Bug 395944

Summary: Multiple Document Mode (Subwindows) is slow when resizing subwindows
Product: [Applications] krita Reporter: Tyson Tan <tysontanx>
Component: GeneralAssignee: Krita Bugs <krita-bugs-null>
Status: RESOLVED INTENTIONAL    
Severity: normal CC: halla
Priority: NOR    
Version First Reported In: 4.1.0   
Target Milestone: ---   
Platform: Other   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:

Description Tyson Tan 2018-06-28 03:08:16 UTC 
When Multiple Document Mode is set to "Subwindows", resizing a subwindow by dragging its frame is now very slow. 

Tested with Krita 4.1.0 and krita-4.2.0-pre-alpha-411dc86-x86_64.appimage, under Manjaro Linux Gnome 17.1.10

Reproduce:
1) Set "Multiple Document Mode" to "Subwindows";
2) Open 2 different documents or Create 2 new documents;
3) Click the "Restore" button on top-right of Krita's workspace;
4) Now all opened documents are displayed as tiles;
5) Drag the boundary of a subwindow to resize it;
6) It's extremely slow.
Comment 1 Halla Rempt 2018-06-28 08:16:01 UTC 
Hm, I cannot reproduce that. What I do see is that the switch for showing the content of the subwindow when moving/resizing no longer works. When you resize the subwindows, is the content being redrawn while resizing?
Comment 2 Tyson Tan 2018-06-28 13:16:39 UTC 
It doesn't happen on Windows 10 either. On Windows 10, when I was dragging the subwindow's boundary, the subwindow grays out, and its canvas doesn't update during the process. And it doesn't lag at all.

However, no matter what Krita version/build I use on Manjaro GNOME 17.1.10, when I drag the subwindow's boundary, it doesn't gray-out, and its canvas constantly updating, slowing down the whole process. So I say your intuition was spot-on.

Maybe it's a specific case of GNOME vs Qt...?
Comment 3 Halla Rempt 2018-06-28 15:11:55 UTC 
That's quite possible! It might also explain why the relevant checkbox doesn't do anything on plasma, if the window manager can override it, while it works on Windows. But there's nothing we can do here, since that code is all in Qt or even lower in the stack. It's just not possible to smoothly redraw the contents of the window while resizing it.
Comment 4 Tyson Tan 2018-06-28 17:00:50 UTC 
OK! Thanks for the explanation. I personally don't use subwindow mode anyway, but I discovered it today when I was testing another bug.