Created attachment 815030 [details]
bug demonstration video
Description of problem:
Please see the video. The first time I open the CPU model drop-down list, I can scroll through all the items. But when I open it for the second time, the little top and bottom arrows disappear and I can't display off-screen items. Mouse scrolling doesn't help, neither manual keyboard arrow traversal.
If I close virt-manager (not just VM window, whole application) and start it again, then the drop-down list is functional again (for the first time).
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. open virt-manager
2. open VM properties
3. open CPU mode drop-down list
4. close the list and open it again
5. try to reach off-screen items
It seems to be related to pygtk. I was able to reproduce it by a simpler python script.
I have reported it here: https://bugzilla.gnome.org/show_bug.cgi?id=711780
Created attachment 822103 [details]
Simple python reproducer
Seems to be a gtk issue, here's a simple reproducer using pygobject. It launches a window with a single ComboBox with a text entry. The combo is filled with enough items to require scrolling.
First click of the combobox arrow works correctly, subsequent clicks show the rows but no scroll arrows as demonstrated in Kamil's reproducer video.
(In reply to Giuseppe Scrivano from comment #1)
> It seems to be related to pygtk. I was able to reproduce it by a simpler
> python script.
> I have reported it here: https://bugzilla.gnome.org/show_bug.cgi?id=711780
Haha I missed your comment and implemented my script separately, glad we were on the same track :)
Please try the gtk3 3.10.5 update that I've just built. It contains fixes for combobox sizing.
Thanks, gtk3-3.10.5-1.fc20.x86_64 fixes this issue.
control-center-3.10.2-3.fc20, gnome-settings-daemon-3.10.2-3.fc20, gtk3-3.10.5-1.fc20 has been submitted as an update for Fedora 20.
control-center-3.10.2-3.fc20, gnome-settings-daemon-3.10.2-3.fc20, gtk3-3.10.5-1.fc20 has been pushed to the Fedora 20 stable repository. If problems still persist, please make note of it in this bug report.