wallpaper can't span across screens
Even if the background picture mode (org.gnome.desktop.background
-> picture-options
) is set to spanned
or wallpaper
, gnome-flashback wants to set the same wallpaper on all screens individually, instead of spanning one wallpaper across the screens.
Test scenario
- have a system with multiple monitors, e.g. 2x 1920x1080 in my case
- (optional) have a wallpaper that's supposed to span across the monitors, e.g. 3840x1080 in my case (but the effect can be observed with any image size)
- set the picture
gsettings set org.gnome.desktop.background picture-uri file:///path/to/some/picture.jpg
gsettings set org.gnome.desktop.background picture-options spanned
What is expected to happen
- image spans across screens (e.g. left half on left screen, right half on right screen)
What happens instead
- the image is zoomed down to fit into a single screen (adding large colored bars at the edges), and the same content is displayed on both screens
Possible reason
It seems that in all cases, gf_background_surface_create
generates a per-screen background image (respecting the configured picture-options
mode) and then combines these per-screen background images into a large composite image that is then used as the X11 root window background. While this is the correct way to do things for most picture-options
modes, the spanned
and wallpaper
modes should act differently: From what I understand, in these cases, the surface created by gnome_bg_create_surface
should be used (more or less) directly.