the icon of thunderbird was not showing up in the systray

@tobiasBora How do you get Thunderbird to show up in the systay? In other words, how does one test this change?

Don't you need a plugin to get a Thunderbird systray on Linux as described on http://kb.mozillazine.org/Minimize_to_system_tray_%28Thunderbird%29?

Oh sorry, I meant the task bar. Basically without this commit I don't have these icons:

The reason is that makeDesktopItem creates a new deviation containing only the .desktop files, so the $out that was in the line icon = "$out/lib/thunderbird/chrome/icons/default/default256.png"; points to the new (nearly empty) folder created by makeDesktopItem instead of the one where thunderbird is installed.

So to test, one solution is to clone this PR, and install it with nix-env (it you don't install it then the icons won't be made available since you need to have the appropriate XDG_DATA_DIR set, so should look like (maybe there is a faster solution, I'm curious if there is one):

$ export NIXPKGS=/tmp/nixpkgs # Import to export for nix-env after
$ git clone https://github.com/NixOS/nixpkgs/ $NIXPKGS
$ cd $NIXPKGS
$ git fetch origin pull/107016/head:2020_thunderbird_add_icon
$ git checkout 2020_thunderbird_add_icon
$ nix-env -f $NIXPKGS -iA thunderbird

It seems reasonable to me. The firefox package already uses an abstract icon name.

Should we copy all icons in chrome/icons/default/? The firefox package copies default16.png, ..., and default128.png.
We should also fix thunderbird-bin.

While it would be reasonable for thunderbird-bin to do the same thing, it doesn’t currently have the missing icon issue, since it doesn’t use makeDesktopItem.