Fix crash when setting separation mode for vehicles with no orders list.

[openttd-joker.git] / src / window.cpp

/* $Id$ */

/*
 * 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 window.cpp Windowing system, widgets and events */

#include "stdafx.h"
#include <stdarg.h>
#include "company_func.h"
#include "gfx_func.h"
#include "console_func.h"
#include "console_gui.h"
#include "viewport_func.h"
#include "progress.h"
#include "blitter/factory.hpp"
#include "zoom_func.h"
#include "vehicle_base.h"
#include "window_func.h"
#include "tilehighlight_func.h"
#include "network/network.h"
#include "querystring_gui.h"
#include "widgets/dropdown_func.h"
#include "strings_func.h"
#include "settings_type.h"
#include "settings_func.h"
#include "ini_type.h"
#include "newgrf_debug.h"
#include "hotkeys.h"
#include "toolbar_gui.h"
#include "statusbar_gui.h"
#include "error.h"
#include "game/game.hpp"
#include "video/video_driver.hpp"

#include "safeguards.h"

/** Values for _settings_client.gui.auto_scrolling */
enum ViewportAutoscrolling {
        VA_DISABLED,                  //!< Do not autoscroll when mouse is at edge of viewport.
        VA_MAIN_VIEWPORT_FULLSCREEN,  //!< Scroll main viewport at edge when using fullscreen.
        VA_MAIN_VIEWPORT,             //!< Scroll main viewport at edge.
        VA_EVERY_VIEWPORT,            //!< Scroll all viewports at their edges.
};

static const int MAX_OFFSET_DOUBLE_CLICK = 5;      ///< How much the mouse is allowed to move to call it a double click
static const uint TIME_BETWEEN_DOUBLE_CLICK = 500; ///< Time between 2 left clicks before it becoming a double click, in ms
static const int MAX_OFFSET_HOVER = 5;             ///< Maximum mouse movement before stopping a hover event.

static Point _drag_delta; ///< delta between mouse cursor and upper left corner of dragged window
static Window *_mouseover_last_w = nullptr; ///< Window of the last #MOUSEOVER event.
static Window *_last_scroll_window = nullptr; ///< Window of the last scroll event.

/** List of windows opened at the screen sorted from the front. */
Window *_z_front_window = nullptr;
/** List of windows opened at the screen sorted from the back. */
Window *_z_back_window  = nullptr;

/** If false, highlight is white, otherwise the by the widget defined colour. */
bool _window_highlight_colour = false;

uint64 _window_update_number = 1;

/*
 * Window that currently has focus. - The main purpose is to generate
 * #FocusLost events, not to give next window in z-order focus when a
 * window is closed.
 */
Window *_focused_window;

Point _cursorpos_drag_start;

int _scrollbar_start_pos;
int _scrollbar_size;
byte _scroller_click_timeout = 0;

Window *_scrolling_viewport; ///< A viewport is being scrolled with the mouse.
static Point _viewport_scroll_start_pos = { -1, -1 }; ///< Viewport position when scrolling with the mouse started.
bool _mouse_hovering;      ///< The mouse is hovering over the same point.

SpecialMouseMode _special_mouse_mode; ///< Mode of the mouse.

/**
 * List of all WindowDescs.
 * This is a pointer to ensure initialisation order with the various static WindowDesc instances.
 */
static SmallVector<WindowDesc*, 16> *_window_descs = nullptr;

/** Config file to store WindowDesc */
char *_windows_file;

/** Window description constructor. */
WindowDesc::WindowDesc(WindowPosition def_pos, const char *ini_key, int16 def_width_trad, int16 def_height_trad,
                        WindowClass window_class, WindowClass parent_class, uint32 flags,
                        const NWidgetPart *nwid_parts, int16 nwid_length, HotkeyList *hotkeys) :
        default_pos(def_pos),
        cls(window_class),
        parent_cls(parent_class),
        ini_key(ini_key),
        flags(flags),
        nwid_parts(nwid_parts),
        nwid_length(nwid_length),
        hotkeys(hotkeys),
        pref_sticky(false),
        pref_width(0),
        pref_height(0),
        default_width_trad(def_width_trad),
        default_height_trad(def_height_trad)
{
        if (_window_descs == nullptr) _window_descs = new SmallVector<WindowDesc*, 16>();
        *_window_descs->Append() = this;
}

WindowDesc::~WindowDesc()
{
        _window_descs->Erase(_window_descs->Find(this));
}

/**
 * Determine default width of window.
 * This is either a stored user preferred size, or the build-in default.
 * @return Width in pixels.
 */
int16 WindowDesc::GetDefaultWidth() const
{
        return this->pref_width != 0 ? this->pref_width : ScaleGUITrad(this->default_width_trad);
}

/**
 * Determine default height of window.
 * This is either a stored user preferred size, or the build-in default.
 * @return Height in pixels.
 */
int16 WindowDesc::GetDefaultHeight() const
{
        return this->pref_height != 0 ? this->pref_height : ScaleGUITrad(this->default_height_trad);
}

/**
 * Load all WindowDesc settings from _windows_file.
 */
void WindowDesc::LoadFromConfig()
{
        IniFile *ini = new IniFile();
        ini->LoadFromDisk(_windows_file, NO_DIRECTORY);
        for (WindowDesc **it = _window_descs->Begin(); it != _window_descs->End(); ++it) {
                if ((*it)->ini_key == nullptr) continue;
                IniLoadWindowSettings(ini, (*it)->ini_key, *it);
        }
        delete ini;
}

/**
 * Sort WindowDesc by ini_key.
 */
static int CDECL DescSorter(WindowDesc * const *a, WindowDesc * const *b)
{
        if ((*a)->ini_key != nullptr && (*b)->ini_key != nullptr) return strcmp((*a)->ini_key, (*b)->ini_key);
        return ((*b)->ini_key != nullptr ? 1 : 0) - ((*a)->ini_key != nullptr ? 1 : 0);
}

/**
 * Save all WindowDesc settings to _windows_file.
 */
void WindowDesc::SaveToConfig()
{
        /* Sort the stuff to get a nice ini file on first write */
        QSortT(_window_descs->Begin(), _window_descs->Length(), DescSorter);

        IniFile *ini = new IniFile();
        ini->LoadFromDisk(_windows_file, NO_DIRECTORY);
        for (WindowDesc **it = _window_descs->Begin(); it != _window_descs->End(); ++it) {
                if ((*it)->ini_key == nullptr) continue;
                IniSaveWindowSettings(ini, (*it)->ini_key, *it);
        }
        ini->SaveToDisk(_windows_file);
        delete ini;
}

/**
 * Read default values from WindowDesc configuration an apply them to the window.
 */
void Window::ApplyDefaults()
{
        if (this->nested_root != nullptr && this->nested_root->GetWidgetOfType(WWT_STICKYBOX) != nullptr) {
                if (this->window_desc->pref_sticky) this->flags |= WF_STICKY;
        } else {
                /* There is no stickybox; clear the preference in case someone tried to be funny */
                this->window_desc->pref_sticky = false;
        }
}

/**
 * Compute the row of a widget that a user clicked in.
 * @param clickpos    Vertical position of the mouse click.
 * @param widget      Widget number of the widget clicked in.
 * @param padding     Amount of empty space between the widget edge and the top of the first row.
 * @param line_height Height of a single row. A negative value means using the vertical resize step of the widget.
 * @return Row number clicked at. If clicked at a wrong position, #INT_MAX is returned.
 * @note The widget does not know where a list printed at the widget ends, so below a list is not a wrong position.
 */
int Window::GetRowFromWidget(int clickpos, int widget, int padding, int line_height) const
{
        const NWidgetBase *wid = this->GetWidget<NWidgetBase>(widget);
        if (line_height < 0) line_height = wid->resize_y;
        if (clickpos < (int)wid->pos_y + padding) return INT_MAX;
        return (clickpos - (int)wid->pos_y - padding) / line_height;
}

/**
 * Disable the highlighted status of all widgets.
 */
void Window::DisableAllWidgetHighlight()
{
        for (uint i = 0; i < this->nested_array_size; i++) {
                NWidgetBase *nwid = this->GetWidget<NWidgetBase>(i);
                if (nwid == nullptr) continue;

                if (nwid->IsHighlighted()) {
                        nwid->SetHighlighted(TC_INVALID);
                        this->SetWidgetDirty(i);
                }
        }

        CLRBITS(this->flags, WF_HIGHLIGHTED);
}

/**
 * Sets the highlighted status of a widget.
 * @param widget_index index of this widget in the window
 * @param highlighted_colour Colour of highlight, or TC_INVALID to disable.
 */
void Window::SetWidgetHighlight(byte widget_index, TextColour highlighted_colour)
{
        assert(widget_index < this->nested_array_size);

        NWidgetBase *nwid = this->GetWidget<NWidgetBase>(widget_index);
        if (nwid == nullptr) return;

        nwid->SetHighlighted(highlighted_colour);
        this->SetWidgetDirty(widget_index);

        if (highlighted_colour != TC_INVALID) {
                /* If we set a highlight, the window has a highlight */
                this->flags |= WF_HIGHLIGHTED;
        } else {
                /* If we disable a highlight, check all widgets if anyone still has a highlight */
                bool valid = false;
                for (uint i = 0; i < this->nested_array_size; i++) {
                        NWidgetBase *nwid = this->GetWidget<NWidgetBase>(i);
                        if (nwid == nullptr) continue;
                        if (!nwid->IsHighlighted()) continue;

                        valid = true;
                }
                /* If nobody has a highlight, disable the flag on the window */
                if (!valid) CLRBITS(this->flags, WF_HIGHLIGHTED);
        }
}

/**
 * Gets the highlighted status of a widget.
 * @param widget_index index of this widget in the window
 * @return status of the widget ie: highlighted = true, not highlighted = false
 */
bool Window::IsWidgetHighlighted(byte widget_index) const
{
        assert(widget_index < this->nested_array_size);

        const NWidgetBase *nwid = this->GetWidget<NWidgetBase>(widget_index);
        if (nwid == nullptr) return false;

        return nwid->IsHighlighted();
}

/**
 * A dropdown window associated to this window has been closed.
 * @param pt the point inside the window the mouse resides on after closure.
 * @param widget the widget (button) that the dropdown is associated with.
 * @param index the element in the dropdown that is selected.
 * @param instant_close whether the dropdown was configured to close on mouse up.
 */
void Window::OnDropdownClose(Point pt, int widget, int index, bool instant_close)
{
        if (widget < 0) return;

        if (instant_close) {
                /* Send event for selected option if we're still
                 * on the parent button of the dropdown (behaviour of the dropdowns in the main toolbar). */
                if (GetWidgetFromPos(this, pt.x, pt.y) == widget) {
                        this->OnDropdownSelect(widget, index);
                }
        }

        /* Raise the dropdown button */
        NWidgetCore *nwi2 = this->GetWidget<NWidgetCore>(widget);
        if ((nwi2->type & WWT_MASK) == NWID_BUTTON_DROPDOWN) {
                nwi2->disp_flags &= ~ND_DROPDOWN_ACTIVE;
        } else {
                this->RaiseWidget(widget);
        }
        this->SetWidgetDirty(widget);
}

/**
 * Return the Scrollbar to a widget index.
 * @param widnum Scrollbar widget index
 * @return Scrollbar to the widget
 */
const Scrollbar *Window::GetScrollbar(uint widnum) const
{
        return this->GetWidget<NWidgetScrollbar>(widnum);
}

/**
 * Return the Scrollbar to a widget index.
 * @param widnum Scrollbar widget index
 * @return Scrollbar to the widget
 */
Scrollbar *Window::GetScrollbar(uint widnum)
{
        return this->GetWidget<NWidgetScrollbar>(widnum);
}

/**
 * Return the querystring associated to a editbox.
 * @param widnum Editbox widget index
 * @return QueryString or nullptr.
 */
const QueryString *Window::GetQueryString(uint widnum) const
{
        const SmallMap<int, QueryString*>::Pair *query = this->querystrings.Find(widnum);
        return query != this->querystrings.End() ? query->second : nullptr;
}

/**
 * Return the querystring associated to a editbox.
 * @param widnum Editbox widget index
 * @return QueryString or nullptr.
 */
QueryString *Window::GetQueryString(uint widnum)
{
        SmallMap<int, QueryString*>::Pair *query = this->querystrings.Find(widnum);
        return query != this->querystrings.End() ? query->second : nullptr;
}

/**
 * Get the current input text if an edit box has the focus.
 * @return The currently focused input text or nullptr if no input focused.
 */
/* virtual */ const char *Window::GetFocusedText() const
{
        if (this->nested_focus != nullptr && this->nested_focus->type == WWT_EDITBOX) {
                return this->GetQueryString(this->nested_focus->index)->GetText();
        }

        return nullptr;
}

/**
 * Get the string at the caret if an edit box has the focus.
 * @return The text at the caret or nullptr if no edit box is focused.
 */
/* virtual */ const char *Window::GetCaret() const
{
        if (this->nested_focus != nullptr && this->nested_focus->type == WWT_EDITBOX) {
                return this->GetQueryString(this->nested_focus->index)->GetCaret();
        }

        return nullptr;
}

/**
 * Get the range of the currently marked input text.
 * @param[out] length Length of the marked text.
 * @return Pointer to the start of the marked text or nullptr if no text is marked.
 */
/* virtual */ const char *Window::GetMarkedText(size_t *length) const
{
        if (this->nested_focus != nullptr && this->nested_focus->type == WWT_EDITBOX) {
                return this->GetQueryString(this->nested_focus->index)->GetMarkedText(length);
        }

        return nullptr;
}

/**
 * Get the current caret position if an edit box has the focus.
 * @return Top-left location of the caret, relative to the window.
 */
/* virtual */ Point Window::GetCaretPosition() const
{
        if (this->nested_focus != nullptr && this->nested_focus->type == WWT_EDITBOX) {
                return this->GetQueryString(this->nested_focus->index)->GetCaretPosition(this, this->nested_focus->index);
        }

        Point pt = {0, 0};
        return pt;
}

/**
 * Get the bounding rectangle for a text range if an edit box has the focus.
 * @param from Start of the string range.
 * @param to End of the string range.
 * @return Rectangle encompassing the string range, relative to the window.
 */
/* virtual */ Rect Window::GetTextBoundingRect(const char *from, const char *to) const
{
        if (this->nested_focus != nullptr && this->nested_focus->type == WWT_EDITBOX) {
                return this->GetQueryString(this->nested_focus->index)->GetBoundingRect(this, this->nested_focus->index, from, to);
        }

        Rect r = {0, 0, 0, 0};
        return r;
}

/**
 * Get the character that is rendered at a position by the focused edit box.
 * @param pt The position to test.
 * @return Pointer to the character at the position or nullptr if no character is at the position.
 */
/* virtual */ const char *Window::GetTextCharacterAtPosition(const Point &pt) const
{
        if (this->nested_focus != nullptr && this->nested_focus->type == WWT_EDITBOX) {
                return this->GetQueryString(this->nested_focus->index)->GetCharAtPosition(this, this->nested_focus->index, pt);
        }

        return nullptr;
}

/**
 * Set the window that has the focus
 * @param w The window to set the focus on
 */
void SetFocusedWindow(Window *w)
{
        if (_focused_window == w) return;

        /* Invalidate focused widget */
        if (_focused_window != nullptr) {
                if (_focused_window->nested_focus != nullptr) _focused_window->nested_focus->SetDirty(_focused_window);
        }

        /* Remember which window was previously focused */
        Window *old_focused = _focused_window;
        _focused_window = w;

        /* So we can inform it that it lost focus */
        if (old_focused != nullptr) old_focused->OnFocusLost(w);
        if (_focused_window != nullptr) _focused_window->OnFocus(old_focused);
}

/**
 * Check if an edit box is in global focus. That is if focused window
 * has a edit box as focused widget, or if a console is focused.
 * @return returns true if an edit box is in global focus or if the focused window is a console, else false
 */
bool EditBoxInGlobalFocus()
{
        if (_focused_window == nullptr) return false;

        /* The console does not have an edit box so a special case is needed. */
        if (_focused_window->window_class == WC_CONSOLE) return true;

        return _focused_window->nested_focus != nullptr && _focused_window->nested_focus->type == WWT_EDITBOX;
}

/**
 * Makes no widget on this window have focus. The function however doesn't change which window has focus.
 */
void Window::UnfocusFocusedWidget()
{
        if (this->nested_focus != nullptr) {
                if (this->nested_focus->type == WWT_EDITBOX) VideoDriver::GetInstance()->EditBoxLostFocus();

                /* Repaint the widget that lost focus. A focused edit box may else leave the caret on the screen. */
                this->nested_focus->SetDirty(this);
                this->nested_focus = nullptr;
        }
}

/**
 * Set focus within this window to the given widget. The function however doesn't change which window has focus.
 * @param widget_index Index of the widget in the window to set the focus to.
 * @return Focus has changed.
 */
bool Window::SetFocusedWidget(int widget_index)
{
        /* Do nothing if widget_index is already focused, or if it wasn't a valid widget. */
        if ((uint)widget_index >= this->nested_array_size) return false;

        assert(this->nested_array[widget_index] != nullptr); // Setting focus to a non-existing widget is a bad idea.
        if (this->nested_focus != nullptr) {
                if (this->GetWidget<NWidgetCore>(widget_index) == this->nested_focus) return false;

                /* Repaint the widget that lost focus. A focused edit box may else leave the caret on the screen. */
                this->nested_focus->SetDirty(this);
                if (this->nested_focus->type == WWT_EDITBOX) VideoDriver::GetInstance()->EditBoxLostFocus();
        }
        this->nested_focus = this->GetWidget<NWidgetCore>(widget_index);
        return true;
}

/**
 * Called when window looses focus
 */
void Window::OnFocusLost(Window *newly_focused_window)
{
        if (this->nested_focus != nullptr && this->nested_focus->type == WWT_EDITBOX) VideoDriver::GetInstance()->EditBoxLostFocus();
}

/**
 * Sets the enabled/disabled status of a list of widgets.
 * By default, widgets are enabled.
 * On certain conditions, they have to be disabled.
 * @param disab_stat status to use ie: disabled = true, enabled = false
 * @param widgets list of widgets ended by WIDGET_LIST_END
 */
void CDECL Window::SetWidgetsDisabledState(bool disab_stat, int widgets, ...)
{
        va_list wdg_list;

        va_start(wdg_list, widgets);

        while (widgets != WIDGET_LIST_END) {
                SetWidgetDisabledState(widgets, disab_stat);
                widgets = va_arg(wdg_list, int);
        }

        va_end(wdg_list);
}

/**
 * Sets the lowered/raised status of a list of widgets.
 * @param lowered_stat status to use ie: lowered = true, raised = false
 * @param widgets list of widgets ended by WIDGET_LIST_END
 */
void CDECL Window::SetWidgetsLoweredState(bool lowered_stat, int widgets, ...)
{
        va_list wdg_list;

        va_start(wdg_list, widgets);

        while (widgets != WIDGET_LIST_END) {
                SetWidgetLoweredState(widgets, lowered_stat);
                widgets = va_arg(wdg_list, int);
        }

        va_end(wdg_list);
}

/**
 * Raise the buttons of the window.
 * @param autoraise Raise only the push buttons of the window.
 */
void Window::RaiseButtons(bool autoraise)
{
        for (uint i = 0; i < this->nested_array_size; i++) {
                if (this->nested_array[i] == nullptr) continue;
                WidgetType type = this->nested_array[i]->type;
                if (((type & ~WWB_PUSHBUTTON) < WWT_LAST || type == NWID_PUSHBUTTON_DROPDOWN) &&
                                (!autoraise || (type & WWB_PUSHBUTTON) || type == WWT_EDITBOX) && this->IsWidgetLowered(i)) {
                        this->RaiseWidget(i);
                        this->SetWidgetDirty(i);
                }
        }

        /* Special widgets without widget index */
        NWidgetCore *wid = this->nested_root != nullptr ? (NWidgetCore*)this->nested_root->GetWidgetOfType(WWT_DEFSIZEBOX) : nullptr;
        if (wid != nullptr) {
                wid->SetLowered(false);
                wid->SetDirty(this);
        }
}

/**
 * Invalidate a widget, i.e. mark it as being changed and in need of redraw.
 * @param widget_index the widget to redraw.
 */
void Window::SetWidgetDirty(byte widget_index) const
{
        /* Sometimes this function is called before the window is even fully initialized */
        if (this->nested_array == nullptr) return;

        this->nested_array[widget_index]->SetDirty(this);
}

/**
 * A hotkey has been pressed.
 * @param hotkey  Hotkey index, by default a widget index of a button or editbox.
 * @return #ES_HANDLED if the key press has been handled, and the hotkey is not unavailable for some reason.
 */
EventState Window::OnHotkey(int hotkey)
{
        if (hotkey < 0) return ES_NOT_HANDLED;

        NWidgetCore *nw = this->GetWidget<NWidgetCore>(hotkey);
        if (nw == nullptr || nw->IsDisabled()) return ES_NOT_HANDLED;

        if (nw->type == WWT_EDITBOX) {
                if (this->IsShaded()) return ES_NOT_HANDLED;

                /* Focus editbox */
                this->SetFocusedWidget(hotkey);
                SetFocusedWindow(this);
        } else {
                /* Click button */
                this->OnClick(Point(), hotkey, 1);
        }
        return ES_HANDLED;
}

/**
 * Do all things to make a button look clicked and mark it to be
 * unclicked in a few ticks.
 * @param widget the widget to "click"
 */
void Window::HandleButtonClick(byte widget)
{
        this->LowerWidget(widget);
        this->SetTimeout();
        this->SetWidgetDirty(widget);
}

static void StartWindowDrag(Window *w);
static void StartWindowSizing(Window *w, bool to_left);

/**
 * Dispatch left mouse-button (possibly double) click in window.
 * @param w Window to dispatch event in
 * @param x X coordinate of the click
 * @param y Y coordinate of the click
 * @param click_count Number of fast consecutive clicks at same position
 */
static void DispatchLeftClickEvent(Window *w, int x, int y, int click_count)
{
        NWidgetCore *nw = w->nested_root->GetWidgetFromPos(x, y);
        WidgetType widget_type = (nw != nullptr) ? nw->type : WWT_EMPTY;

        bool focused_widget_changed = false;
        /* If clicked on a window that previously did dot have focus */
        if (_focused_window != w &&                 // We already have focus, right?
                        (w->window_desc->flags & WDF_NO_FOCUS) == 0 &&  // Don't lose focus to toolbars
                        widget_type != WWT_CLOSEBOX) {          // Don't change focused window if 'X' (close button) was clicked
                focused_widget_changed = true;
                SetFocusedWindow(w);
        }

        if (nw == nullptr) return; // exit if clicked outside of widgets

        /* don't allow any interaction if the button has been disabled */
        if (nw->IsDisabled()) return;

        int widget_index = nw->index; ///< Index of the widget

        /* Clicked on a widget that is not disabled.
         * So unless the clicked widget is the caption bar, change focus to this widget.
         * Exception: In the OSK we always want the editbox to stay focussed. */
        if (widget_type != WWT_CAPTION && w->window_class != WC_OSK) {
                /* focused_widget_changed is 'now' only true if the window this widget
                 * is in gained focus. In that case it must remain true, also if the
                 * local widget focus did not change. As such it's the logical-or of
                 * both changed states.
                 *
                 * If this is not preserved, then the OSK window would be opened when
                 * a user has the edit box focused and then click on another window and
                 * then back again on the edit box (to type some text).
                 */
                focused_widget_changed |= w->SetFocusedWidget(widget_index);
        }

        /* Close any child drop down menus. If the button pressed was the drop down
         * list's own button, then we should not process the click any further. */
        if (HideDropDownMenu(w) == widget_index && widget_index >= 0) return;

        if ((widget_type & ~WWB_PUSHBUTTON) < WWT_LAST && (widget_type & WWB_PUSHBUTTON)) w->HandleButtonClick(widget_index);

        Point pt = { x, y };

        switch (widget_type) {
                case NWID_VSCROLLBAR:
                case NWID_HSCROLLBAR:
                        ScrollbarClickHandler(w, nw, x, y);
                        break;

                case WWT_EDITBOX: {
                        QueryString *query = w->GetQueryString(widget_index);
                        if (query != nullptr) query->ClickEditBox(w, pt, widget_index, click_count, focused_widget_changed);
                        break;
                }

                case WWT_CLOSEBOX: // 'X'
                        delete w;
                        return;

                case WWT_CAPTION: // 'Title bar'
                        StartWindowDrag(w);
                        return;

                case WWT_RESIZEBOX:
                        /* When the resize widget is on the left size of the window
                         * we assume that that button is used to resize to the left. */
                        StartWindowSizing(w, (int)nw->pos_x < (w->width / 2));
                        nw->SetDirty(w);
                        return;

                case WWT_DEFSIZEBOX: {
                        if (_ctrl_pressed) {
                                w->window_desc->pref_width = w->width;
                                w->window_desc->pref_height = w->height;
                        } else {
                                int16 def_width = max<int16>(min(w->window_desc->GetDefaultWidth(), _screen.width), w->nested_root->smallest_x);
                                int16 def_height = max<int16>(min(w->window_desc->GetDefaultHeight(), _screen.height - 50), w->nested_root->smallest_y);

                                int dx = (w->resize.step_width  == 0) ? 0 : def_width  - w->width;
                                int dy = (w->resize.step_height == 0) ? 0 : def_height - w->height;
                                /* dx and dy has to go by step.. calculate it.
                                 * The cast to int is necessary else dx/dy are implicitly casted to unsigned int, which won't work. */
                                if (w->resize.step_width  > 1) dx -= dx % (int)w->resize.step_width;
                                if (w->resize.step_height > 1) dy -= dy % (int)w->resize.step_height;
                                ResizeWindow(w, dx, dy, false);
                        }

                        nw->SetLowered(true);
                        nw->SetDirty(w);
                        w->SetTimeout();
                        break;
                }

                case WWT_DEBUGBOX:
                        w->ShowNewGRFInspectWindow();
                        break;

                case WWT_SHADEBOX:
                        nw->SetDirty(w);
                        w->SetShaded(!w->IsShaded());
                        return;

                case WWT_STICKYBOX:
                        w->flags ^= WF_STICKY;
                        nw->SetDirty(w);
                        if (_ctrl_pressed) w->window_desc->pref_sticky = (w->flags & WF_STICKY) != 0;
                        return;

                default:
                        break;
        }

        /* Widget has no index, so the window is not interested in it. */
        if (widget_index < 0) return;

        /* Check if the widget is highlighted; if so, disable highlight and dispatch an event to the GameScript */
        if (w->IsWidgetHighlighted(widget_index)) {
                w->SetWidgetHighlight(widget_index, TC_INVALID);
                Game::NewEvent(new ScriptEventWindowWidgetClick((ScriptWindow::WindowClass)w->window_class, w->window_number, widget_index));
        }

        w->OnClick(pt, widget_index, click_count);
}

/**
 * Dispatch right mouse-button click in window.
 * @param w Window to dispatch event in
 * @param x X coordinate of the click
 * @param y Y coordinate of the click
 */
static void DispatchRightClickEvent(Window *w, int x, int y)
{
        NWidgetCore *wid = w->nested_root->GetWidgetFromPos(x, y);
        if (wid == nullptr) return;

        /* No widget to handle, or the window is not interested in it. */
        if (wid->index >= 0) {
                Point pt = { x, y };
                w->OnRightClick(pt, wid->index);
        }

        /* Right-click close is enabled and there is a closebox */
        if (_settings_client.gui.right_mouse_wnd_close && w->nested_root->GetWidgetOfType(WWT_CLOSEBOX)) {
                delete w;
        }
}

/**
 * Dispatch tool tip event in a window (e.g. hover of the mouse).
 * @param w Window to dispatch event in.
 * @param x X coordinate of the mouse.
 * @param y Y coordinate of the mouse.
 * @param close_cond How to close tooltips, depands on the way the event was initiated.
 */
static void DispatchToolTipEvent(Window *w, int x, int y, TooltipCloseCondition close_cond)
{
        NWidgetCore *wid = w->nested_root->GetWidgetFromPos(x, y);

        /* No widget to handle, or the window is not interested in it. */
        if (wid != nullptr && wid->index >= 0) {
                Point pt = { x, y };
                w->OnToolTip(pt, wid == nullptr ? -1 : wid->index, close_cond);
        }
}

/**
 * Dispatch the mousewheel-action to the window.
 * The window will scroll any compatible scrollbars if the mouse is pointed over the bar or its contents
 * @param w Window
 * @param nwid the widget where the scrollwheel was used
 * @param wheel scroll up or down
 */
static void DispatchMouseWheelEvent(Window *w, NWidgetCore *nwid, int wheel)
{
        if (nwid == nullptr) return;

        /* Using wheel on caption/shade-box shades or unshades the window. */
        if (nwid->type == WWT_CAPTION || nwid->type == WWT_SHADEBOX) {
                w->SetShaded(wheel < 0);
                return;
        }

        /* Wheeling a vertical scrollbar. */
        if (nwid->type == NWID_VSCROLLBAR) {
                NWidgetScrollbar *sb = static_cast<NWidgetScrollbar *>(nwid);
                if (sb->GetCount() > sb->GetCapacity()) {
                        sb->UpdatePosition(wheel);
                        w->SetDirty();
                }
                return;
        }

        /* Scroll the widget attached to the scrollbar. */
        Scrollbar *sb = (nwid->scrollbar_index >= 0 ? w->GetScrollbar(nwid->scrollbar_index) : nullptr);
        if (sb != nullptr && sb->GetCount() > sb->GetCapacity()) {
                sb->UpdatePosition(wheel);
                w->SetDirty();
        }
}

/**
 * Returns whether a window may be shown or not.
 * @param w The window to consider.
 * @return True iff it may be shown, otherwise false.
 */
static bool MayBeShown(const Window *w)
{
        /* If we're not modal, everything is okay. */
        if (!HasModalProgress()) return true;

        switch (w->window_class) {
                case WC_MAIN_WINDOW:    ///< The background, i.e. the game.
                case WC_MODAL_PROGRESS: ///< The actual progress window.
                case WC_CONFIRM_POPUP_QUERY: ///< The abort window.
                        return true;

                default:
                        return false;
        }
}

/**
 * Generate repaint events for the visible part of window w within the rectangle.
 *
 * The function goes recursively upwards in the window stack, and splits the rectangle
 * into multiple pieces at the window edges, so obscured parts are not redrawn.
 *
 * @param w Window that needs to be repainted
 * @param left Left edge of the rectangle that should be repainted
 * @param top Top edge of the rectangle that should be repainted
 * @param right Right edge of the rectangle that should be repainted
 * @param bottom Bottom edge of the rectangle that should be repainted
 */
static void DrawOverlappedWindow(Window *w, int left, int top, int right, int bottom)
{
        const Window *v;
        FOR_ALL_WINDOWS_FROM_BACK_FROM(v, w->z_front) {
                if (MayBeShown(v) &&
                                right > v->left &&
                                bottom > v->top &&
                                left < v->left + v->width &&
                                top < v->top + v->height) {
                        /* v and rectangle intersect with each other */
                        int x;

                        if (left < (x = v->left)) {
                                DrawOverlappedWindow(w, left, top, x, bottom);
                                DrawOverlappedWindow(w, x, top, right, bottom);
                                return;
                        }

                        if (right > (x = v->left + v->width)) {
                                DrawOverlappedWindow(w, left, top, x, bottom);
                                DrawOverlappedWindow(w, x, top, right, bottom);
                                return;
                        }

                        if (top < (x = v->top)) {
                                DrawOverlappedWindow(w, left, top, right, x);
                                DrawOverlappedWindow(w, left, x, right, bottom);
                                return;
                        }

                        if (bottom > (x = v->top + v->height)) {
                                DrawOverlappedWindow(w, left, top, right, x);
                                DrawOverlappedWindow(w, left, x, right, bottom);
                                return;
                        }

                        return;
                }
        }

        /* Setup blitter, and dispatch a repaint event to window *wz */
        DrawPixelInfo *dp = _cur_dpi;
        dp->width = right - left;
        dp->height = bottom - top;
        dp->left = left - w->left;
        dp->top = top - w->top;
        dp->pitch = _screen.pitch;
        dp->dst_ptr = BlitterFactory::GetCurrentBlitter()->MoveTo(_screen.dst_ptr, left, top);
        dp->zoom = ZOOM_LVL_NORMAL;
        w->OnPaint();
}

/**
 * From a rectangle that needs redrawing, find the windows that intersect with the rectangle.
 * These windows should be re-painted.
 * @param left Left edge of the rectangle that should be repainted
 * @param top Top edge of the rectangle that should be repainted
 * @param right Right edge of the rectangle that should be repainted
 * @param bottom Bottom edge of the rectangle that should be repainted
 */
void DrawOverlappedWindowForAll(int left, int top, int right, int bottom)
{
        Window *w;
        DrawPixelInfo bk;
        _cur_dpi = &bk;

        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (MayBeShown(w) &&
                                right > w->left &&
                                bottom > w->top &&
                                left < w->left + w->width &&
                                top < w->top + w->height) {
                        /* Window w intersects with the rectangle => needs repaint */
                        DrawOverlappedWindow(w, max(left, w->left), max(top, w->top), min(right, w->left + w->width), min(bottom, w->top + w->height));
                }
        }
}

/**
 * Mark entire window as dirty (in need of re-paint)
 * @ingroup dirty
 */
void Window::SetDirty() const
{
        SetDirtyBlocks(this->left, this->top, this->left + this->width, this->top + this->height);
}

/**
 * Re-initialize a window, and optionally change its size.
 * @param rx Horizontal resize of the window.
 * @param ry Vertical resize of the window.
 * @note For just resizing the window, use #ResizeWindow instead.
 */
void Window::ReInit(int rx, int ry)
{
        this->SetDirty(); // Mark whole current window as dirty.

        /* Save current size. */
        int window_width  = this->width;
        int window_height = this->height;

        this->OnInit();
        /* Re-initialize the window from the ground up. No need to change the nested_array, as all widgets stay where they are. */
        this->nested_root->SetupSmallestSize(this, false);
        this->nested_root->AssignSizePosition(ST_SMALLEST, 0, 0, this->nested_root->smallest_x, this->nested_root->smallest_y, _current_text_dir == TD_RTL);
        this->width  = this->nested_root->smallest_x;
        this->height = this->nested_root->smallest_y;
        this->resize.step_width  = this->nested_root->resize_x;
        this->resize.step_height = this->nested_root->resize_y;

        /* Resize as close to the original size + requested resize as possible. */
        window_width  = max(window_width  + rx, this->width);
        window_height = max(window_height + ry, this->height);
        int dx = (this->resize.step_width  == 0) ? 0 : window_width  - this->width;
        int dy = (this->resize.step_height == 0) ? 0 : window_height - this->height;
        /* dx and dy has to go by step.. calculate it.
         * The cast to int is necessary else dx/dy are implicitly casted to unsigned int, which won't work. */
        if (this->resize.step_width  > 1) dx -= dx % (int)this->resize.step_width;
        if (this->resize.step_height > 1) dy -= dy % (int)this->resize.step_height;

        ResizeWindow(this, dx, dy);
        /* ResizeWindow() does this->SetDirty() already, no need to do it again here. */
}

/**
 * Set the shaded state of the window to \a make_shaded.
 * @param make_shaded If \c true, shade the window (roll up until just the title bar is visible), else unshade/unroll the window to its original size.
 * @note The method uses #Window::ReInit(), thus after the call, the whole window should be considered changed.
 */
void Window::SetShaded(bool make_shaded)
{
        if (this->shade_select == nullptr) return;

        int desired = make_shaded ? SZSP_HORIZONTAL : 0;
        if (this->shade_select->shown_plane != desired) {
                if (make_shaded) {
                        if (this->nested_focus != nullptr) this->UnfocusFocusedWidget();
                        this->unshaded_size.width  = this->width;
                        this->unshaded_size.height = this->height;
                        this->shade_select->SetDisplayedPlane(desired);
                        this->ReInit(0, -this->height);
                } else {
                        this->shade_select->SetDisplayedPlane(desired);
                        int dx = ((int)this->unshaded_size.width  > this->width)  ? (int)this->unshaded_size.width  - this->width  : 0;
                        int dy = ((int)this->unshaded_size.height > this->height) ? (int)this->unshaded_size.height - this->height : 0;
                        this->ReInit(dx, dy);
                }
        }
}

/**
 * Find the Window whose parent pointer points to this window
 * @param w parent Window to find child of
 * @param wc Window class of the window to remove; #WC_INVALID if class does not matter
 * @return a Window pointer that is the child of \a w, or \c nullptr otherwise
 */
static Window *FindChildWindow(const Window *w, WindowClass wc)
{
        Window *v;
        FOR_ALL_WINDOWS_FROM_BACK(v) {
                if ((wc == WC_INVALID || wc == v->window_class) && v->parent == w) return v;
        }

        return nullptr;
}

/**
 * Delete all children a window might have in a head-recursive manner
 * @param wc Window class of the window to remove; #WC_INVALID if class does not matter
 */
void Window::DeleteChildWindows(WindowClass wc) const
{
        Window *child = FindChildWindow(this, wc);
        while (child != nullptr) {
                delete child;
                child = FindChildWindow(this, wc);
        }
}

/**
 * Remove window and all its child windows from the window stack.
 */
Window::~Window()
{
        if (_thd.window_class == this->window_class &&
                        _thd.window_number == this->window_number) {
                ResetObjectToPlace();
        }

        /* Prevent Mouseover() from resetting mouse-over coordinates on a non-existing window */
        if (_mouseover_last_w == this) _mouseover_last_w = nullptr;

        /* We can't scroll the window when it's closed. */
        if (_last_scroll_window == this) _last_scroll_window = nullptr;

        /* Make sure we don't try to access this window as the focused window when it doesn't exist anymore. */
        if (_focused_window == this) {
                this->OnFocusLost(nullptr);
                _focused_window = nullptr;
        }

        this->DeleteChildWindows();

        if (this->viewport != nullptr) DeleteWindowViewport(this);

        this->SetDirty();

        free(this->nested_array); // Contents is released through deletion of #nested_root.
        delete this->nested_root;

        /*
         * Make fairly sure that this is written, and not "optimized" away.
         * The delete operator is overwritten to not delete it; the deletion
         * happens at a later moment in time after the window has been
         * removed from the list of windows to prevent issues with items
         * being removed during the iteration as not one but more windows
         * may be removed by a single call to ~Window by means of the
         * DeleteChildWindows function.
         */
        const_cast<volatile WindowClass &>(this->window_class) = WC_INVALID;
}

/**
 * Find a window by its class and window number
 * @param cls Window class
 * @param number Number of the window within the window class
 * @return Pointer to the found window, or \c nullptr if not available
 */
Window *FindWindowById(WindowClass cls, WindowNumber number)
{
        Window *w;
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->window_class == cls && w->window_number == number) return w;
        }

        return nullptr;
}

/**
 * Find any window by its class. Useful when searching for a window that uses
 * the window number as a #WindowType, like #WC_SEND_NETWORK_MSG.
 * @param cls Window class
 * @return Pointer to the found window, or \c nullptr if not available
 */
Window *FindWindowByClass(WindowClass cls)
{
        Window *w;
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->window_class == cls) return w;
        }

        return nullptr;
}

/**
 * Delete a window by its class and window number (if it is open).
 * @param cls Window class
 * @param number Number of the window within the window class
 * @param force force deletion; if false don't delete when stickied
 */
void DeleteWindowById(WindowClass cls, WindowNumber number, bool force)
{
        Window *w = FindWindowById(cls, number);
        if (force || w == nullptr ||
                        (w->flags & WF_STICKY) == 0) {
                delete w;
        }
}

/**
 * Delete all windows of a given class
 * @param cls Window class of windows to delete
 */
void DeleteWindowByClass(WindowClass cls)
{
        Window *w;

restart_search:
        /* When we find the window to delete, we need to restart the search
         * as deleting this window could cascade in deleting (many) others
         * anywhere in the z-array */
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->window_class == cls) {
                        delete w;
                        goto restart_search;
                }
        }
}

/**
 * Delete all windows of a company. We identify windows of a company
 * by looking at the caption colour. If it is equal to the company ID
 * then we say the window belongs to the company and should be deleted
 * @param id company identifier
 */
void DeleteCompanyWindows(CompanyID id)
{
        Window *w;

restart_search:
        /* When we find the window to delete, we need to restart the search
         * as deleting this window could cascade in deleting (many) others
         * anywhere in the z-array */
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->owner == id) {
                        delete w;
                        goto restart_search;
                }
        }

        /* Also delete the company specific windows that don't have a company-colour. */
        DeleteWindowById(WC_BUY_COMPANY, id);
}

/**
 * Change the owner of all the windows one company can take over from another
 * company in the case of a company merger. Do not change ownership of windows
 * that need to be deleted once takeover is complete
 * @param old_owner original owner of the window
 * @param new_owner the new owner of the window
 */
void ChangeWindowOwner(Owner old_owner, Owner new_owner)
{
        Window *w;
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->owner != old_owner) continue;

                switch (w->window_class) {
                        case WC_COMPANY_COLOUR:
                        case WC_FINANCES:
                        case WC_STATION_LIST:
                        case WC_TRAINS_LIST:
                        case WC_TRACE_RESTRICT_SLOTS:
                        case WC_ROADVEH_LIST:
                        case WC_SHIPS_LIST:
                        case WC_AIRCRAFT_LIST:
                        case WC_BUY_COMPANY:
                        case WC_COMPANY:
                        case WC_COMPANY_INFRASTRUCTURE:
                        case WC_VEHICLE_ORDERS: // Changing owner would also require changing WindowDesc, which is not possible; however keeping the old one crashes because of missing widgets etc.. See ShowOrdersWindow().
                                continue;

                        default:
                                w->owner = new_owner;
                                break;
                }
        }
}

static void BringWindowToFront(Window *w);

/**
 * Find a window and make it the relative top-window on the screen.
 * The window gets unshaded if it was shaded, and a white border is drawn at its edges for a brief period of time to visualize its "activation".
 * @param cls WindowClass of the window to activate
 * @param number WindowNumber of the window to activate
 * @return a pointer to the window thus activated
 */
Window *BringWindowToFrontById(WindowClass cls, WindowNumber number)
{
        Window *w = FindWindowById(cls, number);

        if (w != nullptr) {
                if (w->IsShaded()) w->SetShaded(false); // Restore original window size if it was shaded.

                w->SetWhiteBorder();
                BringWindowToFront(w);
                w->SetDirty();
        }

        return w;
}

static inline bool IsVitalWindow(const Window *w)
{
        switch (w->window_class) {
                case WC_MAIN_TOOLBAR:
                case WC_STATUS_BAR:
                case WC_NEWS_WINDOW:
                case WC_SEND_NETWORK_MSG:
                        return true;

                default:
                        return false;
        }
}

/**
 * Get the z-priority for a given window. This is used in comparison with other z-priority values;
 * a window with a given z-priority will appear above other windows with a lower value, and below
 * those with a higher one (the ordering within z-priorities is arbitrary).
 * @param wc The window class of window to get the z-priority for
 * @pre wc != WC_INVALID
 * @return The window's z-priority
 */
static uint GetWindowZPriority(WindowClass wc)
{
        assert(wc != WC_INVALID);

        uint z_priority = 0;

        switch (wc) {
                case WC_ENDSCREEN:
                        ++z_priority;
                        FALLTHROUGH;

                case WC_HIGHSCORE:
                        ++z_priority;
                        FALLTHROUGH;

                case WC_TOOLTIPS:
                        ++z_priority;
                        FALLTHROUGH;

                case WC_DROPDOWN_MENU:
                        ++z_priority;
                        FALLTHROUGH;

                case WC_MAIN_TOOLBAR:
                case WC_STATUS_BAR:
                        ++z_priority;
                        FALLTHROUGH;

                case WC_OSK:
                        ++z_priority;
                        FALLTHROUGH;

                case WC_QUERY_STRING:
                case WC_SEND_NETWORK_MSG:
                        ++z_priority;
                        FALLTHROUGH;

                case WC_ERRMSG:
                case WC_CONFIRM_POPUP_QUERY:
                case WC_MODAL_PROGRESS:
                case WC_NETWORK_STATUS_WINDOW:
                case WC_SAVE_PRESET:
                        ++z_priority;
                        FALLTHROUGH;

                case WC_GENERATE_LANDSCAPE:
                case WC_SAVELOAD:
                case WC_GAME_OPTIONS:
                case WC_CUSTOM_CURRENCY:
                case WC_NETWORK_WINDOW:
                case WC_GRF_PARAMETERS:
                case WC_AI_LIST:
                case WC_AI_SETTINGS:
                case WC_TEXTFILE:
                        ++z_priority;
                        FALLTHROUGH;

                case WC_CONSOLE:
                        ++z_priority;
                        FALLTHROUGH;

                case WC_NEWS_WINDOW:
                        ++z_priority;
                        FALLTHROUGH;

                default:
                        ++z_priority;
                        FALLTHROUGH;

                case WC_MAIN_WINDOW:
                        return z_priority;
        }
}

/**
 * Adds a window to the z-ordering, according to its z-priority.
 * @param w Window to add
 */
static void AddWindowToZOrdering(Window *w)
{
        assert(w->z_front == nullptr && w->z_back == nullptr);

        if (_z_front_window == nullptr) {
                /* It's the only window. */
                _z_front_window = _z_back_window = w;
                w->z_front = w->z_back = nullptr;
        } else {
                /* Search down the z-ordering for its location. */
                Window *v = _z_front_window;
                uint last_z_priority = UINT_MAX;
                while (v != nullptr && (v->window_class == WC_INVALID || GetWindowZPriority(v->window_class) > GetWindowZPriority(w->window_class))) {
                        if (v->window_class != WC_INVALID) {
                                /* Sanity check z-ordering, while we're at it. */
                                assert(last_z_priority >= GetWindowZPriority(v->window_class));
                                last_z_priority = GetWindowZPriority(v->window_class);
                        }

                        v = v->z_back;
                }

                if (v == nullptr) {
                        /* It's the new back window. */
                        w->z_front = _z_back_window;
                        w->z_back = nullptr;
                        _z_back_window->z_back = w;
                        _z_back_window = w;
                } else if (v == _z_front_window) {
                        /* It's the new front window. */
                        w->z_front = nullptr;
                        w->z_back = _z_front_window;
                        _z_front_window->z_front = w;
                        _z_front_window = w;
                } else {
                        /* It's somewhere else in the z-ordering. */
                        w->z_front = v->z_front;
                        w->z_back = v;
                        v->z_front->z_back = w;
                        v->z_front = w;
                }
        }
}


/**
 * Removes a window from the z-ordering.
 * @param w Window to remove
 */
static void RemoveWindowFromZOrdering(Window *w)
{
        if (w->z_front == nullptr) {
                assert(_z_front_window == w);
                _z_front_window = w->z_back;
        } else {
                w->z_front->z_back = w->z_back;
        }

        if (w->z_back == nullptr) {
                assert(_z_back_window == w);
                _z_back_window = w->z_front;
        } else {
                w->z_back->z_front = w->z_front;
        }

        w->z_front = w->z_back = nullptr;
}

/**
 * On clicking on a window, make it the frontmost window of all windows with an equal
 * or lower z-priority. The window is marked dirty for a repaint
 * @param w window that is put into the relative foreground
 */
static void BringWindowToFront(Window *w)
{
        RemoveWindowFromZOrdering(w);
        AddWindowToZOrdering(w);
        SetFocusedWindow(w);

        w->SetDirty();
}

/**
 * Initializes the data (except the position and initial size) of a new Window.
 * @param desc          Window description.
 * @param window_number Number being assigned to the new window
 * @return Window pointer of the newly created window
 * @pre If nested widgets are used (\a widget is \c nullptr), #nested_root and #nested_array_size must be initialized.
 *      In addition, #nested_array is either \c nullptr, or already initialized.
 */
void Window::InitializeData(WindowNumber window_number)
{
        /* Set up window properties; some of them are needed to set up smallest size below */
        this->window_class = this->window_desc->cls;
        this->SetWhiteBorder();
        if (this->window_desc->default_pos == WDP_CENTER) this->flags |= WF_CENTERED;
        this->owner = INVALID_OWNER;
        this->nested_focus = nullptr;
        this->window_number = window_number;

        this->OnInit();
        /* Initialize nested widget tree. */
        if (this->nested_array == nullptr) {
                this->nested_array = CallocT<NWidgetBase *>(this->nested_array_size);
                this->nested_root->SetupSmallestSize(this, true);
        } else {
                this->nested_root->SetupSmallestSize(this, false);
        }
        /* Initialize to smallest size. */
        this->nested_root->AssignSizePosition(ST_SMALLEST, 0, 0, this->nested_root->smallest_x, this->nested_root->smallest_y, _current_text_dir == TD_RTL);

        /* Further set up window properties,
         * this->left, this->top, this->width, this->height, this->resize.width, and this->resize.height are initialized later. */
        this->resize.step_width  = this->nested_root->resize_x;
        this->resize.step_height = this->nested_root->resize_y;

        /* Give focus to the opened window unless a text box
         * of focused window has focus (so we don't interrupt typing). But if the new
         * window has a text box, then take focus anyway.
         * Do not give the focus while scrolling a viewport (like when the News pops up) */
        if (_scrolling_viewport == nullptr && this->window_class != WC_TOOLTIPS && this->window_class != WC_NEWS_WINDOW && this->window_class != WC_OSK && (!EditBoxInGlobalFocus() || this->nested_root->GetWidgetOfType(WWT_EDITBOX) != nullptr)) SetFocusedWindow(this);

        /* Insert the window into the correct location in the z-ordering. */
        AddWindowToZOrdering(this);
}

/**
 * Set the position and smallest size of the window.
 * @param x          Offset in pixels from the left of the screen of the new window.
 * @param y          Offset in pixels from the top of the screen of the new window.
 * @param sm_width   Smallest width in pixels of the window.
 * @param sm_height  Smallest height in pixels of the window.
 */
void Window::InitializePositionSize(int x, int y, int sm_width, int sm_height)
{
        this->left = x;
        this->top = y;
        this->width = sm_width;
        this->height = sm_height;
}

/**
 * Resize window towards the default size.
 * Prior to construction, a position for the new window (for its default size)
 * has been found with LocalGetWindowPlacement(). Initially, the window is
 * constructed with minimal size. Resizing the window to its default size is
 * done here.
 * @param def_width default width in pixels of the window
 * @param def_height default height in pixels of the window
 * @see Window::Window(), Window::InitializeData(), Window::InitializePositionSize()
 */
void Window::FindWindowPlacementAndResize(int def_width, int def_height)
{
        def_width  = max(def_width,  this->width); // Don't allow default size to be smaller than smallest size
        def_height = max(def_height, this->height);
        /* Try to make windows smaller when our window is too small.
         * w->(width|height) is normally the same as min_(width|height),
         * but this way the GUIs can be made a little more dynamic;
         * one can use the same spec for multiple windows and those
         * can then determine the real minimum size of the window. */
        if (this->width != def_width || this->height != def_height) {
                /* Think about the overlapping toolbars when determining the minimum window size */
                int free_height = _screen.height;
                const Window *wt = FindWindowById(WC_STATUS_BAR, 0);
                if (wt != nullptr) free_height -= wt->height;
                wt = FindWindowById(WC_MAIN_TOOLBAR, 0);
                if (wt != nullptr) free_height -= wt->height;

                int enlarge_x = max(min(def_width  - this->width,  _screen.width - this->width),  0);
                int enlarge_y = max(min(def_height - this->height, free_height   - this->height), 0);

                /* X and Y has to go by step.. calculate it.
                 * The cast to int is necessary else x/y are implicitly casted to
                 * unsigned int, which won't work. */
                if (this->resize.step_width  > 1) enlarge_x -= enlarge_x % (int)this->resize.step_width;
                if (this->resize.step_height > 1) enlarge_y -= enlarge_y % (int)this->resize.step_height;

                ResizeWindow(this, enlarge_x, enlarge_y);
                /* ResizeWindow() calls this->OnResize(). */
        } else {
                /* Always call OnResize; that way the scrollbars and matrices get initialized. */
                this->OnResize();
        }

        int nx = this->left;
        int ny = this->top;

        if (nx + this->width > _screen.width) nx -= (nx + this->width - _screen.width);

        const Window *wt = FindWindowById(WC_MAIN_TOOLBAR, 0);
        ny = max(ny, (wt == nullptr || this == wt || this->top == 0) ? 0 : wt->height);
        nx = max(nx, 0);

        if (this->viewport != nullptr) {
                this->viewport->left += nx - this->left;
                this->viewport->top  += ny - this->top;
        }
        this->left = nx;
        this->top = ny;

        this->SetDirty();
}

/**
 * Decide whether a given rectangle is a good place to open a completely visible new window.
 * The new window should be within screen borders, and not overlap with another already
 * existing window (except for the main window in the background).
 * @param left    Left edge of the rectangle
 * @param top     Top edge of the rectangle
 * @param width   Width of the rectangle
 * @param height  Height of the rectangle
 * @param toolbar_y Height of main toolbar
 * @param pos     If rectangle is good, use this parameter to return the top-left corner of the new window
 * @return Boolean indication that the rectangle is a good place for the new window
 */
static bool IsGoodAutoPlace1(int left, int top, int width, int height, int toolbar_y, Point &pos)
{
        int right  = width + left;
        int bottom = height + top;

        if (left < 0 || top < toolbar_y || right > _screen.width || bottom > _screen.height) return false;

        /* Make sure it is not obscured by any window. */
        const Window *w;
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->window_class == WC_MAIN_WINDOW) continue;

                if (right > w->left &&
                                w->left + w->width > left &&
                                bottom > w->top &&
                                w->top + w->height > top) {
                        return false;
                }
        }

        pos.x = left;
        pos.y = top;
        return true;
}

/**
 * Decide whether a given rectangle is a good place to open a mostly visible new window.
 * The new window should be mostly within screen borders, and not overlap with another already
 * existing window (except for the main window in the background).
 * @param left    Left edge of the rectangle
 * @param top     Top edge of the rectangle
 * @param width   Width of the rectangle
 * @param height  Height of the rectangle
 * @param toolbar_y Height of main toolbar
 * @param pos     If rectangle is good, use this parameter to return the top-left corner of the new window
 * @return Boolean indication that the rectangle is a good place for the new window
 */
static bool IsGoodAutoPlace2(int left, int top, int width, int height, int toolbar_y, Point &pos)
{
        bool rtl = _current_text_dir == TD_RTL;

        /* Left part of the rectangle may be at most 1/4 off-screen,
         * right part of the rectangle may be at most 1/2 off-screen
         */
        if (rtl) {
                if (left < -(width >> 1) || left > _screen.width - (width >> 2)) return false;
        } else {
                if (left < -(width >> 2) || left > _screen.width - (width >> 1)) return false;
        }

        /* Bottom part of the rectangle may be at most 1/4 off-screen */
        if (top < toolbar_y || top > _screen.height - (height >> 2)) return false;

        /* Make sure it is not obscured by any window. */
        const Window *w;
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->window_class == WC_MAIN_WINDOW) continue;

                if (left + width > w->left &&
                                w->left + w->width > left &&
                                top + height > w->top &&
                                w->top + w->height > top) {
                        return false;
                }
        }

        pos.x = left;
        pos.y = top;
        return true;
}

/**
 * Find a good place for opening a new window of a given width and height.
 * @param width  Width of the new window
 * @param height Height of the new window
 * @return Top-left coordinate of the new window
 */
static Point GetAutoPlacePosition(int width, int height)
{
        Point pt;

        bool rtl = _current_text_dir == TD_RTL;

        /* First attempt, try top-left of the screen */
        const Window *main_toolbar = FindWindowByClass(WC_MAIN_TOOLBAR);
        const int toolbar_y =  main_toolbar != nullptr ? main_toolbar->height : 0;
        if (IsGoodAutoPlace1(rtl ? _screen.width - width : 0, toolbar_y, width, height, toolbar_y, pt)) return pt;

        /* Second attempt, try around all existing windows.
         * The new window must be entirely on-screen, and not overlap with an existing window.
         * Eight starting points are tried, two at each corner.
         */
        const Window *w;
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->window_class == WC_MAIN_WINDOW) continue;

                if (IsGoodAutoPlace1(w->left + w->width,         w->top,                      width, height, toolbar_y, pt)) return pt;
                if (IsGoodAutoPlace1(w->left            - width, w->top,                      width, height, toolbar_y, pt)) return pt;
                if (IsGoodAutoPlace1(w->left,                    w->top + w->height,          width, height, toolbar_y, pt)) return pt;
                if (IsGoodAutoPlace1(w->left,                    w->top             - height, width, height, toolbar_y, pt)) return pt;
                if (IsGoodAutoPlace1(w->left + w->width,         w->top + w->height - height, width, height, toolbar_y, pt)) return pt;
                if (IsGoodAutoPlace1(w->left            - width, w->top + w->height - height, width, height, toolbar_y, pt)) return pt;
                if (IsGoodAutoPlace1(w->left + w->width - width, w->top + w->height,          width, height, toolbar_y, pt)) return pt;
                if (IsGoodAutoPlace1(w->left + w->width - width, w->top             - height, width, height, toolbar_y, pt)) return pt;
        }

        /* Third attempt, try around all existing windows.
         * The new window may be partly off-screen, and must not overlap with an existing window.
         * Only four starting points are tried.
         */
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->window_class == WC_MAIN_WINDOW) continue;

                if (IsGoodAutoPlace2(w->left + w->width, w->top,             width, height, toolbar_y, pt)) return pt;
                if (IsGoodAutoPlace2(w->left    - width, w->top,             width, height, toolbar_y, pt)) return pt;
                if (IsGoodAutoPlace2(w->left,            w->top + w->height, width, height, toolbar_y, pt)) return pt;
                if (IsGoodAutoPlace2(w->left,            w->top - height,    width, height, toolbar_y, pt)) return pt;
        }

        /* Fourth and final attempt, put window at diagonal starting from (0, toolbar_y), try multiples
         * of the closebox
         */
        int left = rtl ? _screen.width - width : 0, top = toolbar_y;
        int offset_x = rtl ? -(int)NWidgetLeaf::closebox_dimension.width : (int)NWidgetLeaf::closebox_dimension.width;
        int offset_y = max<int>(NWidgetLeaf::closebox_dimension.height, FONT_HEIGHT_NORMAL + WD_CAPTIONTEXT_TOP + WD_CAPTIONTEXT_BOTTOM);

restart:
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->left == left && w->top == top) {
                        left += offset_x;
                        top += offset_y;
                        goto restart;
                }
        }

        pt.x = left;
        pt.y = top;
        return pt;
}

/**
 * Computer the position of the top-left corner of a window to be opened right
 * under the toolbar.
 * @param window_width the width of the window to get the position for
 * @return Coordinate of the top-left corner of the new window.
 */
Point GetToolbarAlignedWindowPosition(int window_width)
{
        const Window *w = FindWindowById(WC_MAIN_TOOLBAR, 0);
        assert(w != nullptr);
        Point pt = { _current_text_dir == TD_RTL ? w->left : (w->left + w->width) - window_width, w->top + w->height };
        return pt;
}

/**
 * Compute the position of the top-left corner of a new window that is opened.
 *
 * By default position a child window at an offset of 10/10 of its parent.
 * With the exception of WC_BUILD_TOOLBAR (build railway/roads/ship docks/airports)
 * and WC_SCEN_LAND_GEN (landscaping). Whose child window has an offset of 0/toolbar-height of
 * its parent. So it's exactly under the parent toolbar and no buttons will be covered.
 * However if it falls too extremely outside window positions, reposition
 * it to an automatic place.
 *
 * @param *desc         The pointer to the WindowDesc to be created.
 * @param sm_width      Smallest width of the window.
 * @param sm_height     Smallest height of the window.
 * @param window_number The window number of the new window.
 *
 * @return Coordinate of the top-left corner of the new window.
 */
static Point LocalGetWindowPlacement(const WindowDesc *desc, int16 sm_width, int16 sm_height, int window_number)
{
        Point pt;
        const Window *w;

        int16 default_width  = max(desc->GetDefaultWidth(),  sm_width);
        int16 default_height = max(desc->GetDefaultHeight(), sm_height);

        if (desc->parent_cls != 0 /* WC_MAIN_WINDOW */ && (w = FindWindowById(desc->parent_cls, window_number)) != nullptr) {
                bool rtl = _current_text_dir == TD_RTL;
                if (desc->parent_cls == WC_BUILD_TOOLBAR || desc->parent_cls == WC_SCEN_LAND_GEN) {
                        pt.x = w->left + (rtl ? w->width - default_width : 0);
                        pt.y = w->top + w->height;
                        return pt;
                } else {
                        /* Position child window with offset of closebox, but make sure that either closebox or resizebox is visible
                         *  - Y position: closebox of parent + closebox of child + statusbar
                         *  - X position: closebox on left/right, resizebox on right/left (depending on ltr/rtl)
                         */
                        int indent_y = max<int>(NWidgetLeaf::closebox_dimension.height, FONT_HEIGHT_NORMAL + WD_CAPTIONTEXT_TOP + WD_CAPTIONTEXT_BOTTOM);
                        if (w->top + 3 * indent_y < _screen.height) {
                                pt.y = w->top + indent_y;
                                int indent_close = NWidgetLeaf::closebox_dimension.width;
                                int indent_resize = NWidgetLeaf::resizebox_dimension.width;
                                if (_current_text_dir == TD_RTL) {
                                        pt.x = max(w->left + w->width - default_width - indent_close, 0);
                                        if (pt.x + default_width >= indent_close && pt.x + indent_resize <= _screen.width) return pt;
                                } else {
                                        pt.x = min(w->left + indent_close, _screen.width - default_width);
                                        if (pt.x + default_width >= indent_resize && pt.x + indent_close <= _screen.width) return pt;
                                }
                        }
                }
        }

        switch (desc->default_pos) {
                case WDP_ALIGN_TOOLBAR: // Align to the toolbar
                        return GetToolbarAlignedWindowPosition(default_width);

                case WDP_AUTO: // Find a good automatic position for the window
                        return GetAutoPlacePosition(default_width, default_height);

                case WDP_CENTER: // Centre the window horizontally
                        pt.x = (_screen.width - default_width) / 2;
                        pt.y = (_screen.height - default_height) / 2;
                        break;

                case WDP_MANUAL:
                        pt.x = 0;
                        pt.y = 0;
                        break;

                default:
                        NOT_REACHED();
        }

        return pt;
}

/* virtual */ Point Window::OnInitialPosition(int16 sm_width, int16 sm_height, int window_number)
{
        return LocalGetWindowPlacement(this->window_desc, sm_width, sm_height, window_number);
}

/**
 * Perform the first part of the initialization of a nested widget tree.
 * Construct a nested widget tree in #nested_root, and optionally fill the #nested_array array to provide quick access to the uninitialized widgets.
 * This is mainly useful for setting very basic properties.
 * @param fill_nested Fill the #nested_array (enabling is expensive!).
 * @note Filling the nested array requires an additional traversal through the nested widget tree, and is best performed by #FinishInitNested rather than here.
 */
void Window::CreateNestedTree(bool fill_nested)
{
        int biggest_index = -1;
        this->nested_root = MakeWindowNWidgetTree(this->window_desc->nwid_parts, this->window_desc->nwid_length, &biggest_index, &this->shade_select);
        this->nested_array_size = (uint)(biggest_index + 1);

        if (fill_nested) {
                this->nested_array = CallocT<NWidgetBase *>(this->nested_array_size);
                this->nested_root->FillNestedArray(this->nested_array, this->nested_array_size);
        }
}

/**
 * Perform the second part of the initialization of a nested widget tree.
 * @param window_number Number of the new window.
 */
void Window::FinishInitNested(WindowNumber window_number)
{
        this->InitializeData(window_number);
        this->ApplyDefaults();
        Point pt = this->OnInitialPosition(this->nested_root->smallest_x, this->nested_root->smallest_y, window_number);
        this->InitializePositionSize(pt.x, pt.y, this->nested_root->smallest_x, this->nested_root->smallest_y);
        this->FindWindowPlacementAndResize(this->window_desc->GetDefaultWidth(), this->window_desc->GetDefaultHeight());
}

/**
 * Perform complete initialization of the #Window with nested widgets, to allow use.
 * @param window_number Number of the new window.
 */
void Window::InitNested(WindowNumber window_number)
{
        this->CreateNestedTree(false);
        this->FinishInitNested(window_number);
}

/**
 * Empty constructor, initialization has been moved to #InitNested() called from the constructor of the derived class.
 * @param desc The description of the window.
 */
Window::Window(WindowDesc *desc) : window_desc(desc), scrolling_scrollbar(-1)
{
}

/**
 * Do a search for a window at specific coordinates. For this we start
 * at the topmost window, obviously and work our way down to the bottom
 * @param x position x to query
 * @param y position y to query
 * @return a pointer to the found window if any, nullptr otherwise
 */
Window *FindWindowFromPt(int x, int y)
{
        Window *w;
        FOR_ALL_WINDOWS_FROM_FRONT(w) {
                if (MayBeShown(w) && IsInsideBS(x, w->left, w->width) && IsInsideBS(y, w->top, w->height)) {
                        return w;
                }
        }

        return nullptr;
}

/**
 * (re)initialize the windowing system
 */
void InitWindowSystem()
{
        IConsoleClose();

        _z_back_window = nullptr;
        _z_front_window = nullptr;
        _focused_window = nullptr;
        _mouseover_last_w = nullptr;
        _last_scroll_window = nullptr;
        _scrolling_viewport = nullptr;
        _mouse_hovering = false;

        NWidgetLeaf::InvalidateDimensionCache(); // Reset cached sizes of several widgets.
        NWidgetScrollbar::InvalidateDimensionCache();

        ShowFirstError();
}

/**
 * Close down the windowing system
 */
void UnInitWindowSystem()
{
        UnshowCriticalError();

        Window *w;
        FOR_ALL_WINDOWS_FROM_FRONT(w) delete w;

        for (w = _z_front_window; w != nullptr; /* nothing */) {
                Window *to_del = w;
                w = w->z_back;
                free(to_del);
        }

        _z_front_window = nullptr;
        _z_back_window = nullptr;
}

/**
 * Reset the windowing system, by means of shutting it down followed by re-initialization
 */
void ResetWindowSystem()
{
        UnInitWindowSystem();
        InitWindowSystem();
        _thd.Reset();
}

static void DecreaseWindowCounters()
{
        Window *w;
        FOR_ALL_WINDOWS_FROM_FRONT(w) {
                if (_scroller_click_timeout == 0) {
                        /* Unclick scrollbar buttons if they are pressed. */
                        for (uint i = 0; i < w->nested_array_size; i++) {
                                NWidgetBase *nwid = w->nested_array[i];
                                if (nwid != nullptr && (nwid->type == NWID_HSCROLLBAR || nwid->type == NWID_VSCROLLBAR)) {
                                        NWidgetScrollbar *sb = static_cast<NWidgetScrollbar*>(nwid);
                                        if (sb->disp_flags & (ND_SCROLLBAR_UP | ND_SCROLLBAR_DOWN)) {
                                                sb->disp_flags &= ~(ND_SCROLLBAR_UP | ND_SCROLLBAR_DOWN);
                                                w->scrolling_scrollbar = -1;
                                                sb->SetDirty(w);
                                        }
                                }
                        }
                }

                /* Handle editboxes */
                for (SmallMap<int, QueryString*>::Pair *it = w->querystrings.Begin(); it != w->querystrings.End(); ++it) {
                        it->second->HandleEditBox(w, it->first);
                }

                w->OnMouseLoop();
        }

        FOR_ALL_WINDOWS_FROM_FRONT(w) {
                if ((w->flags & WF_TIMEOUT) && --w->timeout_timer == 0) {
                        CLRBITS(w->flags, WF_TIMEOUT);

                        w->OnTimeout();
                        w->RaiseButtons(true);
                }
        }
}

static void HandlePlacePresize()
{
        if (_special_mouse_mode != WSM_PRESIZE) return;

        Window *w = _thd.GetCallbackWnd();
        if (w == nullptr) return;

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

        w->OnPlacePresize(pt, TileVirtXY(pt.x, pt.y));
}

/**
 * Handle dragging and dropping in mouse dragging mode (#WSM_DRAGDROP).
 * @return State of handling the event.
 */
static EventState HandleMouseDragDrop()
{
        if (_special_mouse_mode != WSM_DRAGDROP) return ES_NOT_HANDLED;

        if (_left_button_down && _cursor.delta.x == 0 && _cursor.delta.y == 0) return ES_HANDLED; // Dragging, but the mouse did not move.

        Window *w = _thd.GetCallbackWnd();
        if (w != nullptr) {
                /* Send an event in client coordinates. */
                Point pt;
                pt.x = _cursor.pos.x - w->left;
                pt.y = _cursor.pos.y - w->top;
                if (_left_button_down) {
                        w->OnMouseDrag(pt, GetWidgetFromPos(w, pt.x, pt.y));
                } else {
                        w->OnDragDrop(pt, GetWidgetFromPos(w, pt.x, pt.y));
                }
        }

        if (!_left_button_down) ResetObjectToPlace(); // Button released, finished dragging.
        return ES_HANDLED;
}

/** Report position of the mouse to the underlying window. */
static void HandleMouseOver()
{
        Window *w = FindWindowFromPt(_cursor.pos.x, _cursor.pos.y);

        /* We changed window, put a MOUSEOVER event to the last window */
        if (_mouseover_last_w != nullptr && _mouseover_last_w != w) {
                /* Reset mouse-over coordinates of previous window */
                Point pt = { -1, -1 };
                _mouseover_last_w->OnMouseOver(pt, 0);
        }

        /* _mouseover_last_w will get reset when the window is deleted, see DeleteWindow() */
        _mouseover_last_w = w;

        if (w != nullptr) {
                /* send an event in client coordinates. */
                Point pt = { _cursor.pos.x - w->left, _cursor.pos.y - w->top };
                const NWidgetCore *widget = w->nested_root->GetWidgetFromPos(pt.x, pt.y);
                if (widget != nullptr) w->OnMouseOver(pt, widget->index);
        }
}

/** The minimum number of pixels of the title bar must be visible in both the X or Y direction */
static const int MIN_VISIBLE_TITLE_BAR = 13;

/** Direction for moving the window. */
enum PreventHideDirection {
        PHD_UP,   ///< Above v is a safe position.
        PHD_DOWN, ///< Below v is a safe position.
};

/**
 * Do not allow hiding of the rectangle with base coordinates \a nx and \a ny behind window \a v.
 * If needed, move the window base coordinates to keep it visible.
 * @param nx   Base horizontal coordinate of the rectangle.
 * @param ny   Base vertical coordinate of the rectangle.
 * @param rect Rectangle that must stay visible for #MIN_VISIBLE_TITLE_BAR pixels (horizontally, vertically, or both)
 * @param v    Window lying in front of the rectangle.
 * @param px   Previous horizontal base coordinate.
 * @param dir  If no room horizontally, move the rectangle to the indicated position.
 */
static void PreventHiding(int *nx, int *ny, const Rect &rect, const Window *v, int px, PreventHideDirection dir)
{
        if (v == nullptr) return;

        int v_bottom = v->top + v->height;
        int v_right = v->left + v->width;
        int safe_y = (dir == PHD_UP) ? (v->top - MIN_VISIBLE_TITLE_BAR - rect.top) : (v_bottom + MIN_VISIBLE_TITLE_BAR - rect.bottom); // Compute safe vertical position.

        if (*ny + rect.top <= v->top - MIN_VISIBLE_TITLE_BAR) return; // Above v is enough space
        if (*ny + rect.bottom >= v_bottom + MIN_VISIBLE_TITLE_BAR) return; // Below v is enough space

        /* Vertically, the rectangle is hidden behind v. */
        if (*nx + rect.left + MIN_VISIBLE_TITLE_BAR < v->left) { // At left of v.
                if (v->left < MIN_VISIBLE_TITLE_BAR) *ny = safe_y; // But enough room, force it to a safe position.
                return;
        }
        if (*nx + rect.right - MIN_VISIBLE_TITLE_BAR > v_right) { // At right of v.
                if (v_right > _screen.width - MIN_VISIBLE_TITLE_BAR) *ny = safe_y; // Not enough room, force it to a safe position.
                return;
        }

        /* Horizontally also hidden, force movement to a safe area. */
        if (px + rect.left < v->left && v->left >= MIN_VISIBLE_TITLE_BAR) { // Coming from the left, and enough room there.
                *nx = v->left - MIN_VISIBLE_TITLE_BAR - rect.left;
        } else if (px + rect.right > v_right && v_right <= _screen.width - MIN_VISIBLE_TITLE_BAR) { // Coming from the right, and enough room there.
                *nx = v_right + MIN_VISIBLE_TITLE_BAR - rect.right;
        } else {
                *ny = safe_y;
        }
}

/**
 * Make sure at least a part of the caption bar is still visible by moving
 * the window if necessary.
 * @param w The window to check.
 * @param nx The proposed new x-location of the window.
 * @param ny The proposed new y-location of the window.
 */
static void EnsureVisibleCaption(Window *w, int nx, int ny)
{
        /* Search for the title bar rectangle. */
        Rect caption_rect;
        const NWidgetBase *caption = w->nested_root->GetWidgetOfType(WWT_CAPTION);
        if (caption != nullptr) {
                caption_rect.left   = caption->pos_x;
                caption_rect.right  = caption->pos_x + caption->current_x;
                caption_rect.top    = caption->pos_y;
                caption_rect.bottom = caption->pos_y + caption->current_y;

                /* Make sure the window doesn't leave the screen */
                nx = Clamp(nx, MIN_VISIBLE_TITLE_BAR - caption_rect.right, _screen.width - MIN_VISIBLE_TITLE_BAR - caption_rect.left);
                ny = Clamp(ny, 0, _screen.height - MIN_VISIBLE_TITLE_BAR);

                /* Make sure the title bar isn't hidden behind the main tool bar or the status bar. */
                PreventHiding(&nx, &ny, caption_rect, FindWindowById(WC_MAIN_TOOLBAR, 0), w->left, PHD_DOWN);
                PreventHiding(&nx, &ny, caption_rect, FindWindowById(WC_STATUS_BAR,   0), w->left, PHD_UP);
        }

        if (w->viewport != nullptr) {
                w->viewport->left += nx - w->left;
                w->viewport->top  += ny - w->top;
        }

        w->left = nx;
        w->top  = ny;
}

/**
 * Resize the window.
 * Update all the widgets of a window based on their resize flags
 * Both the areas of the old window and the new sized window are set dirty
 * ensuring proper redrawal.
 * @param w       Window to resize
 * @param delta_x Delta x-size of changed window (positive if larger, etc.)
 * @param delta_y Delta y-size of changed window
 * @param clamp_to_screen Whether to make sure the whole window stays visible
 */
void ResizeWindow(Window *w, int delta_x, int delta_y, bool clamp_to_screen)
{
        if (delta_x != 0 || delta_y != 0) {
                if (clamp_to_screen) {
                        /* Determine the new right/bottom position. If that is outside of the bounds of
                         * the resolution clamp it in such a manner that it stays within the bounds. */
                        int new_right  = w->left + w->width  + delta_x;
                        int new_bottom = w->top  + w->height + delta_y;
                        if (new_right  >= (int)_cur_resolution.width)  delta_x -= Ceil(new_right  - _cur_resolution.width,  max(1U, w->nested_root->resize_x));
                        if (new_bottom >= (int)_cur_resolution.height) delta_y -= Ceil(new_bottom - _cur_resolution.height, max(1U, w->nested_root->resize_y));
                }

                w->SetDirty();

                uint new_xinc = max(0, (w->nested_root->resize_x == 0) ? 0 : (int)(w->nested_root->current_x - w->nested_root->smallest_x) + delta_x);
                uint new_yinc = max(0, (w->nested_root->resize_y == 0) ? 0 : (int)(w->nested_root->current_y - w->nested_root->smallest_y) + delta_y);
                assert(w->nested_root->resize_x == 0 || new_xinc % w->nested_root->resize_x == 0);
                assert(w->nested_root->resize_y == 0 || new_yinc % w->nested_root->resize_y == 0);

                w->nested_root->AssignSizePosition(ST_RESIZE, 0, 0, w->nested_root->smallest_x + new_xinc, w->nested_root->smallest_y + new_yinc, _current_text_dir == TD_RTL);
                w->width  = w->nested_root->current_x;
                w->height = w->nested_root->current_y;
        }

        EnsureVisibleCaption(w, w->left, w->top);

        /* Always call OnResize to make sure everything is initialised correctly if it needs to be. */
        w->OnResize();
        w->SetDirty();
}

/**
 * Return the top of the main view available for general use.
 * @return Uppermost vertical coordinate available.
 * @note Above the upper y coordinate is often the main toolbar.
 */
int GetMainViewTop()
{
        Window *w = FindWindowById(WC_MAIN_TOOLBAR, 0);
        return (w == nullptr) ? 0 : w->top + w->height;
}

/**
 * Return the bottom of the main view available for general use.
 * @return The vertical coordinate of the first unusable row, so 'top + height <= bottom' gives the correct result.
 * @note At and below the bottom y coordinate is often the status bar.
 */
int GetMainViewBottom()
{
        Window *w = FindWindowById(WC_STATUS_BAR, 0);
        return (w == nullptr) ? _screen.height : w->top;
}

static bool _dragging_window; ///< A window is being dragged or resized.

/**
 * Handle dragging/resizing of a window.
 * @return State of handling the event.
 */
static EventState HandleWindowDragging()
{
        /* Get out immediately if no window is being dragged at all. */
        if (!_dragging_window) return ES_NOT_HANDLED;

        /* If button still down, but cursor hasn't moved, there is nothing to do. */
        if (_left_button_down && _cursor.delta.x == 0 && _cursor.delta.y == 0) return ES_HANDLED;

        /* Otherwise find the window... */
        Window *w;
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->flags & WF_DRAGGING) {
                        /* Stop the dragging if the left mouse button was released */
                        if (!_left_button_down) {
                                w->flags &= ~WF_DRAGGING;
                                break;
                        }

                        w->SetDirty();

                        int x = _cursor.pos.x + _drag_delta.x;
                        int y = _cursor.pos.y + _drag_delta.y;
                        int nx = x;
                        int ny = y;

                        if (_settings_client.gui.window_snap_radius != 0) {
                                const Window *v;

                                int hsnap = _settings_client.gui.window_snap_radius;
                                int vsnap = _settings_client.gui.window_snap_radius;
                                int delta;

                                FOR_ALL_WINDOWS_FROM_BACK(v) {
                                        if (v == w) continue; // Don't snap at yourself

                                        if (y + w->height > v->top && y < v->top + v->height) {
                                                /* Your left border <-> other right border */
                                                delta = abs(v->left + v->width - x);
                                                if (delta <= hsnap) {
                                                        nx = v->left + v->width;
                                                        hsnap = delta;
                                                }

                                                /* Your right border <-> other left border */
                                                delta = abs(v->left - x - w->width);
                                                if (delta <= hsnap) {
                                                        nx = v->left - w->width;
                                                        hsnap = delta;
                                                }
                                        }

                                        if (w->top + w->height >= v->top && w->top <= v->top + v->height) {
                                                /* Your left border <-> other left border */
                                                delta = abs(v->left - x);
                                                if (delta <= hsnap) {
                                                        nx = v->left;
                                                        hsnap = delta;
                                                }

                                                /* Your right border <-> other right border */
                                                delta = abs(v->left + v->width - x - w->width);
                                                if (delta <= hsnap) {
                                                        nx = v->left + v->width - w->width;
                                                        hsnap = delta;
                                                }
                                        }

                                        if (x + w->width > v->left && x < v->left + v->width) {
                                                /* Your top border <-> other bottom border */
                                                delta = abs(v->top + v->height - y);
                                                if (delta <= vsnap) {
                                                        ny = v->top + v->height;
                                                        vsnap = delta;
                                                }

                                                /* Your bottom border <-> other top border */
                                                delta = abs(v->top - y - w->height);
                                                if (delta <= vsnap) {
                                                        ny = v->top - w->height;
                                                        vsnap = delta;
                                                }
                                        }

                                        if (w->left + w->width >= v->left && w->left <= v->left + v->width) {
                                                /* Your top border <-> other top border */
                                                delta = abs(v->top - y);
                                                if (delta <= vsnap) {
                                                        ny = v->top;
                                                        vsnap = delta;
                                                }

                                                /* Your bottom border <-> other bottom border */
                                                delta = abs(v->top + v->height - y - w->height);
                                                if (delta <= vsnap) {
                                                        ny = v->top + v->height - w->height;
                                                        vsnap = delta;
                                                }
                                        }
                                }
                        }

                        EnsureVisibleCaption(w, nx, ny);

                        w->SetDirty();
                        return ES_HANDLED;
                } else if (w->flags & WF_SIZING) {
                        /* Stop the sizing if the left mouse button was released */
                        if (!_left_button_down) {
                                w->flags &= ~WF_SIZING;
                                w->SetDirty();
                                break;
                        }

                        /* Compute difference in pixels between cursor position and reference point in the window.
                         * If resizing the left edge of the window, moving to the left makes the window bigger not smaller.
                         */
                        int x, y = _cursor.pos.y - _drag_delta.y;
                        if (w->flags & WF_SIZING_LEFT) {
                                x = _drag_delta.x - _cursor.pos.x;
                        } else {
                                x = _cursor.pos.x - _drag_delta.x;
                        }

                        /* resize.step_width and/or resize.step_height may be 0, which means no resize is possible. */
                        if (w->resize.step_width  == 0) x = 0;
                        if (w->resize.step_height == 0) y = 0;

                        /* Check the resize button won't go past the bottom of the screen */
                        if (w->top + w->height + y > _screen.height) {
                                y = _screen.height - w->height - w->top;
                        }

                        /* X and Y has to go by step.. calculate it.
                         * The cast to int is necessary else x/y are implicitly casted to
                         * unsigned int, which won't work. */
                        if (w->resize.step_width  > 1) x -= x % (int)w->resize.step_width;
                        if (w->resize.step_height > 1) y -= y % (int)w->resize.step_height;

                        /* Check that we don't go below the minimum set size */
                        if ((int)w->width + x < (int)w->nested_root->smallest_x) {
                                x = w->nested_root->smallest_x - w->width;
                        }
                        if ((int)w->height + y < (int)w->nested_root->smallest_y) {
                                y = w->nested_root->smallest_y - w->height;
                        }

                        /* Window already on size */
                        if (x == 0 && y == 0) return ES_HANDLED;

                        /* Now find the new cursor pos.. this is NOT _cursor, because we move in steps. */
                        _drag_delta.y += y;
                        if ((w->flags & WF_SIZING_LEFT) && x != 0) {
                                _drag_delta.x -= x; // x > 0 -> window gets longer -> left-edge moves to left -> subtract x to get new position.
                                w->SetDirty();
                                w->left -= x;  // If dragging left edge, move left window edge in opposite direction by the same amount.
                                /* ResizeWindow() below ensures marking new position as dirty. */
                        } else {
                                _drag_delta.x += x;
                        }

                        /* ResizeWindow sets both pre- and after-size to dirty for redrawal */
                        ResizeWindow(w, x, y);
                        return ES_HANDLED;
                }
        }

        _dragging_window = false;
        return ES_HANDLED;
}

/**
 * Start window dragging
 * @param w Window to start dragging
 */
static void StartWindowDrag(Window *w)
{
        w->flags |= WF_DRAGGING;
        w->flags &= ~WF_CENTERED;
        _dragging_window = true;

        _drag_delta.x = w->left - _cursor.pos.x;
        _drag_delta.y = w->top  - _cursor.pos.y;

        DeleteWindowById(WC_DROPDOWN_MENU, 0);
        BringWindowToFront(w);
}

/**
 * Start resizing a window.
 * @param w       Window to start resizing.
 * @param to_left Whether to drag towards the left or not
 */
static void StartWindowSizing(Window *w, bool to_left)
{
        w->flags |= to_left ? WF_SIZING_LEFT : WF_SIZING_RIGHT;
        w->flags &= ~WF_CENTERED;
        _dragging_window = true;

        _drag_delta.x = _cursor.pos.x;
        _drag_delta.y = _cursor.pos.y;

        DeleteWindowById(WC_DROPDOWN_MENU, 0);
        BringWindowToFront(w);
}

/**
 * handle scrollbar scrolling with the mouse.
 * @return State of handling the event.
 */
static EventState HandleScrollbarScrolling()
{
        Window *w;
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->scrolling_scrollbar >= 0) {
                        /* Abort if no button is clicked any more. */
                        if (!_left_button_down) {
                                w->scrolling_scrollbar = -1;
                                w->SetDirty();
                                return ES_HANDLED;
                        }

                        int i;
                        NWidgetScrollbar *sb = w->GetWidget<NWidgetScrollbar>(w->scrolling_scrollbar);
                        bool rtl = false;

                        if (sb->type == NWID_HSCROLLBAR) {
                                i = _cursor.pos.x - _cursorpos_drag_start.x;
                                rtl = _current_text_dir == TD_RTL;
                        } else {
                                i = _cursor.pos.y - _cursorpos_drag_start.y;
                        }

                        if (sb->disp_flags & ND_SCROLLBAR_BTN) {
                                if (_scroller_click_timeout == 1) {
                                        _scroller_click_timeout = 3;
                                        sb->UpdatePosition(rtl == HasBit(sb->disp_flags, NDB_SCROLLBAR_UP) ? 1 : -1);
                                        w->SetDirty();
                                }
                                return ES_HANDLED;
                        }

                        /* Find the item we want to move to and make sure it's inside bounds. */
                        int pos = min(max(0, i + _scrollbar_start_pos) * sb->GetCount() / _scrollbar_size, max(0, sb->GetCount() - sb->GetCapacity()));
                        if (rtl) pos = max(0, sb->GetCount() - sb->GetCapacity() - pos);
                        if (pos != sb->GetPosition()) {
                                sb->SetPosition(pos);
                                w->SetDirty();
                        }
                        return ES_HANDLED;
                }
        }

        return ES_NOT_HANDLED;
}

/**
 * Handle viewport scrolling with the mouse.
 * @return State of handling the event.
 */
static EventState HandleViewportScroll()
{
        bool scrollwheel_scrolling = _settings_client.gui.scrollwheel_scrolling == 1 && (_cursor.v_wheel != 0 || _cursor.h_wheel != 0);

        if (_scrolling_viewport == nullptr) return ES_NOT_HANDLED;

        /* When we don't have a last scroll window we are starting to scroll.
         * When the last scroll window and this are not the same we went
         * outside of the window and should not left-mouse scroll anymore. */
        if (_last_scroll_window == nullptr) _last_scroll_window = FindWindowFromPt(_cursor.pos.x, _cursor.pos.y);

        if (_last_scroll_window == nullptr || !(_right_button_down || scrollwheel_scrolling || (_settings_client.gui.left_mouse_btn_scrolling && _left_button_down))) {
                _cursor.fix_at = false;
                _scrolling_viewport = nullptr;
                _last_scroll_window = nullptr;
                return ES_NOT_HANDLED;
        }

        if (_last_scroll_window == FindWindowById(WC_MAIN_WINDOW, 0) && _last_scroll_window->viewport->follow_vehicle != INVALID_VEHICLE) {
                /* If the main window is following a vehicle, then first let go of it! */
                const Vehicle *veh = Vehicle::Get(_last_scroll_window->viewport->follow_vehicle);
                ScrollMainWindowTo(veh->x_pos, veh->y_pos, veh->z_pos, true); // This also resets follow_vehicle
                return ES_NOT_HANDLED;
        }

        Point delta;
        if (_settings_client.gui.reverse_scroll || (_settings_client.gui.left_mouse_btn_scrolling && _left_button_down)) {
                delta.x = -_cursor.delta.x;
                delta.y = -_cursor.delta.y;
        } else {
                delta.x = _cursor.delta.x;
                delta.y = _cursor.delta.y;
        }

        if (scrollwheel_scrolling) {
                /* We are using scrollwheels for scrolling */
                delta.x = _cursor.h_wheel;
                delta.y = _cursor.v_wheel;
                _cursor.v_wheel = 0;
                _cursor.h_wheel = 0;
        }

        /* Create a scroll-event and send it to the window */
        if (delta.x != 0 || delta.y != 0) {
                _last_scroll_window->OnScroll(delta);

                /* Hide right-click tooltips if scrolling far enough. */
                const ViewPort *vp = _last_scroll_window->viewport;
                if (vp == nullptr || scrollwheel_scrolling ||
                                MAX_OFFSET_HOVER <= UnScaleByZoom(Delta(_viewport_scroll_start_pos.x, vp->virtual_left), vp->zoom) ||
                                MAX_OFFSET_HOVER <= UnScaleByZoom(Delta(_viewport_scroll_start_pos.y, vp->virtual_top), vp->zoom)) {
                        DeleteWindowById(WC_TOOLTIPS, 0);
                }
        }

        _cursor.delta.x = 0;
        _cursor.delta.y = 0;
        return ES_HANDLED;
}

/**
 * Check if a window can be made relative top-most window, and if so do
 * it. If a window does not obscure any other windows, it will not
 * be brought to the foreground. Also if the only obscuring windows
 * are so-called system-windows, the window will not be moved.
 * The function will return false when a child window of this window is a
 * modal-popup; function returns a false and child window gets a white border
 * @param w Window to bring relatively on-top
 * @return false if the window has an active modal child, true otherwise
 */
static bool MaybeBringWindowToFront(Window *w)
{
        bool bring_to_front = false;

        if (w->window_class == WC_MAIN_WINDOW ||
                        IsVitalWindow(w) ||
                        w->window_class == WC_TOOLTIPS ||
                        w->window_class == WC_DROPDOWN_MENU) {
                return true;
        }

        /* Use unshaded window size rather than current size for shaded windows. */
        int w_width  = w->width;
        int w_height = w->height;
        if (w->IsShaded()) {
                w_width  = w->unshaded_size.width;
                w_height = w->unshaded_size.height;
        }

        Window *u;
        FOR_ALL_WINDOWS_FROM_BACK_FROM(u, w->z_front) {
                /* A modal child will prevent the activation of the parent window */
                if (u->parent == w && (u->window_desc->flags & WDF_MODAL)) {
                        u->SetWhiteBorder();
                        u->SetDirty();
                        return false;
                }

                if (u->window_class == WC_MAIN_WINDOW ||
                                IsVitalWindow(u) ||
                                u->window_class == WC_TOOLTIPS ||
                                u->window_class == WC_DROPDOWN_MENU) {
                        continue;
                }

                /* Window sizes don't interfere, leave z-order alone */
                if (w->left + w_width <= u->left ||
                                u->left + u->width <= w->left ||
                                w->top  + w_height <= u->top ||
                                u->top + u->height <= w->top) {
                        continue;
                }

                bring_to_front = true;
        }

        if (bring_to_front) BringWindowToFront(w);
        return true;
}

/**
 * Process keypress for editbox widget.
 * @param wid Editbox widget.
 * @param key     the Unicode value of the key.
 * @param keycode the untranslated key code including shift state.
 * @return #ES_HANDLED if the key press has been handled and no other
 *         window should receive the event.
 */
EventState Window::HandleEditBoxKey(int wid, WChar key, uint16 keycode)
{
        QueryString *query = this->GetQueryString(wid);
        if (query == nullptr) return ES_NOT_HANDLED;

        int action = QueryString::ACTION_NOTHING;

        switch (query->text.HandleKeyPress(key, keycode)) {
                case HKPR_EDITING:
                        this->SetWidgetDirty(wid);
                        this->OnEditboxChanged(wid);
                        break;

                case HKPR_CURSOR:
                        this->SetWidgetDirty(wid);
                        /* For the OSK also invalidate the parent window */
                        if (this->window_class == WC_OSK) this->InvalidateData();
                        break;

                case HKPR_CONFIRM:
                        if (this->window_class == WC_OSK) {
                                this->OnClick(Point(), WID_OSK_OK, 1);
                        } else if (query->ok_button >= 0) {
                                this->OnClick(Point(), query->ok_button, 1);
                        } else {
                                action = query->ok_button;
                        }
                        break;

                case HKPR_CANCEL:
                        if (this->window_class == WC_OSK) {
                                this->OnClick(Point(), WID_OSK_CANCEL, 1);
                        } else if (query->cancel_button >= 0) {
                                this->OnClick(Point(), query->cancel_button, 1);
                        } else {
                                action = query->cancel_button;
                        }
                        break;

                case HKPR_NOT_HANDLED:
                        return ES_NOT_HANDLED;

                default: break;
        }

        switch (action) {
                case QueryString::ACTION_DESELECT:
                        this->UnfocusFocusedWidget();
                        break;

                case QueryString::ACTION_CLEAR:
                        if (query->text.bytes <= 1) {
                                /* If already empty, unfocus instead */
                                this->UnfocusFocusedWidget();
                        } else {
                                query->text.DeleteAll();
                                this->SetWidgetDirty(wid);
                                this->OnEditboxChanged(wid);
                        }
                        break;

                default:
                        break;
        }

        return ES_HANDLED;
}

/**
 * Focus a window by its class and window number (if it is open).
 * @param cls Window class.
 * @param number Number of the window within the window class.
 * @return True if a window answered to the criteria.
 */
bool FocusWindowById(WindowClass cls, WindowNumber number)
{
        Window *w = FindWindowById(cls, number);
        if (w) {
                MaybeBringWindowToFront(w);
                return true;
        }
        return false;
}

/**
 * Handle keyboard input.
 * @param keycode Virtual keycode of the key.
 * @param key Unicode character of the key.
 */
void HandleKeypress(uint keycode, WChar key)
{
        if (InEventLoopPostCrash()) return;

        /* World generation is multithreaded and messes with companies.
         * But there is no company related window open anyway, so _current_company is not used. */
        assert(HasModalProgress() || IsLocalCompany());

        /*
         * The Unicode standard defines an area called the private use area. Code points in this
         * area are reserved for private use and thus not portable between systems. For instance,
         * Apple defines code points for the arrow keys in this area, but these are only printable
         * on a system running OS X. We don't want these keys to show up in text fields and such,
         * and thus we have to clear the unicode character when we encounter such a key.
         */
        if (key >= 0xE000 && key <= 0xF8FF) key = 0;

        /*
         * If both key and keycode is zero, we don't bother to process the event.
         */
        if (key == 0 && keycode == 0) return;

        /* Check if the focused window has a focused editbox */
        if (EditBoxInGlobalFocus()) {
                /* All input will in this case go to the focused editbox */
                if (_focused_window->window_class == WC_CONSOLE) {
                        if (_focused_window->OnKeyPress(key, keycode) == ES_HANDLED) return;
                } else {
                        if (_focused_window->HandleEditBoxKey(_focused_window->nested_focus->index, key, keycode) == ES_HANDLED) return;
                }
        }

        /* Call the event, start with the uppermost window, but ignore the toolbar. */
        Window *w;
        FOR_ALL_WINDOWS_FROM_FRONT(w) {
                if (w->window_class == WC_MAIN_TOOLBAR) continue;
                if (w->window_desc->hotkeys != nullptr) {
                        int hotkey = w->window_desc->hotkeys->CheckMatch(keycode);
                        if (hotkey >= 0 && w->OnHotkey(hotkey) == ES_HANDLED) return;
                }
                if (w->OnKeyPress(key, keycode) == ES_HANDLED) return;
        }

        w = FindWindowById(WC_MAIN_TOOLBAR, 0);
        /* When there is no toolbar w is null, check for that */
        if (w != nullptr) {
                if (w->window_desc->hotkeys != nullptr) {
                        int hotkey = w->window_desc->hotkeys->CheckMatch(keycode);
                        if (hotkey >= 0 && w->OnHotkey(hotkey) == ES_HANDLED) return;
                }
                if (w->OnKeyPress(key, keycode) == ES_HANDLED) return;
        }

        HandleGlobalHotkeys(key, keycode);
}

/**
 * State of CONTROL key has changed
 */
void HandleCtrlChanged()
{
        /* Call the event, start with the uppermost window. */
        Window *w;
        FOR_ALL_WINDOWS_FROM_FRONT(w) {
                if (w->OnCTRLStateChange() == ES_HANDLED) return;
        }
}

/**
 * Insert a text string at the cursor position into the edit box widget.
 * @param wid Edit box widget.
 * @param str Text string to insert.
 */
/* virtual */ void Window::InsertTextString(int wid, const char *str, bool marked, const char *caret, const char *insert_location, const char *replacement_end)
{
        QueryString *query = this->GetQueryString(wid);
        if (query == nullptr) return;

        if (query->text.InsertString(str, marked, caret, insert_location, replacement_end) || marked) {
                this->SetWidgetDirty(wid);
                this->OnEditboxChanged(wid);
        }
}

/**
 * Handle text input.
 * @param str Text string to input.
 * @param marked Is the input a marked composition string from an IME?
 * @param caret Move the caret to this point in the insertion string.
 */
void HandleTextInput(const char *str, bool marked, const char *caret, const char *insert_location, const char *replacement_end)
{
        if (!EditBoxInGlobalFocus()) return;

        _focused_window->InsertTextString(_focused_window->window_class == WC_CONSOLE ? 0 : _focused_window->nested_focus->index, str, marked, caret, insert_location, replacement_end);
}

/**
 * Local counter that is incremented each time an mouse input event is detected.
 * The counter is used to stop auto-scrolling.
 * @see HandleAutoscroll()
 * @see HandleMouseEvents()
 */
static int _input_events_this_tick = 0;

/**
 * If needed and switched on, perform auto scrolling (automatically
 * moving window contents when mouse is near edge of the window).
 */
static void HandleAutoscroll()
{
        if (_game_mode == GM_MENU || _game_mode == GM_BOOTSTRAP || HasModalProgress()) return;
        if (_settings_client.gui.auto_scrolling == VA_DISABLED) return;
        if (_settings_client.gui.auto_scrolling == VA_MAIN_VIEWPORT_FULLSCREEN && !_fullscreen) return;

        int x = _cursor.pos.x;
        int y = _cursor.pos.y;
        Window *w = FindWindowFromPt(x, y);
        if (w == nullptr || w->flags & WF_DISABLE_VP_SCROLL) return;
        if (_settings_client.gui.auto_scrolling != VA_EVERY_VIEWPORT && w->window_class != WC_MAIN_WINDOW) return;

        ViewPort *vp = IsPtInWindowViewport(w, x, y);
        if (vp == nullptr) return;

        x -= vp->left;
        y -= vp->top;

        /* here allows scrolling in both x and y axis */
#define scrollspeed 3
        if (x - 15 < 0) {
                w->viewport->dest_scrollpos_x += ScaleByZoom((x - 15) * scrollspeed, vp->zoom);
        } else if (15 - (vp->width - x) > 0) {
                w->viewport->dest_scrollpos_x += ScaleByZoom((15 - (vp->width - x)) * scrollspeed, vp->zoom);
        }
        if (y - 15 < 0) {
                w->viewport->dest_scrollpos_y += ScaleByZoom((y - 15) * scrollspeed, vp->zoom);
        } else if (15 - (vp->height - y) > 0) {
                w->viewport->dest_scrollpos_y += ScaleByZoom((15 - (vp->height - y)) * scrollspeed, vp->zoom);
        }
#undef scrollspeed
}

enum MouseClick {
        MC_NONE = 0,
        MC_LEFT,
        MC_RIGHT,
        MC_DOUBLE_LEFT,
        MC_HOVER,
};
extern EventState VpHandlePlaceSizingDrag();

static void ScrollMainViewport(int x, int y)
{
        if (_game_mode != GM_MENU && _game_mode != GM_BOOTSTRAP) {
                Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
                assert(w);

                w->viewport->dest_scrollpos_x += ScaleByZoom(x, w->viewport->zoom);
                w->viewport->dest_scrollpos_y += ScaleByZoom(y, w->viewport->zoom);
        }
}

/**
 * Describes all the different arrow key combinations the game allows
 * when it is in scrolling mode.
 * The real arrow keys are bitwise numbered as
 * 1 = left
 * 2 = up
 * 4 = right
 * 8 = down
 */
static const int8 scrollamt[16][2] = {
        { 0,  0}, ///<  no key specified
        {-2,  0}, ///<  1 : left
        { 0, -2}, ///<  2 : up
        {-2, -1}, ///<  3 : left  + up
        { 2,  0}, ///<  4 : right
        { 0,  0}, ///<  5 : left  + right = nothing
        { 2, -1}, ///<  6 : right + up
        { 0, -2}, ///<  7 : right + left  + up = up
        { 0,  2}, ///<  8 : down
        {-2,  1}, ///<  9 : down  + left
        { 0,  0}, ///< 10 : down  + up    = nothing
        {-2,  0}, ///< 11 : left  + up    +  down = left
        { 2,  1}, ///< 12 : down  + right
        { 0,  2}, ///< 13 : left  + right +  down = down
        { 2,  0}, ///< 14 : right + up    +  down = right
        { 0,  0}, ///< 15 : left  + up    +  right + down  = nothing
};

static void HandleKeyScrolling()
{
        /*
         * Check that any of the dirkeys is pressed and that the focused window
         * doesn't have an edit-box as focused widget.
         */
        if (_dirkeys && !EditBoxInGlobalFocus()) {
                int factor = _shift_pressed ? 50 : 10;
                ScrollMainViewport(scrollamt[_dirkeys][0] * factor, scrollamt[_dirkeys][1] * factor);
        }
}

static void MouseLoop(MouseClick click, int mousewheel)
{
        if (InEventLoopPostCrash()) return;

        /* World generation is multithreaded and messes with companies.
         * But there is no company related window open anyway, so _current_company is not used. */
        assert(HasModalProgress() || IsLocalCompany());

        HandlePlacePresize();
        UpdateTileSelection();

        if (VpHandlePlaceSizingDrag()  == ES_HANDLED) return;
        if (HandleMouseDragDrop()      == ES_HANDLED) return;
        if (HandleWindowDragging()     == ES_HANDLED) return;
        if (HandleScrollbarScrolling() == ES_HANDLED) return;
        if (HandleViewportScroll()     == ES_HANDLED) return;

        HandleMouseOver();

        bool scrollwheel_scrolling = _settings_client.gui.scrollwheel_scrolling == 1 && (_cursor.v_wheel != 0 || _cursor.h_wheel != 0);
        if (click == MC_NONE && mousewheel == 0 && !scrollwheel_scrolling) return;

        int x = _cursor.pos.x;
        int y = _cursor.pos.y;
        Window *w = FindWindowFromPt(x, y);
        if (w == nullptr) return;

        if (click != MC_HOVER && !MaybeBringWindowToFront(w)) return;
        ViewPort *vp = IsPtInWindowViewport(w, x, y);

        /* Don't allow any action in a viewport if either in menu or when having a modal progress window */
        if (vp != nullptr && (_game_mode == GM_MENU || _game_mode == GM_BOOTSTRAP || HasModalProgress())) return;

        if (mousewheel != 0) {
                /* Send mousewheel event to window */
                w->OnMouseWheel(mousewheel);

                /* Dispatch a MouseWheelEvent for widgets if it is not a viewport */
                if (vp == nullptr) DispatchMouseWheelEvent(w, w->nested_root->GetWidgetFromPos(x - w->left, y - w->top), mousewheel);
        }

        if (vp != nullptr) {
                if (scrollwheel_scrolling) click = MC_RIGHT; // we are using the scrollwheel in a viewport, so we emulate right mouse button
                switch (click) {
                        case MC_DOUBLE_LEFT:
                                if (HandleViewportDoubleClicked(w, x, y)) break;
                                /* FALL THROUGH */
                        case MC_LEFT:
                                if (!HandleViewportClicked(vp, x, y, click == MC_DOUBLE_LEFT) &&
                                                !(w->flags & WF_DISABLE_VP_SCROLL) &&
                                                _settings_client.gui.left_mouse_btn_scrolling) {
                                        _scrolling_viewport = w;
                                        _cursor.fix_at = false;
                                        _viewport_scroll_start_pos.x = vp->virtual_left;
                                        _viewport_scroll_start_pos.y = vp->virtual_top;
                                }
                                break;

                        case MC_RIGHT:
                                if (!(w->flags & WF_DISABLE_VP_SCROLL)) {
                                        _scrolling_viewport = w;
                                        _cursor.fix_at = true;
                                        _viewport_scroll_start_pos.x = vp->virtual_left;
                                        _viewport_scroll_start_pos.y = vp->virtual_top;

                                        /* clear 2D scrolling caches before we start a 2D scroll */
                                        _cursor.h_wheel = 0;
                                        _cursor.v_wheel = 0;
                                }
                                if (scrollwheel_scrolling || _settings_client.gui.hover_delay_ms != 0) break;
                                HandleViewportToolTip(w, x, y);
                                break;

                        case MC_HOVER:
                                /* Re-show tooltips only if mouse is moving. */
                                if (_cursor.delta.x == 0 && _cursor.delta.y == 0 && FindWindowById(WC_TOOLTIPS, 0) != nullptr) break;
                                HandleViewportToolTip(w, x, y);
                                break;

                        default:
                                break;
                }
        }

        if (vp == nullptr || (w->flags & WF_DISABLE_VP_SCROLL)) {
                switch (click) {
                        case MC_LEFT:
                        case MC_DOUBLE_LEFT:
                                DispatchLeftClickEvent(w, x - w->left, y - w->top, click == MC_DOUBLE_LEFT ? 2 : 1);
                                break;

                        default:
                                if (!scrollwheel_scrolling || w == nullptr || w->window_class != WC_SMALLMAP) break;
                                /* We try to use the scrollwheel to scroll since we didn't touch any of the buttons.
                                 * Simulate a right button click so we can get started. */
                                FALLTHROUGH;
                        case MC_RIGHT:
                                DispatchRightClickEvent(w, x - w->left, y - w->top);
                                if (click != MC_RIGHT || _settings_client.gui.hover_delay_ms != 0) break;
                                DispatchToolTipEvent(w, x - w->left, y - w->top, TCC_RIGHT_CLICK);
                                break;

                        case MC_HOVER:
                                /* Re-show tooltips only if mouse is moving. */
                                if (_cursor.delta.x == 0 && _cursor.delta.y == 0 && FindWindowById(WC_TOOLTIPS, 0) != nullptr) break;
                                DispatchToolTipEvent(w, x - w->left, y - w->top, TCC_HOVER);
                                break;
                }
        }
}

/**
 * Handle a mouse event from the video driver
 */
void HandleMouseEvents()
{
        if (InEventLoopPostCrash()) return;

        /* World generation is multithreaded and messes with companies.
         * But there is no company related window open anyway, so _current_company is not used. */
        assert(HasModalProgress() || IsLocalCompany());

        static int double_click_time = 0;
        static Point double_click_pos = {0, 0};

        /* Mouse event? */
        MouseClick click = MC_NONE;
        if (_left_button_down && !_left_button_clicked) {
                click = MC_LEFT;
                if (double_click_time != 0 && _realtime_tick - double_click_time   < TIME_BETWEEN_DOUBLE_CLICK &&
                                double_click_pos.x != 0 && abs(_cursor.pos.x - double_click_pos.x) < MAX_OFFSET_DOUBLE_CLICK  &&
                                double_click_pos.y != 0 && abs(_cursor.pos.y - double_click_pos.y) < MAX_OFFSET_DOUBLE_CLICK) {
                        click = MC_DOUBLE_LEFT;
                }
                double_click_time = _realtime_tick;
                double_click_pos = _cursor.pos;
                _left_button_clicked = true;
                _input_events_this_tick++;
        } else if (_right_button_clicked) {
                _right_button_clicked = false;
                click = MC_RIGHT;
                _input_events_this_tick++;
        }

        int mousewheel = 0;
        if (_cursor.wheel) {
                mousewheel = _cursor.wheel;
                _cursor.wheel = 0;
                _input_events_this_tick++;
        }

        static uint32 hover_time = 0;
        static Point hover_pos = {0, 0};

        if (_settings_client.gui.hover_delay_ms > 0) {
                if (!_cursor.in_window || click != MC_NONE || mousewheel != 0 || _left_button_down || _right_button_down ||
                                hover_pos.x == 0 || abs(_cursor.pos.x - hover_pos.x) >= MAX_OFFSET_HOVER  ||
                                hover_pos.y == 0 || abs(_cursor.pos.y - hover_pos.y) >= MAX_OFFSET_HOVER) {
                        hover_pos = _cursor.pos;
                        hover_time = _realtime_tick;
                        if (_mouse_hovering) {
                                /* After stopping a hover make sure that next one will not
                                 * happen too quickly. It's to prevent tooltips being
                                 * re-opened too quickly which causes blinking. */
                                static const int re_hover_min_delay_ms = 250;
                                hover_time += max(0, re_hover_min_delay_ms - (int)_settings_client.gui.hover_delay_ms);
                        }
                        _mouse_hovering = false;
                } else {
                        if (hover_time != 0 && _realtime_tick > hover_time + _settings_client.gui.hover_delay_ms) {
                                click = MC_HOVER;
                                _input_events_this_tick++;
                                _mouse_hovering = true;
                                /* Refresh tooltips from time to time. */
                                static const int hover_max_duration_ms = 1500;
                                if ((_realtime_tick > hover_time + hover_max_duration_ms) || (
                                                /* "Drag" the hover start point behind the cursor. The hover will last if
                                                 * mouse is moving slowly enough. This is to prevent tooltips blinking
                                                 * while "hover_delay_ms" is set to some small value. */
                                                (hover_pos.x != _cursor.pos.x || hover_pos.y != _cursor.pos.y) &&
                                                _realtime_tick > hover_time + _settings_client.gui.hover_delay_ms * 3 / 2)) {
                                        hover_pos = _cursor.pos;
                                        hover_time = _realtime_tick - _settings_client.gui.hover_delay_ms;
                                        DeleteWindowById(WC_TOOLTIPS, 0);
                                }
                        }
                }
        }

        /* Handle sprite picker before any GUI interaction */
        if (_newgrf_debug_sprite_picker.mode == SPM_REDRAW && _newgrf_debug_sprite_picker.click_time != _realtime_tick) {
                /* Next realtime tick? Then redraw has finished */
                _newgrf_debug_sprite_picker.mode = SPM_NONE;
                InvalidateWindowData(WC_SPRITE_ALIGNER, 0, 1);
        }

        if (click == MC_LEFT && _newgrf_debug_sprite_picker.mode == SPM_WAIT_CLICK) {
                /* Mark whole screen dirty, and wait for the next realtime tick, when drawing is finished. */
                Blitter *blitter = BlitterFactory::GetCurrentBlitter();
                _newgrf_debug_sprite_picker.clicked_pixel = blitter->MoveTo(_screen.dst_ptr, _cursor.pos.x, _cursor.pos.y);
                _newgrf_debug_sprite_picker.click_time = _realtime_tick;
                _newgrf_debug_sprite_picker.sprites.Clear();
                _newgrf_debug_sprite_picker.mode = SPM_REDRAW;
                MarkWholeScreenDirty();
        } else {
                MouseLoop(click, mousewheel);
        }

        /* We have moved the mouse the required distance,
         * no need to move it at any later time. */
        _cursor.delta.x = 0;
        _cursor.delta.y = 0;
}

/**
 * Check the soft limit of deletable (non vital, non sticky) windows.
 */
static void CheckSoftLimit()
{
        if (_settings_client.gui.window_soft_limit == 0) return;

        for (;;) {
                uint deletable_count = 0;
                Window *w, *last_deletable = nullptr;
                FOR_ALL_WINDOWS_FROM_FRONT(w) {
                        if (w->window_class == WC_MAIN_WINDOW || IsVitalWindow(w) || (w->flags & WF_STICKY)) continue;

                        last_deletable = w;
                        deletable_count++;
                }

                /* We've not reached the soft limit yet. */
                if (deletable_count <= _settings_client.gui.window_soft_limit) break;

                assert(last_deletable != nullptr);
                delete last_deletable;
        }
}

/**
 * Regular call from the global game loop
 */
void InputLoop()
{
        if (InEventLoopPostCrash()) return;

        /* World generation is multithreaded and messes with companies.
         * But there is no company related window open anyway, so _current_company is not used. */
        assert(HasModalProgress() || IsLocalCompany());

        CheckSoftLimit();
        HandleKeyScrolling();

        /* Do the actual free of the deleted windows. */
        for (Window *v = _z_front_window; v != nullptr; /* nothing */) {
                Window *w = v;
                v = v->z_back;

                if (w->window_class != WC_INVALID) continue;

                RemoveWindowFromZOrdering(w);
                free(w);
        }

        if (_scroller_click_timeout != 0) _scroller_click_timeout--;
        DecreaseWindowCounters();

        if (_input_events_this_tick != 0) {
                /* The input loop is called only once per GameLoop() - so we can clear the counter here */
                _input_events_this_tick = 0;
                /* there were some inputs this tick, don't scroll ??? */
                return;
        }

        /* HandleMouseEvents was already called for this tick */
        HandleMouseEvents();
        HandleAutoscroll();
}

/**
 * Update the continuously changing contents of the windows, such as the viewports
 */
void UpdateWindows()
{
        Window *w;

        _window_update_number++;

        static int highlight_timer = 1;
        if (--highlight_timer == 0) {
                highlight_timer = 15;
                _window_highlight_colour = !_window_highlight_colour;
        }

        FOR_ALL_WINDOWS_FROM_FRONT(w) {
                w->ProcessScheduledInvalidations();
                w->ProcessHighlightedInvalidations();
        }

        /* Skip the actual drawing on dedicated servers without screen.
         * But still empty the invalidation queues above. */
        if (_network_dedicated) return;

        static int we4_timer = 0;
        int t = we4_timer + 1;

        if (t >= 100) {
                FOR_ALL_WINDOWS_FROM_FRONT(w) {
                        w->OnHundredthTick();
                }
                t = 0;
        }
        we4_timer = t;

        FOR_ALL_WINDOWS_FROM_FRONT(w) {
                if ((w->flags & WF_WHITE_BORDER) && --w->white_border_timer == 0) {
                        CLRBITS(w->flags, WF_WHITE_BORDER);
                        w->SetDirty();
                }
        }

        DrawDirtyBlocks();

        FOR_ALL_WINDOWS_FROM_BACK(w) {
                /* Update viewport only if window is not shaded. */
                if (w->viewport != nullptr && !w->IsShaded()) UpdateViewportPosition(w);
        }
        NetworkDrawChatMessage();
        /* Redraw mouse cursor in case it was hidden */
        DrawMouseCursor();

        _window_update_number++;
}

/**
 * Mark window as dirty (in need of repainting)
 * @param cls Window class
 * @param number Window number in that class
 */
void SetWindowDirty(WindowClass cls, WindowNumber number)
{
        const Window *w;
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->window_class == cls && w->window_number == number) w->SetDirty();
        }
}

/**
 * Mark a particular widget in a particular window as dirty (in need of repainting)
 * @param cls Window class
 * @param number Window number in that class
 * @param widget_index Index number of the widget that needs repainting
 */
void SetWindowWidgetDirty(WindowClass cls, WindowNumber number, byte widget_index)
{
        const Window *w;
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->window_class == cls && w->window_number == number) {
                        w->SetWidgetDirty(widget_index);
                }
        }
}

/**
 * Mark all windows of a particular class as dirty (in need of repainting)
 * @param cls Window class
 */
void SetWindowClassesDirty(WindowClass cls)
{
        Window *w;
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->window_class == cls) w->SetDirty();
        }
}

/**
 * Mark this window's data as invalid (in need of re-computing)
 * @param data The data to invalidate with
 * @param gui_scope Whether the function is called from GUI scope.
 */
void Window::InvalidateData(int data, bool gui_scope)
{
        this->SetDirty();
        if (!gui_scope) {
                /* Schedule GUI-scope invalidation for next redraw. */
                *this->scheduled_invalidation_data.Append() = data;
        }
        this->OnInvalidateData(data, gui_scope);
}

/**
 * Process all scheduled invalidations.
 */
void Window::ProcessScheduledInvalidations()
{
        for (int *data = this->scheduled_invalidation_data.Begin(); this->window_class != WC_INVALID && data != this->scheduled_invalidation_data.End(); data++) {
                this->OnInvalidateData(*data, true);
        }
        this->scheduled_invalidation_data.Clear();
}

/**
 * Process all invalidation of highlighted widgets.
 */
void Window::ProcessHighlightedInvalidations()
{
        if ((this->flags & WF_HIGHLIGHTED) == 0) return;

        for (uint i = 0; i < this->nested_array_size; i++) {
                if (this->IsWidgetHighlighted(i)) this->SetWidgetDirty(i);
        }
}

/**
 * Mark window data of the window of a given class and specific window number as invalid (in need of re-computing)
 *
 * Note that by default the invalidation is not considered to be called from GUI scope.
 * That means only a part of invalidation is executed immediately. The rest is scheduled for the next redraw.
 * The asynchronous execution is important to prevent GUI code being executed from command scope.
 * When not in GUI-scope:
 *  - OnInvalidateData() may not do test-runs on commands, as they might affect the execution of
 *    the command which triggered the invalidation. (town rating and such)
 *  - OnInvalidateData() may not rely on _current_company == _local_company.
 *    This implies that no NewGRF callbacks may be run.
 *
 * However, when invalidations are scheduled, then multiple calls may be scheduled before execution starts. Earlier scheduled
 * invalidations may be called with invalidation-data, which is already invalid at the point of execution.
 * That means some stuff requires to be executed immediately in command scope, while not everything may be executed in command
 * scope. While GUI-scope calls have no restrictions on what they may do, they cannot assume the game to still be in the state
 * when the invalidation was scheduled; passed IDs may have got invalid in the mean time.
 *
 * Finally, note that invalidations triggered from commands or the game loop result in OnInvalidateData() being called twice.
 * Once in command-scope, once in GUI-scope. So make sure to not process differential-changes twice.
 *
 * @param cls Window class
 * @param number Window number within the class
 * @param data The data to invalidate with
 * @param gui_scope Whether the call is done from GUI scope
 */
void InvalidateWindowData(WindowClass cls, WindowNumber number, int data, bool gui_scope)
{
        Window *w;
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->window_class == cls && w->window_number == number) {
                        w->InvalidateData(data, gui_scope);
                }
        }
}

/**
 * Mark window data of all windows of a given class as invalid (in need of re-computing)
 * Note that by default the invalidation is not considered to be called from GUI scope.
 * See InvalidateWindowData() for details on GUI-scope vs. command-scope.
 * @param cls Window class
 * @param data The data to invalidate with
 * @param gui_scope Whether the call is done from GUI scope
 */
void InvalidateWindowClassesData(WindowClass cls, int data, bool gui_scope)
{
        Window *w;

        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->window_class == cls) {
                        w->InvalidateData(data, gui_scope);
                }
        }
}

/**
 * Dispatch WE_TICK event over all windows
 */
void CallWindowTickEvent()
{
        Window *w;
        FOR_ALL_WINDOWS_FROM_FRONT(w) {
                w->OnTick();
        }
}

/**
 * Try to delete a non-vital window.
 * Non-vital windows are windows other than the game selection, main toolbar,
 * status bar, toolbar menu, and tooltip windows. Stickied windows are also
 * considered vital.
 */
void DeleteNonVitalWindows()
{
        Window *w;

restart_search:
        /* When we find the window to delete, we need to restart the search
         * as deleting this window could cascade in deleting (many) others
         * anywhere in the z-array */
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->window_class != WC_MAIN_WINDOW &&
                                w->window_class != WC_SELECT_GAME &&
                                w->window_class != WC_MAIN_TOOLBAR &&
                                w->window_class != WC_STATUS_BAR &&
                                w->window_class != WC_TOOLTIPS &&
                                (w->flags & WF_STICKY) == 0) { // do not delete windows which are 'pinned'

                        delete w;
                        goto restart_search;
                }
        }
}

/**
 * It is possible that a stickied window gets to a position where the
 * 'close' button is outside the gaming area. You cannot close it then; except
 * with this function. It closes all windows calling the standard function,
 * then, does a little hacked loop of closing all stickied windows. Note
 * that standard windows (status bar, etc.) are not stickied, so these aren't affected
 */
void DeleteAllNonVitalWindows()
{
        Window *w;

        /* Delete every window except for stickied ones, then sticky ones as well */
        DeleteNonVitalWindows();

restart_search:
        /* When we find the window to delete, we need to restart the search
         * as deleting this window could cascade in deleting (many) others
         * anywhere in the z-array */
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->flags & WF_STICKY) {
                        delete w;
                        goto restart_search;
                }
        }
}

/**
 * Delete all windows that are used for construction of vehicle etc.
 * Once done with that invalidate the others to ensure they get refreshed too.
 */
void DeleteConstructionWindows()
{
        Window *w;

restart_search:
        /* When we find the window to delete, we need to restart the search
         * as deleting this window could cascade in deleting (many) others
         * anywhere in the z-array */
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->window_desc->flags & WDF_CONSTRUCTION) {
                        delete w;
                        goto restart_search;
                }
        }

        FOR_ALL_WINDOWS_FROM_BACK(w) w->SetDirty();
}

/** Delete all always on-top windows to get an empty screen */
void HideVitalWindows()
{
        DeleteWindowById(WC_MAIN_TOOLBAR, 0);
        DeleteWindowById(WC_STATUS_BAR, 0);
}

/** Re-initialize all windows. */
void ReInitAllWindows()
{
        NWidgetLeaf::InvalidateDimensionCache(); // Reset cached sizes of several widgets.
        NWidgetScrollbar::InvalidateDimensionCache();

        extern void InitDepotWindowBlockSizes();
        InitDepotWindowBlockSizes();

        Window *w;
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                w->ReInit();
        }
#ifdef ENABLE_NETWORK
        void NetworkReInitChatBoxSize();
        NetworkReInitChatBoxSize();
#endif

        /* Make sure essential parts of all windows are visible */
        RelocateAllWindows(_cur_resolution.width, _cur_resolution.height);
        MarkWholeScreenDirty();
}

/**
 * (Re)position a window at the screen.
 * @param w       Window structure of the window, may also be \c nullptr.
 * @param clss    The class of the window to position.
 * @param setting The actual setting used for the window's position.
 * @return X coordinate of left edge of the repositioned window.
 */
static int PositionWindow(Window *w, WindowClass clss, int setting)
{
        if (w == nullptr || w->window_class != clss) {
                w = FindWindowById(clss, 0);
        }
        if (w == nullptr) return 0;

        int old_left = w->left;
        switch (setting) {
                case 1:  w->left = (_screen.width - w->width) / 2; break;
                case 2:  w->left = _screen.width - w->width; break;
                default: w->left = 0; break;
        }
        if (w->viewport != nullptr) w->viewport->left += w->left - old_left;
        SetDirtyBlocks(0, w->top, _screen.width, w->top + w->height); // invalidate the whole row
        return w->left;
}

/**
 * (Re)position main toolbar window at the screen.
 * @param w Window structure of the main toolbar window, may also be \c nullptr.
 * @return X coordinate of left edge of the repositioned toolbar window.
 */
int PositionMainToolbar(Window *w)
{
        DEBUG(misc, 5, "Repositioning Main Toolbar...");
        return PositionWindow(w, WC_MAIN_TOOLBAR, _settings_client.gui.toolbar_pos);
}

/**
 * (Re)position statusbar window at the screen.
 * @param w Window structure of the statusbar window, may also be \c nullptr.
 * @return X coordinate of left edge of the repositioned statusbar.
 */
int PositionStatusbar(Window *w)
{
        DEBUG(misc, 5, "Repositioning statusbar...");
        return PositionWindow(w, WC_STATUS_BAR, _settings_client.gui.statusbar_pos);
}

/**
 * (Re)position news message window at the screen.
 * @param w Window structure of the news message window, may also be \c nullptr.
 * @return X coordinate of left edge of the repositioned news message.
 */
int PositionNewsMessage(Window *w)
{
        DEBUG(misc, 5, "Repositioning news message...");
        return PositionWindow(w, WC_NEWS_WINDOW, _settings_client.gui.statusbar_pos);
}

/**
 * (Re)position network chat window at the screen.
 * @param w Window structure of the network chat window, may also be \c nullptr.
 * @return X coordinate of left edge of the repositioned network chat window.
 */
int PositionNetworkChatWindow(Window *w)
{
        DEBUG(misc, 5, "Repositioning network chat window...");
        return PositionWindow(w, WC_SEND_NETWORK_MSG, _settings_client.gui.statusbar_pos);
}


/**
 * Switches viewports following vehicles, which get autoreplaced
 * @param from_index the old vehicle ID
 * @param to_index the new vehicle ID
 */
void ChangeVehicleViewports(VehicleID from_index, VehicleID to_index)
{
        Window *w;
        FOR_ALL_WINDOWS_FROM_BACK(w) {
                if (w->viewport != nullptr && w->viewport->follow_vehicle == from_index) {
                        w->viewport->follow_vehicle = to_index;
                        w->SetDirty();
                }
        }
}


/**
 * Relocate all windows to fit the new size of the game application screen
 * @param neww New width of the game application screen
 * @param newh New height of the game application screen.
 */
void RelocateAllWindows(int neww, int newh)
{
        Window *w;

        FOR_ALL_WINDOWS_FROM_BACK(w) {
                int left, top;
                /* XXX - this probably needs something more sane. For example specifying
                 * in a 'backup'-desc that the window should always be centered. */
                switch (w->window_class) {
                        case WC_MAIN_WINDOW:
                        case WC_BOOTSTRAP:
                                ResizeWindow(w, neww, newh);
                                continue;

                        case WC_MAIN_TOOLBAR:
                                ResizeWindow(w, min(neww, _toolbar_width) - w->width, 0, false);

                                top = w->top;
                                left = PositionMainToolbar(w); // changes toolbar orientation
                                break;

                        case WC_NEWS_WINDOW:
                                top = newh - w->height;
                                left = PositionNewsMessage(w);
                                break;

                        case WC_STATUS_BAR:
                                ResizeWindow(w, min(neww, _toolbar_width) - w->width, 0, false);

                                top = newh - w->height;
                                left = PositionStatusbar(w);
                                break;

                        case WC_SEND_NETWORK_MSG:
                                ResizeWindow(w, min(neww, _toolbar_width) - w->width, 0, false);

                                top = newh - w->height - FindWindowById(WC_STATUS_BAR, 0)->height;
                                left = PositionNetworkChatWindow(w);
                                break;

                        case WC_CONSOLE:
                                IConsoleResize(w);
                                continue;

                        default: {
                                if (w->flags & WF_CENTERED) {
                                        top = (newh - w->height) >> 1;
                                        left = (neww - w->width) >> 1;
                                        break;
                                }

                                left = w->left;
                                if (left + (w->width >> 1) >= neww) left = neww - w->width;
                                if (left < 0) left = 0;

                                top = w->top;
                                if (top + (w->height >> 1) >= newh) top = newh - w->height;
                                break;
                        }
                }

                EnsureVisibleCaption(w, left, top);
        }
}

/**
 * Destructor of the base class PickerWindowBase
 * Main utility is to stop the base Window destructor from triggering
 * a free while the child will already be free, in this case by the ResetObjectToPlace().
 */
PickerWindowBase::~PickerWindowBase()
{
        this->window_class = WC_INVALID; // stop the ancestor from freeing the already (to be) child
        ResetObjectToPlace();
}