Bug 463460

Summary:	gtk_clipboard_set_with_owner() does not work on kwin wayland
Product:	[Plasma] kwin	Reporter:	Giovanni <giodev>
Component:	wayland-generic	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED WAITINGFORINFO
Severity:	normal	CC:	kde
Priority:	NOR
Version First Reported In:	5.26.4
Target Milestone:	---
Platform:	Ubuntu
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	GTK+ 3 example program to reproduce the bug.

Description Giovanni 2022-12-25 18:02:25 UTC

Created attachment 154820 [details]
GTK+ 3 example program to reproduce the bug.

Under kwin wayland, GTK+ 3 applications are unable to become clipboard owner via gtk_clipboard_set_with_owner() or provide data via callback.


STEPS TO REPRODUCE
Compile the attached cot.c file, instructions for compilations are at the beginning of the file.
Run "./cot" and then press the button on the main window. The application will try to become clipboard owner and provide a small string of text. But when you paste text in other windows, nothing is pasted, no clibpoard callbacks are called in cot.c.
See also this Remmina bug: https://gitlab.com/Remmina/Remmina/-/issues/2737
The example program shows that text is pasted with no problems under KDE+Xorg, GnomeShell+Wayland, GnomeShell+Xorg. But under KDE+Wayland text is not pasted to the destination application window.

OBSERVED RESULT
Nothing is pasted when the users try to paste. Callbacks of gtk_clipboard_set_with_owner() are not called.

EXPECTED RESULT
Application should become clipboard owner and provide clipboard content when the user pastes to another window.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: KUbuntu 22.10 + backports PPA to have latest plasma (5.26.4)

Comment 1 David Edmundson 2022-12-26 10:27:10 UTC

"UTF8_STRING" is not a valid mimetype.

I can see kwin copy that, but no client will think it has readable clipboard contents. 
If I change your example to "text/plain" or "text/plain;charset=utf-8" it works as expected. 

The way mimetype's name themselves is a bit random. We do have a translation of text mime names for x11 applications in kwin, as well as some translations inside the Qt wayland backend to make apps use the right standard.

Presumably mutter has a translation layer for wayland apps too, which helps hide this? 
But ultimately this is still a client bug and should be fixed at the root.

Can you confirm that this resolves the real problem in Remina?

Comment 2 David Edmundson 2022-12-26 10:28:36 UTC

FYI: if you open krunner (alt+space) and type "kwin" you can get a kwin debug console. 
There is a tab called "Clipboard in there" which can view contents.

Comment 3 Giovanni 2022-12-26 11:54:01 UTC

Thank you, changing UTF8_STRING to text/plain;charset=utf-8 worked.
You saved me ! ;)

But I need to do more regression testing to ensure  text/plain;charset=utf8 works also on older (max 4-6 years) Xorg. If it does not work, the application (Remmina) should expose two different formats to the clipboard, I think.