Keybind case sensitivity, capital letters, and capslock oddities

[alaestor]

I haven't looked into how input is being handled, and I haven't tried this out on anything but my x11 system... I'm sure there's a fine reason, but this kind of hurts my brain.

shift+b print-text "shift+b"
shift+B print-text "shift+B"
b print-text "b"
B print-text "B"

results in... (key -> output)

b -> b
shift+b -> B
(capslock) b -> B

so capital B and indistinguishable from shift+B... What if we change the ordering?

b print-text "b"
B print-text "B"
shift+b print-text "shift+b"
shift+B print-text "shift+B"

results in...

b -> b
shift+b -> shift+B
(capslock) b -> shift+B

Okay, so capslock acts as a shift modifier. Kinda makes sense, I guess... But that's for character keys. What about non-character keys?

RIGHT print-text "right"
SHIFT+RIGHT print-text "shift+right"

results in...

right -> right
shift+right -> shift+right
(capslock) right -> right
(capslock) shift+right -> shift+right

So capslock acts as a shift modifier for characters, but not for non-characters.

On top of that, shift+b is synonymous with shift+B, but ctrl+b is distinct from ctrl+B, the latter implies either capslock be on or ctrl+shift+b be pressed... shift+b can't be distinguished from shift+B, even if you send a lower-case b while holding shift (inverting case with capslock on)

I don't really know why I'm sharing this, but I felt like it had to be mentioned somewhere in case anyone else gets confused by this behavior while troubleshooting their input.conf. I had always assumed that bindings were case-insensitive and that modifiers were all that was relevant; but clearly that's not the case, which is fine, but the rules are a bit unintuitive...

Normally I'd like to see this sort of thing be simplified into a more coherent model, but I'm sure that would be a bad idea since there's bound to be a lot of spacebar heating

[na-na-hi]

This is already documented in https://mpv.io/manual/master/#key-names.

I have added some clarification of this behavior to documentation in #15516.

[alaestor]

Thanks for the explanation & improved documentation