Bug 371480

Summary:	SDL2 Apps causing desktop effects to disappear, task-manager function weirdly, all desktop widgets to disappear and sometimes kwin to crash
Product:	[Plasma] kwin	Reporter:	Martin Chang <marty188586>
Component:	general	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED WORKSFORME
Severity:	normal
Priority:	NOR
Version First Reported In:	5.7.5
Target Milestone:	---
Platform:	unspecified
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Martin Chang 2016-10-22 09:26:36 UTC

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

Comment 1 Martin Flöser 2016-10-22 09:36:49 UTC

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.