GuiTextRenderer.h

/****************************************************************************
 * libgui
 * Daryl Borth 2026
 * GuiTextRenderer.h
 ***************************************************************************/
#pragma once
 
#include <stdint.h>
#include <map>
#include <vector>
#include <ft2build.h>
#include FT_FREETYPE_H
 
#include "Gui.h"
 
// Legacy Text Styling Constants
#define GUI_TEXT_NULL               0x0000
#define GUI_TEXT_JUSTIFY_LEFT       0x0001
#define GUI_TEXT_JUSTIFY_CENTER     0x0002
#define GUI_TEXT_JUSTIFY_RIGHT      0x0004
#define GUI_TEXT_JUSTIFY_MASK       0x000f
 
#define GUI_TEXT_ALIGN_TOP          0x0010
#define GUI_TEXT_ALIGN_MIDDLE       0x0020
#define GUI_TEXT_ALIGN_BOTTOM       0x0040
#define GUI_TEXT_ALIGN_BASELINE     0x0080
#define GUI_TEXT_ALIGN_GLYPH_TOP    0x0100
#define GUI_TEXT_ALIGN_GLYPH_MIDDLE 0x0200
#define GUI_TEXT_ALIGN_GLYPH_BOTTOM 0x0400
#define GUI_TEXT_ALIGN_MASK         0x0ff0
 
#define GUI_TEXT_STYLE_UNDERLINE    0x1000
#define GUI_TEXT_STYLE_STRIKE       0x2000
#define GUI_TEXT_STYLE_MASK         0xf000
 
const PixelColor black = {0, 0, 0, 255};

struct FontOffset {
    int16_t ascender; 
    int16_t descender; 
    int16_t max; 
    int16_t min; 
};

struct GlyphData {
    int16_t renderOffsetX; 
    uint16_t glyphAdvanceX; 
    uint16_t glyphAdvanceY; 
    uint32_t glyphIndex; 

    uint16_t textureWidth;
    uint16_t textureHeight; 

    uint16_t drawWidth;
    uint16_t drawHeight; 
 
    int16_t renderOffsetY; 
    int16_t renderOffsetMax; 
    int16_t renderOffsetMin; 
 
    void* texture; 
};

class GuiTextRenderer {
private:
    FT_Library ftLibrary;
    FT_Face ftFace;
    int16_t currentPixelSize;
    bool ftKerningEnabled;
 
    GlyphRenderer* renderer;
 
    struct ftData {
        FontOffset align;
        bool metricsReady;
        std::map<wchar_t, GlyphData> charMap;
 
        // Direct index for the first 256 characters, so the common lookup is one array read rather than
        // two std::map searches. null: not looked up yet; &missingGlyph: the font has no such glyph.
        GlyphData* fast[256];
 
        ftData() : metricsReady(false) {
            align.ascender = align.descender = align.max = align.min = 0;
            for (int i = 0; i < 256; ++i) fast[i] = nullptr;
        }
    };
 
    std::map<int16_t, ftData> fontData;
    ftData* current;    // fontData[currentPixelSize], or null until it is needed (map nodes never move)
    std::vector<uint16_t> widthScratch; // scrollWindow()'s running widths, kept so it doesn't allocate
    std::vector<wchar_t> lineScratch;
    static GlyphData missingGlyph;
    static uint32_t metricsGeneration;
 
    // Internal Calculations
    int16_t getStyleOffsetWidth(uint16_t width, uint32_t format);
    int16_t getStyleOffsetHeight(FontOffset* offset, uint32_t format);
    void drawTextFeature(int16_t x, int16_t y, uint16_t width, FontOffset* offsetData, uint32_t format, const PixelColor& color);
 
    // Font Management
    void unloadFont();
    GlyphData* cacheGlyphData(wchar_t charCode, int16_t pixelSize);
    // The glyph for a character at the current size: the fast table first, cacheGlyphData() on a miss.
    // null if the font has none.
    GlyphData* glyph(wchar_t charCode);
 
    // Physical-pixels-per-design-pixel glyphs are rasterized at (see
    // VideoDriver::getUIScale()).
    float uiScale;
 
public:
    GuiTextRenderer(const uint8_t* fontBuffer, FT_Long bufferSize, GlyphRenderer* glyphRenderer, float uiScale = 1.0f);
    ~GuiTextRenderer();

    void setPixelSize(int16_t pixelSize);

    void clearGlyphCache() { unloadFont(); }
 
    // Core Drawing Signatures
    uint16_t drawText(int16_t x, int16_t y, const wchar_t* text, PixelColor color = black, uint32_t renderFlags = 0);
    uint16_t drawText(int16_t x, int16_t y, const char* text, PixelColor color = black, uint32_t renderFlags = 0);
 
    // Dimensions & Offsets
    uint16_t getWidth(const wchar_t* text);

    int fitCount(const wchar_t* text, int maxWidth);

    void scrollWindow(const wchar_t* text, uint32_t textlen, uint32_t pos, int maxWidth, wchar_t* out);

    static uint32_t getMetricsGeneration() { return metricsGeneration; }
    uint16_t getWidth(const char* text);
    uint16_t getHeight(const wchar_t* text);
    uint16_t getHeight(const char* text);

    void getOffset(const wchar_t* text, FontOffset* offset);
 
    // Utilities
    static wchar_t* charToWideChar(const char* p);
};
 
extern GuiTextRenderer *fontSystem;