Comment 6 for bug 568507

This is not a duplicate. Bug 388633 talks about extra whitespace in the Gtk combo box. This bug is about the ability to scroll down infinitely past the end of the combo box items. If you scroll down a long way then you have to scroll back just as far to see the list of items again.

This bug occurs only when either the list is so long or the window is positioned near a screen edge so that both ends of the list are not visible at once when the combo is opened. You can then scroll either up or down (depending on which end is hidden) indefinitely past the end of the combo list. However, if you scroll to the other end (i.e. the end that was not visible when the combo opened) the problem goes away until you reopen the combo.

This is not a major issue but it affects a huge number of applications and makes Gtk appear broken. It is much more apparent for large combo box lists.