Bug 368023

Summary: Window system freezes temporarily on application switch
Product: [Frameworks and Libraries] frameworks-kwindowsystem Reporter: Hamidreza Jafari <hamidrjafari>
Component: generalAssignee: Martin Flöser <mgraesslin>
Status: RESOLVED UNMAINTAINED    
Severity: major CC: hamidrjafari, kdelibs-bugs-null
Priority: NOR    
Version First Reported In: unspecified   
Target Milestone: ---   
Platform: Ubuntu   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: (OUTPUT) qdbus org.kde.KWin /KWin supportInformation

Description Hamidreza Jafari 2016-08-30 19:38:30 UTC 
Hi,

When switching to another application its window is drawn but just as it should be fully ready, input (mouse, keyboard, touchpad) for it is not responsive. Wait 5 to 10 seconds and it is responsive. Or send it a wakeup signal by Alt+tabbing and returning to it. After wake up, the input buffer (keystrokes etc if any) are flushed to the window.

Reproducible: Always

Steps to Reproduce:
1. Open a bunch of applications
2. Switch using Alt+tab randomly
3. It is the case that sometimes (more than %50) you have to wait for around 7 seconds to begin working with the application

Actual Results:  
You have to wait around 7 seconds until the activated window is responsive.

Expected Results:  
You should have been immediately able to communicate with the switched to application.

I have recently enabled activities (as virtual desktops) and also often connect to a second screen. It was not the case before this new setting.
Comment 1 Martin Flöser 2016-08-31 05:59:48 UTC 
could you please provide the output of:
qdbus org.kde.KWin /KWin supportInformation
Comment 2 Hamidreza Jafari 2016-08-31 18:03:59 UTC 
Created attachment 100868 [details]
(OUTPUT) qdbus org.kde.KWin /KWin supportInformation

Hi,
KWin information attached.
Comment 3 Martin Flöser 2016-09-02 05:54:22 UTC 
> KWin version: 5.5.5
> Qt Version: 5.5.1

Please upgrade to newer version of both Plasma an Qt. Especially Qt is rather old and known to have had issues. There is a fair amount of chance that the problem is fixed with newer versions. Also it's close to impossible for us to investigate for such old software.