This seems to be the return of bug 113714, which was fixed a couple months back by Miklos.
Steps are the same:
- Switch to default rendering.
- Start Writer.
- Move mouse over main menu.
=> The menu flickers.
Occurs with 126.96.36.199.alpha0+ (0fb2927a8fe06e6c3255544b8e4c4c9c0f5a67d3, 2019-08-27_22:13:47) / Windows 7.
No flicker in 188.8.131.52.alpha0+ (d3d13140f0036c53aa74820b41acfeffa3572168, 2019-08-14_12:05:15).
I'm assuming that only Windows is affected, just like with the original bug, but I haven't checked.
However, it doesn't occur with a fresh master debug build (2bd8e41a0fc10974f81695c1b2e32dc07c569d97).
Maybe it's gone? Let's close tentatively, will recheck with a newer daily build