ILI9341: Provide fix for some Chinese display modules.

DRIVERS.md

@@ -416,6 +416,13 @@ training makes me baulk at exceeding datasheet limits but the choice is yours.
 I raised [this isse](https://github.com/adafruit/Adafruit_CircuitPython_ILI9341/issues/24).
 The response may be of interest.
 
+#### Troubleshooting
+
+Some Chinese modules produce garbled displays. Please try the
+[ILI9486 driver](./DRIVERS.md#34-driver-for-ili94xx) with the `mirror`
+constructor arg set `True`. Patch and testing provided by
+[Abel Deuring](https://github.com/peterhinch/micropython-micro-gui/issues/25#issuecomment-1475329104).
+
 ###### [Contents](./DRIVERS.md#contents)
 
 ## 3.3 Drivers for ST7789
@@ -709,6 +716,8 @@ powered from 5V or 3.3V: there is a regulator on board.
  `height` and `width` values.
  * `width=480`
  * `usd=False` Upside down: set `True` to invert display.
+ * `mirror=False` If `True` reflects display. Has been found necessary for some
+ Chinese ILI9341 modules.
  * `init_spi=False` This optional arg enables flexible options in configuring
  the SPI bus. The default assumes exclusive access to the bus. In this normal
  case, `color_setup.py` initialises it and the settings will be left in place.

drivers/ili94xx/ili9486.py

@@ -66,7 +66,7 @@ class ILI9486(framebuf.FrameBuffer):
         return cls.COLOR_INVERT ^ ((r & 0xF8) | (g & 0xE0) >> 5 | (g & 0x1C) << 11 | (b & 0xF8) << 5)
 
     # Transpose width & height for landscape mode
-    def __init__(self, spi, cs, dc, rst, height=320, width=480, usd=False, init_spi=False):
+    def __init__(self, spi, cs, dc, rst, height=320, width=480, usd=False, mirror=False, init_spi=False):
         self._spi = spi
         self._cs = cs
         self._dc = dc
@@ -107,7 +107,11 @@ class ILI9486(framebuf.FrameBuffer):
         # Default page address start == 0 end == 0x1DF (479)
         if self._long != 480:
             self._wcd(b"\x2b", int.to_bytes(self._long - 1, 4, "big"))  # SET_PAGE ht
-        self._wcd(b"\x36", b"\x48" if usd else b"\x88")  # MADCTL: RGB portrait mode
+#        self._wcd(b"\x36", b"\x48" if usd else b"\x88")  # MADCTL: RGB portrait mode
+        madctl = 0x48 if usd else 0x88
+        if mirror:
+            madctl ^= 0x80
+        self._wcd(b"\x36", madctl.to_bytes(1, 'big'))  # MADCTL: RGB portrait mode
         self._wcmd(b"\x11")  # sleep out
         self._wcmd(b"\x29")  # display on