Comment 16 for bug 746028

Right now on my machine, with the default wallpaper:
timestamp of the cache:
$ ls -l ~/.cache/wallpaper/zoom_1920_1080__usr_share_backgrounds_warty-final-ubuntu.png
-rw-r--r-- 1 didrocks didrocks 392625 2011-04-19 09:23 /home/didrocks/.cache/wallpaper/zoom_1920_1080__usr_share_backgrounds_warty-final-ubuntu.png

timestamp of the source image (0.31.9)
$ ls -l /usr/share/backgrounds/warty-final-ubuntu.png
-rw-r--r-- 1 root root 231208 2011-03-23 23:34 /usr/share/backgrounds/warty-final-ubuntu.png

So, I created ubuntu-wallpapers 0.31.9ppa1 with a totally new wallpaper (still warty-final-ubuntu, expressing all my artistic creation writing "BRAND NEW!" on it ;)
You can find it in my ppa: https://launchpad.net/~didrocks/+archive/ppa
When I install it, I see the wallpaper changing, showing a nice "Brand New!". That's also confirmed by the timestamps:

$ ls -l ~/.cache/wallpaper/zoom_1920_1080__usr_share_backgrounds_warty-final-ubuntu.png
-rw-r--r-- 1 didrocks didrocks 670582 2011-04-19 09:30 /home/didrocks/.cache/wallpaper/zoom_1920_1080__usr_share_backgrounds_warty-final-ubuntu.png

$ ls -l /usr/share/backgrounds/warty-final-ubuntu.png
-rw-r--r-- 1 root root 713318 2011-04-19 09:28 /usr/share/backgrounds/warty-final-ubuntu.png

Any hint? This should reproduce the upgrade case (we are using nautilus in the gnome session, but it's calling the same library, and if, after this, I try to start gdm (using g-s-d), I see the new wallpaper as well. Can you try with the wallpaper asset in my ppa (I only changed warty-final-ubuntu.png)

For Jonathan, here is the screenshot :)

PS: the exact same code is now in GNOME3 (I ported it, but no change at all in the logic) and there is no bug opened against it.