In dual-screen, wallpaper scaled to the left-most monitor after reboot

[Łukasz Zemczak]

This bug is present in Ubuntu since at least 3 or 4 cycles. It's always reproducible with my current dual-monitor positioning and setup. It only happens when a smaller screen is configured for the left-most position. Seems like some code after reboot assumes that the left-most screen is the main screen.

Steps to reproduce:
 * Create a dual-monitor setup with 2 different sized screens
 * Configure the smaller screen to be the left-most screen, while the bigger - to the right
 * Configure the right bigger monitor as the main screen (with the launcher etc.)
 * Setup a high-resolution wallpaper as 'Zoom'
   -> Notice that the wallpaper looks good on the big screen and is scaled down on the smaller screen, which is good
 * Reboot your system (a session restart is probably enough)

Actual result:
 * Notice that now the wallpaper on the big screen has the left-most monitor resolution and is scaled up, looking pixelated

Expected result:
 * The wallpaper stays the same as it was originally, with both screens scaling down the high-res image to their respective resolutions

[Łukasz Zemczak (sil2100)]

I might be able to dig into it deeper myself, but first I'd need to know what component is responsible for actually setting up and displaying the wallpaper. I know that in the past nautilus had something to do with it, but is it still the case?

[Stephen M. Webb (bregma)]

In a Unity desktop, Nautilus is the component that displays the wallpaper.

Nautilus is a part of the Gnome suite, and the philosophy in Gnome is that you shall not run your desktop in a heterogenous multiple-display environment. There is one single integer-valued scaling factor to which Gnome applications respond; it would be no surprise to me if Nautilus internally does not save per-display scaling values for wallpapers.

[Łukasz Zemczak (sil2100)]

That sounds like the case here indeed! Since after initial changing of the wallpaper, the scaling values seem to be good for both screens. After a reboot though I guess it's simply saving and using the scaling value of the left-most monitor (in my case, the smaller one), making the wallpaper ugly.

Thanks for the info. It's certainly no priority, as I suppose my use-case is rather specific ;) I might look into that later.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.