input-method module: use xim for GTK Fcitx

[sorpaas]

Things done

• Tested using sandboxing
  (nix.useSandbox on NixOS,
  or option build-use-sandbox in nix.conf
  on non-NixOS)
• Built on platform(s)
  • NixOS
  • OS X
  • Linux
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

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Fcitx has a xim interface, which works better for GTK applications. On my KDE desktop, the fcitx IM module doesn't work for GTK applications. Only xim works.

[mention-bot]

By analyzing the blame information on this pull request, we identified @ericsagnes and @ttuegel to be potential reviewers

[ericsagnes]

This is related to GTK_IM_MODULE cache problems. (see #14019)
#14568 should fix this problem and is close to merge.

IMHO we shouldn't set xim as default as it has issues.
For the record, Fcitx main developer explained the details of xim problems in this comment :

... XIM is extremely outdated (90s), buggy (synchronous call everywhere, can easily freeze app if input method server quits), unmaintained (many TODOs in source which is never implemented for years), and lacks of important features comparing with what an native im module can provides, e.g. surrounding text support which is commonly used in Japanese input method.

[sorpaas]

Thanks! Closing this pull request.