Integrate upstream #1392 by adriancaruana

lib/EpdFont/SdCardFontManager.h

@@ -0,0 +1,50 @@
+#pragma once
+
+#include <cstdint>
+#include <string>
+#include <vector>
+
+class GfxRenderer;
+class SdCardFont;
+struct SdCardFontFamilyInfo;
+
+class SdCardFontManager {
+ public:
+  SdCardFontManager() = default;
+  ~SdCardFontManager();
+  SdCardFontManager(const SdCardFontManager&) = delete;
+  SdCardFontManager& operator=(const SdCardFontManager&) = delete;
+
+  // Load the single size closest to targetPtSize for a discovered family.
+  // Only one .cpfont file is loaded; other sizes remain on disk. This keeps
+  // resident interval + kern/ligature tables to one size's worth of memory
+  // (see PR #1327 discussion re: Literata OOM).
+  // Returns true on success.
+  bool loadFamily(const SdCardFontFamilyInfo& family, GfxRenderer& renderer, uint8_t targetPtSize);
+
+  // Unload everything, unregister from renderer.
+  void unloadAll(GfxRenderer& renderer);
+
+  // Look up the font ID for the loaded family. Returns 0 if nothing loaded
+  // or familyName doesn't match.
+  int getFontId(const std::string& familyName) const;
+
+  // Get name of currently loaded family (empty if none).
+  const std::string& currentFamilyName() const { return loadedFamilyName_; };
+
+  // Point size that was actually loaded (closest match to targetPtSize).
+  // 0 if nothing loaded.
+  uint8_t currentPointSize() const { return loadedPointSize_; };
+
+ private:
+  struct LoadedFont {
+    SdCardFont* font;  // heap-allocated, owned
+    int fontId;
+    uint8_t size;
+  };
+  static int computeFontId(uint32_t contentHash, const char* familyName, uint8_t pointSize);
+
+  std::string loadedFamilyName_;
+  uint8_t loadedPointSize_ = 0;
+  std::vector<LoadedFont> loaded_;
+};