Config output id doesn't match swaybg

[yorickvP]

Please fill out the following:

• Sway Version: 1c368fb

• Configuration File:

# needed for position to work
output "HYC CO., LTD.  Unknown" {
   bg /home/yorick/wp/beyond-4k-2560×1440.jpg fill
   position 0 0
}
# needed for bg to work
output "HYC CO., LTD.  " {
   bg /home/yorick/wp/beyond-4k-2560×1440.jpg fill
   position 0 0
}

$ swaymsg -t get_outputs
Output DVI-D-1 'HYC CO., LTD.  Unknown'

$ swaybg
2022-09-15 09:55:00 - [main.c:260] Found config HYC CO., LTD.  for output DVI-D-1 (HYC CO., LTD. )

• Description:
  Handle NULL output make/model/serial #7031 changed the output description that's used to match config sections, but didn't update the wl_output::description that's used in swaybg. This causes a mismatch between these settings, causing the bg not to show in some cases.

[emersion]

Hm, right. The root cause is that swaybg uses a hack to match output identifiers: https://github.com/swaywm/swaybg/blob/c9608982d2a8bf0e70291a7a1b8cade1ca06f36f/main.c#L303

[emersion]

Duplicate of swaywm/swaybg#44

[mstoeckl]

If we were to ignore backwards compatibility entirely, one way to fix this would be make Sway adopt the wlroots output description value for its output identifiers everywhere. (That is, the value which swaybg receives through the wl_output::description event) See for example the following patch 0001-Use-the-wlroots-wl_output-description-as-output-iden.patch.txt. There probably is a better solution that I haven't thought of, so I'm not planning on making a PR out of the patch myself.

[emersion]

I'd prefer not to rely on the output description, because this makes swaybg incompatible with any compositor which uses a different format (either non-wlroots, or a wlroots compositor which sets a custom output description).

More discussions:

• https://gitlab.freedesktop.org/wayland/wayland/-/merge_requests/109#note_970789
• https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/3979