xfdesktop4: make default wallpaper tuneable

[basak-qcom]

Use the system configured
/usr/share/images/desktop-base/desktop-background (as maintained by update-alternatives) as the default backdrop.

[basak-qcom]

I'd like review on this entire approach, please. Is there a better way to solve this problem entirely?

[github-actions]

Test Results

 2 files  ±0   4 suites  ±0   6m 15s ⏱️ ±0s
15 tests ±0  15 ✅ ±0  0 💤 ±0  0 ❌ ±0 
38 runs  ±0  38 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 7a6b112. ± Comparison against base commit 5bb8015.

[github-actions]

Test jobs for commit 7a6b112

• Job 86185 on qrb2210-rb1
• Job 86184 on qcs6490

[lool]

Hey, thanks for the PR!

So we want an easy way to configure the desktop background image.

The Xfce desktop defaults to /usr/share/backgrounds/xfce/xfce-x.svg.

Debian has the desktop-base package which amongst other things centralizes artwork across desktop environments. Unfortunately, Xfce doesn't seem to use it, even if the xfce4 package depends on it.

The patch you attach in the debdiff for overlay-debs seems to be exactly what Debian should merge to use desktop-base, so I guess we should propose that there.

I guess xfdesktop4 should also gain a Recommends on desktop-base to make sure the target image is present.

Wrapping my head around this, I personally wanted to avoid patching system packages and instead do some config changes for the default user. I'm not sure why, I guess it depends if we want to implement more of a "derivative" approach or follow the idea of making a cozy configuration for our default user in that image.

This should be possible with something like:

xfconf-query --channel xfce4-desktop --list |
    grep last-image$ |
    xargs xfconf-query -c xfce4-desktop -s /usr/share/images/desktop-base/desktop-background -p

but when I tried doing that, it didn't work. I did try to do it while lightdm was stopped, and from the serial console, as I wanted to see if I could query/set xfce settings during an image build, but perhaps I'm setting the wrong key, or perhaps some settings daemon didn't pick up on my changes, not sure.

The lightdm background would be another place that might have to be customized, and that should also ambition to follow desktop-base.

I think Ubuntu tried to use desktop-base to override defaults for a while, but I believe has since resorted to just patching the packages that need patching, much like in your patch.

(I'm hitting Request changes in this review for the "Recommends" suggestion)

[basak-qcom]

Wrapping my head around this, I personally wanted to avoid patching system packages and instead do some config changes for the default user.

I agree this would be preferable to avoid a delta, but I think ideally the existing update-alternatives would be used, and any new user created should probably also have the derivative-customised theme by default. And like you, I couldn't find a clean way to implement this just for the default user :-/

I guess xfdesktop4 should also gain a Recommends on desktop-base to make sure the target image is present.

I also wondered that, but I found that the main xfce4 metapackage (that we also pull in) already recommends desktop-base and depends on xfdesktop4. It would be possible to install xfdesktop4 directly, but then I think one wouldn't expect all XFCE desktop integration to work smoothly anyway.

Do you think that's sufficient?

[basak-qcom]

I sent this to Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1110124

[lool]

Wrapping my head around this, I personally wanted to avoid patching system packages and instead do some config changes for the default user.

I agree this would be preferable to avoid a delta, but I think ideally the existing update-alternatives would be used, and any new user created should probably also have the derivative-customised theme by default. And like you, I couldn't find a clean way to implement this just for the default user :-/

I guess xfdesktop4 should also gain a Recommends on desktop-base to make sure the target image is present.

I also wondered that, but I found that the main xfce4 metapackage (that we also pull in) already recommends desktop-base and depends on xfdesktop4. It would be possible to install xfdesktop4 directly, but then I think one wouldn't expect all XFCE desktop integration to work smoothly anyway.

Do you think that's sufficient?

I think this is sufficient from the perspective of delivering the bits to users, but personally I would imagine some kind of dependency between this package and dekstop-base if there are specific runtime dependencies introduced, but I guess this is more for the Debian maintainers to worry about here