Make it easy to set MADCTL for rotation

[jepler]

The upper 3 bits of the MADCTL register can set a rotation that occurs within the LCD controller. Particularly when working with OnDiskBitmaps, displayio can be much more efficient when the displayio rotation is 0. By exposing the ability to modify the initialization string's MADCTL value, the more efficient in-controller rotation can be used instead.

Locally, I am using this code, but it's a bit gross:

def init_with_madctl(madctl):
    return adafruit_ili9341._INIT_SEQUENCE.replace(b'\x36\x01\x38',
            bytes([0x36, 1, madctl]))
…
display = displayio.Display(display_bus,
        init_with_madctl(0b010_110_00), width=320, height=240)

Section 9.3 and the figure on page 209 of https://cdn-shop.adafruit.com/datasheets/ILI9341.pdf show how these 3 bits of MADCTL are interpreted.

[makermelissa]

Why are you using MADCTL for rotation? CircuitPython handles the rotation itself and then draws in the normal orientation. I believe this is to help with screen tearing according to @tannewt.

[jepler]

Using MADCTL for rotation usually performs better, especially for OnDiskBitmaps where displayio rotation gives pathologically poor behavior.

[tannewt]

I never did the full tearing work I intended to do. So I wouldn't block this on that goal. Tearing happens with CP now and there isn't much we can do.

[makermelissa]

Fair enough. Should be easy enough to refactor this driver to allow easier modification of MADCTL.