src/gfx_layout.h

   1 /*
   2  * This file is part of OpenTTD.
   3  * 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.
   4  * 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.
   5  * 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/>.
   6  */
   7
   8 /** @file gfx_layout.h Functions related to laying out the texts. */
   9
  10 #ifndef GFX_LAYOUT_H
  11 #define GFX_LAYOUT_H
  12
  13 #include "fontcache.h"
  14 #include "gfx_func.h"
  15 #include "core/math_func.hpp"
  16
  17 #include <stack>
  18 #include <string_view>
  19
  20 /**
  21  * Text drawing parameters, which can change while drawing a line, but are kept between multiple parts
  22  * of the same text, e.g. on line breaks.
  23  */
  24 struct FontState {
  25         FontSize fontsize;       ///< Current font size.
  26         TextColour cur_colour;   ///< Current text colour.
  27
  28         std::stack<TextColour, std::vector<TextColour>> colour_stack; ///< Stack of colours to assist with colour switching.
  29
  30         FontState() : fontsize(FS_END), cur_colour(TC_INVALID) {}
  31         FontState(TextColour colour, FontSize fontsize) : fontsize(fontsize), cur_colour(colour) {}
  32
  33         /**
  34          * Switch to new colour \a c.
  35          * @param c New colour to use.
  36          */
  37         inline void SetColour(TextColour c)
  38         {
  39                 assert(((c & TC_COLOUR_MASK) >= TC_BLUE && (c & TC_COLOUR_MASK) <= TC_BLACK) || (c & TC_COLOUR_MASK) == TC_INVALID);
  40                 assert((c & (TC_COLOUR_MASK | TC_FLAGS_MASK)) == c);
  41                 if ((this->cur_colour & TC_FORCED) == 0) this->cur_colour = c;
  42         }
  43
  44         /**
  45          * Switch to and pop the last saved colour on the stack.
  46          */
  47         inline void PopColour()
  48         {
  49                 if (colour_stack.empty()) return;
  50                 SetColour(colour_stack.top());
  51                 colour_stack.pop();
  52         }
  53
  54         /**
  55          * Push the current colour on to the stack.
  56          */
  57         inline void PushColour()
  58         {
  59                 colour_stack.push(this->cur_colour);
  60         }
  61
  62         /**
  63          * Switch to using a new font \a f.
  64          * @param f New font to use.
  65          */
  66         inline void SetFontSize(FontSize f)
  67         {
  68                 this->fontsize = f;
  69         }
  70 };
  71
  72 /**
  73  * Container with information about a font.
  74  */
  75 class Font {
  76 public:
  77         FontCache *fc;     ///< The font we are using.
  78         TextColour colour; ///< The colour this font has to be.
  79
  80         Font(FontSize size, TextColour colour);
  81 };
  82
  83 /** Mapping from index to font. The pointer is owned by FontColourMap. */
  84 using FontMap = std::map<int, Font *>;
  85
  86 /**
  87  * Interface to glue fallback and normal layouter into one.
  88  */
  89 class ParagraphLayouter {
  90 public:
  91         virtual ~ParagraphLayouter() = default;
  92
  93         /** Position of a glyph within a VisualRun. */
  94         class Position {
  95         public:
  96                 int16_t left; ///< Left-most position of glyph.
  97                 int16_t right; ///< Right-most position of glyph.
  98                 int16_t top; ///< Top-most position of glyph.
  99
 100                 constexpr inline Position(int16_t left, int16_t right, int16_t top) : left(left), right(right), top(top) { }
 101
 102                 /** Conversion from a single point to a Position. */
 103                 constexpr inline Position(const Point &pt) : left(pt.x), right(pt.x), top(pt.y) { }
 104         };
 105
 106         /** Visual run contains data about the bit of text with the same font. */
 107         class VisualRun {
 108         public:
 109                 virtual ~VisualRun() = default;
 110                 virtual const Font *GetFont() const = 0;
 111                 virtual int GetGlyphCount() const = 0;
 112                 virtual std::span<const GlyphID> GetGlyphs() const = 0;
 113                 virtual std::span<const Position> GetPositions() const = 0;
 114                 virtual int GetLeading() const = 0;
 115                 virtual std::span<const int> GetGlyphToCharMap() const = 0;
 116         };
 117
 118         /** A single line worth of VisualRuns. */
 119         class Line {
 120         public:
 121                 virtual ~Line() = default;
 122                 virtual int GetLeading() const = 0;
 123                 virtual int GetWidth() const = 0;
 124                 virtual int CountRuns() const = 0;
 125                 virtual const VisualRun &GetVisualRun(int run) const = 0;
 126                 virtual int GetInternalCharLength(char32_t c) const = 0;
 127         };
 128
 129         virtual void Reflow() = 0;
 130         virtual std::unique_ptr<const Line> NextLine(int max_width) = 0;
 131 };
 132
 133 /**
 134  * The layouter performs all the layout work.
 135  *
 136  * It also accounts for the memory allocations and frees.
 137  */
 138 class Layouter : public std::vector<std::unique_ptr<const ParagraphLayouter::Line>> {
 139         std::string_view string; ///< Pointer to the original string.
 140
 141         /** Key into the linecache */
 142         struct LineCacheKey {
 143                 FontState state_before;  ///< Font state at the beginning of the line.
 144                 std::string str;         ///< Source string of the line (including colour and font size codes).
 145         };
 146
 147         struct LineCacheQuery {
 148                 const FontState &state_before; ///< Font state at the beginning of the line.
 149                 std::string_view str;    ///< Source string of the line (including colour and font size codes).
 150         };
 151
 152         /** Comparator for std::map */
 153         struct LineCacheCompare {
 154                 using is_transparent = void; ///< Enable map queries with various key types
 155
 156                 /** Comparison operator for LineCacheKey and LineCacheQuery */
 157                 template<typename Key1, typename Key2>
 158                 bool operator()(const Key1 &lhs, const Key2 &rhs) const
 159                 {
 160                         if (lhs.state_before.fontsize != rhs.state_before.fontsize) return lhs.state_before.fontsize < rhs.state_before.fontsize;
 161                         if (lhs.state_before.cur_colour != rhs.state_before.cur_colour) return lhs.state_before.cur_colour < rhs.state_before.cur_colour;
 162                         if (lhs.state_before.colour_stack != rhs.state_before.colour_stack) return lhs.state_before.colour_stack < rhs.state_before.colour_stack;
 163                         return lhs.str < rhs.str;
 164                 }
 165         };
 166 public:
 167         /** Item in the linecache */
 168         struct LineCacheItem {
 169                 /* Stuff that cannot be freed until the ParagraphLayout is freed */
 170                 void *buffer;              ///< Accessed by our ParagraphLayout::nextLine.
 171                 FontMap runs;              ///< Accessed by our ParagraphLayout::nextLine.
 172
 173                 FontState state_after;     ///< Font state after the line.
 174                 ParagraphLayouter *layout; ///< Layout of the line.
 175
 176                 LineCacheItem() : buffer(nullptr), layout(nullptr) {}
 177                 ~LineCacheItem() { delete layout; free(buffer); }
 178         };
 179 private:
 180         typedef std::map<LineCacheKey, LineCacheItem, LineCacheCompare> LineCache;
 181         static LineCache *linecache;
 182
 183         static LineCacheItem &GetCachedParagraphLayout(std::string_view str, const FontState &state);
 184
 185         using FontColourMap = std::map<TextColour, std::unique_ptr<Font>>;
 186         static FontColourMap fonts[FS_END];
 187 public:
 188         static Font *GetFont(FontSize size, TextColour colour);
 189
 190         Layouter(std::string_view str, int maxw = INT32_MAX, FontSize fontsize = FS_NORMAL);
 191         Dimension GetBounds();
 192         ParagraphLayouter::Position GetCharPosition(std::string_view::const_iterator ch) const;
 193         ptrdiff_t GetCharAtPosition(int x, size_t line_index) const;
 194
 195         static void Initialize();
 196         static void ResetFontCache(FontSize size);
 197         static void ResetLineCache();
 198         static void ReduceLineCache();
 199 };
 200
 201 ParagraphLayouter::Position GetCharPosInString(std::string_view str, const char *ch, FontSize start_fontsize = FS_NORMAL);
 202 ptrdiff_t GetCharAtPosition(std::string_view str, int x, FontSize start_fontsize = FS_NORMAL);
 203
 204 #endif /* GFX_LAYOUT_H */