT>(0, left);
                                        break;
                                } else {
                                        /* Set all bits for middle blocks in column */
                                        vp->dirty_blocks[pos] = ~static_cast<ViewPortBlockT>(0);
                                }
                                left -= VP_BLOCK_BITS;
                        }
                }
        }
        vp->is_dirty = true;

        if (unlikely(vp->zoom >= ZOOM_LVL_DRAW_MAP && !(flags & VMDF_NOT_LANDSCAPE))) {
                uint l = UnScaleByZoomLower(left, vp->zoom);
                uint t = UnScaleByZoomLower(top, vp->zoom);
                uint w = UnScaleByZoom(right, vp->zoom) - l;
                uint h = UnScaleByZoom(bottom, vp->zoom) - t;
                uint bitdepth = BlitterFactory::GetCurrentBlitter()->GetScreenDepth() / 8;
                uint8_t *land_cache = vp->land_pixel_cache.data() + ((l + (t * vp->width)) * bitdepth);
                while (--h) {
                        memset(land_cache, 0xD7, (size_t)w * bitdepth);
                        land_cache += vp->width * bitdepth;
                }
        }
}

/**
 * Mark all viewports that display an area as dirty (in need of repaint).
 * @param left   Left   edge of area to repaint. (viewport coordinates, that is wrt. #ZOOM_LVL_MIN)
 * @param top    Top    edge of area to repaint. (viewport coordinates, that is wrt. #ZOOM_LVL_MIN)
 * @param right  Right  edge of area to repaint. (viewport coordinates, that is wrt. #ZOOM_LVL_MIN)
 * @param bottom Bottom edge of area to repaint. (viewport coordinates, that is wrt. #ZOOM_LVL_MIN)
 * @param flags  To tell if an update is relevant or not (for example, animations in map mode are not)
 * @ingroup dirty
 */
void MarkAllViewportsDirty(int left, int top, int right, int bottom, ViewportMarkDirtyFlags flags)
{
        for (uint i = 0; i < _viewport_window_cache.size(); i++) {
                if (flags & VMDF_NOT_MAP_MODE && _viewport_window_cache[i]->zoom >= ZOOM_LVL_DRAW_MAP) continue;
                if (flags & VMDF_NOT_MAP_MODE_NON_VEG && _viewport_window_cache[i]->zoom >= ZOOM_LVL_DRAW_MAP && _viewport_window_cache[i]->map_type != VPMT_VEGETATION) continue;
                const Rect &r = _viewport_coverage_rects[i];
                if (left >= r.right ||
                                right <= r.left ||
                                top >= r.bottom ||
                                bottom <= r.top) {
                        continue;
                }
                MarkViewportDirty(_viewport_window_cache[i], left, top, right, bottom, flags);
        }
}

static void MarkRouteStepDirty(RouteStepsMap::const_iterator cit)
{
        const uint size = cit->second.size() > max_rank_order_type_count ? 1 : (uint)cit->second.size();
        MarkRouteStepDirty(cit->first, size);
}

static void MarkRouteStepDirty(const TileIndex tile, uint order_nr)
{
        dbg_assert(tile != INVALID_TILE);
        const Point pt = RemapCoords2(TileX(tile) * TILE_SIZE + TILE_SIZE / 2, TileY(tile) * TILE_SIZE + TILE_SIZE / 2);
        const int char_height = GetCharacterHeight(FS_SMALL) + 1;
        const int max_width = _vp_route_step_base_width + _vp_route_step_string_width[3];
        const int half_width_base = (max_width / 2) + 1;
        for (Viewport * const vp : _viewport_window_cache) {
                const int half_width = ScaleByZoom(half_width_base, vp->zoom);
                const int height = ScaleByZoom(_vp_route_step_height_top + char_height * order_nr + _vp_route_step_height_bottom, vp->zoom);
                MarkViewportDirty(vp, pt.x - half_width, pt.y - height, pt.x + half_width, pt.y, VMDF_NOT_LANDSCAPE);
        }
}

void ViewportRouteOverlay::PrepareRouteStepsAndMarkDirtyIfChanged(const Vehicle *veh)
{
        this->PrepareRouteSteps(veh);
        if (this->route_steps != this->route_steps_last_mark_dirty) {
                for (RouteStepsMap::const_iterator cit = this->route_steps_last_mark_dirty.begin(); cit != this->route_steps_last_mark_dirty.end(); cit++) {
                        MarkRouteStepDirty(cit);
                }
                for (RouteStepsMap::const_iterator cit = this->route_steps.begin(); cit != this->route_steps.end(); ++cit) {
                        MarkRouteStepDirty(cit);
                }
                this->route_steps_last_mark_dirty = this->route_steps;
        }
}

/**
 * Mark all viewports in map mode that display an area as dirty (in need of repaint).
 * @param left   Left edge of area to repaint
 * @param top    Top edge of area to repaint
 * @param right  Right edge of area to repaint
 * @param bottom Bottom edge of area to repaint
 * @ingroup dirty
 */
void MarkAllViewportMapsDirty(int left, int top, int right, int bottom)
{
        for (Viewport *vp : _viewport_window_cache) {
                if (vp->zoom >= ZOOM_LVL_DRAW_MAP) {
                        MarkViewportDirty(vp, left, top, right, bottom, VMDF_NOT_LANDSCAPE);
                }
        }
}

void MarkAllViewportMapLandscapesDirty()
{
        for (Window *w : Window::Iterate()) {
                Viewport *vp = w->viewport;
                if (vp != nullptr && vp->zoom >= ZOOM_LVL_DRAW_MAP) {
                        ClearViewportLandPixelCache(vp);
                        w->SetDirty();
                }
        }
}

void MarkWholeNonMapViewportsDirty()
{
        for (Window *w : Window::Iterate()) {
                Viewport *vp = w->viewport;
                if (vp != nullptr && vp->zoom < ZOOM_LVL_DRAW_MAP) {
                        w->SetDirty();
                }
        }
}

/**
 * Mark all viewport overlays for a specific station dirty (in need of repaint).
 * @param st     Station
 * @ingroup dirty
 */
void MarkAllViewportOverlayStationLinksDirty(const Station *st)
{
        for (Viewport *vp : _viewport_window_cache) {
                if (vp->overlay != nullptr) {
                        vp->overlay->MarkStationViewportLinksDirty(st);
                }
        }
}

void ConstrainAllViewportsZoom()
{
        for (Window *w : Window::Iterate()) {
                if (w->viewport == nullptr) continue;

                ZoomLevel zoom = static_cast<ZoomLevel>(Clamp(w->viewport->zoom, _settings_client.gui.zoom_min, _settings_client.gui.zoom_max));
                if (zoom != w->viewport->zoom) {
                        while (w->viewport->zoom < zoom) DoZoomInOutWindow(ZOOM_OUT, w);
                        while (w->viewport->zoom > zoom) DoZoomInOutWindow(ZOOM_IN, w);
                }
        }
}

/**
 * Mark a tile given by its index dirty for repaint.
 * @param tile The tile to mark dirty.
 * @param flags To tell if an update is relevant or not (for example, animations in map mode are not).
 * @param bridge_level_offset Height of bridge on tile to also mark dirty. (Height level relative to north corner.)
 * @param tile_height_override Height of the tile (#TileHeight).
 * @ingroup dirty
 */
void MarkTileDirtyByTile(TileIndex tile, ViewportMarkDirtyFlags flags, int bridge_level_offset, int tile_height_override)
{
        Point pt = RemapCoords(TileX(tile) * TILE_SIZE, TileY(tile) * TILE_SIZE, tile_height_override * TILE_HEIGHT);
        MarkAllViewportsDirty(
                        pt.x - 31  * ZOOM_BASE,
                        pt.y - 122 * ZOOM_BASE - ZOOM_BASE * TILE_HEIGHT * bridge_level_offset,
                        pt.x - 31  * ZOOM_BASE + 67  * ZOOM_BASE,
                        pt.y - 122 * ZOOM_BASE + 154 * ZOOM_BASE,
                        flags
        );
}

void MarkTileGroundDirtyByTile(TileIndex tile, ViewportMarkDirtyFlags flags)
{
        int x = TileX(tile) * TILE_SIZE;
        int y = TileY(tile) * TILE_SIZE;
        Point top = RemapCoords(x, y, GetTileMaxPixelZ(tile));
        Point bot = RemapCoords(x + TILE_SIZE, y + TILE_SIZE, GetTilePixelZ(tile));
        MarkAllViewportsDirty(top.x - TILE_PIXELS * ZOOM_BASE, top.y - TILE_HEIGHT * ZOOM_BASE, top.x + TILE_PIXELS * ZOOM_BASE, bot.y, flags);
}

void MarkViewportLineDirty(Viewport * const vp, const Point from_pt, const Point to_pt, const int block_radius, ViewportMarkDirtyFlags flags)
{
        int x1 = from_pt.x / block_radius;
        int y1 = from_pt.y / block_radius;
        const int x2 = to_pt.x / block_radius;
        const int y2 = to_pt.y / block_radius;

        /* http://en.wikipedia.org/wiki/Bresenham%27s_line_algorithm#Simplification */
        const int dx = abs(x2 - x1);
        const int dy = abs(y2 - y1);
        const int sx = (x1 < x2) ? 1 : -1;
        const int sy = (y1 < y2) ? 1 : -1;
        int err = dx - dy;
        for (;;) {
                MarkViewportDirty(
                                vp,
                                (x1 - 2) * block_radius,
                                (y1 - 2) * block_radius,
                                (x1 + 2) * block_radius,
                                (y1 + 2) * block_radius,
                                flags
                );
                if (x1 == x2 && y1 == y2) break;
                const int e2 = 2 * err;
                if (e2 > -dy) {
                        err -= dy;
                        x1 += sx;
                }
                if (e2 < dx) {
                        err += dx;
                        y1 += sy;
                }
        }
}

void MarkTileLineDirty(const TileIndex from_tile, const TileIndex to_tile, ViewportMarkDirtyFlags flags)
{
        dbg_assert(from_tile != INVALID_TILE);
        dbg_assert(to_tile != INVALID_TILE);

        const Point from_pt = RemapCoords2(TileX(from_tile) * TILE_SIZE + TILE_SIZE / 2, TileY(from_tile) * TILE_SIZE + TILE_SIZE / 2);
        const Point to_pt = RemapCoords2(TileX(to_tile) * TILE_SIZE + TILE_SIZE / 2, TileY(to_tile) * TILE_SIZE + TILE_SIZE / 2);

        for (Viewport * const vp : _viewport_window_cache) {
                if (flags & VMDF_NOT_MAP_MODE && vp->zoom >= ZOOM_LVL_DRAW_MAP) continue;

                const int block_shift = 2 + vp->zoom;

                int x1 = from_pt.x >> block_shift;
                int y1 = from_pt.y >> block_shift;
                const int x2 = to_pt.x >> block_shift;
                const int y2 = to_pt.y >> block_shift;

                /* http://en.wikipedia.org/wiki/Bresenham%27s_line_algorithm#Simplification */
                const int dx = abs(x2 - x1);
                const int dy = abs(y2 - y1);
                const int sx = (x1 < x2) ? 1 : -1;
                const int sy = (y1 < y2) ? 1 : -1;
                int err = dx - dy;
                for (;;) {
                        MarkViewportDirty(
                                        vp,
                                        (x1 - 1) << block_shift,
                                        (y1 - 1) << block_shift,
                                        (x1 + 2) << block_shift,
                                        (y1 + 2) << block_shift,
                                        flags
                        );
                        if (x1 == x2 && y1 == y2) break;
                        const int e2 = 2 * err;
                        if (e2 > -dy) {
                                err -= dy;
                                x1 += sx;
                        }
                        if (e2 < dx) {
                                err += dx;
                                y1 += sy;
                        }
                }
        }
}

static void MarkRoutePathsDirty(const std::vector<DrawnPathRouteTileLine> &lines)
{
        for (const DrawnPathRouteTileLine &it : lines) {
                MarkTileLineDirty(it.from_tile, it.to_tile, VMDF_NOT_LANDSCAPE);
        }
}

void ViewportRouteOverlay::PrepareRoutePathsAndMarkDirtyIfChanged(const Vehicle *veh)
{
        this->PrepareRoutePaths(veh);
        if (this->route_paths_last_mark_dirty != this->route_paths) {
                MarkRoutePathsDirty(this->route_paths_last_mark_dirty);
                MarkRoutePathsDirty(this->route_paths);
                this->route_paths_last_mark_dirty = this->route_paths;
        }
}

void ViewportRouteOverlay::PrepareRouteAndMarkDirtyIfChanged(const Vehicle *veh)
{
        this->PrepareRoutePathsAndMarkDirtyIfChanged(veh);
        this->PrepareRouteStepsAndMarkDirtyIfChanged(veh);
}

void HandleViewportRoutePathFocusChange(const Window *old, const Window *focused)
{
        const Vehicle *old_v = (old != nullptr) ? GetVehicleFromWindow(old) : nullptr;
        const Vehicle *new_v = (focused != nullptr) ? GetVehicleFromWindow(focused) : nullptr;
        if (old_v != new_v) {
                _vp_focused_window_route_overlay.PrepareRouteAndMarkDirtyIfChanged(new_v);
        }
}

void AddFixedViewportRoutePath(VehicleID veh)
{
        FixedVehicleViewportRouteOverlay &overlay = _vp_fixed_route_overlays.emplace_back();
        overlay.veh = veh;
}

void RemoveFixedViewportRoutePath(VehicleID veh)
{
        container_unordered_remove_if(_vp_fixed_route_overlays, [&](FixedVehicleViewportRouteOverlay &it) -> bool {
                if (it.veh == veh) {
                        it.PrepareRouteAndMarkDirtyIfChanged(nullptr);
                        return true;
                }
                return false;
        });
}

void ChangeFixedViewportRoutePath(VehicleID from, VehicleID to)
{
        for (auto &it : _vp_fixed_route_overlays) {
                if (it.veh == from) it.veh = to;
        }
}

/**
 * Marks the selected tiles as dirty.
 *
 * This function marks the selected tiles as dirty for repaint
 *
 * @ingroup dirty
 */
static void SetSelectionTilesDirty()
{
        int x_size = _thd.size.x;
        int y_size = _thd.size.y;

        if (!_thd.diagonal) { // Selecting in a straight rectangle (or a single square)
                int x_start = _thd.pos.x;
                int y_start = _thd.pos.y;

                if (_thd.outersize.x != 0 || _thd.outersize.y != 0) {
                        x_size  += _thd.outersize.x;
                        x_start += _thd.offs.x;
                        y_size  += _thd.outersize.y;
                        y_start += _thd.offs.y;
                }

                x_size -= TILE_SIZE;
                y_size -= TILE_SIZE;

                dbg_assert(x_size >= 0);
                dbg_assert(y_size >= 0);

                int x_end = Clamp(x_start + x_size, 0, MapSizeX() * TILE_SIZE - TILE_SIZE);
                int y_end = Clamp(y_start + y_size, 0, MapSizeY() * TILE_SIZE - TILE_SIZE);

                x_start = Clamp(x_start, 0, MapSizeX() * TILE_SIZE - TILE_SIZE);
                y_start = Clamp(y_start, 0, MapSizeY() * TILE_SIZE - TILE_SIZE);

                /* make sure everything is multiple of TILE_SIZE */
                dbg_assert((x_end | y_end | x_start | y_start) % TILE_SIZE == 0);

                /* How it works:
                 * Suppose we have to mark dirty rectangle of 3x4 tiles:
                 *   x
                 *  xxx
                 * xxxxx
                 *  xxxxx
                 *   xxx
                 *    x
                 * This algorithm marks dirty columns of tiles, so it is done in 3+4-1 steps:
                 * 1)  x     2)  x
                 *    xxx       Oxx
                 *   Oxxxx     xOxxx
                 *    xxxxx     Oxxxx
                 *     xxx       xxx
                 *      x         x
                 * And so forth...
                 */

                int top_x = x_end; // coordinates of top dirty tile
                int top_y = y_start;
                int bot_x = top_x; // coordinates of bottom dirty tile
                int bot_y = top_y;

                const bool conservative_mode = (_thd.place_mode & HT_MAP) && !_viewport_vehicle_map_redraw_rects.empty();

                do {
                        /* topmost dirty point */
                        TileIndex top_tile = TileVirtXY(top_x, top_y);
                        Point top = RemapCoords(top_x, top_y, conservative_mode ? _settings_game.construction.map_height_limit * TILE_HEIGHT : GetTileMaxPixelZ(top_tile));

                        /* bottommost point */
                        TileIndex bottom_tile = TileVirtXY(bot_x, bot_y);
                        Point bot = RemapCoords(bot_x + TILE_SIZE, bot_y + TILE_SIZE, conservative_mode ? 0 : GetTilePixelZ(bottom_tile)); // bottommost point

                        /* the 'x' coordinate of 'top' and 'bot' is the same (and always in the same distance from tile middle),
                         * tile height/slope affects only the 'y' on-screen coordinate! */

                        int l = top.x - TILE_PIXELS * ZOOM_BASE; // 'x' coordinate of left   side of the dirty rectangle
                        int t = top.y;                           // 'y' coordinate of top    side of the dirty rectangle
                        int r = top.x + TILE_PIXELS * ZOOM_BASE; // 'x' coordinate of right  side of the dirty rectangle
                        int b = bot.y;                           // 'y' coordinate of bottom side of the dirty rectangle

                        static const int OVERLAY_WIDTH = conservative_mode ? 2 << ZOOM_LVL_END : 4 * ZOOM_BASE; // part of selection sprites is drawn outside the selected area (in particular: terraforming)

                        /* For halftile foundations on SLOPE_STEEP_S the sprite extents some more towards the top */
                        ViewportMarkDirtyFlags mode = (_thd.place_mode & HT_MAP) ? VMDF_NOT_LANDSCAPE : VMDF_NOT_MAP_MODE;
                        MarkAllViewportsDirty(l - OVERLAY_WIDTH, t - OVERLAY_WIDTH - TILE_HEIGHT * ZOOM_BASE, r + OVERLAY_WIDTH, b + OVERLAY_WIDTH, mode);

                        /* haven't we reached the topmost tile yet? */
                        if (top_x != x_start) {
                                top_x -= TILE_SIZE;
                        } else {
                                top_y += TILE_SIZE;
                        }

                        /* the way the bottom tile changes is different when we reach the bottommost tile */
                        if (bot_y != y_end) {
                                bot_y += TILE_SIZE;
                        } else {
                                bot_x -= TILE_SIZE;
                        }
                } while (bot_x >= top_x);
        } else { // Selecting in a 45 degrees rotated (diagonal) rectangle.
                /* a_size, b_size describe a rectangle with rotated coordinates */
                int a_size = x_size + y_size, b_size = x_size - y_size;

                int interval_a = a_size < 0 ? -(int)TILE_SIZE : (int)TILE_SIZE;
                int interval_b = b_size < 0 ? -(int)TILE_SIZE : (int)TILE_SIZE;

                for (int a = -interval_a; a != a_size + interval_a; a += interval_a) {
                        for (int b = -interval_b; b != b_size + interval_b; b += interval_b) {
                                uint x = (_thd.pos.x + (a + b) / 2) / TILE_SIZE;
                                uint y = (_thd.pos.y + (a - b) / 2) / TILE_SIZE;

                                if (x < MapMaxX() && y < MapMaxY()) {
                                        MarkTileDirtyByTile(TileXY(x, y), VMDF_NOT_MAP_MODE);
                                }
                        }
                }
        }
}


void SetSelectionRed(bool b)
{
        SetSelectionPalette(b ? PALETTE_SEL_TILE_RED : PAL_NONE);
}

void SetSelectionPalette(PaletteID pal)
{
        _thd.square_palette = pal;
        SetSelectionTilesDirty();
}

/**
 * Test whether a sign is below the mouse
 * @param vp the clicked viewport
 * @param x X position of click
 * @param y Y position of click
 * @param sign the sign to check
 * @return true if the sign was hit
 */
static bool CheckClickOnViewportSign(const Viewport *vp, int x, int y, const ViewportSign *sign)
{
        bool small = (vp->zoom >= ZOOM_LVL_OUT_4X);
        int sign_half_width = ScaleByZoom((small ? sign->width_small : sign->width_normal) / 2, vp->zoom);
        int sign_height = ScaleByZoom(WidgetDimensions::scaled.fullbevel.top + GetCharacterHeight(small ? FS_SMALL : FS_NORMAL) + WidgetDimensions::scaled.fullbevel.bottom, vp->zoom);

        return y >= sign->top && y < sign->top + sign_height &&
                        x >= sign->center - sign_half_width && x < sign->center + sign_half_width;
}


/**
 * Check whether any viewport sign was clicked, and dispatch the click.
 * @param vp the clicked viewport
 * @param x X position of click
 * @param y Y position of click
 * @return true if the sign was hit
 */
static bool CheckClickOnViewportSign(const Viewport *vp, int x, int y)
{
        if (_game_mode == GM_MENU) return false;

        x = ScaleByZoom(x - vp->left, vp->zoom) + vp->virtual_left;
        y = ScaleByZoom(y - vp->top, vp->zoom) + vp->virtual_top;

        Rect search_rect{ x - 1, y - 1, x + 1, y + 1 };
        search_rect = ExpandRectWithViewportSignMargins(search_rect, vp->zoom);

        bool show_stations = HasBit(_display_opt, DO_SHOW_STATION_NAMES) && !IsInvisibilitySet(TO_SIGNS);
        bool show_waypoints = HasBit(_display_opt, DO_SHOW_WAYPOINT_NAMES) && !IsInvisibilitySet(TO_SIGNS);
        bool show_towns = HasBit(_display_opt, DO_SHOW_TOWN_NAMES);
        bool show_signs = HasBit(_display_opt, DO_SHOW_SIGNS) && !IsInvisibilitySet(TO_SIGNS);
        bool show_competitors = HasBit(_display_opt, DO_SHOW_COMPETITOR_SIGNS);
        bool hide_hidden_waypoints = _settings_client.gui.allow_hiding_waypoint_labels && !HasBit(_extra_display_opt, XDO_SHOW_HIDDEN_SIGNS);

        /* Topmost of each type that was hit */
        BaseStation *st = nullptr, *last_st = nullptr;
        Town *t = nullptr, *last_t = nullptr;
        Sign *si = nullptr, *last_si = nullptr;

        /* See ViewportAddKdtreeSigns() for details on the search logic */
        _viewport_sign_kdtree.FindContained(search_rect.left, search_rect.top, search_rect.right, search_rect.bottom, [&](const ViewportSignKdtreeItem & item) {
                switch (item.type) {
                        case ViewportSignKdtreeItem::VKI_STATION:
                                if (!show_stations) break;
                                st = BaseStation::Get(item.id.station);
                                if (!show_competitors && _local_company != st->owner && st->owner != OWNER_NONE) break;
                                if (CheckClickOnViewportSign(vp, x, y, &st->sign)) last_st = st;
                                break;

                        case ViewportSignKdtreeItem::VKI_WAYPOINT:
                                if (!show_waypoints) break;
                                st = BaseStation::Get(item.id.station);
                                if (!show_competitors && _local_company != st->owner && st->owner != OWNER_NONE) break;
                                if (hide_hidden_waypoints && HasBit(Waypoint::From(st)->waypoint_flags, WPF_HIDE_LABEL)) break;
                                if (CheckClickOnViewportSign(vp, x, y, &st->sign)) last_st = st;
                                break;

                        case ViewportSignKdtreeItem::VKI_TOWN:
                                if (!show_towns) break;
                                t = Town::Get(item.id.town);
                                if (CheckClickOnViewportSign(vp, x, y, &t->cache.sign)) last_t = t;
                                break;

                        case ViewportSignKdtreeItem::VKI_SIGN:
                                if (!show_signs) break;
                                si = Sign::Get(item.id.sign);
                                if (!show_competitors && _local_company != si->owner && si->owner != OWNER_DEITY) break;
                                if (CheckClickOnViewportSign(vp, x, y, &si->sign)) last_si = si;
                                break;

                        default:
                                NOT_REACHED();
                }
        });

        /* Select which hit to handle based on priority */
        if (last_st != nullptr) {
                if (Station::IsExpected(last_st)) {
                        ShowStationViewWindow(last_st->index);
                } else {
                        ShowWaypointWindow(Waypoint::From(last_st));
                }
                return true;
        } else if (last_t != nullptr) {
                ShowTownViewWindow(last_t->index);
                return true;
        } else if (last_si != nullptr) {
                HandleClickOnSign(last_si);
                return true;
        } else {
                return false;
        }
}


ViewportSignKdtreeItem ViewportSignKdtreeItem::MakeStation(StationID id)
{
        ViewportSignKdtreeItem item;
        item.type = VKI_STATION;
        item.id.station = id;

        const Station *st = Station::Get(id);
        assert(st->sign.kdtree_valid);
        item.center = st->sign.center;
        item.top = st->sign.top;

        /* Assume the sign can be a candidate for drawing, so measure its width */
        _viewport_sign_maxwidth = std::max<int>({_viewport_sign_maxwidth, st->sign.width_normal, st->sign.width_small});

        return item;
}

ViewportSignKdtreeItem ViewportSignKdtreeItem::MakeWaypoint(StationID id)
{
        ViewportSignKdtreeItem item;
        item.type = VKI_WAYPOINT;
        item.id.station = id;

        const Waypoint *st = Waypoint::Get(id);
        assert(st->sign.kdtree_valid);
        item.center = st->sign.center;
        item.top = st->sign.top;

        /* Assume the sign can be a candidate for drawing, so measure its width */
        _viewport_sign_maxwidth = std::max<int>({_viewport_sign_maxwidth, st->sign.width_normal, st->sign.width_small});

        return item;
}

ViewportSignKdtreeItem ViewportSignKdtreeItem::MakeTown(TownID id)
{
        ViewportSignKdtreeItem item;
        item.type = VKI_TOWN;
        item.id.town = id;

        const Town *town = Town::Get(id);
        assert(town->cache.sign.kdtree_valid);
        item.center = town->cache.sign.center;
        item.top = town->cache.sign.top;

        /* Assume the sign can be a candidate for drawing, so measure its width */
        _viewport_sign_maxwidth = std::max<int>({_viewport_sign_maxwidth, town->cache.sign.width_normal, town->cache.sign.width_small});

        return item;
}

ViewportSignKdtreeItem ViewportSignKdtreeItem::MakeSign(SignID id)
{
        ViewportSignKdtreeItem item;
        item.type = VKI_SIGN;
        item.id.sign = id;

        const Sign *sign = Sign::Get(id);
        assert(sign->sign.kdtree_valid);
        item.center = sign->sign.center;
        item.top = sign->sign.top;

        /* Assume the sign can be a candidate for drawing, so measure its width */
        _viewport_sign_maxwidth = std::max<int>({_viewport_sign_maxwidth, sign->sign.width_normal, sign->sign.width_small});

        return item;
}

void RebuildViewportKdtree()
{
        /* Reset biggest size sign seen */
        _viewport_sign_maxwidth = 0;

        if (IsHeadless()) {
                _viewport_sign_kdtree_valid = false;
                _viewport_sign_kdtree.Build<ViewportSignKdtreeItem*>(nullptr, nullptr);
                return;
        }

        _viewport_sign_kdtree_valid = true;

        std::vector<ViewportSignKdtreeItem> items;
        items.reserve(BaseStation::GetNumItems() + Town::GetNumItems() + Sign::GetNumItems());

        for (const Station *st : Station::Iterate()) {
                if (st->sign.kdtree_valid) items.push_back(ViewportSignKdtreeItem::MakeStation(st->index));
        }

        for (const Waypoint *wp : Waypoint::Iterate()) {
                if (wp->sign.kdtree_valid) items.push_back(ViewportSignKdtreeItem::MakeWaypoint(wp->index));
        }

        for (const Town *town : Town::Iterate()) {
                if (town->cache.sign.kdtree_valid) items.push_back(ViewportSignKdtreeItem::MakeTown(town->index));
        }

        for (const Sign *sign : Sign::Iterate()) {
                if (sign->sign.kdtree_valid) items.push_back(ViewportSignKdtreeItem::MakeSign(sign->index));
        }

        _viewport_sign_kdtree.Build(items.begin(), items.end());
}


static bool CheckClickOnLandscape(const Viewport *vp, int x, int y)
{
        Point pt = TranslateXYToTileCoord(vp, x, y);

        _tile_fract_coords.x = pt.x & TILE_UNIT_MASK;
        _tile_fract_coords.y = pt.y & TILE_UNIT_MASK;

        if (pt.x != -1) return ClickTile(TileVirtXY(pt.x, pt.y));
        return true;
}

static void PlaceObject()
{
        Point pt;
        Window *w;

        pt = GetTileBelowCursor();
        if (pt.x == -1) return;

        if ((_thd.place_mode & HT_DRAG_MASK) == HT_POINT) {
                pt.x += TILE_SIZE / 2;
                pt.y += TILE_SIZE / 2;
        }

        _tile_fract_coords.x = pt.x & TILE_UNIT_MASK;
        _tile_fract_coords.y = pt.y & TILE_UNIT_MASK;

        w = _thd.GetCallbackWnd();
        if (w != nullptr) w->OnPlaceObject(pt, TileVirtXY(pt.x, pt.y));
}

bool HandleViewportDoubleClicked(Window *w, int x, int y)
{
        Viewport *vp = w->viewport;
        if (vp->zoom < ZOOM_LVL_DRAW_MAP) return false;

        switch (_settings_client.gui.action_when_viewport_map_is_dblclicked) {
                case 0: // Do nothing
                        return false;
                case 1: // Zoom in main viewport
                        while (vp->zoom != ZOOM_LVL_VIEWPORT)
                                ZoomInOrOutToCursorWindow(true, w);
                        return true;
                case 2: // Open an extra viewport
                        ShowExtraViewportWindowForTileUnderCursor();
                        return true;
                default:
                        return false;
        }
}

HandleViewportClickedResult HandleViewportClicked(const Viewport *vp, int x, int y, bool double_click)
{
        /* No click in smallmap mode except for plan making and left-button scrolling. */
        if (vp->zoom >= ZOOM_LVL_DRAW_MAP && !(_thd.place_mode & HT_MAP)) return HVCR_SCROLL_ONLY;

        const Vehicle *v = CheckClickOnVehicle(vp, x, y);

        if (_thd.place_mode & HT_VEHICLE) {
                if (v != nullptr && VehicleClicked(v)) return HVCR_DENY;
        }

        /* Vehicle placement mode already handled above. */
        if ((_thd.place_mode & HT_DRAG_MASK) != HT_NONE) {
                if (_thd.place_mode & HT_POLY) {
                        /* In polyline mode double-clicking on a single white line, finishes current polyline.
                         * If however the user double-clicks on a line that has a white and a blue section,
                         * both lines (white and blue) will be constructed consecutively. */
                        static bool stop_snap_on_double_click = false;
                        if (double_click && stop_snap_on_double_click) {
                                SetRailSnapMode(RSM_NO_SNAP);
                                HideMeasurementTooltips();
                                return HVCR_DENY;
                        }
                        stop_snap_on_double_click = !(_thd.drawstyle & HT_LINE) || (_thd.dir2 == HT_DIR_END);
                }

                PlaceObject();
                return HVCR_DENY;
        }

        if (vp->zoom >= ZOOM_LVL_DRAW_MAP) return HVCR_SCROLL_ONLY;

        if (CheckClickOnViewportSign(vp, x, y)) return HVCR_DENY;
        bool result = CheckClickOnLandscape(vp, x, y);

        if (v != nullptr) {
                Debug(misc, 2, "Vehicle {} (index {}) at {}", v->unitnumber, v->index, fmt::ptr(v));
                if (IsCompanyBuildableVehicleType(v)) {
                        v = v->First();
                        WindowClass wc = _thd.GetCallbackWnd()->window_class;
                        if (_ctrl_pressed && IsVehicleControlAllowed(v, _local_company)) {
                                StartStopVehicle(v, true);
                        } else if (wc != WC_CREATE_TEMPLATE && wc != WC_TEMPLATEGUI_MAIN) {
                                ShowVehicleViewWindow(v);
                        }
                }
                return HVCR_DENY;
        }
        return result ? HVCR_DENY : HVCR_ALLOW;
}

void RebuildViewportOverlay(Window *w, bool incremental)
{
        if (w->viewport->overlay != nullptr &&
                        w->viewport->overlay->GetCompanyMask() != 0 &&
                        w->viewport->overlay->GetCargoMask() != 0) {
                w->viewport->overlay->RebuildCache(incremental);
                if (!incremental) w->SetDirty();
        }
}

/**
 * Scrolls the viewport in a window to a given location.
 * @param x       Desired x location of the map to scroll to (world coordinate).
 * @param y       Desired y location of the map to scroll to (world coordinate).
 * @param z       Desired z location of the map to scroll to (world coordinate). Use \c -1 to scroll to the height of the map at the \a x, \a y location.
 * @param w       %Window containing the viewport.
 * @param instant Jump to the location instead of slowly moving to it.
 * @return Destination of the viewport was changed (to activate other actions when the viewport is already at the desired position).
 */
bool ScrollWindowTo(int x, int y, int z, Window *w, bool instant)
{
        /* The slope cannot be acquired outside of the map, so make sure we are always within the map. */
        if (z == -1) {
                if ( x >= 0 && x <= (int)MapSizeX() * (int)TILE_SIZE - 1
                                && y >= 0 && y <= (int)MapSizeY() * (int)TILE_SIZE - 1) {
                        z = GetSlopePixelZ(x, y);
                } else {
                        z = TileHeightOutsideMap(x / (int)TILE_SIZE, y / (int)TILE_SIZE);
                }
        }

        Point pt = MapXYZToViewport(w->viewport, x, y, z);
        w->viewport->follow_vehicle = INVALID_VEHICLE;

        if (w->viewport->dest_scrollpos_x == pt.x && w->viewport->dest_scrollpos_y == pt.y) return false;

        if (instant) {
                w->viewport->scrollpos_x = pt.x;
                w->viewport->scrollpos_y = pt.y;
                RebuildViewportOverlay(w, true);
        }

        w->viewport->dest_scrollpos_x = pt.x;
        w->viewport->dest_scrollpos_y = pt.y;
        return true;
}

/**
 * Scrolls the viewport in a window to a given location.
 * @param tile    Desired tile to center on.
 * @param w       %Window containing the viewport.
 * @param instant Jump to the location instead of slowly moving to it.
 * @return Destination of the viewport was changed (to activate other actions when the viewport is already at the desired position).
 */
bool ScrollWindowToTile(TileIndex tile, Window *w, bool instant)
{
        return ScrollWindowTo(TileX(tile) * TILE_SIZE, TileY(tile) * TILE_SIZE, -1, w, instant);
}

/**
 * Scrolls the viewport of the main window to a given location.
 * @param tile    Desired tile to center on.
 * @param instant Jump to the location instead of slowly moving to it.
 * @return Destination of the viewport was changed (to activate other actions when the viewport is already at the desired position).
 */
bool ScrollMainWindowToTile(TileIndex tile, bool instant)
{
        return ScrollMainWindowTo(TileX(tile) * TILE_SIZE + TILE_SIZE / 2, TileY(tile) * TILE_SIZE + TILE_SIZE / 2, -1, instant);
}

/**
 * Set a tile to display a red error square.
 * @param tile Tile that should show the red error square.
 */
void SetRedErrorSquare(TileIndex tile)
{
        TileIndex old;

        old = _thd.redsq;
        _thd.redsq = tile;

        if (tile != old) {
                if (tile != INVALID_TILE) MarkTileDirtyByTile(tile, VMDF_NOT_MAP_MODE);
                if (old  != INVALID_TILE) MarkTileDirtyByTile(old, VMDF_NOT_MAP_MODE);
        }
}

/**
 * Highlight \a w by \a h tiles at the cursor.
 * @param w Width of the highlighted tiles rectangle.
 * @param h Height of the highlighted tiles rectangle.
 */
void SetTileSelectSize(int w, int h)
{
        _thd.new_size.x = w * TILE_SIZE;
        _thd.new_size.y = h * TILE_SIZE;
        _thd.new_outersize.x = 0;
        _thd.new_outersize.y = 0;
}

void SetTileSelectBigSize(int ox, int oy, int sx, int sy)
{
        _thd.new_offs.x = ox * TILE_SIZE;
        _thd.new_offs.y = oy * TILE_SIZE;
        _thd.new_outersize.x = sx * TILE_SIZE;
        _thd.new_outersize.y = sy * TILE_SIZE;
}

/** returns the best autorail highlight type from map coordinates */
static HighLightStyle GetAutorailHT(int x, int y)
{
        return HT_RAIL | _autorail_piece[x & TILE_UNIT_MASK][y & TILE_UNIT_MASK];
}

/**
 * Reset tile highlighting.
 */
void TileHighlightData::Reset()
{
        this->pos.x = 0;
        this->pos.y = 0;
        this->new_pos.x = 0;
        this->new_pos.y = 0;
}

/**
 * Is the user dragging a 'diagonal rectangle'?
 * @return User is dragging a rotated rectangle.
 */
bool TileHighlightData::IsDraggingDiagonal()
{
        return (this->place_mode & HT_DIAGONAL) != 0 && _ctrl_pressed && _left_button_down;
}

/**
 * Get the window that started the current highlighting.
 * @return The window that requested the current tile highlighting, or \c nullptr if not available.
 */
Window *TileHighlightData::GetCallbackWnd()
{
        if (this->window_token != WindowToken(0)) {
                return FindWindowByToken(this->window_token);
        }
        return FindWindowById(this->window_class, this->window_number);
}

static HighLightStyle CalcPolyrailDrawstyle(Point pt, bool dragging);

static inline void CalcNewPolylineOutersize()
{
        /* use the 'outersize' to mark the second (blue) part of a polyline selection */
        if (_thd.dir2 < HT_DIR_END) {
                /* get bounds of the second part */
                int outer_x1 = _thd.selstart2.x & ~TILE_UNIT_MASK;
                int outer_y1 = _thd.selstart2.y & ~TILE_UNIT_MASK;
                int outer_x2 = _thd.selend2.x & ~TILE_UNIT_MASK;
                int outer_y2 = _thd.selend2.y & ~TILE_UNIT_MASK;
                if (outer_x1 > outer_x2) Swap(outer_x1, outer_x2);
                if (outer_y1 > outer_y2) Swap(outer_y1, outer_y2);
                /* include the first part */
                outer_x1 = std::min<int>(outer_x1, _thd.new_pos.x);
                outer_y1 = std::min<int>(outer_y1, _thd.new_pos.y);
                outer_x2 = std::max<int>(outer_x2, _thd.new_pos.x + _thd.new_size.x - TILE_SIZE);
                outer_y2 = std::max<int>(outer_y2, _thd.new_pos.y + _thd.new_size.y - TILE_SIZE);
                /* write new values */
                _thd.new_offs.x = outer_x1 - _thd.new_pos.x;
                _thd.new_offs.y = outer_y1 - _thd.new_pos.y;
                _thd.new_outersize.x = outer_x2 - outer_x1 + TILE_SIZE - _thd.new_size.x;
                _thd.new_outersize.y = outer_y2 - outer_y1 + TILE_SIZE - _thd.new_size.y;
        } else {
                _thd.new_offs.x = 0;
                _thd.new_offs.y = 0;
                _thd.new_outersize.x = 0;
                _thd.new_outersize.y = 0;
        }
}

/**
 * Updates tile highlighting for all cases.
 * Uses _thd.selstart and _thd.selend and _thd.place_mode (set elsewhere) to determine _thd.pos and _thd.size
 * Also drawstyle is determined. Uses _thd.new.* as a buffer and calls SetSelectionTilesDirty() twice,
 * Once for the old and once for the new selection.
 * _thd is TileHighlightData, found in viewport.h
 */
void UpdateTileSelection()
{
        int x1;
        int y1;

        if (_thd.freeze) return;

        HighLightStyle new_drawstyle = HT_NONE;
        bool new_diagonal = false;

        if ((_thd.place_mode & HT_DRAG_MASK) == HT_SPECIAL) {
                x1 = _thd.selend.x;
                y1 = _thd.selend.y;
                if (x1 != -1) {
                        int x2 = _thd.selstart.x & ~TILE_UNIT_MASK;
                        int y2 = _thd.selstart.y & ~TILE_UNIT_MASK;
                        x1 &= ~TILE_UNIT_MASK;
                        y1 &= ~TILE_UNIT_MASK;

                        if (_thd.IsDraggingDiagonal()) {
                                new_diagonal = true;
                        } else {
                                if (x1 >= x2) Swap(x1, x2);
                                if (y1 >= y2) Swap(y1, y2);
                        }
                        _thd.new_pos.x = x1;
                        _thd.new_pos.y = y1;
                        _thd.new_size.x = x2 - x1;
                        _thd.new_size.y = y2 - y1;
                        if (!new_diagonal) {
                                _thd.new_size.x += TILE_SIZE;
                                _thd.new_size.y += TILE_SIZE;
                        }
                        new_drawstyle = _thd.next_drawstyle;
                }
        } else if ((_thd.place_mode & HT_DRAG_MASK) != HT_NONE) {
                Point pt = GetTileBelowCursor();
                x1 = pt.x;
                y1 = pt.y;
                if (x1 != -1) {
                        switch (_thd.place_mode & HT_DRAG_MASK) {
                                case HT_RECT:
                                        new_drawstyle = HT_RECT;
                                        break;
                                case HT_POINT:
                                        new_drawstyle = HT_POINT;
                                        x1 += TILE_SIZE / 2;
                                        y1 += TILE_SIZE / 2;
                                        break;
                                case HT_RAIL:
                                case HT_LINE:
                                        /* HT_POLY */
                                        if (_thd.place_mode & HT_POLY) {
                                                RailSnapMode snap_mode = GetRailSnapMode();
                                                if (snap_mode == RSM_NO_SNAP ||
                                                                (snap_mode == RSM_SNAP_TO_TILE && GetRailSnapTile() == TileVirtXY(pt.x, pt.y))) {
                                                        new_drawstyle = GetAutorailHT(pt.x, pt.y);
                                                        _thd.new_offs.x = 0;
                                                        _thd.new_offs.y = 0;
                                                        _thd.new_outersize.x = 0;
                                                        _thd.new_outersize.y = 0;
                                                        _thd.dir2 = HT_DIR_END;
                                                } else {
                                                        new_drawstyle = CalcPolyrailDrawstyle(pt, false);
                                                        if (new_drawstyle != HT_NONE) {
                                                                x1 = _thd.selstart.x & ~TILE_UNIT_MASK;
                                                                y1 = _thd.selstart.y & ~TILE_UNIT_MASK;
                                                                int x2 = _thd.selend.x & ~TILE_UNIT_MASK;
                                                                int y2 = _thd.selend.y & ~TILE_UNIT_MASK;
                                                                if (x1 > x2) Swap(x1, x2);
                                                                if (y1 > y2) Swap(y1, y2);
                                                                _thd.new_pos.x = x1;
                                                                _thd.new_pos.y = y1;
                                                                _thd.new_size.x = x2 - x1 + TILE_SIZE;
                                                                _thd.new_size.y = y2 - y1 + TILE_SIZE;
                                                        }
                                                }
                                                break;
                                        }
                                        /* HT_RAIL */
                                        if (_thd.place_mode & HT_RAIL) {
                                                /* Draw one highlighted tile in any direction */
                                                new_drawstyle = GetAutorailHT(pt.x, pt.y);
                                                break;
                                        }
                                        /* HT_LINE */
                                        switch (_thd.place_mode & HT_DIR_MASK) {
                                                case HT_DIR_X: new_drawstyle = HT_LINE | HT_DIR_X; break;
                                                case HT_DIR_Y: new_drawstyle = HT_LINE | HT_DIR_Y; break;

                                                case HT_DIR_HU:
                                                case HT_DIR_HL:
                                                        new_drawstyle = (pt.x & TILE_UNIT_MASK) + (pt.y & TILE_UNIT_MASK) <= TILE_SIZE ? HT_LINE | HT_DIR_HU : HT_LINE | HT_DIR_HL;
                                                        break;

                                                case HT_DIR_VL:
                                                case HT_DIR_VR:
                                                        new_drawstyle = (pt.x & TILE_UNIT_MASK) > (pt.y & TILE_UNIT_MASK) ? HT_LINE | HT_DIR_VL : HT_LINE | HT_DIR_VR;
                                                        break;

                                                default: NOT_REACHED();
                                        }
                                        _thd.selstart.x = x1 & ~TILE_UNIT_MASK;
                                        _thd.selstart.y = y1 & ~TILE_UNIT_MASK;
                                        _thd.selend.x = x1;
                                        _thd.selend.y = y1;
                                        break;
                                default:
                                        NOT_REACHED();
                        }
                        _thd.new_pos.x = x1 & ~TILE_UNIT_MASK;
                        _thd.new_pos.y = y1 & ~TILE_UNIT_MASK;
                }
        }

        if (new_drawstyle & HT_LINE) CalcNewPolylineOutersize();

        /* redraw selection */
        if (_thd.drawstyle != new_drawstyle ||
                        _thd.pos.x != _thd.new_pos.x || _thd.pos.y != _thd.new_pos.y ||
                        _thd.size.x != _thd.new_size.x || _thd.size.y != _thd.new_size.y ||
                        _thd.offs.x != _thd.new_offs.x || _thd.offs.y != _thd.new_offs.y ||
                        _thd.outersize.x != _thd.new_outersize.x ||
                        _thd.outersize.y != _thd.new_outersize.y ||
                        _thd.diagonal    != new_diagonal) {
                /* Clear the old tile selection? */
                if ((_thd.drawstyle & HT_DRAG_MASK) != HT_NONE) SetSelectionTilesDirty();

                _thd.drawstyle = new_drawstyle;
                _thd.pos = _thd.new_pos;
                _thd.size = _thd.new_size;
                _thd.offs = _thd.new_offs;
                _thd.outersize = _thd.new_outersize;
                _thd.diagonal = new_diagonal;
                _thd.dirty = 0xff;

                /* Draw the new tile selection? */
                if ((new_drawstyle & HT_DRAG_MASK) != HT_NONE) SetSelectionTilesDirty();
        }
}

/**
 * Displays the measurement tooltips when selecting multiple tiles
 * @param str String to be displayed
 * @param paramcount number of params to deal with
 * @param params (optional) up to 5 pieces of additional information that may be added to a tooltip
 * @param close_cond Condition for closing this tooltip.
 */
static inline void ShowMeasurementTooltips(StringID str, uint paramcount, TooltipCloseCondition close_cond = TCC_EXIT_VIEWPORT)
{
        if (!_settings_client.gui.measure_tooltip) return;
        GuiShowTooltips(_thd.GetCallbackWnd(), str, close_cond, paramcount);
}

static void HideMeasurementTooltips()
{
        CloseWindowById(WC_TOOLTIPS, 0);
}

/** highlighting tiles while only going over them with the mouse */
void VpStartPlaceSizing(TileIndex tile, ViewportPlaceMethod method, ViewportDragDropSelectionProcess process)
{
        _thd.select_method = method;
        _thd.select_proc   = process;
        _thd.selend.x = TileX(tile) * TILE_SIZE;
        _thd.selstart.x = TileX(tile) * TILE_SIZE;
        _thd.selend.y = TileY(tile) * TILE_SIZE;
        _thd.selstart.y = TileY(tile) * TILE_SIZE;

        /* Needed so several things (road, autoroad, bridges, ...) are placed correctly.
         * In effect, placement starts from the centre of a tile
         */
        if (method == VPM_X_OR_Y || method == VPM_FIX_X || method == VPM_FIX_Y) {
                _thd.selend.x += TILE_SIZE / 2;
                _thd.selend.y += TILE_SIZE / 2;
                _thd.selstart.x += TILE_SIZE / 2;
                _thd.selstart.y += TILE_SIZE / 2;
        }

        HighLightStyle others = _thd.place_mode & ~(HT_DRAG_MASK | HT_DIR_MASK);
        if ((_thd.place_mode & HT_DRAG_MASK) == HT_RECT) {
                _thd.place_mode = HT_SPECIAL | others;
                _thd.next_drawstyle = HT_RECT | others;
        } else if (_thd.place_mode & (HT_RAIL | HT_LINE)) {
                _thd.place_mode = HT_SPECIAL | others;
                _thd.next_drawstyle = _thd.drawstyle | others;
                _current_snap_lock.x = -1;
                if ((_thd.place_mode & HT_POLY) != 0 && GetRailSnapMode() == RSM_NO_SNAP) {
                        SetRailSnapMode(RSM_SNAP_TO_TILE);
                        SetRailSnapTile(tile);
                }
        } else {
                _thd.place_mode = HT_SPECIAL | others;
                _thd.next_drawstyle = HT_POINT | others;
        }
        _special_mouse_mode = WSM_SIZING;
}

/** Drag over the map while holding the left mouse down. */
void VpStartDragging(ViewportDragDropSelectionProcess process)
{
        _thd.select_method = VPM_X_AND_Y;
        _thd.select_proc = process;
        _thd.selstart.x = 0;
        _thd.selstart.y = 0;
        _thd.next_drawstyle = HT_RECT;

        _special_mouse_mode = WSM_DRAGGING;
}

void VpSetPlaceSizingLimit(int limit)
{
        _thd.sizelimit = limit;
}

/**
 * Highlights all tiles between a set of two tiles. Used in dock and tunnel placement
 * @param from TileIndex of the first tile to highlight
 * @param to TileIndex of the last tile to highlight
 */
void VpSetPresizeRange(TileIndex from, TileIndex to)
{
        uint64_t distance = DistanceManhattan(from, to) + 1;

        _thd.selend.x = TileX(to) * TILE_SIZE;
        _thd.selend.y = TileY(to) * TILE_SIZE;
        _thd.selstart.x = TileX(from) * TILE_SIZE;
        _thd.selstart.y = TileY(from) * TILE_SIZE;
        _thd.next_drawstyle = HT_RECT;

        /* show measurement only if there is any length to speak of */
        if (distance > 1) {
                SetDParam(0, distance);
                ShowMeasurementTooltips(STR_MEASURE_LENGTH, 1);
        } else {
                HideMeasurementTooltips();
        }
}

static void VpStartPreSizing()
{
        _thd.selend.x = -1;
        _special_mouse_mode = WSM_PRESIZE;
}

/**
 * returns information about the 2x1 piece to be build.
 * The lower bits (0-3) are the track type.
 */
static HighLightStyle Check2x1AutoRail(int mode)
{
        int fxpy = _tile_fract_coords.x + _tile_fract_coords.y;
        int sxpy = (_thd.selend.x & TILE_UNIT_MASK) + (_thd.selend.y & TILE_UNIT_MASK);
        int fxmy = _tile_fract_coords.x - _tile_fract_coords.y;
        int sxmy = (_thd.selend.x & TILE_UNIT_MASK) - (_thd.selend.y & TILE_UNIT_MASK);

        switch (mode) {
                default: NOT_REACHED();
                case 0: // end piece is lower right
                        if (fxpy >= 20 && sxpy <= 12) return HT_DIR_HL;
                        if (fxmy < -3 && sxmy > 3) return HT_DIR_VR;
                        return HT_DIR_Y;

                case 1:
                        if (fxmy > 3 && sxmy < -3) return HT_DIR_VL;
                        if (fxpy <= 12 && sxpy >= 20) return HT_DIR_HU;
                        return HT_DIR_Y;

                case 2:
                        if (fxmy > 3 && sxmy < -3) return HT_DIR_VL;
                        if (fxpy >= 20 && sxpy <= 12) return HT_DIR_HL;
                        return HT_DIR_X;

                case 3:
                        if (fxmy < -3 && sxmy > 3) return HT_DIR_VR;
                        if (fxpy <= 12 && sxpy >= 20) return HT_DIR_HU;
                        return HT_DIR_X;
        }
}

/**
 * Check if the direction of start and end tile should be swapped based on
 * the dragging-style. Default directions are:
 * in the case of a line (HT_RAIL, HT_LINE):  DIR_NE, DIR_NW, DIR_N, DIR_E
 * in the case of a rect (HT_RECT, HT_POINT): DIR_S, DIR_E
 * For example dragging a rectangle area from south to north should be swapped to
 * north-south (DIR_S) to obtain the same results with less code. This is what
 * the return value signifies.
 * @param style HighLightStyle dragging style
 * @param start_tile start tile of drag
 * @param end_tile end tile of drag
 * @return boolean value which when true means start/end should be swapped
 */
static bool SwapDirection(HighLightStyle style, TileIndex start_tile, TileIndex end_tile)
{
        uint start_x = TileX(start_tile);
        uint start_y = TileY(start_tile);
        uint end_x = TileX(end_tile);
        uint end_y = TileY(end_tile);

        switch (style & HT_DRAG_MASK) {
                case HT_RAIL:
                case HT_LINE: return (end_x > start_x || (end_x == start_x && end_y > start_y));

                case HT_RECT:
                case HT_POINT: return (end_x != start_x && end_y < start_y);
                default: NOT_REACHED();
        }

        return false;
}

/**
 * Calculates height difference between one tile and another.
 * Multiplies the result to suit the standard given by #TILE_HEIGHT_STEP.
 *
 * To correctly get the height difference we need the direction we are dragging
 * in, as well as with what kind of tool we are dragging. For example a horizontal
 * autorail tool that starts in bottom and ends at the top of a tile will need the
 * maximum of SW, S and SE, N corners respectively. This is handled by the lookup table below
 * See #_tileoffs_by_dir in map.cpp for the direction enums if you can't figure out the values yourself.
 * @param style      Highlighting style of the drag. This includes direction and style (autorail, rect, etc.)
 * @param distance   Number of tiles dragged, important for horizontal/vertical drags, ignored for others.
 * @param start_tile Start tile of the drag operation.
 * @param end_tile   End tile of the drag operation.
 * @return Height difference between two tiles. The tile measurement tool utilizes this value in its tooltip.
 */
static int CalcHeightdiff(HighLightStyle style, uint distance, TileIndex start_tile, TileIndex end_tile)
{
        bool swap = SwapDirection(style, start_tile, end_tile);
        uint h0, h1; // Start height and end height.

        if (start_tile == end_tile) return 0;
        if (swap) Swap(start_tile, end_tile);

        switch (style & HT_DRAG_MASK) {
                case HT_RECT:
                        /* In the case of an area we can determine whether we were dragging south or
                         * east by checking the X-coordinates of the tiles */
                        if (TileX(end_tile) > TileX(start_tile)) {
                                /* Dragging south does not need to change the start tile. */
                                end_tile = TileAddByDir(end_tile, DIR_S);
                        } else {
                                /* Dragging east. */
                                start_tile = TileAddByDir(start_tile, DIR_SW);
                                end_tile = TileAddByDir(end_tile, DIR_SE);
                        }
                        [[fallthrough]];

                case HT_POINT:
                        h0 = TileHeight(start_tile);
                        h1 = TileHeight(end_tile);
                        break;
                default: { // All other types, this is mostly only line/autorail
                        static const HighLightStyle flip_style_direction[] = {
                                HT_DIR_X, HT_DIR_Y, HT_DIR_HL, HT_DIR_HU, HT_DIR_VR, HT_DIR_VL
                        };
                        static const std::pair<TileIndexDiffC, TileIndexDiffC> start_heightdiff_line_by_dir[] = {
                                { {1, 0}, {1, 1} }, // HT_DIR_X
                                { {0, 1}, {1, 1} }, // HT_DIR_Y
                                { {1, 0}, {0, 0} }, // HT_DIR_HU
                                { {1, 0}, {1, 1} }, // HT_DIR_HL
                                { {1, 0}, {1, 1} }, // HT_DIR_VL
                                { {0, 1}, {1, 1} }, // HT_DIR_VR
                        };
                        static const std::pair<TileIndexDiffC, TileIndexDiffC> end_heightdiff_line_by_dir[] = {
                                { {0, 1}, {0, 0} }, // HT_DIR_X
                                { {1, 0}, {0, 0} }, // HT_DIR_Y
                                { {0, 1}, {0, 0} }, // HT_DIR_HU
                                { {1, 1}, {0, 1} }, // HT_DIR_HL
                                { {1, 0}, {0, 0} }, // HT_DIR_VL
                                { {0, 0}, {0, 1} }, // HT_DIR_VR
                        };
                        static_assert(std::size(start_heightdiff_line_by_dir) == HT_DIR_END);
                        static_assert(std::size(end_heightdiff_line_by_dir) == HT_DIR_END);

                        distance %= 2; // we're only interested if the distance is even or uneven
                        style &= HT_DIR_MASK;
                        dbg_assert(style < HT_DIR_END);

                        /* To handle autorail, we do some magic to be able to use a lookup table.
                         * Firstly if we drag the other way around, we switch start&end, and if needed
                         * also flip the drag-position. Eg if it was on the left, and the distance is even
                         * that means the end, which is now the start is on the right */
                        if (swap && distance == 0) style = flip_style_direction[style];

                        /* Lambda to help calculating the height at one side of the line. */
                        auto get_height = [](auto &tile, auto &heightdiffs) {
                                return std::max(
                                        TileHeight(TileAdd(tile, ToTileIndexDiff(heightdiffs.first))),
                                        TileHeight(TileAdd(tile, ToTileIndexDiff(heightdiffs.second))));
                        };

                        /* Use lookup table for start-tile based on HighLightStyle direction */
                        h0 = get_height(start_tile, start_heightdiff_line_by_dir[style]);

                        /* Use lookup table for end-tile based on HighLightStyle direction
                         * flip around side (lower/upper, left/right) based on distance */
                        if (distance == 0) style = flip_style_direction[style];
                        h1 = get_height(end_tile, end_heightdiff_line_by_dir[style]);
                        break;
                }
        }

        if (swap) Swap(h0, h1);
        return (int)(h1 - h0) * TILE_HEIGHT_STEP;
}

static void ShowLengthMeasurement(HighLightStyle style, TileIndex start_tile, TileIndex end_tile, TooltipCloseCondition close_cond = TCC_EXIT_VIEWPORT, bool show_single_tile_length = false)
{
        static const StringID measure_strings_length[] = {STR_NULL, STR_MEASURE_LENGTH, STR_MEASURE_LENGTH_HEIGHTDIFF};

        if (_settings_client.gui.measure_tooltip) {
                uint distance = DistanceManhattan(start_tile, end_tile) + 1;
                uint index = 0;

                if (show_single_tile_length || distance != 1) {
                        int heightdiff = CalcHeightdiff(style, distance, start_tile, end_tile);
                        /* If we are showing a tooltip for horizontal or vertical drags,
                         * 2 tiles have a length of 1. To bias towards the ceiling we add
                         * one before division. It feels more natural to count 3 lengths as 2 */
                        if ((style & HT_DIR_MASK) != HT_DIR_X && (style & HT_DIR_MASK) != HT_DIR_Y) {
                                distance = CeilDiv(distance, 2);
                        }

                        SetDParam(index++, distance);
                        if (heightdiff != 0) SetDParam(index++, heightdiff);
                }

                ShowMeasurementTooltips(measure_strings_length[index], index, close_cond);
        }
}

/**
 * Check for underflowing the map.
 * @param test  the variable to test for underflowing
 * @param other the other variable to update to keep the line
 * @param mult  the constant to multiply the difference by for \c other
 */
static void CheckUnderflow(int &test, int &other, int mult)
{
        if (test >= 0) return;

        other += mult * test;
        test = 0;
}

/**
 * Check for overflowing the map.
 * @param test  the variable to test for overflowing
 * @param other the other variable to update to keep the line
 * @param max   the maximum value for the \c test variable
 * @param mult  the constant to multiply the difference by for \c other
 */
static void CheckOverflow(int &test, int &other, int max, int mult)
{
        if (test <= max) return;

        other += mult * (test - max);
        test = max;
}

[[maybe_unused]] static const uint X_DIRS = (1 << DIR_NE) | (1 << DIR_SW);
[[maybe_unused]] static const uint Y_DIRS = (1 << DIR_SE) | (1 << DIR_NW);
static const uint HORZ_DIRS = (1 << DIR_W) | (1 << DIR_E);
//static const uint VERT_DIRS = (1 << DIR_N) | (1 << DIR_S);

Trackdir PointDirToTrackdir(const Point &pt, Direction dir)
{
        Trackdir ret;

        if (IsDiagonalDirection(dir)) {
                ret = DiagDirToDiagTrackdir(DirToDiagDir(dir));
        } else {
                int x = pt.x & TILE_UNIT_MASK;
                int y = pt.y & TILE_UNIT_MASK;
                int ns = x + y;
                int we = y - x;
                if (HasBit(HORZ_DIRS, dir)) {
                        ret = TrackDirectionToTrackdir(ns < (int)TILE_SIZE ? TRACK_UPPER : TRACK_LOWER, dir);
                } else {
                        ret = TrackDirectionToTrackdir(we < 0 ? TRACK_LEFT : TRACK_RIGHT, dir);
                }
        }

        return ret;
}

static bool FindPolyline(const Point &pt, const LineSnapPoint &start, PolylineInfo *ret)
{
        /* relative coordinats of the mouse point (offset against the snap point) */
        int x = pt.x - start.x;
        int y = pt.y - start.y;
        int we = y - x;
        int ns = x + y;

        /* in-tile alignment of the snap point (there are two variants: [0, 8] or [8, 0]) */
        uint align_x = start.x & TILE_UNIT_MASK;
        uint align_y = start.y & TILE_UNIT_MASK;
        assert((align_x == TILE_SIZE / 2 && align_y == 0 && !(start.dirs & X_DIRS)) || (align_x == 0 && align_y == TILE_SIZE / 2 && !(start.dirs & Y_DIRS)));

        /* absolute distance between points (in tiles) */
        uint d_x = abs(RoundDivSU(x < 0 ? x - align_y : x + align_y, TILE_SIZE));
        uint d_y = abs(RoundDivSU(y < 0 ? y - align_x : y + align_x, TILE_SIZE));
        uint d_ns = abs(RoundDivSU(ns, TILE_SIZE));
        uint d_we = abs(RoundDivSU(we, TILE_SIZE));

        /* Find on which quadrant is the mouse point (reltively to the snap point).
         * Numeration (clockwise like in Direction):
         * ortho            diag
         *   \   2   /       2 | 3
         *     \   /         --+---> [we]
         *  1    X    3      1 | 0
         *     /   \           v
         *  [x]  0  [y]       [ns]          */
        uint ortho_quadrant = 2 * (x < 0) + ((x < 0) != (y < 0)); // implicit cast: false/true --> 0/1
        uint diag_quadrant = 2 * (ns < 0) + ((ns < 0) != (we < 0));

        /* direction from the snap point to the mouse point */
        Direction ortho_line_dir = ChangeDir(DIR_S, (DirDiff)(2 * ortho_quadrant)); // DIR_S is the middle of the ortho quadrant no. 0
        Direction diag_line_dir = ChangeDir(DIR_SE, (DirDiff)(2 * diag_quadrant));  // DIR_SE is the middle of the diag quadrant no. 0
        if (!HasBit(start.dirs, ortho_line_dir) && !HasBit(start.dirs, diag_line_dir)) return false;

        /* length of booth segments of auto line (choosing orthogonal direction first) */
        uint ortho_len = 0, ortho_len2 = 0;
        if (HasBit(start.dirs, ortho_line_dir)) {
                bool is_len_even = (align_x != 0) ? d_x >= d_y : d_x <= d_y;
                ortho_len = 2 * std::min(d_x, d_y) - (int)is_len_even;
                assert((int)ortho_len >= 0);
                if (d_ns == 0 || d_we == 0) { // just single segment?
                        ortho_len++;
                } else {
                        ortho_len2 = abs((int)d_x - (int)d_y) + (int)is_len_even;
                }
        }

        /* length of booth segments of auto line (choosing diagonal direction first) */
        uint diag_len = 0, diag_len2 = 0;
        if (HasBit(start.dirs, diag_line_dir)) {
                if (d_x == 0 || d_y == 0) { // just single segment?
                        diag_len = d_x + d_y;
                } else {
                        diag_len = std::min(d_ns, d_we);
                        diag_len2 = d_x + d_y - diag_len;
                }
        }

        /* choose the best variant */
        if (ortho_len != 0 && diag_len != 0) {
                /* in the first place, choose this line whose first segment ends up closer
                 * to the mouse point (thus the second segment is shorter) */
                int cmp = ortho_len2 - diag_len2;
                /* if equeal, choose the shorter line */
                if (cmp == 0) cmp = ortho_len - diag_len;
                /* finally look at small "units" and choose the line which is closer to the mouse point */
                if (cmp == 0) cmp = std::min(abs(we), abs(ns)) - std::min(abs(x), abs(y));
                /* based on comparison, disable one of variants */
                if (cmp > 0) {
                        ortho_len = 0;
                } else {
                        diag_len = 0;
                }
        }

        /* store results */
        if (ortho_len != 0) {
                ret->first_dir = ortho_line_dir;
                ret->first_len = ortho_len;
                ret->second_dir = (ortho_len2 != 0) ? diag_line_dir : INVALID_DIR;
                ret->second_len = ortho_len2;
        } else if (diag_len != 0) {
                ret->first_dir = diag_line_dir;
                ret->first_len = diag_len;
                ret->second_dir = (diag_len2 != 0) ? ortho_line_dir : INVALID_DIR;
                ret->second_len = diag_len2;
        } else {
                return false;
        }

        ret->start = start;
        return true;
}

/**
 * Calculate squared euclidean distance between two points.
 * @param a the first point
 * @param b the second point
 * @return |b - a| ^ 2
 */
static inline uint SqrDist(const Point &a, const Point &b)
{
        return (b.x - a.x) * (b.x - a.x) + (b.y - a.y) * (b.y - a.y);
}

static LineSnapPoint *FindBestPolyline(const Point &pt, LineSnapPoint *snap_points, uint num_points, PolylineInfo *ret)
{
        /* Find the best polyline (a pair of two lines - the white one and the blue
         * one) led from any of saved snap points to the mouse cursor. */

        LineSnapPoint *best_snap_point = nullptr; // the best polyline we found so far is led from this snap point

        for (int i = 0; i < (int)num_points; i++) {
                /* try to fit a polyline */
                PolylineInfo polyline;
                if (!FindPolyline(pt, snap_points[i], &polyline)) continue; // skip non-matching snap points
                /* check whether we've found a better polyline */
                if (best_snap_point != nullptr) {
                        /* firstly choose shorter polyline (the one with smaller amount of
                         * track pieces composing booth the white and the blue line) */
                        uint cur_len = polyline.first_len + polyline.second_len;
                        uint best_len = ret->first_len + ret->second_len;
                        if (cur_len > best_len) continue;
                        /* secondly choose that polyline which has longer first (white) line */
                        if (cur_len == best_len && polyline.first_len < ret->first_len) continue;
                        /* finally check euclidean distance to snap points and choose the
                         * one which is closer */
                        if (cur_len == best_len && polyline.first_len == ret->first_len && SqrDist(pt, snap_points[i]) >= SqrDist(pt, *best_snap_point)) continue;
                }
                /* save the found polyline */
                *ret = polyline;
                best_snap_point = &snap_points[i];
        }

        return best_snap_point;
}

/** while dragging */
static void CalcRaildirsDrawstyle(int x, int y, int method)
{
        HighLightStyle b;

        int dx = _thd.selstart.x - (_thd.selend.x & ~TILE_UNIT_MASK);
        int dy = _thd.selstart.y - (_thd.selend.y & ~TILE_UNIT_MASK);
        uint w = abs(dx) + TILE_SIZE;
        uint h = abs(dy) + TILE_SIZE;

        if (method & ~(VPM_RAILDIRS | VPM_SIGNALDIRS)) {
                /* We 'force' a selection direction; first four rail buttons. */
                method &= ~(VPM_RAILDIRS | VPM_SIGNALDIRS);
                int raw_dx = _thd.selstart.x - _thd.selend.x;
                int raw_dy = _thd.selstart.y - _thd.selend.y;
                switch (method) {
                        case VPM_FIX_X:
                                b = HT_LINE | HT_DIR_Y;
                                x = _thd.selstart.x;
                                break;

                        case VPM_FIX_Y:
                                b = HT_LINE | HT_DIR_X;
                                y = _thd.selstart.y;
                                break;

                        case VPM_FIX_HORIZONTAL:
                                if (dx == -dy) {
                                        /* We are on a straight horizontal line. Determine the 'rail'
                                         * to build based the sub tile location. */
                                        b = (x & TILE_UNIT_MASK) + (y & TILE_UNIT_MASK) >= TILE_SIZE ? HT_LINE | HT_DIR_HL : HT_LINE | HT_DIR_HU;
                                } else {
                                        /* We are not on a straight line. Determine the rail to build
                                         * based on whether we are above or below it. */
                                        b = dx + dy >= (int)TILE_SIZE ? HT_LINE | HT_DIR_HU : HT_LINE | HT_DIR_HL;

                                        /* Calculate where a horizontal line through the start point and
                                         * a vertical line from the selected end point intersect and
                                         * use that point as the end point. */
                                        int offset = (raw_dx - raw_dy) / 2;
                                        x = _thd.selstart.x - (offset & ~TILE_UNIT_MASK);
                                        y = _thd.selstart.y + (offset & ~TILE_UNIT_MASK);

                                        /* 'Build' the last half rail tile if needed */
                                        if ((offset & TILE_UNIT_MASK) > (TILE_SIZE / 2)) {
                                                if (dx + dy >= (int)TILE_SIZE) {
                                                        x += (dx + dy < 0) ? (int)TILE_SIZE : -(int)TILE_SIZE;
                                                } else {
                                                        y += (dx + dy < 0) ? (int)TILE_SIZE : -(int)TILE_SIZE;
                                                }
                                        }

                                        /* Make sure we do not overflow the map! */
                                        CheckUnderflow(x, y, 1);
                                        CheckUnderflow(y, x, 1);
                                        CheckOverflow(x, y, (MapMaxX() - 1) * TILE_SIZE, 1);
                                        CheckOverflow(y, x, (MapMaxY() - 1) * TILE_SIZE, 1);
                                        assert(x >= 0 && y >= 0 && x <= (int)(MapMaxX() * TILE_SIZE) && y <= (int)(MapMaxY() * TILE_SIZE));
                                }
                                break;

                        case VPM_FIX_VERTICAL:
                                if (dx == dy) {
                                        /* We are on a straight vertical line. Determine the 'rail'
                                         * to build based the sub tile location. */
                                        b = (x & TILE_UNIT_MASK) > (y & TILE_UNIT_MASK) ? HT_LINE | HT_DIR_VL : HT_LINE | HT_DIR_VR;
                                } else {
                                        /* We are not on a straight line. Determine the rail to build
                                         * based on whether we are left or right from it. */
                                        b = dx < dy ? HT_LINE | HT_DIR_VL : HT_LINE | HT_DIR_VR;

                                        /* Calculate where a vertical line through the start point and
                                         * a horizontal line from the selected end point intersect and
                                         * use that point as the end point. */
                                        int offset = (raw_dx + raw_dy + (int)TILE_SIZE) / 2;
                                        x = _thd.selstart.x - (offset & ~TILE_UNIT_MASK);
                                        y = _thd.selstart.y - (offset & ~TILE_UNIT_MASK);

                                        /* 'Build' the last half rail tile if needed */
                                        if ((offset & TILE_UNIT_MASK) > (TILE_SIZE / 2)) {
                                                if (dx - dy < 0) {
                                                        y += (dx > dy) ? (int)TILE_SIZE : -(int)TILE_SIZE;
                                                } else {
                                                        x += (dx < dy) ? (int)TILE_SIZE : -(int)TILE_SIZE;
                                                }
                                        }

                                        /* Make sure we do not overflow the map! */
                                        CheckUnderflow(x, y, -1);
                                        CheckUnderflow(y, x, -1);
                                        CheckOverflow(x, y, (MapMaxX() - 1) * TILE_SIZE, -1);
                                        CheckOverflow(y, x, (MapMaxY() - 1) * TILE_SIZE, -1);
                                        assert(x >= 0 && y >= 0 && x <= (int)(MapMaxX() * TILE_SIZE) && y <= (int)(MapMaxY() * TILE_SIZE));
                                }
                                break;

                        default:
                                NOT_REACHED();
                }
        } else if (TileVirtXY(_thd.selstart.x, _thd.selstart.y) == TileVirtXY(x, y)) { // check if we're only within one tile
                if (method & VPM_RAILDIRS) {
                        b = GetAutorailHT(x, y);
                } else { // rect for autosignals on one tile
                        b = HT_RECT;
                }
        } else if (h == TILE_SIZE) { // Is this in X direction?
                if (dx == (int)TILE_SIZE) { // 2x1 special handling
                        b = (Check2x1AutoRail(3)) | HT_LINE;
                } else if (dx == -(int)TILE_SIZE) {
                        b = (Check2x1AutoRail(2)) | HT_LINE;
                } else {
                        b = HT_LINE | HT_DIR_X;
                }
                y = _thd.selstart.y;
        } else if (w == TILE_SIZE) { // Or Y direction?
                if (dy == (int)TILE_SIZE) { // 2x1 special handling
                        b = (Check2x1AutoRail(1)) | HT_LINE;
                } else if (dy == -(int)TILE_SIZE) { // 2x1 other direction
                        b = (Check2x1AutoRail(0)) | HT_LINE;
                } else {
                        b = HT_LINE | HT_DIR_Y;
                }
                x = _thd.selstart.x;
        } else if (w > h * 2) { // still count as x dir?
                b = HT_LINE | HT_DIR_X;
                y = _thd.selstart.y;
        } else if (h > w * 2) { // still count as y dir?
                b = HT_LINE | HT_DIR_Y;
                x = _thd.selstart.x;
        } else { // complicated direction
                int d = w - h;
                _thd.selend.x = _thd.selend.x & ~TILE_UNIT_MASK;
                _thd.selend.y = _thd.selend.y & ~TILE_UNIT_MASK;

                /* four cases. */
                if (x > _thd.selstart.x) {
                        if (y > _thd.selstart.y) {
                                /* south */
                                if (d == 0) {
                                        b = (x & TILE_UNIT_MASK) > (y & TILE_UNIT_MASK) ? HT_LINE | HT_DIR_VL : HT_LINE | HT_DIR_VR;
                                } else if (d >= 0) {
                                        x = _thd.selstart.x + h;
                                        b = HT_LINE | HT_DIR_VL;
                                } else {
                                        y = _thd.selstart.y + w;
                                        b = HT_LINE | HT_DIR_VR;
                                }
                        } else {
                                /* west */
                                if (d == 0) {
                                        b = (x & TILE_UNIT_MASK) + (y & TILE_UNIT_MASK) >= TILE_SIZE ? HT_LINE | HT_DIR_HL : HT_LINE | HT_DIR_HU;
                                } else if (d >= 0) {
                                        x = _thd.selstart.x + h;
                                        b = HT_LINE | HT_DIR_HL;
                                } else {
                                        y = _thd.selstart.y - w;
                                        b = HT_LINE | HT_DIR_HU;
                                }
                        }
                } else {
                        if (y > _thd.selstart.y) {
                                /* east */
                                if (d == 0) {
                                        b = (x & TILE_UNIT_MASK) + (y & TILE_UNIT_MASK) >= TILE_SIZE ? HT_LINE | HT_DIR_HL : HT_LINE | HT_DIR_HU;
                                } else if (d >= 0) {
                                        x = _thd.selstart.x - h;
                                        b = HT_LINE | HT_DIR_HU;
                                } else {
                                        y = _thd.selstart.y + w;
                                        b = HT_LINE | HT_DIR_HL;
                                }
                        } else {
                                /* north */
                                if (d == 0) {
                                        b = (x & TILE_UNIT_MASK) > (y & TILE_UNIT_MASK) ? HT_LINE | HT_DIR_VL : HT_LINE | HT_DIR_VR;
                                } else if (d >= 0) {
                                        x = _thd.selstart.x - h;
                                        b = HT_LINE | HT_DIR_VR;
                                } else {
                                        y = _thd.selstart.y - w;
                                        b = HT_LINE | HT_DIR_VL;
                                }
                        }
                }
        }

        _thd.selend.x = x;
        _thd.selend.y = y;
        _thd.dir2 = HT_DIR_END;
        _thd.next_drawstyle = b;

        ShowLengthMeasurement(b, TileVirtXY(_thd.selstart.x, _thd.selstart.y), TileVirtXY(_thd.selend.x, _thd.selend.y));
}

static HighLightStyle CalcPolyrailDrawstyle(Point pt, bool dragging)
{
        RailSnapMode snap_mode = GetRailSnapMode();

        /* are we only within one tile? */
        if (snap_mode == RSM_SNAP_TO_TILE && GetRailSnapTile() == TileVirtXY(pt.x, pt.y)) {
                _thd.selend.x = pt.x;
                _thd.selend.y = pt.y;
                HideMeasurementTooltips();
                return GetAutorailHT(pt.x, pt.y);
        }

        /* find the best track */
        PolylineInfo line;

        bool lock_snapping = dragging && snap_mode == RSM_SNAP_TO_RAIL;
        if (!lock_snapping) _current_snap_lock.x = -1;

        const LineSnapPoint *snap_point;
        if (_current_snap_lock.x != -1) {
                snap_point = FindBestPolyline(pt, &_current_snap_lock, 1, &line);
        } else if (snap_mode == RSM_SNAP_TO_TILE) {
                snap_point = FindBestPolyline(pt, _tile_snap_points.data(), (uint)_tile_snap_points.size(), &line);
        } else {
                assert(snap_mode == RSM_SNAP_TO_RAIL);
                snap_point = FindBestPolyline(pt, _rail_snap_points.data(), (uint)_rail_snap_points.size(), &line);
        }

        if (snap_point == nullptr) {
                HideMeasurementTooltips();
                return HT_NONE; // no match
        }

        if (lock_snapping && _current_snap_lock.x == -1) {
                /* lock down the snap point */
                _current_snap_lock = *snap_point;
                _current_snap_lock.dirs &= (1 << line.first_dir) | (1 << ReverseDir(line.first_dir));
        }

        TileIndexDiffC first_dir = TileIndexDiffCByDir(line.first_dir);
        _thd.selstart.x  = line.start.x;
        _thd.selstart.y  = line.start.y;
        _thd.selend.x    = _thd.selstart.x + line.first_len * first_dir.x * (IsDiagonalDirection(line.first_dir) ? TILE_SIZE : TILE_SIZE / 2);
        _thd.selend.y    = _thd.selstart.y + line.first_len * first_dir.y * (IsDiagonalDirection(line.first_dir) ? TILE_SIZE : TILE_SIZE / 2);
        _thd.selstart2.x = _thd.selend.x;
        _thd.selstart2.y = _thd.selend.y;
        _thd.selstart.x  += first_dir.x;
        _thd.selstart.y  += first_dir.y;
        _thd.selend.x    -= first_dir.x;
        _thd.selend.y    -= first_dir.y;
        Trackdir seldir = PointDirToTrackdir(_thd.selstart, line.first_dir);
        _thd.selstart.x  &= ~TILE_UNIT_MASK;
        _thd.selstart.y  &= ~TILE_UNIT_MASK;

        if (line.second_len != 0) {
                TileIndexDiffC second_dir = TileIndexDiffCByDir(line.second_dir);
                _thd.selend2.x   = _thd.selstart2.x + line.second_len * second_dir.x * (IsDiagonalDirection(line.second_dir) ? TILE_SIZE : TILE_SIZE / 2);
                _thd.selend2.y   = _thd.selstart2.y + line.second_len * second_dir.y * (IsDiagonalDirection(line.second_dir) ? TILE_SIZE : TILE_SIZE / 2);
                _thd.selstart2.x += second_dir.x;
                _thd.selstart2.y += second_dir.y;
                _thd.selend2.x   -= second_dir.x;
                _thd.selend2.y   -= second_dir.y;
                Trackdir seldir2 = PointDirToTrackdir(_thd.selstart2, line.second_dir);
                _thd.selstart2.x &= ~TILE_UNIT_MASK;
                _thd.selstart2.y &= ~TILE_UNIT_MASK;
                _thd.dir2 = (HighLightStyle)TrackdirToTrack(seldir2);
        } else {
                _thd.dir2 = HT_DIR_END;
        }

        HighLightStyle ret = HT_LINE | (HighLightStyle)TrackdirToTrack(seldir);
        ShowLengthMeasurement(ret, TileVirtXY(_thd.selstart.x, _thd.selstart.y), TileVirtXY(_thd.selend.x, _thd.selend.y), TCC_EXIT_VIEWPORT, true);
        return ret;
}

/**
 * Selects tiles while dragging
 * @param x X coordinate of end of selection
 * @param y Y coordinate of end of selection
 * @param method modifies the way tiles are selected. Possible
 * methods are VPM_* in viewport.h
 */
void VpSelectTilesWithMethod(int x, int y, ViewportPlaceMethod method)
{
        int sx, sy;
        HighLightStyle style;

        if (x == -1) {
                _thd.selend.x = -1;
                return;
        }

        if ((_thd.place_mode & HT_POLY) && GetRailSnapMode() != RSM_NO_SNAP) {
                Point pt = { x, y };
                _thd.next_drawstyle = CalcPolyrailDrawstyle(pt, true);
                return;
        }

        /* Special handling of drag in any (8-way) direction */
        if (method & (VPM_RAILDIRS | VPM_SIGNALDIRS)) {
                _thd.selend.x = x;
                _thd.selend.y = y;
                CalcRaildirsDrawstyle(x, y, method);
                return;
        }

        /* Needed so level-land is placed correctly */
        if ((_thd.next_drawstyle & HT_DRAG_MASK) == HT_POINT) {
                x += TILE_SIZE / 2;
                y += TILE_SIZE / 2;
        }

        sx = _thd.selstart.x;
        sy = _thd.selstart.y;

        int limit = 0;

        switch (method) {
                case VPM_X_OR_Y: // drag in X or Y direction
                        if (abs(sy - y) < abs(sx - x)) {
                                y = sy;
                                style = HT_DIR_X;
                        } else {
                                x = sx;
                                style = HT_DIR_Y;
                        }
                        goto calc_heightdiff_single_direction;

                case VPM_X_LIMITED: // Drag in X direction (limited size).
                        limit = (_thd.sizelimit - 1) * TILE_SIZE;
                        [[fallthrough]];

                case VPM_FIX_X: // drag in Y direction
                        x = sx;
                        style = HT_DIR_Y;
                        goto calc_heightdiff_single_direction;

                case VPM_Y_LIMITED: // Drag in Y direction (limited size).
                        limit = (_thd.sizelimit - 1) * TILE_SIZE;
                        [[fallthrough]];

                case VPM_FIX_Y: // drag in X direction
                        y = sy;
                        style = HT_DIR_X;

calc_heightdiff_single_direction:;
                        if (limit > 0) {
                                x = sx + Clamp(x - sx, -limit, limit);
                                y = sy + Clamp(y - sy, -limit, limit);
                        }
                        /* With current code passing a HT_LINE style to calculate the height
                         * difference is enough. However if/when a point-tool is created
                         * with this method, function should be called with new_style (below)
                         * instead of HT_LINE | style case HT_POINT is handled specially
                         * new_style := (_thd.next_drawstyle & HT_RECT) ? HT_LINE | style : _thd.next_drawstyle; */
                        ShowLengthMeasurement(HT_LINE | style, TileVirtXY(sx, sy), TileVirtXY(x, y));
                        break;

                case VPM_A_B_LINE: { // drag an A to B line
                        TileIndex t0 = TileVirtXY(sx, sy);
                        TileIndex t1 = TileVirtXY(x, y);
                        uint dx = Delta(TileX(t0), TileX(t1)) + 1;
                        uint dy = Delta(TileY(t0), TileY(t1)) + 1;

                        /* If dragging an area (eg dynamite tool) and it is actually a single
                         * row/column, change the type to 'line' to get proper calculation for height */
                        style = (HighLightStyle)_thd.next_drawstyle;
                        if (style & HT_RECT) {
                                if (dx == 1) {
                                        style = HT_LINE | HT_DIR_Y;
                                } else if (dy == 1) {
                                        style = HT_LINE | HT_DIR_X;
                                }
                        }

                        int heightdiff = 0;

                        if (dx != 1 || dy != 1) {
                                heightdiff = CalcHeightdiff(style, 0, t0, t1);
                                SetDParam(0, DistanceManhattan(t0, t1));
                                SetDParam(1, IntSqrt64(DistanceSquare64(t0, t1))); // Avoid overflow in DistanceSquare
                        } else {
                                SetDParam(0, 0);
                                SetDParam(1, 0);
                        }

                        SetDParam(2, DistanceFromEdge(t1));
                        SetDParam(3, GetTileMaxZ(t1) * TILE_HEIGHT_STEP);
                        SetDParam(4, heightdiff);
                        /* Always show the measurement tooltip */
                        GuiShowTooltips(_thd.GetCallbackWnd(), STR_MEASURE_DIST_HEIGHTDIFF, TCC_EXIT_VIEWPORT, 5);
                        break;
                }

                case VPM_X_AND_Y_LIMITED: // Drag an X by Y constrained rect area.
                        limit = (_thd.sizelimit - 1) * TILE_SIZE;
                        x = sx + Clamp(x - sx, -limit, limit);
                        y = sy + Clamp(y - sy, -limit, limit);
                        [[fallthrough]];

                case VPM_X_AND_Y: // drag an X by Y area
                        if (_settings_client.gui.measure_tooltip) {
                                static const StringID measure_strings_area[] = {
                                        STR_NULL, STR_NULL, STR_MEASURE_AREA, STR_MEASURE_AREA_HEIGHTDIFF
                                };

                                TileIndex t0 = TileVirtXY(sx, sy);
                                TileIndex t1 = TileVirtXY(x, y);
                                uint dx = Delta(TileX(t0), TileX(t1)) + 1;
                                uint dy = Delta(TileY(t0), TileY(t1)) + 1;
                                uint index = 0;

                                /* If dragging an area (eg dynamite tool) and it is actually a single
                                 * row/column, change the type to 'line' to get proper calculation for height */
                                style = (HighLightStyle)_thd.next_drawstyle;
                                if (_thd.IsDraggingDiagonal()) {
                                        /* Determine the "area" of the diagonal dragged selection.
                                         * We assume the area is the number of tiles along the X
                                         * edge and the number of tiles along the Y edge. However,
                                         * multiplying these two numbers does not give the exact
                                         * number of tiles; basically we are counting the black
                                         * squares on a chess board and ignore the white ones to
                                         * make the tile counts at the edges match up. There is no
                                         * other way to make a proper count though.
                                         *
                                         * First convert to the rotated coordinate system. */
                                        int dist_x = TileX(t0) - TileX(t1);
                                        int dist_y = TileY(t0) - TileY(t1);
                                        int a_max = dist_x + dist_y;
                                        int b_max = dist_y - dist_x;

                                        /* Now determine the size along the edge, but due to the
                                         * chess board principle this counts double. */
                                        a_max = abs(a_max + (a_max > 0 ? 2 : -2)) / 2;
                                        b_max = abs(b_max + (b_max > 0 ? 2 : -2)) / 2;

                                        /* We get a 1x1 on normal 2x1 rectangles, due to it being
                                         * a seen as two sides. As the result for actual building
                                         * will be the same as non-diagonal dragging revert to that
                                         * behaviour to give it a more normally looking size. */
                                        if (a_max != 1 || b_max != 1) {
                                                dx = a_max;
                                                dy = b_max;
                                        }
                                } else if (style & HT_RECT) {
                                        if (dx == 1) {
                                                style = HT_LINE | HT_DIR_Y;
                                        } else if (dy == 1) {
                                                style = HT_LINE | HT_DIR_X;
                                        }
                                }

                                if (dx != 1 || dy != 1) {
                                        int heightdiff = CalcHeightdiff(style, 0, t0, t1);

                                        SetDParam(index++, dx - (style & HT_POINT ? 1 : 0));
                                        SetDParam(index++, dy - (style & HT_POINT ? 1 : 0));
                                        if (heightdiff != 0) SetDParam(index++, heightdiff);
                                }

                                ShowMeasurementTooltips(measure_strings_area[index], index);
                        }
                        break;

                default: NOT_REACHED();
        }

        _thd.selend.x = x;
        _thd.selend.y = y;
        _thd.dir2 = HT_DIR_END;
}

/**
 * Handle the mouse while dragging for placement/resizing.
 * @return State of handling the event.
 */
EventState VpHandlePlaceSizingDrag()
{
        if (_special_mouse_mode != WSM_SIZING && _special_mouse_mode != WSM_DRAGGING) return ES_NOT_HANDLED;

        /* stop drag mode if the window has been closed */
        Window *w = _thd.GetCallbackWnd();
        if (w == nullptr) {
                ResetObjectToPlace();
                return ES_HANDLED;
        }

        if (_left_button_down && _special_mouse_mode == WSM_DRAGGING) {
                /* Only register a drag event when the mouse moved. */
                if (_thd.new_pos.x == _thd.selstart.x && _thd.new_pos.y == _thd.selstart.y) return ES_HANDLED;
                _thd.selstart.x = _thd.new_pos.x;
                _thd.selstart.y = _thd.new_pos.y;
        }

        /* While dragging execute the drag procedure of the corresponding window (mostly VpSelectTilesWithMethod() ).
         * Do it even if the button is no longer pressed to make sure that OnPlaceDrag was called at least once. */
        w->OnPlaceDrag(_thd.select_method, _thd.select_proc, GetTileBelowCursor());
        if (_left_button_down) return ES_HANDLED;

        /* Mouse button released. */
        _special_mouse_mode = WSM_NONE;
        if (_special_mouse_mode == WSM_DRAGGING) return ES_HANDLED;

        /* Keep the selected tool, but reset it to the original mode. */
        HighLightStyle others = _thd.place_mode & ~(HT_DRAG_MASK | HT_DIR_MASK);
        if ((_thd.next_drawstyle & HT_DRAG_MASK) == HT_RECT) {
                _thd.place_mode = HT_RECT | others;
        } else if (_thd.select_method & VPM_SIGNALDIRS) {
                _thd.place_mode = HT_RECT | others;
        } else if (_thd.select_method & VPM_RAILDIRS) {
                _thd.place_mode = (_thd.select_method & ~VPM_RAILDIRS ? _thd.next_drawstyle : HT_RAIL) | others;
        } else {
                _thd.place_mode = HT_POINT | others;
        }
        SetTileSelectSize(1, 1);

        if (_thd.place_mode & HT_POLY) {
                if (GetRailSnapMode() == RSM_SNAP_TO_TILE) SetRailSnapMode(RSM_NO_SNAP);
                if (_thd.drawstyle == HT_NONE) return ES_HANDLED;
        }
        HideMeasurementTooltips();

        w->OnPlaceMouseUp(_thd.select_method, _thd.select_proc, _thd.selend, TileVirtXY(_thd.selstart.x, _thd.selstart.y), TileVirtXY(_thd.selend.x, _thd.selend.y));
        return ES_HANDLED;
}

/**
 * Change the cursor and mouse click/drag handling to a mode for performing special operations like tile area selection, object placement, etc.
 * @param icon New shape of the mouse cursor.
 * @param pal Palette to use.
 * @param mode Mode to perform.
 * @param w %Window requesting the mode change.
 */
void SetObjectToPlaceWnd(CursorID icon, PaletteID pal, HighLightStyle mode, Window *w)
{
        SetObjectToPlace(icon, pal, mode, w->window_class, w->window_number, w->GetWindowToken());
}

#include "table/animcursors.h"

/**
 * Change the cursor and mouse click/drag handling to a mode for performing special operations like tile area selection, object placement, etc.
 * @param icon New shape of the mouse cursor.
 * @param pal Palette to use.
 * @param mode Mode to perform.
 * @param window_class %Window class of the window requesting the mode change.
 * @param window_num Number of the window in its class requesting the mode change.
 * @param window_token Window token of the window in its class requesting the mode change, if non-zero.
 */
void SetObjectToPlace(CursorID icon, PaletteID pal, HighLightStyle mode, WindowClass window_class, WindowNumber window_num, WindowToken window_token)
{
        if (_thd.window_class != WC_INVALID) {
                /* Undo clicking on button and drag & drop */
                Window *w = _thd.GetCallbackWnd();
                /* Call the abort function, but set the window class to something
                 * that will never be used to avoid infinite loops. Setting it to
                 * the 'next' window class must not be done because recursion into
                 * this function might in some cases reset the newly set object to
                 * place or not properly reset the original selection. */
                _thd.window_class = WC_INVALID;
                _thd.window_token = WindowToken(0);
                if (w != nullptr) {
                        w->OnPlaceObjectAbort();
                        HideMeasurementTooltips();
                }
        }

        /* Mark the old selection dirty, in case the selection shape or colour changes */
        if ((_thd.drawstyle & HT_DRAG_MASK) != HT_NONE) SetSelectionTilesDirty();

        SetTileSelectSize(1, 1);

        _thd.square_palette = PAL_NONE;

        if (mode == HT_DRAG) { // HT_DRAG is for dragdropping trains in the depot window
                mode = HT_NONE;
                _special_mouse_mode = WSM_DRAGDROP;
        } else {
                _special_mouse_mode = WSM_NONE;
        }

        _thd.place_mode = mode;
        _thd.window_class = window_class;
        _thd.window_number = window_num;
        _thd.window_token = window_token;

        if ((mode & HT_DRAG_MASK) == HT_SPECIAL) { // special tools, like tunnels or docks start with presizing mode
                VpStartPreSizing();
        }

        if (mode & HT_POLY) {
                SetRailSnapMode((mode & HT_NEW_POLY) == HT_NEW_POLY ? RSM_NO_SNAP : RSM_SNAP_TO_RAIL);
        }

        if ((icon & ANIMCURSOR_FLAG) != 0) {
                SetAnimatedMouseCursor(_animcursors[icon & ~ANIMCURSOR_FLAG]);
        } else {
                SetMouseCursor(icon, pal);
        }

}

/** Reset the cursor and mouse mode handling back to default (normal cursor, only clicking in windows). */
void ResetObjectToPlace()
{
        SetObjectToPlace(SPR_CURSOR_MOUSE, PAL_NONE, HT_NONE, WC_MAIN_WINDOW, 0);
}

void ChangeRenderMode(Viewport *vp, bool down) {
        ViewportMapType map_type = vp->map_type;
        if (vp->zoom < ZOOM_LVL_DRAW_MAP) return;
        ClearViewportLandPixelCache(vp);
        if (down) {
                vp->map_type = (map_type == VPMT_MIN) ? VPMT_MAX : (ViewportMapType) (map_type - 1);
        } else {
                vp->map_type = (map_type == VPMT_MAX) ? VPMT_MIN : (ViewportMapType) (map_type + 1);
        }
}

Point GetViewportStationMiddle(const Viewport *vp, const Station *st)
{
        int x = TileX(st->xy) * TILE_SIZE;
        int y = TileY(st->xy) * TILE_SIZE;

        /* Be faster/less precise in viewport map mode, sub-pixel precision is not needed.
         * Don't rebase point into screen coordinates in viewport map mode.
         */
        if (vp->zoom < ZOOM_LVL_DRAW_MAP) {
                int z = GetSlopePixelZ(Clamp(x, 0, MapSizeX() * TILE_SIZE - 1), Clamp(y, 0, MapSizeY() * TILE_SIZE - 1));
                Point p = RemapCoords(x, y, z);
                p.x = UnScaleByZoom(p.x - vp->virtual_left, vp->zoom) + vp->left;
                p.y = UnScaleByZoom(p.y - vp->virtual_top, vp->zoom) + vp->top;
                return p;
        } else {
                int z = st->xy < MapSize() ? TILE_HEIGHT * TileHeight(st->xy) : 0;
                Point p = RemapCoords(x, y, z);
                p.x = UnScaleByZoomLower(p.x, vp->zoom);
                p.y = UnScaleByZoomLower(p.y, vp->zoom);
                return p;
        }
}

/** Helper class for getting the best sprite sorter. */
struct ViewportSSCSS {
        VpSorterChecker fct_checker; ///< The check function.
        VpSpriteSorter fct_sorter;   ///< The sorting function.
};

/** List of sorters ordered from best to worst. */
static ViewportSSCSS _vp_sprite_sorters[] = {
#ifdef WITH_SSE
        { &ViewportSortParentSpritesSSE41Checker, &ViewportSortParentSpritesSSE41 },
#endif
        { &ViewportSortParentSpritesChecker, &ViewportSortParentSprites }
};

/** Choose the "best" sprite sorter and set _vp_sprite_sorter. */
void InitializeSpriteSorter()
{
        for (const auto &sprite_sorter : _vp_sprite_sorters) {
                if (sprite_sorter.fct_checker()) {
                        _vp_sprite_sorter = sprite_sorter.fct_sorter;
                        break;
                }
        }
        dbg_assert(_vp_sprite_sorter != nullptr);
}

/**
 * Scroll players main viewport.
 * @param tile tile to center viewport on
 * @param flags type of operation
 * @param p1 ViewportScrollTarget of scroll target
 * @param p2 company or client id depending on the target
 * @param text unused
 * @return the cost of this operation or an error
 */
CommandCost CmdScrollViewport(TileIndex tile, DoCommandFlag flags, uint32_t p1, uint32_t p2, const char *text)
{
        if (_current_company != OWNER_DEITY) return CMD_ERROR;
        ViewportScrollTarget target = (ViewportScrollTarget)p1;
        switch (target) {
                case VST_EVERYONE:
                        break;
                case VST_COMPANY:
                        if (_local_company != (CompanyID)p2) return CommandCost();
                        break;
                case VST_CLIENT:
                        if (_network_own_client_id != (ClientID)p2) return CommandCost();
                        break;
                default:
                        return CMD_ERROR;
        }

        if (flags & DC_EXEC) {
                ResetObjectToPlace();
                ScrollMainWindowToTile(tile);
        }
        return CommandCost();
}

static LineSnapPoint LineSnapPointAtRailTrackEndpoint(TileIndex tile, DiagDirection exit_dir, bool bidirectional)
{
        LineSnapPoint ret;
        ret.x = (TILE_SIZE / 2) * (uint)(2 * TileX(tile) + TileIndexDiffCByDiagDir(exit_dir).x + 1);
        ret.y = (TILE_SIZE / 2) * (uint)(2 * TileY(tile) + TileIndexDiffCByDiagDir(exit_dir).y + 1);

        ret.dirs = 0;
        SetBit(ret.dirs, DiagDirToDir(exit_dir));
        SetBit(ret.dirs, ChangeDir(DiagDirToDir(exit_dir), DIRDIFF_45LEFT));
        SetBit(ret.dirs, ChangeDir(DiagDirToDir(exit_dir), DIRDIFF_45RIGHT));
        if (bidirectional) ret.dirs |= std::rotr<uint8_t>(ret.dirs, DIRDIFF_REVERSE);

        return ret;
}

/**
 * Store the position of lastly built rail track; for highlighting purposes.
 *
 * In "polyline" highlighting mode, the stored end point will be used as a snapping point for new
 * tracks allowing to place multi-segment polylines.
 *
 * @param start_tile         tile where the track starts
 * @param end_tile           tile where the track ends
 * @param start_track        track piece on the start_tile
 * @param bidirectional_exit whether to allow to highlight next track in any direction; otherwise new track will have to fallow the stored one (usefull when placing tunnels and bridges)
 */
void StoreRailPlacementEndpoints(TileIndex start_tile, TileIndex end_tile, Track start_track, bool bidirectional_exit)
{
        if (start_tile != INVALID_TILE && end_tile != INVALID_TILE) {
                /* calculate trackdirs at booth ends of the track */
                Trackdir exit_trackdir_at_start = TrackToTrackdir(start_track);
                Trackdir exit_trackdir_at_end = ReverseTrackdir(TrackToTrackdir(start_track));
                if (start_tile != end_tile) { // multi-tile case
                        /* determine proper direction (pointing outside of the track) */
                        uint distance = DistanceManhattan(start_tile, end_tile);
                        if (distance > DistanceManhattan(TileAddByDiagDir(start_tile, TrackdirToExitdir(exit_trackdir_at_start)), end_tile)) {
                                Swap(exit_trackdir_at_start, exit_trackdir_at_end);
                        }
                        /* determine proper track on the end tile - switch between upper/lower or left/right based on the length */
                        if (distance % 2 != 0) exit_trackdir_at_end = NextTrackdir(exit_trackdir_at_end);
                }

                LineSnapPoint snap_start = LineSnapPointAtRailTrackEndpoint(start_tile, TrackdirToExitdir(exit_trackdir_at_start), bidirectional_exit);
                LineSnapPoint snap_end = LineSnapPointAtRailTrackEndpoint(end_tile, TrackdirToExitdir(exit_trackdir_at_end), bidirectional_exit);
                /* Find if we already had these coordinates before. */
                bool had_start = false;
                bool had_end = false;
                for (const LineSnapPoint &snap : _rail_snap_points) {
                        had_start |= (snap.x == snap_start.x && snap.y == snap_start.y);
                        had_end |= (snap.x == snap_end.x && snap.y == snap_end.y);
                }
                /* Create new snap point set. */
                if (had_start && had_end) {
                        /* just stop snaping, don't forget snap points */
                        SetRailSnapMode(RSM_NO_SNAP);
                } else {
                        /* include only new points */
                        _rail_snap_points.clear();
                        if (!had_start) _rail_snap_points.push_back(snap_start);
                        if (!had_end) _rail_snap_points.push_back(snap_end);
                        SetRailSnapMode(RSM_SNAP_TO_RAIL);
                }
        }
}

static void MarkCatchmentTilesDirty()
{
        if (_viewport_highlight_town != nullptr) {
                MarkWholeNonMapViewportsDirty();
                return;
        }
        if (_viewport_highlight_station != nullptr) {
                if (_viewport_highlight_station->catchment_tiles.tile == INVALID_TILE) {
                        MarkWholeNonMapViewportsDirty();
                        _viewport_highlight_station = nullptr;
                } else {
                        BitmapTileIterator it(_viewport_highlight_station->catchment_tiles);
                        for (TileIndex tile = it; tile != INVALID_TILE; tile = ++it) {
                                MarkTileDirtyByTile(tile, VMDF_NOT_MAP_MODE);
                        }
                }
        }
        if (_viewport_highlight_waypoint != nullptr) {
                if (!_viewport_highlight_waypoint->IsInUse()) {
                        _viewport_highlight_waypoint = nullptr;
                }
                MarkWholeNonMapViewportsDirty();
        }
}

bool CurrentlySnappingRailPlacement()
{
        return (_thd.place_mode & HT_POLY) && GetRailSnapMode() == RSM_SNAP_TO_RAIL;
}

static RailSnapMode GetRailSnapMode()
{
        if (_rail_snap_mode == RSM_SNAP_TO_TILE && _tile_snap_points.size() == 0) return RSM_NO_SNAP;
        if (_rail_snap_mode == RSM_SNAP_TO_RAIL && _rail_snap_points.size() == 0) return RSM_NO_SNAP;
        return _rail_snap_mode;
}

static void SetRailSnapMode(RailSnapMode mode)
{
        _rail_snap_mode = mode;

        if ((_thd.place_mode & HT_POLY) && (GetRailSnapMode() == RSM_NO_SNAP)) {
                SetTileSelectSize(1, 1);
        }
}

static TileIndex GetRailSnapTile()
{
        if (_tile_snap_points.size() == 0) return INVALID_TILE;
        return TileVirtXY(_tile_snap_points[DIAGDIR_NE].x, _tile_snap_points[DIAGDIR_NE].y);
}

static void SetRailSnapTile(TileIndex tile)
{
        _tile_snap_points.clear();
        if (tile == INVALID_TILE) return;

        for (DiagDirection dir = DIAGDIR_BEGIN; dir < DIAGDIR_END; dir++) {
                _tile_snap_points.push_back(LineSnapPointAtRailTrackEndpoint(tile, dir, false));
                LineSnapPoint &point = _tile_snap_points.back();
                point.dirs = std::rotr<uint8_t>(point.dirs, DIRDIFF_REVERSE);
        }
}

void ResetRailPlacementSnapping()
{
        _rail_snap_mode = RSM_NO_SNAP;
        _tile_snap_points.clear();
        _rail_snap_points.clear();
        _current_snap_lock.x = -1;
}

static void SetWindowDirtyForViewportCatchment()
{
        if (_viewport_highlight_station != nullptr) SetWindowDirty(WC_STATION_VIEW, _viewport_highlight_station->index);
        if (_viewport_highlight_waypoint != nullptr) SetWindowDirty(WC_WAYPOINT_VIEW, _viewport_highlight_waypoint->index);
        if (_viewport_highlight_town != nullptr) SetWindowDirty(WC_TOWN_VIEW, _viewport_highlight_town->index);
        if (_viewport_highlight_tracerestrict_program != nullptr) InvalidateWindowClassesData(WC_TRACE_RESTRICT);
}

static void ClearViewportCatchment()
{
        MarkCatchmentTilesDirty();
        _viewport_highlight_station = nullptr;
        _viewport_highlight_waypoint = nullptr;
        _viewport_highlight_town = nullptr;
        _viewport_highlight_tracerestrict_program = nullptr;
}

/**
 * Select or deselect station for coverage area highlight.
 * Selecting a station will deselect a town.
 * @param *st Station in question
 * @param sel Select or deselect given station
 */
void SetViewportCatchmentStation(const Station *st, bool sel)
{
        SetWindowDirtyForViewportCatchment();
        if (sel && _viewport_highlight_station != st) {
                ClearViewportCatchment();
                _viewport_highlight_station = st;
                MarkCatchmentTilesDirty();
        } else if (!sel && _viewport_highlight_station == st) {
                MarkCatchmentTilesDirty();
                _viewport_highlight_station = nullptr;
        }
        if (_viewport_highlight_station != nullptr) SetWindowDirty(WC_STATION_VIEW, _viewport_highlight_station->index);
}

/**
 * Select or deselect waypoint for coverage area highlight.
 * Selecting a waypoint will deselect a town.
 * @param *wp Waypoint in question
 * @param sel Select or deselect given waypoint
 */
void SetViewportCatchmentWaypoint(const Waypoint *wp, bool sel)
{
        SetWindowDirtyForViewportCatchment();
        if (sel && _viewport_highlight_waypoint != wp) {
                ClearViewportCatchment();
                _viewport_highlight_waypoint = wp;
                MarkCatchmentTilesDirty();
        } else if (!sel && _viewport_highlight_waypoint == wp) {
                MarkCatchmentTilesDirty();
                _viewport_highlight_waypoint = nullptr;
        }
        if (_viewport_highlight_waypoint != nullptr) SetWindowDirty(WC_WAYPOINT_VIEW, _viewport_highlight_waypoint->index);
}

/**
 * Select or deselect town for coverage area highlight.
 * Selecting a town will deselect a station.
 * @param *t Town in question
 * @param sel Select or deselect given town
 */
void SetViewportCatchmentTown(const Town *t, bool sel)
{
        SetWindowDirtyForViewportCatchment();
        if (sel && _viewport_highlight_town != t) {
                ClearViewportCatchment();
                _viewport_highlight_town = t;
                MarkWholeNonMapViewportsDirty();
        } else if (!sel && _viewport_highlight_town == t) {
                _viewport_highlight_town = nullptr;
                MarkWholeNonMapViewportsDirty();
        }
        if (_viewport_highlight_town != nullptr) SetWindowDirty(WC_TOWN_VIEW, _viewport_highlight_town->index);
}

void SetViewportCatchmentTraceRestrictProgram(const TraceRestrictProgram *prog, bool sel)
{
        SetWindowDirtyForViewportCatchment();
        if (sel && _viewport_highlight_tracerestrict_program != prog) {
                ClearViewportCatchment();
                _viewport_highlight_tracerestrict_program = prog;
                MarkWholeNonMapViewportsDirty();
        } else if (!sel && _viewport_highlight_tracerestrict_program == prog) {
                _viewport_highlight_tracerestrict_program = nullptr;
                MarkWholeNonMapViewportsDirty();
        }
        if (_viewport_highlight_tracerestrict_program != nullptr) InvalidateWindowClassesData(WC_TRACE_RESTRICT);
}

int GetSlopeTreeBrightnessAdjust(Slope slope)
{
        switch (slope) {
                case SLOPE_NW:
                case SLOPE_STEEP_N:
                case SLOPE_STEEP_W:
                        return 8;
                case SLOPE_N:
                case SLOPE_W:
                case SLOPE_ENW:
                case SLOPE_NWS:
                        return 4;
                case SLOPE_SE:
                        return -10;
                case SLOPE_STEEP_S:
                case SLOPE_STEEP_E:
                        return -4;
                case SLOPE_NE:
                        return -8;
                case SLOPE_SW:
                        return -4;
                case SLOPE_S:
                case SLOPE_E:
                case SLOPE_SEN:
                case SLOPE_WSE:
                        return -6;
                default:
                        return 0;
        }
}

bool IsViewportMouseHoverActive()
{
        if (_settings_client.gui.hover_delay_ms == 0) {
                /* right click mode */
                return _right_button_down || _settings_client.gui.instant_tile_tooltip;
        } else {
                /* normal mode */
                return _mouse_hovering;
        }
}