Ghost menus in Thunderbird and Betterbird 140

We already talked about ghost menus in this article. Here is some more information.

For some users these ghost menus (occasionally) happen, when this Windows performance option is selected:

This setting determines the internal value of preference ui.prefersReducedMotion, for those interested in code, this can be found here. The problem in Betterbird was that we exposed the preference, and set its value to 0 with the effect that the system behaved as if the Windows performance option were set. Since Betterbird 140.6.0 the preference is no longer set and its internal value depends on the Windows option again.

To get rid of the ghost menus there are three options:

• Switch off the Windows performance option
• Set preference ui.prefersReducedMotion to a value of 1
• Set preference widget.windows.mica.popups to a value of 0.

The root cause of the issue is that the newly introduced translucent mica menus aren't stable enough in the Mozilla platform code at version 140. Users who wish to have animation should switch off those menus. In later versions of the Mozilla platform code, the problem appears to be fixed.