Bug 501355

Summary:	Default window placement is unclear on X11 with Plasma 6
Product:	[Plasma] kwin	Reporter:	Riccardo Robecchi <sephiroth_pk>
Component:	multi-screen	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED DOWNSTREAM
Severity:	normal	CC:	anhollander516, john.kizer, nate, xaver.hugl
Priority:	NOR	Keywords:	regression, usability
Version First Reported In:	6.3.2
Target Milestone:	---
Platform:	Neon
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:
Attachments:	Screenshot of the setup

Description Riccardo Robecchi 2025-03-11 12:58:37 UTC

SUMMARY
It is not immediately clear what the rationale is behind which screen new windows open on: sometimes they open where the mouse is, sometimes they don't. Sometimes they open where the previously-active window is, sometimes they don't. The behaviour is erratic and difficult to predict. This also doesn't seem to be configurable. I have tried disabling "allow apps to remember the positions...", to no effect.
Under Plasma 5, there was a third-party script which made KWin always open windows in the screen where the mouse was; that allowed for a very consistent and predictable experience and it would be ideal to see something similar in Plasma 6 as the default.

STEPS TO REPRODUCE
1. Open an app (in my case, as an example, Vivaldi)

OBSERVED RESULT
The window is not opened on the active screen, i.e. where the mouse is.

EXPECTED RESULT
The window is opened on the active screen.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: KDE Neon
KDE Plasma Version: 6.3.2
KDE Frameworks Version: 6.11.0
Qt Version: 6.8.2

ADDITIONAL INFORMATION

Comment 1 Avraham Hollander 2025-03-16 00:59:08 UTC

In System Settings --> Window Behavior --> Advanced, set "Window placement" to "Under mouse." That should do what you want.

I'm also pretty sure the default in Plasma 6 is to center windows on the active display, but it may have been changed again.

Comment 2 Riccardo Robecchi 2025-03-16 08:53:06 UTC

Unfortunately it doesn't, hence my bug report.

Comment 3 John Kizer 2025-03-28 02:53:17 UTC

Hi - can you please specify:

* What your arrangement of displays and panels is - ex. Display 1 on the left with a panel, containing a task manager and application launcher; Display 2 on the right, empty by default (a screenshot across your desktops might be easiest here?)

* Where you are clicking to launch an application?

* Where it's actually appearing?

* Whether the same issue is observed with Qt-based KDE applications, like Dolphin, KWrite, etc.?

Thanks!

Comment 4 Riccardo Robecchi 2025-03-28 09:39:18 UTC

Created attachment 179811 [details]
Screenshot of the setup

Here is a description of my setup:
- display 1 (laptop's) is mirrored by display 2 and sits on the bottom; there is a small dock-like panel on the bottom (with icons-only task manager) and a full-width panel on top
- display 3 is on top of display 1/2 and has an identical panel setup, so a small dock-like panel on the bottom with icons-only task manager and a full-width panel on top.
You can also find a screenshot attached.

I am clicking on either of the icons-only task managers. It doesn't really matter as windows open on whichever display they feel like. As an example, I might click on the Vivaldi icon on the bottom screen, but the application always opens on the top one.
The issue is inconsistent with KDE applications; Kate works as expected, but Dolphin does not, as an example.

Comment 5 Zamundaaa 2025-05-26 15:25:22 UTC

This is an inherent issue with X11, as some applications just force their own placement. There's nothing we can do about it without breaking some applications.