GFX: Add gfx_clearRows() implementation

openrtx/include/interfaces/graphics.h

@@ -147,7 +147,18 @@ void gfx_render();
 bool gfx_renderingInProgress();
 
 /**
- * Makes the screen black.
+ * Clears a portion of the screen content
+ * This results in a black screen on color displays
+ * And a white screen on B/W displays
+ * @param startRow: first row of the framebuffer section to be cleared
+ * @param endRow: last row of the framebuffer section to be cleared
+ */
+void gfx_clearRows(uint8_t startRow, uint8_t endRow);
+
+/**
+ * Clears the content of the screen
+ * This results in a black screen on color displays
+ * And a white screen on B/W displays
  */
 void gfx_clearScreen();
 

openrtx/src/graphics/graphics_rgb565.c

@@ -85,6 +85,16 @@ rgb565_t _true2highColor(color_t true_color)
     return high_color;
 }
 
+void gfx_clearRows(uint8_t startRow, uint8_t endRow)
+{
+    if(!initialized) return;
+    if(endRow < startRow) return;
+    uint16_t start = startRow * SCREEN_WIDTH * sizeof(rgb565_t);
+    uint16_t height = endRow - startRow * SCREEN_WIDTH * sizeof(rgb565_t);
+    // Set the specified rows to 0x00 = make the screen black
+    memset(buf + start, 0x00, height);
+}
+
 void gfx_clearScreen()
 {
     if(!initialized) return;