While I'm working on my Ray Tracer I found that causes the entire desktop to lose all the effects, task-manager function weirdly (missing some opened window), all desktop widgets to disappear and sometimes kwin to crash. Everything will comeback to normal after closing the SDL2 window. After more testing, I found that its SDL2 causing it. Even running simple SDL2 tutorial codes will resulting in the situation described above. Note that I seems to only happen with SDL2. Creating and running SDL1 windows does not cause the problem. My ray tracer: https://bitbucket.org/Seanstone5923/simpleray SDL2 tutorial code that I found that can reproduce the issue: http://lazyfoo.net/tutorials/SDL/02_getting_an_image_on_the_screen/index.php Reproducible: Always Steps to Reproduce: 1. Compile and run any SDL2 program (LazyFoo's tutoral or my Ray Tracer will do the job) 2. Weird things described above starts to happen Actual Results: Weird things described above starts to happen Expected Results: Work properly. - Happens on both Intel and Nvidia GPU(proprietary driver, not tested on Mesa), not tested on AMD GPUs. - No matter what composting back-end I'm using. It will happen. - Tested with SDL 2.0.4
This is expected behavior. SDL sets a hint to disable the compositor for better performance and KWin honors this. With Plasma 5.8 we introduced a GUI config option where you can disable this behavior in general. With Plasma 5.7 you can already create a window specific rule to disallow "Block Compositing". Create a rule for the window and select "Force" "No". That will ensure that the compositing does not get disabled.