How to implement custom dead keys on XKB?

[devnoname120]

Some ideas:

• Use a .XCompose file.
  • Problem: not layout specific, instead it's shared across all keyboard layouts (minimum granularity: locale-level).
• Emulate dead keys using latches.
  • Problem: not compatible with some apps, few available (level 5 + maybe level 3, not sure how other levels behave in some apps). See example of implementation on the qwerty-lafayette layout.

👍 .XCompose supports multi-codepoint characters: https://unix.stackexchange.com/a/549228

[devnoname120]

I think .XCompose is the best way forward. The whole point of qwerty-fr is to give the chance never to switch your keyboard layout ever again thanks to its comprehensive languages support.

For this reason it makes sense to replace the default .XCompose.

See this for an example:

• https://gist.githubusercontent.com/guiambros/b773ee85746e06454596/raw/0ea6d7f7cf9a6ff38b4cafde24dd43852e46d5e3/.XCompose
• https://github.com/fabi1cazenave/qwerty-lafayette/blob/0964736541b6a0e207605b2d60dea2a17a172ecc/XCompose (2015)

[Schnouki]

Should we use ~/.XCompose (and require user intervention), or try to patch the system-wide compose file, e.g. /usr/share/X11/locale/en_US.UTF-8/Compose?

The former is of course easier to develop, but the latter could be nicer for users, as they wouldn't have to change a dotfile in their $HOME. Just install the package and it works 🎉. It also makes sense since the Debian postinst/postrm scripts (also used by the Archlinux AUR package) already patches a few files in /usr/share/X11.

[devnoname120]

Installing the keyboard globally and then requiring each user to apply the changes to ~/.XCompose would make for an awkward user experience in my opinion.

What would you think about using dpkg diversions (tutorial here) instead of directly patching the system file?

How are other keyboard layouts solving this issue? Are they all just replacing the system-level Compose files?