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Fostbite2D/include/fostbite2D/render/opengl/gl_font_atlas.h

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+#pragma once
+
+#include <fostbite2D/core/color.h>
+#include <fostbite2D/core/math_types.h>
+#include <fostbite2D/core/types.h>
+#include <fostbite2D/render/font.h>
+#include <fostbite2D/render/opengl/gl_texture.h>
+#include <fostbite2D/render/texture.h>
+#include <memory>
+#include <stb/stb_rect_pack.h>
+#include <stb/stb_truetype.h>
+#include <unordered_map>
+#include <vector>
+
+namespace frostbite2D {
+
+// ============================================================================
+// OpenGL 字体图集实现 - 使用 stb_rect_pack 进行矩形打包
+// ============================================================================
+class GLFontAtlas : public FontAtlas {
+public:
+  /**
+   * @brief 构造函数，从字体文件初始化字体图集
+   * @param filepath 字体文件路径
+   * @param fontSize 字体大小（像素）
+   * @param useSDF 是否使用有符号距离场渲染
+   */
+  GLFontAtlas(const std::string &filepath, int fontSize, bool useSDF = false);
+
+  /**
+   * @brief 析构函数
+   */
+  ~GLFontAtlas();
+
+  // FontAtlas 接口实现
+  const Glyph *getGlyph(char32_t codepoint) const override;
+  Texture *getTexture() const override { return texture_.get(); }
+  int getFontSize() const override { return fontSize_; }
+  float getAscent() const override { return ascent_; }
+  float getDescent() const override { return descent_; }
+  float getLineGap() const override { return lineGap_; }
+  float getLineHeight() const override { return ascent_ - descent_ + lineGap_; }
+  Vec2 measureText(const std::string &text) override;
+  bool isSDF() const override { return useSDF_; }
+
+private:
+  // 图集配置 - 增大尺寸以支持更多字符
+  static constexpr int ATLAS_WIDTH = 1024;
+  static constexpr int ATLAS_HEIGHT = 1024;
+  static constexpr int PADDING = 2; // 字形之间的间距
+
+  int fontSize_;
+  bool useSDF_;
+  mutable std::unique_ptr<GLTexture> texture_;
+  mutable std::unordered_map<char32_t, Glyph> glyphs_;
+
+  // stb_rect_pack 上下文
+  mutable stbrp_context packContext_;
+  mutable std::vector<stbrp_node> packNodes_;
+  mutable int currentY_;
+
+  std::vector<unsigned char> fontData_;
+  stbtt_fontinfo fontInfo_;
+  float scale_;
+  float ascent_;
+  float descent_;
+  float lineGap_;
+
+  // 预分配字形位图缓冲区，避免每次动态分配
+  mutable std::vector<uint8_t> glyphBitmapCache_;
+  mutable std::vector<uint8_t> glyphRgbaCache_;
+
+  /**
+   * @brief 创建字体图集纹理
+   */
+  void createAtlas();
+
+  /**
+   * @brief 缓存字形到图集
+   * @param codepoint Unicode码点
+   */
+  void cacheGlyph(char32_t codepoint) const;
+};
+
+} // namespace frostbite2D