Open the download manager and select a row. Then switch to any other open window (doesn't matter if it's a Firefox window) that partially overlaps the download manager window. Only the parts of non-native elements (including the bar at the bottom with the Clear List button and the selected row) beneath the shadow of the newly-focused window get redrawn. The rest of the (partial) elements still appear active even though they should be completely redrawn. The main firefox window also exhibits this behavior except the elements seem to redraw on a timer. Sometimes you need to switch back and forth between windows a few times to see the effect, but I haven't been able to reproduce it when switching between windows that don't overlap at all (including the window shadow).
Please add a screenshot of the issue and also post the MacOS version that you are using. Thanks
These screenshots were created on Mac OS X 10.7.1 and Aurora build 2011-08-16.
Bug 644494 is similar.
Although Bug 644494 is similar, Firefox stays responsive and the widgets redraw correctly when the window becomes active again. The widgets also sometimes redraw when the mouse passes over them.
Interesting. But you do have hardware acceleration enabled, don't you? (Check about:support, if it says GPU Accelerated Windows: 1/1 OpenGL then you're accelerated)
Hardware acceleration is on. To add more information (that could potentially make this WONTFIX), I just realized that this issue only occurs when I force my late 2011 macbook pro to use intel HD 3000 graphics when Firefox starts. When the discrete Radeon is enabled when Firefox starts, I can no longer repro the problem. Changing the graphics card setting after Firefox has already started seems to have no effect. I suppose that makes it possible, if not likely, that this is an issue with the Mac OS Intel drivers, but I haven't experienced it in any other program.
I wasn't able to reproduce this on the latest nightly: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:9.0a1) Gecko/20110915 Firefox/9.0a1, so it's WFM.
I had to manually switch to Intel HD3000 graphics before the symptoms materialized. While running on discrete graphics (which Firefox normally forces), the issue doesn't occur.