User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.0b4) Gecko/20100818 Firefox/4.0b4 ( .NET CLR 3.5.30729; .NET4.0C) Build Identifier: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.0b4) Gecko/20100818 Firefox/4.0b4 ( .NET CLR 3.5.30729; .NET4.0C) Using the Windows 7 Taskbar Preview and TabCandy together can cause a number of visual errors. Reproducible: Always Steps to Reproduce: 1. Open a few tabs in different Tab Groups (the bug is most pronounced with multiple Tab Groups with only one tab in each). 2. Bring up the Firefox Windows 7 Taskbar Preview Thumbnails (hover over Firefox icon or click it). 3. Hover over different Thumbnails to preview tabs in Firefox. Actual Results: 4. Each tab previewed is visually added to the tab bar if it it not part of the current Tab Group. 5. These added tabs will be removed if no tab is previewed twice or if a Thumbnail is clicked that belongs to a group with multiple tabs in it. But otherwise the visual effect will remain and the added tabs will be clickable in the Tab bar or able to be switched to (Ctrl + Tab). 6. Switching Tabs corrects the visual bug (Tabs that don't belong to the current Tab Group will be removed from the Tab Bar). Alternatively, if Firefox is in TabCandy when the Windows 7 Taskbar Preview is used: 4. The tab contents are shown, but the Firefox toolbar is not (TabCandy can still be seen where the toolbar would be). 5. Clicking a Preview Thumbnail does not switch Firefox to that tab, but brings back up TabCandy. Expected Results: Firefox should respect the Tab Groups and not show Tabs on the Tab Bar that don't belong to that group. If the Windows 7 Taskbar Preview is used to view tabs that are not part of the currently active group, Firefox should switch to showing the Group that the previewed Tab belongs to. When Firefox is in TabCandy when the Windows 7 Taskbar Preview is used, Firefox should draw the Toolbar when previewing Tabs and should switch to that tab when it is selected from the Windows 7 Taskbar Preview.

Build identifier: Mozilla/5.0 (Windows NT 6.1; rv:2.0b7pre) Gecko/20100915 Firefox/4.0b7pre Able to reproduce. Tabs from different tab groups when hovered on Windows 7 taskbar preview thumbnails are added to the thumbnail even if it is not part of present tab group which is hovered on and are also seen added to current tab group. Also, when firefox is in tab candy and hovered on Windows 7 taskbar preview thumbnails, able to see the current tab contents but without the toolbar and tab candy can be seen in the place of toolbar.

There are two different bugs being described here. The first appears to be a duplicate of bug 591434. The second is less clearly described, but seems to be a duplicate of bug 581726. I think it may be better to invalidate this bug and resubmit it with the second part if it's definitely not the behavior described in bug 581726.

It is a duplicate of those two bugs. I didn't see them.

As noted above, resolved as a duplicate.