Much faster input processing (avoid the whole stack)

Input can be sped up quite a bit with a tiny hack:

JUST_KEYS = []
# adds all alpha keyboard keys to an exclusion list
JUST_KEYS.extend([Key[x] for x in "QWERTYUIOPASDFGHJKLZXCVBNM"])

def on_event(event, device_name, quiet):
    if event.type != ecodes.EV_KEY:
        _output.send_event(event)
        return

    if len(_pressed_modifier_keys) == 0 and event.code in JUST_KEYS:
        _output.send_event(event)
        return

This avoids the whole keymapping stack when there are no modifiers down and you're just typing regularly. In my testing the difference is pronounced:

~60 microseconds to fasttrack
~1.6 MILLI-seconds to handle full stack

I'm guessing a lot of the expense is asking X for the current window, but I haven't done any real testing yet.

mooz / xkeysnail

Much faster input processing (avoid the whole stack) #162