black desktop background. Unable to load and apply wallpaper on wayland sesssion

Issue Description

Totally black desktop background in wayland session. When trying to apply settings, the desktop was still in black. However, when in X11 session the xfdesktop able to load the wallpaper.

Steps to Reproduce Issue

1. Start xfce in wayland session
2. Right-click desktop and select desktop settings
3. Select wallpaper

Expected Behavior

The select wallpaper must shown on desktop

Environment & Versions

• OS distribution and version: slackware current
• Overall Xfce version: 4.20
• xfdesktop version (git hash if not a release): 4.20.1
• Windowing system (X11/Wayland): wayland
• Compositor and version (if Wayland): labwc 0.8.3
• GTK Theme: Breeze
• Icon Theme: Papirus
• UI Scale Factor: 1

changed the description

added 5. Background 5. Wayland labels

I encountered the same issue (unable to change background) while using the Xfce wayfire session.

The cause seems to be a problem with the monitor name:

• icons.screen0.yaml: display_name: "(null) (null) (Virtual-1)"
• xfconf: /backdrop/screen0/monitorUnknown
• wlr-randr: Virtual-1 "(null) (null) (Virtual-1)"

changed the description

mentioned in issue #380 (closed)