SUMMARY For some reasons some blending modes like the "Dissolve" mode, are UNBEARABLY LAGGY In THIS VERSION oF Krita STEPS TO REPRODUCE 1. Put the "Dissolve" blend mode either on layer or soft brush 2. Paint with it on the canvas OBSERVED RESULT The canvas renders the result as an unbearably and unexpected slow speed( can take up to two minutes and even more ) EXPECTED RESULT No lag at all SOFTWARE/OS VERSIONS Windows 10 Pro ADDITIONAL INFORMATION ( this issue is not present in Krita 5.2.2 nightly ) The issue might also affect some other blend modes. I am not sure, but please double check if possible.
It seems like the bug is a regression from my refactoring in December
Git commit d211566997174204c611148941f8683399c76678 by Dmitry Kazakov. Committed on 27/03/2025 at 13:20. Pushed by dkazakov into branch 'master'. Fix speed regression in Dissolve blendmode When porting to Qt6 qrand() was directly replaced to QRandomGenerator::global(), while the latter one uses a global mutex inside, which makes Dissolve blendmode work extremely slow. Hence we should use a local copy of a random generator to remove this bottle-neck. The bug was introduced by: https://invent.kde.org/graphics/krita/-/commit/af99e90fa8a4dbbb98059c3c8a4d72daffbbda1d M +14 -2 libs/pigment/compositeops/KoCompositeOpDissolve.h M +4 -3 plugins/tools/basictools/kis_tool_multihand.cpp M +2 -0 plugins/tools/basictools/kis_tool_multihand.h https://invent.kde.org/graphics/krita/-/commit/d211566997174204c611148941f8683399c76678