feat: add turnOffScreen parameter for sunlight fading fix

Add optional turnOffScreen parameter to displayBuffer() and displayWindow()
to allow turning off the screen after refresh, mitigating sunlight fading issues.

libs/display/EInkDisplay/include/EInkDisplay.h

@@ -42,9 +42,9 @@ class EInkDisplay {
   void cleanupGrayscaleBuffers(const uint8_t* bwBuffer);
 #endif
 
-  void displayBuffer(RefreshMode mode = FAST_REFRESH);
+  void displayBuffer(RefreshMode mode = FAST_REFRESH, bool turnOffScreen = false);
   // EXPERIMENTAL: Windowed update - display only a rectangular region
-  void displayWindow(uint16_t x, uint16_t y, uint16_t w, uint16_t h);
+  void displayWindow(uint16_t x, uint16_t y, uint16_t w, uint16_t h, bool turnOffScreen = false);
   void displayGrayBuffer(bool turnOffScreen = false);
 
   void refreshDisplay(RefreshMode mode = FAST_REFRESH, bool turnOffScreen = false);

libs/display/EInkDisplay/src/EInkDisplay.cpp

@@ -399,25 +399,34 @@ void EInkDisplay::copyGrayscaleBuffers(const uint8_t* lsbBuffer, const uint8_t*
 #ifdef EINK_DISPLAY_SINGLE_BUFFER_MODE
 /**
  * In single buffer mode, this should be called with the previously written BW buffer
- * to reconstruct the RED buffer for proper differential fast refreshes following a
+ * to restore proper BW state after a grayscale display.
- * grayscale display.
+ * 
+ * The approach: Don't call grayscaleRevert() at all. Instead, just sync the RAMs with
+ * BW data and clear the grayscale mode flag. The physical pixels will stay in their
+ * current grayscale states, but subsequent refreshes will naturally transition them
+ * as the new BW content is displayed.
  */
 void EInkDisplay::cleanupGrayscaleBuffers(const uint8_t* bwBuffer) {
+  // Clear grayscale mode - we don't want grayscaleRevert to be called later
+  // because the RAMs won't have valid grayscale data anymore
+  inGrayscaleMode = false;
+  
+  // Sync both RAMs with BW content for proper fast refresh behavior
   setRamArea(0, 0, DISPLAY_WIDTH, DISPLAY_HEIGHT);
+  writeRamBuffer(CMD_WRITE_RAM_BW, bwBuffer, BUFFER_SIZE);
   writeRamBuffer(CMD_WRITE_RAM_RED, bwBuffer, BUFFER_SIZE);
 }
 #endif
 
-void EInkDisplay::displayBuffer(RefreshMode mode) {
+void EInkDisplay::displayBuffer(RefreshMode mode, const bool turnOffScreen) {
-  if (!isScreenOn) {
+  if (!isScreenOn && !turnOffScreen) {
     // Force half refresh if screen is off
     mode = HALF_REFRESH;
   }
 
   // If currently in grayscale mode, revert first to black/white
   if (inGrayscaleMode) {
-    inGrayscaleMode = false;
+    grayscaleRevert();  // grayscaleRevert() sets inGrayscaleMode = false internally
-    grayscaleRevert();
   }
 
   // Set up full screen RAM area
@@ -442,7 +451,7 @@ void EInkDisplay::displayBuffer(RefreshMode mode) {
 #endif
 
   // Refresh the display
-  refreshDisplay(mode);
+  refreshDisplay(mode, turnOffScreen);
 
 #ifdef EINK_DISPLAY_SINGLE_BUFFER_MODE
   // In single buffer mode always sync RED RAM after refresh to prepare for next fast refresh
@@ -455,7 +464,7 @@ void EInkDisplay::displayBuffer(RefreshMode mode) {
 // EXPERIMENTAL: Windowed update support
 // Displays only a rectangular region of the frame buffer, preserving the rest of the screen.
 // Requirements: x and w must be byte-aligned (multiples of 8 pixels)
-void EInkDisplay::displayWindow(uint16_t x, uint16_t y, uint16_t w, uint16_t h) {
+void EInkDisplay::displayWindow(uint16_t x, uint16_t y, uint16_t w, uint16_t h, const bool turnOffScreen) {
   Serial.printf("[%lu]   Displaying window at (%d,%d) size (%dx%d)\n", millis(), x, y, w, h);
 
   // Validate bounds
@@ -477,8 +486,7 @@ void EInkDisplay::displayWindow(uint16_t x, uint16_t y, uint16_t w, uint16_t h)
 
   // displayWindow is not supported while the rest of the screen has grayscale content, revert it
   if (inGrayscaleMode) {
-    inGrayscaleMode = false;
+    grayscaleRevert();  // grayscaleRevert() sets inGrayscaleMode = false internally
-    grayscaleRevert();
   }
 
   // Calculate window buffer size
@@ -517,7 +525,7 @@ void EInkDisplay::displayWindow(uint16_t x, uint16_t y, uint16_t w, uint16_t h)
 #endif
 
   // Perform fast refresh
-  refreshDisplay(FAST_REFRESH);
+  refreshDisplay(FAST_REFRESH, turnOffScreen);
 
 #ifdef EINK_DISPLAY_SINGLE_BUFFER_MODE
   // Post-refresh: Sync RED RAM with current window (for next fast refresh)

libs/hardware/SDCardManager/include/SDCardManager.h

@@ -29,6 +29,7 @@ class SDCardManager {
   bool exists(const char* path) { return sd.exists(path); }
   bool remove(const char* path) { return sd.remove(path); }
   bool rmdir(const char* path) { return sd.rmdir(path); }
+  bool rename(const char* oldPath, const char* newPath) { return sd.rename(oldPath, newPath); }
 
   bool openFileForRead(const char* moduleName, const char* path, FsFile& file);
   bool openFileForRead(const char* moduleName, const std::string& path, FsFile& file);