Detect keyboard layouts (azerty, qwertz, others) using SDL2

layouts.py

#clone https://bitbucket.org/marcusva/py-sdl2

"""
Distinguish azerty/qwerty/qwertz

After experimenting, must SDL_INIT_VIDEO and use
SDL_GetKeyFromScancode or SDL_GetScancodeFromKey

The mapping is cached by SDL2;
enable the event loop or use SDL_Quit to detect again.

Alternatively, just use layout-independent
scancodes in your application.
"""

import sdl2
import sdl2.keyboard
import sdl2.keycode
from sdl2.keycode import *

# required, on Linux anyway
sdl2.SDL_Init(sdl2.SDL_INIT_VIDEO)

# unnecessary
#sdl2.SDL_Init(sdl2.SDL_INIT_EVERYTHING)

assert sdl2.keyboard.SDL_GetScancodeFromName(b'A') == sdl2.keycode.SDL_SCANCODE_A == 4
assert sdl2.keyboard.SDL_GetKeyFromName(b'A') == ord('a') == b'a'[0] == 97
assert sdl2.keyboard.SDL_GetScancodeName(4) == b'A'
assert sdl2.keyboard.SDL_GetKeyName(97) == b'A'

# Mapping keys to a scancode (position) allows to discriminate layouts
for keycode in b'aqwzy':
    print('{}: {}'.format(chr(keycode), sdl2.keyboard.SDL_GetScancodeFromKey(keycode)))

# Using the reverse mapping makes more sense;
# map select scancodes of the top row to a layout
keys = bytes(sdl2.keyboard.SDL_GetKeyFromScancode(sc) for sc in (SDL_SCANCODE_Q, SDL_SCANCODE_W, SDL_SCANCODE_Y))
if keys == b'qwy':
    print('qwerty')
elif keys == b'azy':
    print('azerty')
elif keys == b'qwz':
    print('qwertz')
elif keys == b'qwj':
    print('colemak')
elif keys == b'q,f':
    print('dvorak')
elif keys == b'b\xe9y':
    # SDL2 doesn't seem to map deadkey ^ and falls back to y
    print('bépo')
else:
    print('unknown', keys)