home screen performance fix

src/CrossPointState.cpp

@@ -5,7 +5,7 @@
 #include <Serialization.h>
 
 namespace {
-constexpr uint8_t STATE_FILE_VERSION = 2;
+constexpr uint8_t STATE_FILE_VERSION = 3;
 constexpr char STATE_FILE[] = "/.crosspoint/state.bin";
 }  // namespace
 
@@ -20,6 +20,9 @@ bool CrossPointState::saveToFile() const {
   serialization::writePod(outputFile, STATE_FILE_VERSION);
   serialization::writeString(outputFile, openEpubPath);
   serialization::writePod(outputFile, lastSleepImage);
+  // Version 3: add cached book title and author
+  serialization::writeString(outputFile, openBookTitle);
+  serialization::writeString(outputFile, openBookAuthor);
   outputFile.close();
   return true;
 }
@@ -45,6 +48,15 @@ bool CrossPointState::loadFromFile() {
     lastSleepImage = 0;
   }
 
+  // Version 3: read cached book title and author
+  if (version >= 3) {
+    serialization::readString(inputFile, openBookTitle);
+    serialization::readString(inputFile, openBookAuthor);
+  } else {
+    openBookTitle.clear();
+    openBookAuthor.clear();
+  }
+
   inputFile.close();
   return true;
 }

src/CrossPointState.h

@@ -8,6 +8,8 @@ class CrossPointState {
 
  public:
   std::string openEpubPath;
+  std::string openBookTitle;   // Cached title for the current book
+  std::string openBookAuthor;  // Cached author for the current book
   uint8_t lastSleepImage;
   ~CrossPointState() = default;
 

src/ScreenComponents.cpp

@@ -42,6 +42,41 @@ void ScreenComponents::drawBattery(const GfxRenderer& renderer, const int left,
   renderer.fillRect(x + 2, y + 2, filledWidth, batteryHeight - 4);
 }
 
+void ScreenComponents::drawBatteryLarge(const GfxRenderer& renderer, const int left, const int top,
+                                        const bool showPercentage) {
+  // Larger battery icon with UI_10 font for bottom button hint area
+  const uint16_t percentage = battery.readPercentage();
+  const auto percentageText = showPercentage ? std::to_string(percentage) + "%" : "";
+  renderer.drawText(UI_10_FONT_ID, left + 28, top, percentageText.c_str());
+
+  // Scaled up battery dimensions (~33% larger)
+  constexpr int batteryWidth = 20;
+  constexpr int batteryHeight = 16;
+  const int x = left;
+  const int y = top + 6;
+
+  // Top line
+  renderer.drawLine(x + 1, y, x + batteryWidth - 4, y);
+  // Bottom line
+  renderer.drawLine(x + 1, y + batteryHeight - 1, x + batteryWidth - 4, y + batteryHeight - 1);
+  // Left line
+  renderer.drawLine(x, y + 1, x, y + batteryHeight - 2);
+  // Battery end (right side with nub)
+  renderer.drawLine(x + batteryWidth - 3, y + 1, x + batteryWidth - 3, y + batteryHeight - 2);
+  // Battery nub
+  renderer.drawPixel(x + batteryWidth - 2, y + 4);
+  renderer.drawPixel(x + batteryWidth - 2, y + batteryHeight - 5);
+  renderer.drawLine(x + batteryWidth - 1, y + 5, x + batteryWidth - 1, y + batteryHeight - 6);
+
+  // The +1 is to round up, so that we always fill at least one pixel
+  int filledWidth = percentage * (batteryWidth - 6) / 100 + 1;
+  if (filledWidth > batteryWidth - 6) {
+    filledWidth = batteryWidth - 6;  // Ensure we don't overflow
+  }
+
+  renderer.fillRect(x + 2, y + 2, filledWidth, batteryHeight - 4);
+}
+
 int ScreenComponents::drawTabBar(const GfxRenderer& renderer, const int y, const std::vector<TabInfo>& tabs) {
   constexpr int tabPadding = 20;      // Horizontal padding between tabs
   constexpr int leftMargin = 20;      // Left margin for first tab

src/ScreenComponents.h

@@ -15,6 +15,9 @@ class ScreenComponents {
  public:
   static void drawBattery(const GfxRenderer& renderer, int left, int top, bool showPercentage = true);
 
+  // Draw a larger battery icon suitable for bottom button hint area
+  static void drawBatteryLarge(const GfxRenderer& renderer, int left, int top, bool showPercentage = true);
+
   // Draw a horizontal tab bar with underline indicator for selected tab
   // Returns the height of the tab bar (for positioning content below)
   static int drawTabBar(const GfxRenderer& renderer, int y, const std::vector<TabInfo>& tabs);

src/activities/home/HomeActivity.cpp

@@ -18,6 +18,12 @@
 #include "fontIds.h"
 #include "util/StringUtils.h"
 
+// Static member definitions for persistent cover buffer
+bool HomeActivity::coverRendered = false;
+bool HomeActivity::coverBufferStored = false;
+uint8_t* HomeActivity::coverBuffer = nullptr;
+std::string HomeActivity::cachedCoverPath;
+
 void HomeActivity::taskTrampoline(void* param) {
   auto* self = static_cast<HomeActivity*>(param);
   self->displayTaskLoop();
@@ -41,36 +47,77 @@ void HomeActivity::onEnter() {
   // Check if OPDS browser URL is configured
   hasOpdsUrl = strlen(SETTINGS.opdsServerUrl) > 0;
 
-  if (hasContinueReading) {
-    // Extract filename from path for display
-    lastBookTitle = APP_STATE.openEpubPath;
-    const size_t lastSlash = lastBookTitle.find_last_of('/');
+  if (!hasContinueReading) {
+    // No book to continue reading - clear any stale cover cache
+    if (coverBufferStored) {
+      freeCoverBuffer();
+      coverRendered = false;
+      cachedCoverPath.clear();
+    }
+  } else {
+    // Extract filename from path for display (fallback if no cached title)
+    std::string filenameFromPath = APP_STATE.openEpubPath;
+    const size_t lastSlash = filenameFromPath.find_last_of('/');
     if (lastSlash != std::string::npos) {
-      lastBookTitle = lastBookTitle.substr(lastSlash + 1);
+      filenameFromPath = filenameFromPath.substr(lastSlash + 1);
     }
 
-    // If epub, try to load the metadata for title/author and cover
-    if (StringUtils::checkFileExtension(lastBookTitle, ".epub")) {
+    // Check if we have cached title/author from CrossPointState
+    const bool hasCachedMetadata = !APP_STATE.openBookTitle.empty();
+
+    if (hasCachedMetadata) {
+      // Use cached title and author - no need to load the book file
+      lastBookTitle = APP_STATE.openBookTitle;
+      lastBookAuthor = APP_STATE.openBookAuthor;
+    } else {
+      // No cached metadata - use filename as fallback
+      lastBookTitle = filenameFromPath;
+    }
+
+    // If epub, try to get cover image (and populate cache if needed)
+    if (StringUtils::checkFileExtension(filenameFromPath, ".epub")) {
       Epub epub(APP_STATE.openEpubPath, "/.crosspoint");
+      // Only load epub metadata if we don't have cached title/author
+      if (!hasCachedMetadata) {
         epub.load(false);
         if (!epub.getTitle().empty()) {
           lastBookTitle = std::string(epub.getTitle());
+          APP_STATE.openBookTitle = lastBookTitle;
         }
         if (!epub.getAuthor().empty()) {
           lastBookAuthor = std::string(epub.getAuthor());
+          APP_STATE.openBookAuthor = lastBookAuthor;
+        }
+        // Save updated cache to file
+        APP_STATE.saveToFile();
       }
       // Try to generate thumbnail image for Continue Reading card
       if (epub.generateThumbBmp()) {
         coverBmpPath = epub.getThumbBmpPath();
         hasCoverImage = true;
       }
-    } else if (StringUtils::checkFileExtension(lastBookTitle, ".xtch") ||
-               StringUtils::checkFileExtension(lastBookTitle, ".xtc")) {
+    } else if (StringUtils::checkFileExtension(filenameFromPath, ".xtch") ||
+               StringUtils::checkFileExtension(filenameFromPath, ".xtc")) {
       // Handle XTC file
       Xtc xtc(APP_STATE.openEpubPath, "/.crosspoint");
+      if (!hasCachedMetadata) {
         if (xtc.load()) {
           if (!xtc.getTitle().empty()) {
             lastBookTitle = std::string(xtc.getTitle());
+            APP_STATE.openBookTitle = lastBookTitle;
+            APP_STATE.saveToFile();
+          }
+        }
+        // Remove extension from title if we don't have metadata
+        if (StringUtils::checkFileExtension(lastBookTitle, ".xtch")) {
+          lastBookTitle.resize(lastBookTitle.length() - 5);
+          APP_STATE.openBookTitle = lastBookTitle;
+          APP_STATE.saveToFile();
+        } else if (StringUtils::checkFileExtension(lastBookTitle, ".xtc")) {
+          lastBookTitle.resize(lastBookTitle.length() - 4);
+          APP_STATE.openBookTitle = lastBookTitle;
+          APP_STATE.saveToFile();
+        }
       }
       // Try to generate thumbnail image for Continue Reading card
       if (xtc.generateThumbBmp()) {
@@ -78,12 +125,15 @@ void HomeActivity::onEnter() {
         hasCoverImage = true;
       }
     }
-      // Remove extension from title if we don't have metadata
-      if (StringUtils::checkFileExtension(lastBookTitle, ".xtch")) {
-        lastBookTitle.resize(lastBookTitle.length() - 5);
-      } else if (StringUtils::checkFileExtension(lastBookTitle, ".xtc")) {
-        lastBookTitle.resize(lastBookTitle.length() - 4);
-      }
+
+    // Check if cached cover buffer is still valid (same book)
+    if (hasCoverImage && coverBufferStored && cachedCoverPath == coverBmpPath) {
+      // Cover buffer is still valid, mark as rendered to skip reload
+      coverRendered = true;
+    } else if (hasCoverImage && coverBufferStored && cachedCoverPath != coverBmpPath) {
+      // Book changed, invalidate cached buffer
+      freeCoverBuffer();
+      coverRendered = false;
     }
   }
 
@@ -112,8 +162,8 @@ void HomeActivity::onExit() {
   vSemaphoreDelete(renderingMutex);
   renderingMutex = nullptr;
 
-  // Free the stored cover buffer if any
-  freeCoverBuffer();
+  // NOTE: Do NOT free cover buffer here - keep it cached for fast re-entry
+  // The buffer will be freed/replaced when the book changes
 }
 
 bool HomeActivity::storeCoverBuffer() {
@@ -291,6 +341,9 @@ void HomeActivity::render() {
 
           // Store the buffer with cover image for fast navigation
           coverBufferStored = storeCoverBuffer();
+          if (coverBufferStored) {
+            cachedCoverPath = coverBmpPath;  // Remember which cover is cached
+          }
           coverRendered = true;
 
           // First render: if selected, draw selection indicators now
@@ -552,13 +605,12 @@ void HomeActivity::render() {
   const auto labels = mappedInput.mapLabels("", "Select", "Up", "Down");
   renderer.drawButtonHints(UI_10_FONT_ID, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
 
+  // Draw battery in bottom-left where the back button hint would normally be
   const bool showBatteryPercentage =
       SETTINGS.hideBatteryPercentage != CrossPointSettings::HIDE_BATTERY_PERCENTAGE::HIDE_ALWAYS;
-  // get percentage so we can align text properly
-  const uint16_t percentage = battery.readPercentage();
-  const auto percentageText = showBatteryPercentage ? std::to_string(percentage) + "%" : "";
-  const auto batteryX = pageWidth - 25 - renderer.getTextWidth(SMALL_FONT_ID, percentageText.c_str());
-  ScreenComponents::drawBattery(renderer, batteryX, 10, showBatteryPercentage);
+  constexpr int batteryX = 25;  // Align with first button hint position
+  const int batteryY = pageHeight - 34;  // Vertically centered in button hint area
+  ScreenComponents::drawBatteryLarge(renderer, batteryX, batteryY, showBatteryPercentage);
 
   renderer.displayBuffer();
 }

src/activities/home/HomeActivity.h

@@ -15,9 +15,13 @@ class HomeActivity final : public Activity {
   bool hasContinueReading = false;
   bool hasOpdsUrl = false;
   bool hasCoverImage = false;
-  bool coverRendered = false;      // Track if cover has been rendered once
-  bool coverBufferStored = false;  // Track if cover buffer is stored
-  uint8_t* coverBuffer = nullptr;  // HomeActivity's own buffer for cover image
+
+  // Static cover buffer - persists across activity changes to avoid reloading from SD
+  static bool coverRendered;       // Track if cover has been rendered once
+  static bool coverBufferStored;   // Track if cover buffer is stored
+  static uint8_t* coverBuffer;     // HomeActivity's own buffer for cover image
+  static std::string cachedCoverPath;  // Path of the cached cover (to detect book changes)
+
   std::string lastBookTitle;
   std::string lastBookAuthor;
   std::string coverBmpPath;

src/activities/reader/EpubReaderActivity.cpp

@@ -120,8 +120,10 @@ void EpubReaderActivity::onEnter() {
     }
   }
 
-  // Save current epub as last opened epub and add to recent books
+  // Save current epub as last opened epub and cache title/author for home screen
   APP_STATE.openEpubPath = epub->getPath();
+  APP_STATE.openBookTitle = epub->getTitle();
+  APP_STATE.openBookAuthor = epub->getAuthor();
   APP_STATE.saveToFile();
   RECENT_BOOKS.addBook(epub->getPath(), epub->getTitle(), epub->getAuthor());
 

src/activities/reader/TxtReaderActivity.cpp

@@ -97,8 +97,10 @@ void TxtReaderActivity::onEnter() {
     });
   }
 
-  // Save current txt as last opened file
+  // Save current txt as last opened file and cache title for home screen
   APP_STATE.openEpubPath = txt->getPath();
+  APP_STATE.openBookTitle = txt->getTitle();
+  APP_STATE.openBookAuthor.clear();  // TXT files don't have author metadata
   APP_STATE.saveToFile();
 
   // Trigger first update

src/activities/reader/XtcReaderActivity.cpp

@@ -83,8 +83,10 @@ void XtcReaderActivity::onEnter() {
   // Load saved progress
   loadProgress();
 
-  // Save current XTC as last opened book and add to recent books
+  // Save current XTC as last opened book and cache title for home screen
   APP_STATE.openEpubPath = xtc->getPath();
+  APP_STATE.openBookTitle = xtc->getTitle();
+  APP_STATE.openBookAuthor.clear();  // XTC files don't have author metadata
   APP_STATE.saveToFile();
   RECENT_BOOKS.addBook(xtc->getPath(), xtc->getTitle(), "");