added frontBuffer method, like backBuffer

Author: rfugina

RGBmatrixPanel.cpp

@@ -349,6 +349,11 @@ void RGBmatrixPanel::fillScreen(uint16_t c) {
   }
 }
 
+// Return address of front buffer -- can then read display directly
+uint8_t *RGBmatrixPanel::frontBuffer() {
+  return matrixbuff[1-backindex];
+}
+
 // Return address of back buffer -- can then load/store data directly
 uint8_t *RGBmatrixPanel::backBuffer() {
   return matrixbuff[backindex];

RGBmatrixPanel.h

@@ -26,6 +26,7 @@ class RGBmatrixPanel : public Adafruit_GFX {
     swapBuffers(boolean),
     dumpMatrix(void);
   uint8_t
+    *frontBuffer(void),
     *backBuffer(void);
   uint16_t
     Color333(uint8_t r, uint8_t g, uint8_t b),