screenkey: unset XMODIFIERS to avoid XOpenIM err

[vidbina]

Motivation for this change

I know you're tired. So instead of asking you to do it I figured I'll propose a PR. Perhaps it's not as clean as it should be... In that case I'll just keep track of the status on GitHub and submit fixes until we get it right.

point is... on my setup this fails with

DEBUG:Screenkey:Options loaded.
DEBUG:Screenkey:Restarting LabelManager.
DEBUG:Screenkey:Thread started.
DEBUG:Screenkey:Restarting LabelManager.
Exception in thread Thread-1:
Traceback (most recent call last):
  File /nix/store/i3bx1iw2d0i3vh9sa1nf92ynlrw324w8-python-2.7.14/lib/python2.7/threading.py, line 801, in __bootstrap_inner
    self.run()
  File /nix/store/r7dqmjgcp6y72939rwsm0x941k7kd78y-screenkey-0.9/lib/python2.7/site-packages/Screenkey/keylistener.py, line 245, in run
    raise Exception(Cannot initialize input method)
Exception: Cannot initialize input method

zsh: terminated  ./result/bin/screenkey -d

I resolved this in my old PR (NixOS#34898) by unsetting XMODIFIERS. Using wrapProgram, I kind of know how to do this the "right" way, but with wrapGAppsHook I figured appending to gappsWrapperArgs would suffice even though there aren't any examples of unsetting variables this way in the entire nixpkgs repository so far... or my grep was lousy. So I don't really know if this is a clean way of doing this. I already mentioned this PR in NixOS#34167 so I'm counting on feedback soon enough.

Things done

• Tested using sandboxing
  (nix.useChroot on NixOS,
  or option build-use-chroot 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.

---

[vidbina]

@rasendubi could you review this and possibly merge it such that we can keep the conversation going on NixOS#34167?

[Mic92]

What is the current value of $XMODIFIER in your shell?

[Mic92]

screenkey was merged into nixpkgs.

[vidbina]

XMODIFIERS is set to @im=ibus which is a side-effect of having the ibus package installed as evident in https://github.com/NixOS/nixpkgs/blob/7ef26640f604f7745d07fde71aaa401a3c211149/nixos/modules/i18n/input-method/ibus.nix#L64

[Mic92]

So does this only happen with ibus or also the other input methods?

[rasendubi]

@vidbina given my PR is merged now, I think it's better you open a new PR against upstream nixpkgs (and add link here)