Thank you for contributing to Nix.

Since you are using the XDG variables for the data path, how about XDG_CACHE_HOME for the default location of the compose cache (if xcomposecache isn't set)?

Aren't these env vars usually set up after this point and potentially in the sessions themselves? I for example have a ~/.xsession file that ends up setting the correct XDG_DATA_HOME, which happens here:

@peterhoeg ~/.compose-cache is the default location, so if it has not been set by the user, other applications (e.g compose (5)) will read from ~/.compose-cache. This patch would have no effect unless the user specifically exports XCOMPOSECACHE.
I also think we should in general try not to change things from the upstream default, as it can cause confusion and inconsistent behavior between distros.

@infinisil The exact time that the environment variables are set depends on where they are defined. You are correct that, if they are set in ~/.xsession, then they will not be available at the time the script is run. This can be solved by either:

• move the sourcing ~/.xsession at the beginning
• defining your environment variables elsewhere, such as /etc/profile (this is can be used in NixOS by setting environment.sessionVariables. However this doesn't allow you to have different per-user values (e.g. user A wants XDG_DATA_HOME to be ~/.local/share, and user B wants XDG_DATA_HOME to be ~/.hidden/local/share)

The problem is that ~/.xsession isn't a file you source, but rather execute. It represents the full user session, and it only exits once the user logs out.

It also occurred to me that we could expose services.xserver.displayManager.session.script as an option. This would allow people with niche setups to override the default script. Currently services.xserver.displayManager.sessionCommands only appends to the default script.

@infinisil Apologies, I am not familiar with "manual" Xorg setups (I use KDE plasma). From looking at the xsession script, it seems like these env vars could be set in ~/.xprofile if we move the sourcing of ~/.xprofile to the beginning.

That might work

@infinisil Bump? Is there some proper way to request attention? I'm new to git/github, so sorry if this is the wrong way to go about it

@infinisil
ping?

Not sure, maybe try pinging some people that were involved with this part of the code in the past

As a KDE user, how would you go about overriding the location of the compose cache? Otherwise this looks fine to me but please run the various tests (sddm, plasma5, xfce, gnome3) to ensure this isn't breaking anything.

@peterhoeg Personally, I set XCOMPOSECACHE in /etc/profile, though I imagine you could do it on a per-user basis with ~/.xprofile or ~/.pam_environment

What is the status of this pull request?

While trying to declutter my $HOME I ran into this issue. It would be nice to have this rebased and merged at some point.