Bug 511810

Summary:	Kwin switches to resizing if mouse moves to a subwindow outside the main window
Product:	[Plasma] kwin	Reporter:	ggarra13
Component:	wayland-generic	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED INTENTIONAL
Severity:	normal	CC:	xaver.hugl
Priority:	NOR
Version First Reported In:	unspecified
Target Milestone:	---
Platform:	openSUSE
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description ggarra13 2025-11-08 08:44:59 UTC

SUMMARY
KWin seems to assume subwindows cannot extend beyond the surface of the main window, compared to GNOME 48 that does.

STEPS TO REPRODUCE
1. Download mrv2-v1.4.5-Linux-amd64.rpm from https://github.com/ggarra13/mrv2/releases/tag/v1.4.5
2. Install it and start the application.  Go to Panels->Logs.  Try moving the log panel.  If the mouse goes out the main window, it turns into a resize icon incorrectly.
3. If you don't want to install anything, see: https://github.com/ggarra13/mrv2/discussions/444 (go below to where movies are posted)

OBSERVED RESULT
Moving the mouse outside the main window makes Kwin switch to resizing.

EXPECTED RESULT
The icon and dragging should not get overriden for resizing.  It should work like GNOME.

SOFTWARE/OS VERSIONS
See thread posted.

ADDITIONAL INFORMATION

Comment 1 Zamundaaa 2025-11-27 23:31:20 UTC

It is indeed expected that window contents are within the window geometry (https://gitlab.freedesktop.org/wayland/wayland-protocols/-/blob/6141e1154303dadd5c3e480bc4a16e26f1dcb2af/stable/xdg-shell/xdg-shell.xml#L514), you can't expect putting things outside of it to work or even show up at all - when the window decoration has rounded corners for example, KWin will clip subsurfaces to the window geometry.
That also applies to CSD, it working on Gnome is by coincidence, not something you can rely on.

If you want to allow users to drag such a subwindow out of its toplevel and interact with it outside of the main window, you could use the toplevel drag protocol for example.