Bug#1110124: Default wallpaper does not respect update-alternatives

[Robie Basak <robibasa@qti.qualcomm.com>]

Package: xfdesktop4
Version:  4.20.1-1
Tags: patch

The xfce4 metapackage depends on desktop-base, which provides a bunch of theme-based update-alternatives, such as "desktop-background". But it doesn't seem to use this mechanism by default, instead falling back to /usr/share/backgrounds/xfce/xfce-x.svg.

This makes it difficult to ship a customised, themed image. But also, it means that by default the Debian themes are not used, which I presume we want the Debian packaging to do by default?

Steps to reproduce:

I used the Trixie RC 2 netinst iso from https://www.debian.org/devel/debian-installer/

Select XFCE during installation

Log in and observe the default wallpaper.

Expected results: a Debian-themed wallpaper from desktop-base

Actual results: the wallpaper is non-Debian-specific and seems to use /usr/share/backgrounds/xfce/xfce-x.svg

Further, I expect to be able to use update-alternatives to change the default wallpaper for new users, and that doesn't seem to work either.

Here's a patch that fixes this for me:

--- xfdesktop4-4.20.1/debian/rules	2025-03-03 01:34:50.000000000 +0000
+++ xfdesktop4-4.20.1/debian/rules	2025-07-29 13:48:35.000000000 +0100
@@ -8,7 +8,8 @@

 override_dh_auto_configure:
 	dh_auto_configure -- --enable-thunarx \
-		--docdir=\$${prefix}/share/doc/xfdesktop4-data
+		--docdir=\$${prefix}/share/doc/xfdesktop4-data \
+		--with-default-backdrop-filename=/usr/share/images/desktop-base/desktop-background

 override_dh_install:
 	dh_install