Refresh screen on reader exit to heal ghosting

src/activities/reader/EpubReaderActivity.cpp

@@ -185,6 +185,7 @@ void EpubReaderActivity::loop() {
 
   // Long press BACK (1s+) goes to home screen
   if (mappedInput.isPressed(MappedInputManager::Button::Back) && mappedInput.getHeldTime() >= ReaderUtils::GO_HOME_MS) {
+    ReaderUtils::enforceExitFullRefresh(renderer);
     onGoHome();
     return;
   }
@@ -196,6 +197,7 @@ void EpubReaderActivity::loop() {
       restoreSavedPosition();
       return;
     }
+    ReaderUtils::enforceExitFullRefresh(renderer);
     finish();
     return;
   }

src/activities/reader/ReaderUtils.h

@@ -59,6 +59,12 @@ inline void displayWithRefreshCycle(const GfxRenderer& renderer, int& pagesUntil
   }
 }
 
+inline void enforceExitFullRefresh(const GfxRenderer& renderer) {
+  // Reader exits can leave visible ghosting when the next screen is rendered with a fast LUT.
+  // Force one full waveform pass before leaving the reader stack.
+  renderer.displayBuffer(HalDisplay::FULL_REFRESH);
+}
+
 // Grayscale anti-aliasing pass. Renders content twice (LSB + MSB) to build
 // the grayscale buffer. Only the content callback is re-rendered — status bars
 // and other overlays should be drawn before calling this.

src/activities/reader/TxtReaderActivity.cpp

@@ -119,6 +119,7 @@ void TxtReaderActivity::onExit() {
 void TxtReaderActivity::loop() {
   // Long press BACK (1s+) goes to home screen
   if (mappedInput.isPressed(MappedInputManager::Button::Back) && mappedInput.getHeldTime() >= ReaderUtils::GO_HOME_MS) {
+    ReaderUtils::enforceExitFullRefresh(renderer);
     onGoHome();
     return;
   }
@@ -126,6 +127,7 @@ void TxtReaderActivity::loop() {
   // Short press BACK returns to the calling activity
   if (mappedInput.wasReleased(MappedInputManager::Button::Back) &&
       mappedInput.getHeldTime() < ReaderUtils::GO_HOME_MS) {
+    ReaderUtils::enforceExitFullRefresh(renderer);
     finish();
     return;
   }

src/activities/reader/XtcReaderActivity.cpp

@@ -73,12 +73,14 @@ void XtcReaderActivity::loop() {
 
   // Long press BACK (1s+) goes to home screen
   if (mappedInput.isPressed(MappedInputManager::Button::Back) && mappedInput.getHeldTime() >= goHomeMs) {
+    ReaderUtils::enforceExitFullRefresh(renderer);
     onGoHome();
     return;
   }
 
   // Short press BACK returns to the calling activity
   if (mappedInput.wasReleased(MappedInputManager::Button::Back) && mappedInput.getHeldTime() < goHomeMs) {
+    ReaderUtils::enforceExitFullRefresh(renderer);
     finish();
     return;
   }