Merge pull request #201 from adafruit/pb-tft8

Add 8-bit parallel interface support

Author: PaintYourDragon

Adafruit_GFX.cpp

@@ -103,6 +103,9 @@ WIDTH(w), HEIGHT(h)
 /**************************************************************************/
 void Adafruit_GFX::writeLine(int16_t x0, int16_t y0, int16_t x1, int16_t y1,
         uint16_t color) {
+#if defined(ESP8266)
+    yield();
+#endif
     int16_t steep = abs(y1 - y0) > abs(x1 - x0);
     if (steep) {
         _swap_int16_t(x0, y0);
@@ -317,6 +320,9 @@ void Adafruit_GFX::drawLine(int16_t x0, int16_t y0, int16_t x1, int16_t y1,
 /**************************************************************************/
 void Adafruit_GFX::drawCircle(int16_t x0, int16_t y0, int16_t r,
         uint16_t color) {
+#if defined(ESP8266)
+    yield();
+#endif
     int16_t f = 1 - r;
     int16_t ddF_x = 1;
     int16_t ddF_y = -2 * r;