User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.0b9pre) Gecko/20110107 Firefox/4.0b9pre Build Identifier: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.0b9pre) Gecko/20110107 Firefox/4.0b9pre When using the Windows Classic or Windows Basic theme, if the window is maximized on my secondary monitor the window border resembles an unmaximized window, with a border along the top and the titlebar buttons in positions like an unmaximized window. The bottom of the window is cut off and a single pixel line of the background can be seen at the very bottom of the screen. Additionally, when in this state, when performing some actions (opening tabs, opening context menus) the window momentarily shakes into its correct position and look, and then snaps back to the incorrect look again. Context menus flicker madly when navigating them. Reproducible: Always Steps to Reproduce: 1. Set windows theme to Windows Basic or Windows Classic. 2. Move window to secondary screen. 3. Maximize window. Actual Results: There is a window border along the top of the maximized titlebar, and window buttons are not in the proper location for a maximized window. A single pixel line of the background can be seen at the bottom of the window. Expected Results: A stable properly maximized window, with none of the effects described. This happens with a fresh profile, with the standard Windows Basic (the non-accelerated Aero one) and Windows Classic (the XP-like look).

Observe the border on top, buttons in upper right corner, cut off window at bottom and single pixel line of background at the bottom.

For comparison, a properly maximized window on primary monitor.

I notice that the single pixel background line is not a result of this bug, as it appears on the primary screenshot as well. Time to split that out as a separate bug, I guess.

This has been present since at least the build where the window buttons had their clickable area properly extended to the edge of the screen and the buttons were moved a pixel to the left. I can sadly not find the bug number of that, but it should be a few months ago.

(In reply to comment #1) > Created attachment 502242 [details] > Maximized on secondary monitor > > Observe the border on top, buttons in upper right corner, cut off window at > bottom and single pixel line of background at the bottom. Lars, are all the symptoms regressions? This is at least partly, if not entirely, a duplicate of bug 629267

The single-pixel gap seems to be the same problem as 629267, but the flickering/juddering is not mentioned in that bug at all. Everything under the "additionally" section still held the last time I ran a Firefox under the themes mentioned, which was maybe a month ago. This bug is so severe that I cannot use said themes at all, as they make me smash things when FF bugs out.

I was hit by this bug today when using the Basic theme (I normally use Aero), Firefox 12.0. I have four monitors and the problem only occurs on one of them: the one in portrait mode (just like Lars' secondary monitor) located to the left of the primary monitor (which means negative x coordinates). I rotated one of the monitors to the right into portrait mode and that did not cause the problem to appear there. I then rotated the leftmost monitor into landscape mode and the problem went away. Maybe these observations can help?