Created attachment 74488 [details] the bug I'm not sure whether this is ddx or kde or kernel. When I disabled VGA1 output in the settings window (the window in the background of the picture), windows are no longer redrawn and height of their frames is too big. A particular window is rendered even after switching windows by alt-tab. It happens with 2.21.0-3-g9640640.
Created attachment 74489 [details] xorg.log
If it was windows not being redrawn after the output was disabled, I would have said it was a Damage tracking bug on the root window. But that the window frames do not match the window geometry suggests that KDE is not entirely innocent. Just IVB? Nothing strikes me as being chipset specific here. I think trying the combinations of Desktop Effects (off / xrender / gl) would be useful to test.
(In reply to comment #2) > I think trying the combinations of Desktop Effects (off / xrender / gl) > would be useful to test. It never happened with off and xrender. It happens only with gl. I don't know the exact steps to reproduce though, it suffices to switch resolution, position of both VGA and display and turn off and on the VGA output a couple of times. Anyway, when it happens with gl, disabling and re-enabling effects fixes the issue.
I just wonder if any of the recent fixes take effect here (specifically the read-read optimisation fixes, including the wait-seqno kernel fix).
Is this still happening on current kernels?
I strongly suspect this is (accidentally) fixed.
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