Add display invert setting for e-paper displays

examples/companion_radio/DataStore.cpp

@@ -222,6 +222,7 @@ void DataStore::loadPrefsInt(const char *filename, NodePrefs& _prefs, double& no
     file.read(pad, 2);                                                                     // 78
     file.read((uint8_t *)&_prefs.ble_pin, sizeof(_prefs.ble_pin));                         // 80
     file.read((uint8_t *)&_prefs.buzzer_quiet, sizeof(_prefs.buzzer_quiet));               // 84
+    file.read((uint8_t *)&_prefs.invert_display, sizeof(_prefs.invert_display));           // 85
 
     file.close();
   }
@@ -254,6 +255,7 @@ void DataStore::savePrefs(const NodePrefs& _prefs, double node_lat, double node_
     file.write(pad, 2);                                                                     // 78
     file.write((uint8_t *)&_prefs.ble_pin, sizeof(_prefs.ble_pin));                         // 80
     file.write((uint8_t *)&_prefs.buzzer_quiet, sizeof(_prefs.buzzer_quiet));               // 84
+    file.write((uint8_t *)&_prefs.invert_display, sizeof(_prefs.invert_display));           // 85
 
     file.close();
   }

examples/companion_radio/NodePrefs.h

@@ -25,4 +25,5 @@ struct NodePrefs {  // persisted to file
   uint32_t ble_pin;
   uint8_t  advert_loc_policy;
   uint8_t  buzzer_quiet;
+  uint8_t  invert_display;   // 0 = normal (black on white), 1 = inverted (white on black)
 };

examples/companion_radio/ui-new/UITask.cpp

@@ -79,6 +79,7 @@ class HomeScreen : public UIScreen {
     RADIO,
     BLUETOOTH,
     ADVERT,
+    INVERT,
 #if ENV_INCLUDE_GPS == 1
     GPS,
 #endif
@@ -257,6 +258,12 @@ class HomeScreen : public UIScreen {
       display.setColor(DisplayDriver::GREEN);
       display.drawXbm((display.width() - 32) / 2, 18, advert_icon, 32, 32);
       display.drawTextCentered(display.width() / 2, 64 - 11, "advert: " PRESS_LABEL);
+    } else if (_page == HomePage::INVERT) {
+      display.setColor(DisplayDriver::GREEN);
+      char buf[24];
+      sprintf(buf, "Invert: %s", _node_prefs->invert_display ? "ON" : "OFF");
+      display.drawTextCentered(display.width() / 2, 32, buf);
+      display.drawTextCentered(display.width() / 2, 64 - 11, "toggle: " PRESS_LABEL);
 #if ENV_INCLUDE_GPS == 1
     } else if (_page == HomePage::GPS) {
       LocationProvider* nmea = sensors.getLocationProvider();
@@ -423,6 +430,10 @@ class HomeScreen : public UIScreen {
       return true;
     }
 #endif
+    if (c == KEY_ENTER && _page == HomePage::INVERT) {
+      _task->toggleInvertDisplay();
+      return true;
+    }
     if (c == KEY_ENTER && _page == HomePage::SHUTDOWN) {
       _shutdown_init = true;  // need to wait for button to be released
       return true;
@@ -538,6 +549,7 @@ void UITask::begin(DisplayDriver* display, SensorManager* sensors, NodePrefs* no
 
   _node_prefs = node_prefs;
   if (_display != NULL) {
+    _display->setInverted(_node_prefs->invert_display);  // apply saved inversion state
     _display->turnOn();
   }
 
@@ -893,3 +905,15 @@ void UITask::toggleBuzzer() {
     _next_refresh = 0;  // trigger refresh
   #endif
 }
+
+void UITask::toggleInvertDisplay() {
+  // Toggle display inversion
+  _node_prefs->invert_display = !_node_prefs->invert_display;
+  if (_display != NULL) {
+    _display->setInverted(_node_prefs->invert_display);
+  }
+  notify(UIEventType::ack);
+  showAlert(_node_prefs->invert_display ? "Invert: ON" : "Invert: OFF", 800);
+  the_mesh.savePrefs();
+  _next_refresh = 0;  // trigger immediate refresh
+}

examples/companion_radio/ui-new/UITask.h

@@ -77,6 +77,7 @@ class UITask : public AbstractUITask {
   void toggleBuzzer();
   bool getGPSState();
   void toggleGPS();
+  void toggleInvertDisplay();
 
 
   // from AbstractUITask

src/helpers/ui/DisplayDriver.h

@@ -6,12 +6,15 @@
 class DisplayDriver {
   int _w, _h;
 protected:
+  bool _inverted = false;  // display inversion state
   DisplayDriver(int w, int h) { _w = w; _h = h; }
 public:
   enum Color { DARK=0, LIGHT, RED, GREEN, BLUE, YELLOW, ORANGE }; // on b/w screen, colors will be !=0 synonym of light
 
   int width() const { return _w; }
   int height() const { return _h; }
+  bool isInverted() const { return _inverted; }
+  virtual void setInverted(bool inv) { _inverted = inv; }
 
   virtual bool isOn() = 0;
   virtual void turnOn() = 0;

src/helpers/ui/GxEPDDisplay.cpp

@@ -56,15 +56,17 @@ void GxEPDDisplay::turnOff() {
 }
 
 void GxEPDDisplay::clear() {
-  display.fillScreen(GxEPD_WHITE);
-  display.setTextColor(GxEPD_BLACK);
+  display.fillScreen(_inverted ? GxEPD_BLACK : GxEPD_WHITE);
+  display.setTextColor(_inverted ? GxEPD_WHITE : GxEPD_BLACK);
   display_crc.reset();
 }
 
 void GxEPDDisplay::startFrame(Color bkg) {
-  display.fillScreen(GxEPD_WHITE);
-  display.setTextColor(_curr_color = GxEPD_BLACK);
+  // use inverted background if inversion is enabled
+  display.fillScreen(_inverted ? GxEPD_BLACK : GxEPD_WHITE);
+  display.setTextColor(_curr_color = (_inverted ? GxEPD_WHITE : GxEPD_BLACK));
   display_crc.reset();
+  display_crc.update<bool>(_inverted);  // include inversion state in CRC
 }
 
 void GxEPDDisplay::setTextSize(int sz) {
@@ -87,11 +89,13 @@ void GxEPDDisplay::setTextSize(int sz) {
 
 void GxEPDDisplay::setColor(Color c) {
   display_crc.update<Color> (c);
-  // colours need to be inverted for epaper displays
+  // On e-paper: GxEPD_WHITE = white pixels, GxEPD_BLACK = black pixels
+  // Normal mode (white bg): DARK->white (bg), others->black (visible)
+  // Inverted mode (black bg): DARK->black (bg), others->white (visible)
   if (c == DARK) {
-    display.setTextColor(_curr_color = GxEPD_WHITE);
+    display.setTextColor(_curr_color = _inverted ? GxEPD_BLACK : GxEPD_WHITE);
   } else {
-    display.setTextColor(_curr_color = GxEPD_BLACK);
+    display.setTextColor(_curr_color = _inverted ? GxEPD_WHITE : GxEPD_BLACK);
   }
 }
 
@@ -177,3 +181,9 @@ void GxEPDDisplay::endFrame() {
     last_display_crc_value = crc;
   }
 }
+
+void GxEPDDisplay::setInverted(bool inv) {
+  _inverted = inv;
+  // Invalidate CRC to force redraw on next frame
+  last_display_crc_value = 0;
+}

src/helpers/ui/GxEPDDisplay.h

@@ -60,4 +60,5 @@ class GxEPDDisplay : public DisplayDriver {
   void drawXbm(int x, int y, const uint8_t* bits, int w, int h) override;
   uint16_t getTextWidth(const char* str) override;
   void endFrame() override;
+  void setInverted(bool inv) override;
 };