Comment # 84 on bug 1112963 from Jean Delvare

(In reply to Edward Van Every from comment #73)
> OK, Here is what the video corruption looks like (attached).

That I can reproduce. It seems to be a resolution disagreement. By default I
get a 1024x768 resolution in Plasma, which looks ugly. The best my AST2050
chipset can do is 1600x900, which is not screen-native, but at least matches
the 16:9 ratio of my screen, so I used "xrandr -s 1600x900" to get that. Some
time after, I called "xrandr" without argument, and the corruption started
immediately. The output of xrandr at that moment was different from what it is
usually (different list of resolutions and refresh frequencies).

Note that SDDM does use the best resolution by default: 1600x900. And for
example IceWM sticks to that. So I think the problem happens when Plasma tries
to change the resolution when the user logs in, to something different from
what SDDM had.

When the corruption happens, I am able to get things back to a correct state by
switching to a text console (Ctrl+Alt+F2) and then back to X.org (Ctrl+Alt+F7).

Note that I can also get the "wrong" xrandr output, but without the corruption,
under IceWM. So it is not Plasma-specific. The problem is that 1600x900 is not
in the wrong list, so once it happens, I'm stuck with lower resolutions.

I'll do some more tests and post my findings here. At any rate this seems to be
a separate issue from the performance issue(s) reported before.