- start X with your screen in landscape orientation
- use pcmanfm to manage your desktop
- use xrandr (or a gui like arandr) to rotate your screen 90 degrees
- the wallpaper will not be stretched correctly (see after_rotation.jpg)
- kill pcmanfm and restart it
- the wallpaper will be stretched correctly (see after_restart.jpg)
Fixing this simpler case may completely fix 3614780 - I'm not sure.