When the second to last tab is removed from a GroupItem, the Group Item continues to be rendered as if there are two tabs and therefore must have two columns. While mostly visual in nature, it seems like this may be one part of bug 622872 (blocker).

I believe that the original design was that above a certain width, a lone tab would take only half the available width of the group. Otherwise you end up with a huge tab that fills the group entirely. By providing that extra space, we invite more tabs to be dropped in, and we avoid having the group just be an extra frame around the tab. Of course below a certain width, it made sense for the tab to fill the group, other wise it would be too small. It appears that the code that did that has eroded such that it kind of does it sometimes. I would propose we use this bug to reinstate the original design. Also note that when you first go into Panorama, if there's a group with a single tab, that tab fills the group at first, but then stops doing so when you start messing with it. That should be fixed as well (so it starts out half-width if need be).

(In reply to Ian Gilman [:iangilman] from comment #1) > I believe that the original design was that above a certain width, a lone > tab would take only half the available width of the group. Otherwise you end > up with a huge tab that fills the group entirely. By providing that extra > space, we invite more tabs to be dropped in, and we avoid having the group > just be an extra frame around the tab. Of course below a certain width, it > made sense for the tab to fill the group, other wise it would be too small. > Not exactly. The original design is to make tabs flexible and fills the group space as much as possible. Whenever you drag a tab into a group, before you drop that tab, tabs inside the targeting group will automatically rearrange to make space for the new comer. I think this "half width tab" is just a kind mistake.

This root cause is that the group is reluctant to update column information when there is only one tab in the group. Thus, when a tab is removed from a two-columns-two-tabs group, the column number remains 2.

Comment on attachment 557397 [details] [diff] [review] update column number even if there is only one tab in the group Request a review

Comment on attachment 557397 [details] [diff] [review] update column number even if there is only one tab in the group Review of attachment 557397 [details] [diff] [review]: ----------------------------------------------------------------- Thanks, that looks good to me! Let's add a test for this. r- only for the missing test.

Thanks for advice from Tim.

Comment on attachment 562951 [details] [diff] [review] patch with testcase Review of attachment 562951 [details] [diff] [review]: ----------------------------------------------------------------- Great, thanks! Can you please prepare the patch for checkin? Here's some advice on how to do that: http://blog.bonardo.net/2010/06/22/so-youre-about-to-use-checkin-needed

r=ttaubert

Thanks for the patch! https://hg.mozilla.org/integration/fx-team/rev/268ba6fecae0