Optimized setAddrWindow() to only set the axis which changes

Author: bitbank2

Adafruit_ILI9341.cpp

@@ -302,13 +302,22 @@ void Adafruit_ILI9341::setScrollMargins(uint16_t top, uint16_t bottom) {
 /**************************************************************************/
 void Adafruit_ILI9341::setAddrWindow(uint16_t x1, uint16_t y1, uint16_t w,
                                      uint16_t h) {
+static uint16_t old_x1 = 0xffff, old_x2 = 0xffff;
+static uint16_t old_y1 = 0xffff, old_y2 = 0xffff;
+
   uint16_t x2 = (x1 + w - 1), y2 = (y1 + h - 1);
-  writeCommand(ILI9341_CASET); // Column address set
-  SPI_WRITE16(x1);
-  SPI_WRITE16(x2);
-  writeCommand(ILI9341_PASET); // Row address set
-  SPI_WRITE16(y1);
-  SPI_WRITE16(y2);
+  if (x1 != old_x1 || x2 != old_x2) {
+    writeCommand(ILI9341_CASET); // Column address set
+    SPI_WRITE16(x1);
+    SPI_WRITE16(x2);
+    old_x1 = x1; old_x2 = x2;
+  }
+  if (y1 != old_y1 || y2 != old_y2) {
+    writeCommand(ILI9341_PASET); // Row address set
+    SPI_WRITE16(y1);
+    SPI_WRITE16(y2);
+    old_y1 = y1; old_y2 = y2;
+  }
   writeCommand(ILI9341_RAMWR); // Write to RAM
 }