xkbcommon: Converting keysym to keycode

[adlo]

> On 5 Dec 2021, at 05:15, Peter Hutterer <peter.hutterer at who-t.net> wrote:
> 
> please look at the source, it's not a huge program.

I have looked at the source, it’s just that I can’t see anything that’s directly related to what I’m trying to do. It calls xkb_keymap_key_get_mods_for_level(), which seems to be related to getting the mods, and it seems to have things that get the name of a key, or get a key from the name, but I can’t see anything that looks like it’s related to getting or approximating a keycode from a keysym.