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On Ubuntu 25.10 (Questing) with KDE Plasma Wayland session, screen
casting is completely broken. The zkde_screencast_unstable_v1 Wayland
protocol is not exposed by kwin_wayland, making any application relying
on the XDG Desktop Portal screencast interface (such as gnome-network-
displays, OBS, browser screen sharing, etc.) fail with CreateSession
failed.
-Environment
OS: Ubuntu 25.10 (Questing)
KWin version: 4:6.4.5-0ubuntu3
KDE Plasma version: 6.4.5
Session type: Wayland (XDG_SESSION_TYPE=wayland)
GPU: Intel Iris Xe Graphics (TGL GT2)
Mesa: 25.2.8-0ubuntu0.25.10.1
PipeWire: 1.4.7
-Steps to reproduce
1. Log into a KDE Plasma Wayland session on Ubuntu 25.10
2. Run wayland-info | grep zkde
3. Run strings /usr/bin/kwin_wayland | grep zkde_screencast
4. Try any screencasting application (gnome-network-displays, OBS screen
capture, browser screen share)
-Expected result
wayland-info should list zkde_screencast_unstable_v1 as an available Wayland
protocol, and screencasting should work.
-Actual result
wayland-info returns no result for zkde_screencast. strings
/usr/bin/kwin_wayland | grep zkde_screencast_unstable also returns nothing,
confirming the protocol is not compiled into the binary.
The xdg-desktop-portal-kde service logs the following repeatedly:
xdp-kde-screencast: zkde_screencast_unstable_v1 does not seem to be available
-Root cause identified
The zkde_screencast_unstable_v1 Wayland protocol string is entirely absent from
the kwin_wayland binary, despite the screencast plugin
(/usr/lib/x86_64-linux-gnu/qt6/plugins/kwin/plugins/screencast.so) being
present and listed as loaded by KWin:
$ strings /usr/bin/kwin_wayland | grep -i "zkde_screencast\|screencast_unstable"
(no output)
$ qdbus6 org.kde.KWin /Plugins \
org.freedesktop.DBus.Properties.Get \
org.kde.KWin.Plugins LoadedPlugins
...
screencast
...
The plugin loads but fails to register the Wayland protocol silently. KWin
produces no log output when the plugin is loaded/unloaded. No /ScreenCast D-Bus
object is created. No PipeWire video node is created for screencasting.
Note: the screencast.so plugin binary itself does contain the expected PipeWire
and screencast symbols (ScreencastV1Interface, ScreenCastStream, etc.),
suggesting the issue is in kwin_wayland itself being compiled without the
screencast Wayland protocol support.
-Workaround
None found. The bug is present regardless of whether PipeWire is started before
or after KWin.
-References
KDE bug 483137: "Screencast plugin fails if PipeWire is started after KWin"
(different root cause, but related symptom)
ProblemType: Bug
DistroRelease: Ubuntu 25.10
Package: kwin-wayland 4:6.4.5-0ubuntu3
ProcVersionSignature: Ubuntu 6.17.0-19.19-generic 6.17.13
Uname: Linux 6.17.0-19-generic x86_64
ApportVersion: 2.33.1-0ubuntu3
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: KDE
Date: Wed Mar 25 10:52:13 2026
InstallationDate: Installed on 2022-09-02 (1300 days ago)
InstallationMedia: Ubuntu 22.04.1 LTS "Jammy Jellyfish" - Release amd64
(20220809.1)
SourcePackage: kwin
UpgradeStatus: Upgraded to questing on 2025-10-24 (153 days ago)
** Affects: kwin (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug questing
--
kwin_wayland: zkde_screencast_unstable_v1 Wayland protocol missing from binary,
screencast completely non-functional
https://bugs.launchpad.net/bugs/2146379
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