Two monitor setup, on the left screen rotated left, plasmoids are unusably laggy. Mouse clicks and tooltips are delayed, cursor-over highlights lags, even wallpaper change fade-out effect is slow. Some few windows also: desktop settings lags, while other qt apps like kate, krita, kwrite, or gtk ones (Thunderbird, libreoffice) work OK. This only appears if the monitor is rotated, not on normal orientation. It is NOT related to the compositor, I've tested both cases, switching with shift+alt+F12. The linked video is with compositor disabled, I've got exact same behavior with all other compositing options, oGl 2, 3.1, glx, egl. I had this landscape+portrait monitor setup since kde 4.2 and never had a similar problem.... Reproducible: Always The box is a i7-4770 without a dedicated card, so mesa+intel UXA all the way, on F23, kde from Rex Dieter's kde-testing, actually on 5.6.2 $ uname -a Linux cy 4.4.7-300.fc23.x86_64 #1 SMP Wed Apr 13 02:52:52 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux $ xrandr -q Screen 0: minimum 320 x 200, current 2944 x 1280, maximum 8192 x 8192 HDMI1 connected primary 1920x1200+0+0 (normal left inverted right x axis y axis) 518mm x 324mm 1920x1200 59.95*+ ... HDMI2 connected 1024x1280+1920+0 left (normal left inverted right x axis y axis) 376mm x 301mm 1280x1024 60.02 + 75.02* ... $ qdbus org.kde.KWin /KWin supportInformation http://paste.fedoraproject.org/359513/95542146/
> It is NOT related to the compositor And then why do you report it to kwin? Qt 5.6? See also bug #360137
(In reply to Thomas Lübking from comment #1) > > It is NOT related to the compositor > And then why do you report it to kwin? Ok to reassign to plasmashell then. > Qt 5.6? I see this since 5.5.95, maybe a little earlier. > See also bug #360137 I've looked to #360137 and seems a but similar, except that I only have trouble on the rotated monitor. QtQuick seems a possible culprit but why also Ive got this on the desktop settings window ? Is it QML too ?
OK, apparently this is related to Fedora recently enabling DRI3 by default on intel. Putting << option "DRI" "2" >> in a relevant xorg.conf.d file fix it. Is it something to report to upstream Intel then ? I still don't get why some windows or apps are affected and not others. By the way, google-chrome is affected and it isn't Qt at all AFAIK.