LGUG2Z 4386003e30 feat(kwin): survive KWin restarting ...

KWin can go away under a running daemon while the session bus stays: it crashed,
or kwin_wayland --replace took its place. Its windows go with it, and so does
the bridge, which would have reported them closing; in the spikes the old
windows vanished without a single removed event. What the daemon does see is the
bus, so the thread that serves the connection watches NameOwnerChanged for
org.kde.KWin. When the name loses its owner, Table::compositor_lost marks every
window closed and returns a Destroy for each, so the window manager takes them
out of its layout, and their ids are not given out again. When the name has an
owner again, the daemon loads the bridge into the new KWin, trying for up to 15
seconds while KWin is not ready for it, and the bridge reports the new desktop
in a snapshot.

zbus does not end a held call when its caller leaves the bus, so the Poll of the
old bridge is still waiting when the new bridge calls, and it was woken first:
it took the commands for the new KWin and answered them to nobody.
vm-kwin-restart lost the tile of a window opened in the third KWin that way in
one run of three, and a recording of the bus showed the batch going to the old
bridge. A Poll held since before KWin last left the bus is answered with nothing
and passes its wake-up on to the next call, which a unit test holds.

The VM suite vm-kwin-restart (from the spike's spike7-resync) restarts the
headless KWin twice under a running daemon, through Kde.restart_kwin in the VM
library, and checks that the daemon sees KWin go, takes the old windows out of
its layout, loads the bridge into the new KWin, and tiles the windows that open
there.

2026-10-27 14:50:53 -07:00

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dev

feat(kwin): survive KWin restarting

2026-10-27 14:50:53 -07:00