Emacs alt-v keybinding triggering solo Alt key in firefox

[anaxonda]

One minor thing...

I'm using the provided emacs keybindings. In Firefox when I use alt-v (page-up), page-up does successfully work, but it also triggers a solo alt press (open menu).

Is there any way to separate an alt pressed separately with one thats part of a key sequence?

[k0kubun]

You could try the virtual_modifiers feature, or use Super instead of Alt. I personally use the latter method myself for this exact problem.

[anaxonda]

You use Super systemwide in lieu of Alt (except in emacs I guess)? Or just in firefox?

Is there any way to make Alt behave as normal Alt when pressed singly, and ignored when held?

[k0kubun]

Yes. This is what you said:

modmap:
  - remap:
      Alt_L:
        held: KEY_UNKNOWN
        alone: Alt_L

but I think you want to put Alt_L in held and Unknown in alone?