Implement shaddow frame buffer for TFT display

lib/obp60task/OBP60Extensions.cpp

@@ -57,9 +57,30 @@ GxEPD2_BW<GxEPD2_420_SE0420NQ04, GxEPD2_420_SE0420NQ04::HEIGHT> & getdisplay(){r
 #endif
 
 #ifdef DISPLAY_ST7796
-// only instantiate; class defined in header
-static LGFX display;
-LGFX & getdisplay(){return display;}
+// panel device + offscreen shadow framebuffer
+static LGFX panelDisplay;
+static LGFXCanvas shadowDisplay(&panelDisplay);
+static bool shadowDisplayInitialized = false;
+
+LGFXCanvas & getdisplay(){return shadowDisplay;}
+LGFX & getpaneldisplay(){return panelDisplay;}
+
+bool initDisplayShadowBuffer(){
+    if (shadowDisplayInitialized) return true;
+
+    shadowDisplay.setPsram(true);
+    shadowDisplay.setColorDepth(16);
+    shadowDisplay.setTextDatum(textdatum_t::baseline_left);
+
+    if (shadowDisplay.createSprite(GxEPD_WIDTH, GxEPD_HEIGHT) == nullptr) {
+        shadowDisplayInitialized = false;
+        return false;
+    }
+
+    shadowDisplay.fillScreen(GxEPD_BLACK);
+    shadowDisplayInitialized = true;
+    return true;
+}
 #endif
 
 // Horter I2C moduls
@@ -258,7 +279,9 @@ void deepSleep(CommonData &common){
     getdisplay().setCursor(65, 175);
     getdisplay().print("To wake up press key and wait 5s");
     displayNextPage();                // Update display contents
-    #ifndef DISPLAY_ST7796
+    #ifdef DISPLAY_ST7796
+    getpaneldisplay().powerSave(true);      // Display power save
+    #else
     getdisplay().powerOff();                // Display power off
     #endif
     setPortPin(OBP_POWER_50, false);        // Power off ePaper display
@@ -285,7 +308,9 @@ void deepSleep(CommonData &common){
     getdisplay().setCursor(65, 175);
     getdisplay().print("To wake up press wheel and wait 5s");
     displayNextPage();                // Partial update
-    #ifndef DISPLAY_ST7796
+    #ifdef DISPLAY_ST7796
+    getpaneldisplay().powerSave(true);      // Display power save
+    #else
     getdisplay().powerOff();                // Display power off
     #endif
     setPortPin(OBP_POWER_EPD, false);       // Power off ePaper display

lib/obp60task/OBP60Extensions.h

@@ -268,7 +268,148 @@ private:
   lgfx::Panel_ST7796 _panel_instance;
 };
 
-LGFX & getdisplay();
+class LGFXCanvas : public lgfx::LGFX_Sprite {
+public:
+    explicit LGFXCanvas(lgfx::LGFX_Device* parent = nullptr) : lgfx::LGFX_Sprite(parent) {}
+
+    using lgfx::LGFX_Sprite::setFont;
+    void setFont(const GFXfont *font) {
+        if (font == nullptr) {
+            _currentAdfFont = nullptr;
+            lgfx::LGFX_Sprite::setFont(nullptr);
+            return;
+        }
+
+        if (font->glyph == nullptr || font->bitmap == nullptr || font->last < font->first) {
+            _currentAdfFont = nullptr;
+            lgfx::LGFX_Sprite::setFont(nullptr);
+            return;
+        }
+
+        const uint16_t glyphCount = static_cast<uint16_t>(font->last - font->first + 1);
+        if (glyphCount == 0) {
+            lgfx::LGFX_Sprite::setFont(nullptr);
+            return;
+        }
+
+        if (_adfGlyphCount != glyphCount || _adfGlyphBridge == nullptr) {
+            if (_adfGlyphBridge != nullptr) {
+                free(_adfGlyphBridge);
+                _adfGlyphBridge = nullptr;
+                _adfGlyphCount = 0;
+            }
+            _adfGlyphBridge = static_cast<lgfx::GFXglyph*>(malloc(sizeof(lgfx::GFXglyph) * glyphCount));
+            if (_adfGlyphBridge == nullptr) {
+                lgfx::LGFX_Sprite::setFont(nullptr);
+                return;
+            }
+            _adfGlyphCount = glyphCount;
+        }
+
+        for (uint16_t index = 0; index < glyphCount; ++index) {
+            _adfGlyphBridge[index].bitmapOffset = font->glyph[index].bitmapOffset;
+            _adfGlyphBridge[index].width = font->glyph[index].width;
+            _adfGlyphBridge[index].height = font->glyph[index].height;
+            _adfGlyphBridge[index].xAdvance = font->glyph[index].xAdvance;
+            _adfGlyphBridge[index].xOffset = font->glyph[index].xOffset;
+            _adfGlyphBridge[index].yOffset = font->glyph[index].yOffset;
+        }
+
+        _adfFontBridge = lgfx::GFXfont(
+            const_cast<uint8_t*>(font->bitmap),
+            _adfGlyphBridge,
+            font->first,
+            font->last,
+            font->yAdvance
+        );
+        _currentAdfFont = font;
+        lgfx::LGFX_Sprite::setFont(&_adfFontBridge);
+    }
+
+    void getTextBounds(const String &txt, int16_t x, int16_t y,
+                       int16_t *x0, int16_t *y0,
+                       uint16_t *w, uint16_t *h) {
+        if (w == nullptr || h == nullptr) {
+            return;
+        }
+        if (_currentAdfFont == nullptr || txt.length() == 0) {
+            *w = textWidth(txt);
+            *h = fontHeight();
+            if (x0) *x0 = x;
+            if (y0) *y0 = y - static_cast<int16_t>(*h);
+            return;
+        }
+
+        const float sx = getTextSizeX();
+        const float sy = getTextSizeY();
+
+        int32_t cursorX = x;
+        int32_t cursorY = y;
+        int32_t minX = 0;
+        int32_t minY = 0;
+        int32_t maxX = 0;
+        int32_t maxY = 0;
+        bool hasPixel = false;
+
+        for (size_t i = 0; i < txt.length(); ++i) {
+            char c = txt[i];
+            if (c == '\r') continue;
+            if (c == '\n') {
+                cursorX = x;
+                cursorY += static_cast<int32_t>(_currentAdfFont->yAdvance * sy);
+                continue;
+            }
+            if (c < _currentAdfFont->first || c > _currentAdfFont->last) {
+                continue;
+            }
+
+            const GFXglyph* glyph = &_currentAdfFont->glyph[static_cast<uint16_t>(c) - _currentAdfFont->first];
+            const int32_t gw = static_cast<int32_t>(glyph->width * sx);
+            const int32_t gh = static_cast<int32_t>(glyph->height * sy);
+            const int32_t gx1 = cursorX + static_cast<int32_t>(glyph->xOffset * sx);
+            const int32_t gy1 = cursorY + static_cast<int32_t>(glyph->yOffset * sy);
+
+            if (gw > 0 && gh > 0) {
+                const int32_t gx2 = gx1 + gw - 1;
+                const int32_t gy2 = gy1 + gh - 1;
+                if (!hasPixel) {
+                    minX = gx1; minY = gy1; maxX = gx2; maxY = gy2;
+                    hasPixel = true;
+                } else {
+                    if (gx1 < minX) minX = gx1;
+                    if (gy1 < minY) minY = gy1;
+                    if (gx2 > maxX) maxX = gx2;
+                    if (gy2 > maxY) maxY = gy2;
+                }
+            }
+            cursorX += static_cast<int32_t>(glyph->xAdvance * sx);
+        }
+
+        if (hasPixel) {
+            if (x0) *x0 = static_cast<int16_t>(minX);
+            if (y0) *y0 = static_cast<int16_t>(minY);
+            *w = static_cast<uint16_t>(maxX - minX + 1);
+            *h = static_cast<uint16_t>(maxY - minY + 1);
+        } else {
+            if (x0) *x0 = x;
+            if (y0) *y0 = y;
+            *w = 0;
+            *h = 0;
+        }
+    }
+
+    void setFullWindow() { /* no-op on TFT */ }
+
+private:
+    lgfx::GFXfont _adfFontBridge { nullptr, nullptr, 0, 0, 0 };
+    lgfx::GFXglyph* _adfGlyphBridge = nullptr;
+    uint16_t _adfGlyphCount = 0;
+    const GFXfont* _currentAdfFont = nullptr;
+};
+
+LGFXCanvas & getdisplay();
+LGFX & getpaneldisplay();
+bool initDisplayShadowBuffer();
 #endif
 
 // Page display return values
@@ -344,7 +485,7 @@ inline void displayDrawBitmap(int16_t x, int16_t y,
 
 inline void displayFirstPage() {
     #ifdef DISPLAY_ST7796
-    // TFT LCD doesn't need firstPage() 
+    initDisplayShadowBuffer();
     #else
     getdisplay().firstPage();
     #endif
@@ -352,7 +493,9 @@ inline void displayFirstPage() {
 
 inline void displayNextPage() {
     #ifdef DISPLAY_ST7796
-    // TFT LCD doesn't need nextPage() for refresh
+    if (initDisplayShadowBuffer()) {
+        getdisplay().pushSprite(0, 0);
+    }
     #else
     getdisplay().nextPage();
     #endif

lib/obp60task/obp60task.cpp

@@ -285,7 +285,9 @@ void underVoltageError(CommonData &common) {
     getdisplay().setCursor(65, 175);
     getdisplay().print("Charge battery and restart system");
     displayNextPage();                // Partial update
-    #ifndef DISPLAY_ST7796
+    #ifdef DISPLAY_ST7796
+    getpaneldisplay().powerSave(true);      // Display power save
+    #else
     getdisplay().powerOff();                // Display power off
     #endif
     setPortPin(OBP_POWER_EPD, false);       // Power off ePaper display
@@ -307,7 +309,9 @@ void underVoltageError(CommonData &common) {
     getdisplay().setCursor(65, 175);
     getdisplay().print("To wake up repower system");
     displayNextPage();                // Partial update
-    #ifndef DISPLAY_ST7796
+    #ifdef DISPLAY_ST7796
+    getpaneldisplay().powerSave(true);      // Display power save
+    #else
     getdisplay().powerOff();                // Display power off
     #endif
 #endif
@@ -380,12 +384,16 @@ void OBP60Task(GwApi *api){
     #ifdef DISPLAY_GDEY042T81
         getdisplay().init(115200, true, 2, false);  // Init for Waveshare boards with "clever" reset circuit, 2ms reset pulse
     #elif defined DISPLAY_ST7796
-        getdisplay().init();                        // Init for ST7796 TFT LCD
+        getpaneldisplay().init();                   // Init for ST7796 TFT LCD panel
     #else
         getdisplay().init(115200);                  // Init for normal displays
     #endif
 
+    #ifdef DISPLAY_ST7796
+    getpaneldisplay().setRotation(0);            // Set display orientation (horizontal)
+    #else
     getdisplay().setRotation(0);                 // Set display orientation (horizontal)
+    #endif
     displaySetFullWindow();                       // Set full Refresh (E-Ink only)
     displayFirstPage();                           // set first page
     getdisplay().fillScreen(commonData.bgcolor);