Bug 385276

Summary: Krita canvas lags on larger displays on macOS
Product: [Applications] krita Reporter: Bernhard Liebl <poke1024>
Component: GeneralAssignee: Krita Bugs <krita-bugs-null>
Status: RESOLVED UPSTREAM    
Severity: normal CC: alvin, ceryslhancock, halla
Priority: NOR    
Version: unspecified   
Target Milestone: ---   
Platform: Compiled Sources   
OS: macOS   
Latest Commit: Version Fixed In:
Sentry Crash Report:

Description Bernhard Liebl 2017-10-01 20:45:30 UTC 
Krita's graphics output on macOS is relatively slow, and it is very slow on 5k iMacs.

This seems to be related to QT's QWidget implementation on macOS. And this is probably a well-known problem.

If not, this ticket can keep track of infos about QT's state of things. 

Two useful pointers I found:

https://forum.qt.io/topic/59578/rendering-performance-problems-on-imac-with-retina-5k/24

https://bugreports.qt.io/browse/QTBUG-44228

As QT's OpenGL compositing internally happens with and without Krita's OpenGL canvas, switching to Krita's raster canvas does not make a difference.
Comment 1 Alvin Wong 2017-10-02 04:49:31 UTC 
Well, if you apply these patches does it get even slower?

https://phabricator.kde.org/D7973
https://phabricator.kde.org/D7982
https://phabricator.kde.org/D7984
Comment 2 Halla Rempt 2018-02-02 10:54:03 UTC 
*** Bug 373676 has been marked as a duplicate of this bug. ***
Comment 3 Halla Rempt 2018-02-06 09:46:08 UTC 
Let's just close this as upstream: there isn't anything we can do about it ourselves. For tracking what is being done in Qt, it would be better to use Phabricator.