Reduce memory need

src/components/themes/BaseTheme.h

@@ -193,6 +193,10 @@ class BaseTheme {
   // Only one of epub/xtc/txt will be non-null depending on the reader.
   virtual void onBookWillClose(const std::string& path, Epub* epub, Xtc* xtc, Txt* txt) {}
 
+  // Called when HomeActivity exits. Themes that hold heap-allocated render caches
+  // should free them here so the memory is available to child activities.
+  virtual void invalidateFrameCache() {}
+
   // ---- Shared constants and helpers for battery drawing (used by all themes) ----
   static constexpr int batteryPercentSpacing = 4;
   static void drawBatteryOutline(const GfxRenderer& renderer, int x, int y, int battWidth, int rectHeight);

src/components/themes/lyra/LyraCarouselTheme.cpp

@@ -90,9 +90,9 @@ const uint8_t* iconBitmapFor(UIIcon icon) {
 // home after settings doesn't re-read covers from SD.
 // Freed explicitly via invalidateFrameCache() before entering the reader.
 // ---------------------------------------------------------------------------
-constexpr int kFrameCount = 3;
+constexpr int kFrameCount = 1;
 uint8_t* gCachedFrames[kFrameCount] = {};
-int gCachedFrameBookIdx[kFrameCount] = {-1, -1, -1};
+int gCachedFrameBookIdx[kFrameCount] = {-1};
 int gCachedFrameCount = 0;
 std::string gCacheKey;
 
@@ -102,14 +102,8 @@ int findFrameSlot(int bookIdx) {
   }
   return -1;
 }
-}  // namespace
 
-// ---------------------------------------------------------------------------
-// Static helpers
-// ---------------------------------------------------------------------------
-void LyraCarouselTheme::setPreRenderIndex(int idx) { lastCarouselSelectorIndex = idx; }
-
-void LyraCarouselTheme::invalidateFrameCache() const {
+void freeFrameCache() {
   for (int i = 0; i < kFrameCount; ++i) {
     if (gCachedFrames[i]) {
       free(gCachedFrames[i]);
@@ -120,6 +114,14 @@ void LyraCarouselTheme::invalidateFrameCache() const {
   gCachedFrameCount = 0;
   gCacheKey.clear();
 }
+}  // namespace
+
+// ---------------------------------------------------------------------------
+// Static helpers
+// ---------------------------------------------------------------------------
+void LyraCarouselTheme::setPreRenderIndex(int idx) { lastCarouselSelectorIndex = idx; }
+
+void LyraCarouselTheme::invalidateFrameCache() { freeFrameCache(); }
 
 void LyraCarouselTheme::onBookWillClose(const std::string& /*path*/, Epub* epub, Xtc* xtc, Txt* /*txt*/) {
   if (epub) {
@@ -212,13 +214,13 @@ bool LyraCarouselTheme::tryFastHomeRender(GfxRenderer& renderer, const std::vect
 
   if (!framesReady) {
     // Free old cache and allocate fresh frames
-    invalidateFrameCache();
+    freeFrameCache();
     const int frameCount = std::min(bookCount, kFrameCount);
     for (int i = 0; i < frameCount; ++i) {
       gCachedFrames[i] = static_cast<uint8_t*>(malloc(bufferSize));
       if (!gCachedFrames[i]) {
         LOG_ERR("CAROUSEL", "tryFastHomeRender: malloc failed for frame %d", i);
-        invalidateFrameCache();
+        freeFrameCache();
         return false;
       }
     }

src/components/themes/lyra/LyraCarouselTheme.h

@@ -72,7 +72,7 @@ class LyraCarouselTheme : public LyraTheme {
                          const std::function<UIIcon(int)>& menuIcon, const char* hintBtn1, const char* hintBtn2,
                          const char* hintBtn3, const char* hintBtn4) const override;
   void onBookWillClose(const std::string& path, Epub* epub, Xtc* xtc, Txt* txt) override;
-  void invalidateFrameCache() const;
+  void invalidateFrameCache() override;
 
   void drawRecentBookCover(GfxRenderer& renderer, Rect rect, const std::vector<RecentBook>& recentBooks,
                            const int selectorIndex, bool& coverRendered, bool& coverBufferStored, bool& bufferRestored,