Assuming that you are seeing this in 3.11.x, my casual guess is that this is related to bug 720188

sure, same thing

After playing with ./panels/background/test-chooser-dialog I found that the icon view becomes wider when data is inserted into the list store. This might be due to a GTK+ change within the 3.11.2 and 3.11.3 timeframe, but the way we were restricting the icon view to have 3 columns looks wrong to me.

We were (arbitrarily?) setting the size request on the big grid so that it is just wide enough to have 3 columns. See:

commit a4cf2839378c09e756c9c1ebe07adb036f7d3f26
Author: Bastien Nocera <hadess@hadess.net>
Date:   Wed Nov 14 23:06:07 2012 +0100

    background: Fix not having 3 columns in high contrast
    
    Increase the width slightly to 860 from 850.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=683499

commit 79ec684fa4912a1e5bff17ce11b036cef4a298aa
Author: William Jon McCann <jmccann@redhat.com>
Date:   Tue May 22 11:34:20 2012 -0400

    background: New background panel design
    
    Implement a new design for the wallpaper selection.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=676539

Using gtk_icon_view_set_columns looks more correct to me, and it fixes this problem.

Created attachment 264555 [details] [review]
background: The chooser should have exactly 3 columns

Created attachment 265709 [details] [review]
background: The chooser should have exactly 3 columns

Review of attachment 265709 [details] [review]:

Sure, please commit to gnome-3-10 and master.

Comment on attachment 265709 [details] [review]
background: The chooser should have exactly 3 columns

Committed to both master and gnome-3-10. Thanks for the review.