Please describe the problem:
with the recent "improvements" in the task list layout in gnome 2.20 it is even more broken than with previous versions when putting it on a vertical panel.

Steps to reproduce:
1. Create a vertical panel
2. put a task list on it
3. increase its width (40-50px)
4. open some windows until the problem shows up


Actual results:
first the task list is not expanding to the whole available panel height.
when the window count reaches a critical point, the layout is rapidly switching between one and two columns of buttons making it impossible to even click on one of them.

Expected results:
the buttons should use all available space, and always display in one column (or at least have a predicable layout without flickering

Does this happen every time?
yes

Other information:
i looked into the source code, finding vertical layout is not handled at all.
this is so annoying for me (using only vertical panels) i plan to fix this myself. any suggestions regarding the correct behavior?