Public bug reported:
[Impact]
On Ubuntu 26.04, sharing a single window via the screencast portal fails
silently in every consumer (Firefox, Chromium). Whole-monitor sharing works;
picking a window never starts and the portal dies. 26.04 ships
xdg-desktop-portal-wlr 0.8.1 with PipeWire 1.6.x. The per-window path
(ext-image-copy-capture) negotiates a variable-framerate stream (framerate ==
0); 0.8.1 then emits an invalid maxFramerate and divides by zero, so
negotiation exhausts: core error res:-32 "no more output formats" → stream
error → portal exits.
[Fix]
Two upstream commits, both released in 0.8.2, backported as minimal DEP-3
patches (no version bump):
- 896cee82 — skip maxFramerate / guard division when framerate == 0 (the
negotiation fix)
- 459831374 — set READABLE/MAPPABLE buffer flags (prevents a client segfault
after negotiation succeeds)
Both touch only src/screencast/pipewire_screencast.c (+26 LoC). Debdiff
attached.
[Test Plan]
sway session, share a single window in Meet/Firefox. On 0.8.1 it never starts
and journalctl --user -u xdg-desktop-portal-wlr shows pipewire: fatal error
event from core; with the fix the window shares and the stream stays up.
Whole-monitor sharing must keep working.
[Where problems could occurr]
Confined to screencast format negotiation and buffer flags in the wlr portal;
cannot affect other portal backends or non-screencast interfaces. The framerate
change only wraps an existing maxFramerate constraint in if (framerate >
0) and guards a division; worst case would be screencast framerate
misreporting, visible in the same test. SPA_DATA_FLAG_MAPPABLE is
#ifdef-guarded. Both patches are verbatim cherry-picks shipped in upstream
0.8.2 and Debian 0.8.3.
** Affects: xdg-desktop-portal-wlr (Ubuntu)
Importance: Undecided
Status: New
** Tags: resolute
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https://bugs.launchpad.net/bugs/2159516
Title:
xdg-desktop-portal-wlr: single-window screencast fails on PipeWire
1.6.x ("no more output formats")
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