渲染后端加入
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313
Fostbite2D/src/fostbite2D/render/opengl/gl_font_atlas.cpp
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313
Fostbite2D/src/fostbite2D/render/opengl/gl_font_atlas.cpp
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#include <SDL.h>
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#include <fostbite2D/render/opengl/gl_font_atlas.h>
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#include <fstream>
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#define STB_TRUETYPE_IMPLEMENTATION
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#include <stb/stb_truetype.h>
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#define STB_RECT_PACK_IMPLEMENTATION
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#include <algorithm>
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#include <stb/stb_rect_pack.h>
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namespace frostbite2D {
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// ============================================================================
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// 构造函数 - 初始化字体图集
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// ============================================================================
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/**
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* @brief 构造函数，从字体文件初始化字体图集
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* @param filepath 字体文件路径
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* @param fontSize 字体大小（像素）
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* @param useSDF 是否使用有符号距离场渲染
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*/
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GLFontAtlas::GLFontAtlas(const std::string &filepath, int fontSize, bool useSDF)
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: fontSize_(fontSize), useSDF_(useSDF), currentY_(0), scale_(0.0f),
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ascent_(0.0f), descent_(0.0f), lineGap_(0.0f) {
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// 加载字体文件
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std::ifstream file(filepath, std::ios::binary | std::ios::ate);
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if (!file.is_open()) {
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SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Failed to load font: %s",
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filepath.c_str());
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return;
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}
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std::streamsize size = file.tellg();
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file.seekg(0, std::ios::beg);
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fontData_.resize(size);
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if (!file.read(reinterpret_cast<char *>(fontData_.data()), size)) {
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SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Failed to read font file: %s",
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filepath.c_str());
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return;
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}
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// 初始化 stb_truetype
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if (!stbtt_InitFont(&fontInfo_, fontData_.data(),
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stbtt_GetFontOffsetForIndex(fontData_.data(), 0))) {
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SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Failed to init font: %s",
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filepath.c_str());
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return;
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}
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scale_ = stbtt_ScaleForPixelHeight(&fontInfo_, static_cast<float>(fontSize_));
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int ascent, descent, lineGap;
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stbtt_GetFontVMetrics(&fontInfo_, &ascent, &descent, &lineGap);
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ascent_ = static_cast<float>(ascent) * scale_;
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descent_ = static_cast<float>(descent) * scale_;
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lineGap_ = static_cast<float>(lineGap) * scale_;
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createAtlas();
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}
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// ============================================================================
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// 析构函数
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// ============================================================================
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/**
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* @brief 析构函数
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*/
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GLFontAtlas::~GLFontAtlas() = default;
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// ============================================================================
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// 获取字形 - 如果字形不存在则缓存它
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// ============================================================================
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/**
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* @brief 获取字形信息，如果字形不存在则动态缓存
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* @param codepoint Unicode码点
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* @return 字形信息指针，如果获取失败返回nullptr
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*/
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const Glyph *GLFontAtlas::getGlyph(char32_t codepoint) const {
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auto it = glyphs_.find(codepoint);
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if (it == glyphs_.end()) {
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cacheGlyph(codepoint);
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it = glyphs_.find(codepoint);
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}
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return (it != glyphs_.end()) ? &it->second : nullptr;
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}
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// ============================================================================
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// 测量文本尺寸
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// ============================================================================
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/**
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* @brief 测量文本渲染后的尺寸
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* @param text 要测量的文本
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* @return 文本的宽度和高度
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*/
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Vec2 GLFontAtlas::measureText(const std::string &text) {
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float width = 0.0f;
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float height = getAscent() - getDescent();
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float currentWidth = 0.0f;
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for (char c : text) {
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char32_t codepoint = static_cast<char32_t>(static_cast<unsigned char>(c));
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if (codepoint == '\n') {
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width = std::max(width, currentWidth);
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currentWidth = 0.0f;
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height += getLineHeight();
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continue;
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}
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const Glyph *glyph = getGlyph(codepoint);
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if (glyph) {
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currentWidth += glyph->advance;
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}
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}
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width = std::max(width, currentWidth);
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return Vec2(width, height);
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}
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// ============================================================================
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// 创建图集纹理 - 初始化空白纹理和矩形打包上下文
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// ============================================================================
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/**
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* @brief 创建字体图集纹理，初始化空白纹理和矩形打包上下文
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*/
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void GLFontAtlas::createAtlas() {
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// 统一使用 4 通道格式
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int channels = 4;
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std::vector<uint8_t> emptyData(ATLAS_WIDTH * ATLAS_HEIGHT * channels, 0);
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texture_ = std::make_unique<GLTexture>(ATLAS_WIDTH, ATLAS_HEIGHT,
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emptyData.data(), channels);
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texture_->setFilter(true);
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// 初始化矩形打包上下文
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packNodes_.resize(ATLAS_WIDTH);
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stbrp_init_target(&packContext_, ATLAS_WIDTH, ATLAS_HEIGHT, packNodes_.data(),
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ATLAS_WIDTH);
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// 预分配字形缓冲区
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// 假设最大字形尺寸为 fontSize * fontSize * 4 (RGBA)
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size_t maxGlyphSize = static_cast<size_t>(fontSize_ * fontSize_ * 4 * 4);
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glyphBitmapCache_.reserve(maxGlyphSize);
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glyphRgbaCache_.reserve(maxGlyphSize);
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}
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// ============================================================================
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// 缓存字形 - 渲染字形到图集并存储信息
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// 使用 stb_rect_pack 进行矩形打包
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// ============================================================================
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/**
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* @brief 缓存字形到图集，渲染字形位图并存储字形信息
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* @param codepoint Unicode码点
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*/
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void GLFontAtlas::cacheGlyph(char32_t codepoint) const {
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int advance = 0;
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stbtt_GetCodepointHMetrics(&fontInfo_, static_cast<int>(codepoint), &advance,
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nullptr);
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float advancePx = advance * scale_;
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if (useSDF_) {
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constexpr int SDF_PADDING = 8;
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constexpr unsigned char ONEDGE_VALUE = 128;
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constexpr float PIXEL_DIST_SCALE = 64.0f;
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int w = 0, h = 0, xoff = 0, yoff = 0;
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unsigned char *sdf = stbtt_GetCodepointSDF(
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&fontInfo_, scale_, static_cast<int>(codepoint), SDF_PADDING,
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ONEDGE_VALUE, PIXEL_DIST_SCALE, &w, &h, &xoff, &yoff);
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if (!sdf || w <= 0 || h <= 0) {
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if (sdf)
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stbtt_FreeSDF(sdf, nullptr);
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Glyph glyph{};
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glyph.advance = advancePx;
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glyphs_[codepoint] = glyph;
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return;
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}
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stbrp_rect rect;
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rect.id = static_cast<int>(codepoint);
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rect.w = w + PADDING * 2;
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rect.h = h + PADDING * 2;
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stbrp_pack_rects(&packContext_, &rect, 1);
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if (!rect.was_packed) {
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SDL_LogWarn(SDL_LOG_CATEGORY_APPLICATION,
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"Font atlas is full, cannot cache codepoint: %d",
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static_cast<int>(codepoint));
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stbtt_FreeSDF(sdf, nullptr);
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return;
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}
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int atlasX = rect.x + PADDING;
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int atlasY = rect.y + PADDING;
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Glyph glyph;
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glyph.width = static_cast<float>(w);
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glyph.height = static_cast<float>(h);
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glyph.bearingX = static_cast<float>(xoff);
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glyph.bearingY = static_cast<float>(yoff);
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glyph.advance = advancePx;
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// stb_rect_pack 使用左上角为原点，OpenGL纹理使用左下角为原点
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// 需要翻转V坐标
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float v0 = static_cast<float>(atlasY) / ATLAS_HEIGHT;
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float v1 = static_cast<float>(atlasY + h) / ATLAS_HEIGHT;
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glyph.u0 = static_cast<float>(atlasX) / ATLAS_WIDTH;
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glyph.v0 = 1.0f - v1; // 翻转V坐标
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glyph.u1 = static_cast<float>(atlasX + w) / ATLAS_WIDTH;
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glyph.v1 = 1.0f - v0; // 翻转V坐标
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glyphs_[codepoint] = glyph;
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// 将 SDF 单通道数据转换为 RGBA 格式（统一格式）
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size_t pixelCount = static_cast<size_t>(w) * static_cast<size_t>(h);
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glyphRgbaCache_.resize(pixelCount * 4);
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for (size_t i = 0; i < pixelCount; ++i) {
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uint8_t alpha = sdf[i];
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glyphRgbaCache_[i * 4 + 0] = 255; // R
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glyphRgbaCache_[i * 4 + 1] = 255; // G
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glyphRgbaCache_[i * 4 + 2] = 255; // B
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glyphRgbaCache_[i * 4 + 3] = alpha; // A - SDF 值存储在 Alpha 通道
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}
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// 直接设置像素对齐为 4，无需查询当前状态
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glBindTexture(GL_TEXTURE_2D, texture_->getTextureID());
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glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
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// OpenGL纹理坐标原点在左下角，需要将Y坐标翻转
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glTexSubImage2D(GL_TEXTURE_2D, 0, atlasX, ATLAS_HEIGHT - atlasY - h, w, h,
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GL_RGBA, GL_UNSIGNED_BYTE, glyphRgbaCache_.data());
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stbtt_FreeSDF(sdf, nullptr);
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return;
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}
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int x0 = 0, y0 = 0, x1 = 0, y1 = 0;
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stbtt_GetCodepointBitmapBox(&fontInfo_, static_cast<int>(codepoint), scale_,
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scale_, &x0, &y0, &x1, &y1);
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int w = x1 - x0;
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int h = y1 - y0;
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int xoff = x0;
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int yoff = y0;
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if (w <= 0 || h <= 0) {
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Glyph glyph{};
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glyph.advance = advancePx;
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glyphs_[codepoint] = glyph;
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return;
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}
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// 使用预分配缓冲区
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size_t pixelCount = static_cast<size_t>(w) * static_cast<size_t>(h);
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glyphBitmapCache_.resize(pixelCount);
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stbtt_MakeCodepointBitmap(&fontInfo_, glyphBitmapCache_.data(), w, h, w,
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scale_, scale_, static_cast<int>(codepoint));
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// 使用 stb_rect_pack 打包矩形
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stbrp_rect rect;
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rect.id = static_cast<int>(codepoint);
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rect.w = w + PADDING * 2;
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rect.h = h + PADDING * 2;
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stbrp_pack_rects(&packContext_, &rect, 1);
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if (!rect.was_packed) {
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// 图集已满，无法缓存更多字形
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SDL_LogWarn(SDL_LOG_CATEGORY_APPLICATION,
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"Font atlas is full, cannot cache codepoint: %d",
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static_cast<int>(codepoint));
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return;
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}
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int atlasX = rect.x + PADDING;
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int atlasY = rect.y + PADDING;
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// 创建字形信息
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Glyph glyph;
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glyph.width = static_cast<float>(w);
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glyph.height = static_cast<float>(h);
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glyph.bearingX = static_cast<float>(xoff);
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glyph.bearingY = static_cast<float>(yoff);
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glyph.advance = advancePx;
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// 计算纹理坐标（相对于图集）
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// stb_rect_pack 使用左上角为原点，OpenGL纹理使用左下角为原点
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// 需要翻转V坐标
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float v0 = static_cast<float>(atlasY) / ATLAS_HEIGHT;
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float v1 = static_cast<float>(atlasY + h) / ATLAS_HEIGHT;
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glyph.u0 = static_cast<float>(atlasX) / ATLAS_WIDTH;
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glyph.v0 = 1.0f - v1; // 翻转V坐标
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glyph.u1 = static_cast<float>(atlasX + w) / ATLAS_WIDTH;
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glyph.v1 = 1.0f - v0; // 翻转V坐标
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// 存储字形
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glyphs_[codepoint] = glyph;
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// 将单通道字形数据转换为 RGBA 格式（白色字形，Alpha 通道存储灰度）
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glyphRgbaCache_.resize(pixelCount * 4);
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for (size_t i = 0; i < pixelCount; ++i) {
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uint8_t alpha = glyphBitmapCache_[i];
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glyphRgbaCache_[i * 4 + 0] = 255; // R
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glyphRgbaCache_[i * 4 + 1] = 255; // G
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glyphRgbaCache_[i * 4 + 2] = 255; // B
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glyphRgbaCache_[i * 4 + 3] = alpha; // A
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}
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// 更新纹理 - 将字形数据上传到图集的指定位置
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// 直接设置像素对齐为 4，无需查询当前状态
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glBindTexture(GL_TEXTURE_2D, texture_->getTextureID());
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glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
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// OpenGL纹理坐标原点在左下角，需要将Y坐标翻转
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glTexSubImage2D(GL_TEXTURE_2D, 0, atlasX, ATLAS_HEIGHT - atlasY - h, w, h,
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GL_RGBA, GL_UNSIGNED_BYTE, glyphRgbaCache_.data());
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}
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} // namespace frostbite2D
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