Per key keyboard lighting to indicate valid sequences

[aviraldg]

On keyboards that support it (such as some Logitech and Razer keyboards), highlight keys to indicate valid sequences

Would a PR adding this be welcome?

[samhocevar]

If you believe this would be useful and you know how to access the keyboard highlight, then I’ll happily review a PR, yes.

Note that I have concerns about the performance implications, because with the current architecture it would probably have to run in the keyboard hook. However this can be dealt with later.