https://bugs.kde.org/show_bug.cgi?id=413504
--- Comment #9 from andrei <akela1...@gmail.com> --- I really doubt somebody is reading this thread, but anyway I'd like to keep my research results somewhere... At first, some more information about my setup. ANGLE is used, Nvidia vertical sync disabled - no difference. Also, I'm testing on 4K monitor. With smaller monitor the lag is less noticeable, but still present. Image size is not so relevant, you can take 256x256 with the same effect. The main factor is canvas widget size. To be sure it's software problem, I run application on the same PC under Ubuntu - no lag. So, I tried to build from source and check what's taking so much GPU resource when mouse is just moving. It happened to be KisToolPaint::requestUpdateOutline with funny commentaries like: // DIRTY HACK ALERT: we should fetch the assistant's dirty rect when requesting the update, instead of just dumbly update the entire canvas! So, I commented out all that block and tried to run again. This time there was no GPU load during mouse move, but I started to notice the same effect when drawing with freehand brush. Apparently it does full canvas refresh too. I think, even the canvas rendering is not 100% optimized, this problem is mainly due to Nvidia Optimus brokenness and it is not possible to disable integrated GPU for me now. On ubuntu, iGPU is not used, and everything is fine (some other stuff is not fine, but it's not related to krita). Maybe I'll try to fix this in future, but it seems much easier way is to buy normal PC with GPU directly connected to monitor. -- You are receiving this mail because: You are watching all bug changes.
