Bug 389405

Summary: When using multiple displays and setting a main display, new windows always open in leftmost one
Product: [Plasma] kwin Reporter: David <david.cortes.rivera>
Component: generalAssignee: KWin default assignee <kwin-bugs-null>
Status: RESOLVED NOT A BUG    
Severity: normal    
Priority: NOR    
Version First Reported In: unspecified   
Target Milestone: ---   
Platform: Debian testing   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:

Description David 2018-01-25 10:10:10 UTC 
When using multiple displays and setting one of them other than the leftmost (systemsettings5 --> Display and Monitor --> arrange them in a row) as the main display, all new windows still open in the leftmost display rather than the main one.

This is very annoying if you have two screens and want to use the right one rather than the left one as main display. 

Happens with KDE 5.10.5 (not available to select in the version menu when reporting this bug).
Comment 1 Martin Flöser 2018-01-25 15:52:25 UTC 
The option does not what you think it does. It does not have any influence on where the windows open. It is only for where the panel is.
Comment 2 David 2018-01-25 19:19:51 UTC 
It'd then be helpful if there were an option to configure new windows not to always open in the leftmost screen. It's quite common to use two screens together and not everyone wants the left one to be the main one.
Comment 3 Martin Flöser 2018-01-25 20:32:47 UTC 
Unfortunately that's mostly out of our control. I would love to be able to control it, because it would mean we can do sane things.

But the ICCCM standard describes what a window manager is allowed to do:
"To indicate that the size and position of the window (when a transition from the Withdrawn state occurs) was specified by the user, the client should set the USPosition and USSize flags, which allow a window manager to know that the user specifically asked where the window should be placed or how the window should be sized and that further interaction is superfluous. To indicate that it was specified by the client without any user involvement, the client should set PPosition and PSize ."

The idea is that for a user specified position the window manager does not "improve" the position. Unfortunately many windows set it although it's not user specified. We could ignore it, but then we would get bug reports about windows opening at random position and not at the last one.

With other words: we are in a position where we always lose.

On Wayland the situation is improved, there KWin positions the windows - always.