I can reproduce this on Zorin OS 18 (Ubuntu 24.04 base, mutter
46.2-1ubuntu0.24.04.18 with a Zorin rebuild), X11 session under xrdp
0.10 in a KVM VM. Before any fix, 4 of 6 first logins after boot stayed
black with the X cursor.
I attached gdb to gnome-shell in a black session and found a cause that
matches mutter issue #3804, which may be separate from the hardware
cursor problem in #4548 since this one also hits X11 and remote
sessions:
- The stage is mapped and realized, but clutter_stage_get_frame_counter() is 0
and the view's frame clock is idle.
- clutter_stage_schedule_update() runs on every mouse move but never reaches
clutter_frame_clock_schedule_update().
- ClutterStagePrivate.update_scheduled is TRUE while event_queue holds 242
unprocessed events, so every call returns early at "if (priv->update_scheduled
&& !first_event) return".
- Setting update_scheduled to FALSE from gdb and calling
clutter_stage_schedule_update() made the desktop paint immediately and drained
the queue.
So an early frame is discarded because the stage is not mapped yet,
update_scheduled stays TRUE, and input that arrives before the stage is
shown turns every later update into a no-op. That fits "moving the mouse
during login".
The upstream fix is commit 24083e1e5851a13b9d307d538d84f42091a7b220
("stage: Clear update_scheduled field when update discarded", MR !4152),
released in mutter 48.0 and backported to 47 in MR !4153. It is not in
the gnome-46 branch or in the Noble package.
I rebuilt the mutter 46.2 package with that one commit (test case left
out) and the problem is gone. After the patch, 6 of 6 first logins after
boot painted, 4 of them while I kept moving the mouse the whole time
during login. The backported patch is attached.
Could this commit be included in the Noble SRU?
** Patch added: "Backport of upstream commit 24083e1e to mutter 46.2 (Noble)"
https://bugs.launchpad.net/ubuntu/+source/mutter/+bug/2089709/+attachment/6011479/+files/fix-update-scheduled.patch
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https://bugs.launchpad.net/bugs/2089709
Title:
Ubuntu 24.04 sometimes logs in to a black screen if the mouse is moved
during login
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