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

@@ -418,8 +418,8 @@ void EInkDisplay::cleanupGrayscaleBuffers(const uint8_t* bwBuffer) {
 }
 #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;
   }
@@ -451,7 +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
@@ -464,7 +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
@@ -525,7 +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)