This is (luckily!) unused, and it's inconvenient to have a toggle to
break the input model we are striving towards. Drop this function
and stick to the default behavior.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2099>
This looks like a relic of glReadPixels-based picking, the pointer
might well be outside redrawn areas, yet still require a device
update (e.g. in order to reflect the actor layout changes in the
"clear area" info).
Instead, always update all devices that are inside the view after
relayouts, the tracking on the need for that update is now done
on each ClutterStageView, instead of globally in the ClutterStage.
This theoretically fixes situations where pointers might miss
updating their "clear area" after the actor tree changed.
Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/2117
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2257>
The stage window is an interface, that added properties, that were only
then actually managed by MetaStageImpl. Shuffle things slightly, and let
the MetaStageImpl object deal with these things itself.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2014>
As ClutterGrab is a stack, the backend only cares about some grab
existing currently or not. Make it sure that we grab whenever we
go to >=1 grabs, and ungrab whenever we go to <1.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2068>
Dissociate clutter_stage_set_key_focus() from the actors focused
state, so that it obeys stage grabs. The key focus actor state may
also change due to grab changes, add the code to notify about this.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2068>
Emit crossing events whenever a grab coming or going would cause a
pointer/touchpoint to become inactive on their position. Depending
on whether the pointer lies inside the old or new grab widgets,
enter or leave events would be generated.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2068>
We will want to be more specific about the portions of the actor
hierarchy that receive this event, separate creation and emission
so each place does what is relevant.
However, this commit brings no functional changes.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2068>
These events are not meant to be ever silenced away, every actor
that is meant to receive one should do so. Make it sure that those
events cannot be stopped, despite the event signal handlers return
values.
This opens the debate about whether crossing events should be
ClutterEvents, since they are more and more uncommon at being one,
maybe this notification mechanism should be taken away from the
event machinery, but that's something for future refactors.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2068>
Hopefully, the one to make them all converge. This new ClutterGrab
represents a handle on a created grab. These are stacked, so grabs
can be overridden and remain inactive until there is a time that
they become active again, although undoing these early is optional.
These grabs are global, they do apply to all pointer, touchpoint
and keyboard foci.
At the moment, only the API to create and stack those is added,
the actual functionality is added in future commits.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2068>
A property for reversing the visible order of children is a bit odd.
It has also been unused by actual gnome-shell code since 2010, and the
somewhat related pack_start()/pack_end() API in GtkBox(Layout) is gone
in GTK4.
With that in mind, turn the property into a no-op and deprecate it,
so that it can be dropped next cycle.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2206>
This ensures they remain perfectly smooth regardless of how the
dispatch time has been adjusted/optimized/delayed/jittered.
Idea by Ivan Molodetskikh <yalterz@gmail.com>
For example, dragging a window on a 60Hz monitor:
BEFORE
delta(time_us) = 17014μs
delta(time_us) = 15998μs
delta(time_us) = 17006μs
delta(time_us) = 16975μs
delta(time_us) = 16001μs
delta(time_us) = 17002μs
delta(time_us) = 17006μs
delta(time_us) = 16004μs
AFTER
delta(time_us) = 16667μs
delta(time_us) = 16667μs
delta(time_us) = 16670μs
delta(time_us) = 16667μs
delta(time_us) = 16669μs
delta(time_us) = 16668μs
delta(time_us) = 16664μs
delta(time_us) = 16674μs
Caveat 1: Because we don't know a "next presentation time" on the first
frame, the interval between the first and second frame will usually be
different to the subsequent steady interval. So this change increases the
jitter of just frame 2, but eliminates jitter thereafter.
Caveat 2: `clutter_frame_clock_schedule_update_now` schedules updates
earlier than `clutter_frame_clock_schedule_update`. This means potentially
you could get multiple frames targeting the same "next presentation time".
That doesn't really change here though - we're dispatching at the same
times as we used to and just giving timelines a better vsync-aligned
timestamp now.
Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/25
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2161>
This won't change anything for 60Hz displays but higher refresh rate
users will benefit.
Using Nvidia EGLStreams on a 240Hz monitor for example (refresh interval
~4.1ms), the maximum render time allowed before dropping to 120Hz is now
3.6ms whereas it was previously 2.1ms.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2158>
This is notably necessary with transformations, since these don't
trigger allocation machinery, but may affect the actor under the
pointer.
Visible e.g. with GNOME Shell's "Application does not respond"
dialogs.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1915>
With Wayland handling all events as they come, this code now just
performs motion compression for events that will be handled by Clutter
widgetry.
The intent to opt tablets and styli out of motion compression was
early and fast client handling, since that is now covered in a generic
manner, this code is superfluous. We don't really need the extra events
for these devices in compositor widgetry either.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1915>
We essentially create those at the time they need to be handled, and
use shortcuts that avoid the event from being queued up. It's too much
of a short cut though, these events are also of interest to the Wayland
event handlers, e.g. to handle pointer state changes (e.g. repicks due
to the pick actor being destroyed) immediately, instead of at the next
event.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1915>
If we are still under the "clear area" of the pick actor, we forget
to update the coordinates. This is usually not needed, unless we
need to repick again for non-event circumstances (e.g. pick actor
is destroyed). This will ensure the right pointer coordinates are
used afterwards in those situations.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1915>
Traditionally, the next repaint would also involve picking, which
would correct the actor under the pointer. This now does not happen
out of the box, so we really are waiting for the next pointer event
here.
To avoid the pointer/cursor to lag behind, trigger an immediate
repick here, that will look up the new actor under the pointer
coordinates.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1915>
And resort to it first, unless we are told to ignore the cache
(e.g. after relayouts). This avoids further pick context operations
while the pointer is on the current actor.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1915>
This safe area is the region (in stage coordinates) where the pointer
is ensured to stay within the current actor. This is not used yet, but
will be used for optimizations in pointer picking.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1915>
These may be used for optimizations once we find the pick actor,
so picking can be avoided in areas we know didn't cross into
other actors. Nothing makes use of it yet though, just log these
so far.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1915>
Add a clutter_stage_pick_and_update_device() method that is the only
single entry point for updating a device position as seen by the
stage.
Also, update all callers to use it.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1915>
The clutter_stage_get_actor_at_pos() calls it almost 1:1 underneath
and is public API, we can have all callers use this, and stop using
this function outside of clutter-stage.c.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1915>
As event handling goes:
1) Events get generated and queued by the seat (from another thread in
native, in the same thread in X11)
2) The MetaBackend gets those events and forwards them to Clutter
via clutter_do_event()
3) The events get queued in the ClutterStage
4) At the time of processing a frame, the input events are processed,
5) Motion events are throttled, only the last is effectively handled
6) Events are filtered, wayland and WM handling happens here
7) Events maybe reach to clutter
This commit moves 6 to happen between 2 and 3. The end result is that:
- Throttling only applies to Clutter event handling, The wayland event
forwarding bits will handle the event stream as soon as it comes, as
timely as possible.
- WM event handling is also unthrottled, but that's more of a side
effect.
- This all still happens on the main thread, so there's the possibility
that other busy areas (e.g. relayout) temporarily block this event
forwarding.
- Sending events unthrottled inherently means more CPU, probably
dependent on input devices' frequency. The impact is not measured.
This should bring the best of both worlds with e.g. 1000Hz mice, wayland
clients get unthrottled events, while GNOME Shell UI still behaves like
it used to do.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1915>
If we wait till finalize, dispose will destroy the actor hierarchy
and cause untimely repicks. Ensure to free the pointer/touch info
first, so the hooked signal callbacks are gone when destroying the
actors.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1915>
In the case a11y is required, the screen reader is very much
interested in getting an uninterrupted flow of key events. It attempts
so by setting a ::captured-event callback on the ClutterStage, but
that falls short with our MetaDisplay event handler, as clutter events
can be stopped before a11y gets a chance to see them.
This kind of selective amnesia wrt key events is not new, in X11 those
go unheard of by the WM as long as a client is focused and no grabs hold,
so it is clients' responsibility to talk with AT bridge.
This commit doesn't yet change that for X11, but we can do this right
away from the compositor on Wayland, and without any chance to be
tampered by clients.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1328>
If one would end up with an actor attached to mapped actor, where the
attached actor doesn't itself have an up to date stage view list while
listening on the stage for updating, when clearing the stage views of
the list, anything that would query the stage views list at this time
would end up accessing freed memory.
This could happen if
1) An actor was added to a newly created container actor attached to
the stage
2) The actor got a timeline attached to it
3) The actor was moved to a container that already was mapped
4) A hotplug happened
After (1) both the container and actor would not have any stage views.
After (2) the timeline would listen on the stage for stage views
updates. After (3) the actor would still listen on the stage for stage
views updates. When (4) happened, the actor would be signalled when the
stage got its stage view cleared, at which point it would traverse up
its actor's tree finding an appropriate stage view to base its animation
on. The problem here would be that it'd query the already mapped
container and its yet-to-be-cleared stage view list, resulting in
use-after free, resulting in for example the following backtrace:
0) g_type_check_instance_cast ()
1) CLUTTER_STAGE_VIEW ()
2) clutter_actor_pick_frame_clock ()
3) clutter_actor_pick_frame_clock ()
4) update_frame_clock ()
5) on_frame_clock_actor_stage_views_changed ()
6) g_closure_invoke ()
7) signal_emit_unlocked_R ()
8) g_signal_emit_valist ()
9) g_signal_emit ()
10) clear_stage_views_cb ()
11) _clutter_actor_traverse_depth ()
12) _clutter_actor_traverse ()
13) clutter_actor_clear_stage_views_recursive ()
14) clutter_stage_clear_stage_views ()
...
Avoid this issue by making sure that we don't emit 'stage-views-changed'
signals while the actor tree is in an invalid state. While we now end up
traversing tree twice, it doesn't change the Big-O notation. It has not
been measured whether this has any noticible performance impact.
Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/1950
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2025>
This does two things to frown upon:
- Modifies ClutterEvent structs, while the effort is to have those
completely opaque, and readonly after creation from the input
thread side.
- Stores state in the ClutterInputDevice struct, event though those
are also considered static after creation, managed by the input
thread, etc.
Stop doing that. This makes all events just forwarded as-is in
the ClutterStage/clutter-main.c code.
Handling of click count sounds like material for a ClutterGestureAction
(or perhaps ClutterClickAction), all of both callers now do it in place
at the moment, while gestures lack a better state tracking and management.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2024>
This will not try the captured-event shenanigans to emulate grab
behavior, instead relying on event delivery being influenced by
other grab mechanisms.
While at it, improve handling of additional touchpoints by
cancelling the click action right away, as the differences in
event handling make this unwanted behavior surface.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2024>
By default, the pan action performs matrix translations on the
child widget. Nobody wants that (or, nobody wants *just* that).
It's cleaner not to mix mechanism and effect in ClutterGestureAction
subclasses, so drop this base implementation, and change the signal
accumulator so it's more similar to event signals (not that it's
used any longer, anyway).
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2024>
This warning is actually dead code, since should_be_mapped and
must_be_realized are always set to the same value, so it does not
make sense to check for "a && !b".
Turn this into an assert so we avoid the dead branch, but do not
remove the variable duplication so the more aptly named variable
is used where it belongs, for clarity.
CID: #1506254
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2061>
It was a feature relevant for when Clutter was an application toolkit
that wanted the application window to communicate a minimum size to the
windowing system.
Now, clutter is part of the windowing system component, so this feature
doesn't make any sense, so remove it.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2002>
This feature was configured depending on whether the Cogl backend
reported COGL_WINSYS_FEATURE_MULTIPLE_ONSCREEN or not. All cogl backends
do report this, so any code handled the 'static' case were never used.
While we only ever use one stage, it's arguable more correct to
consilidate on the single stage case, but multiple stages is something
that might be desirable for e.g. a remote lock screen, so lets keep this
logic intact.
This has the side effect of completely removing backend features, as
this was the only left-over feature detection that they handled.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2002>
This changes the setup phase of clutter to not be result of calling an
init function that sets up a few global singletons, via global singleton
setup vfuncs.
The way it worked was that mutter first did some initial setup
(connecting to the X11 server), then set a "custom backend" setup vfunc
global, before calling clutter_init().
During the clutter_init() call, the context and backend was setup by
calling the global singleton getters, which implicitly created the
backend and context on-demand.
This has now changed to mutter explicitly creating a `ClutterContext`
(which is actually a `ClutterMainContext`, but with the name shortened to
be consistent with `CoglContext` and `MetaContext`), calling it with a
backend constructor vfunc and user data pointer.
This function now explicitly creates the backend, without having to go
via the previously set global vfunc.
This changes the behavior of some "get_default()" like functions, which
will now fail if called after mutter has shut down, as when it does so,
it now destroys the backends and contexts, not only its own, but the
clutter ones too.
The "ownership" of the clutter backend is also moved to
`ClutterContext`, and MetaBackend is changed to fetch it via the clutter
context.
This also removed the unused option parsing that existed in clutter.
In some places, NULL checks for fetching the clutter context, or
backend, and fetching the cogl context from the clutter backend, had to
be added.
The reason for this is that some code that handles EGL contexts attempts
to restore the cogl EGL context tracking so that the right EGL context
is used by cogl the next time. This makes no sense to do before Cogl and
Clutter are even initialized, which was the case. It wasn't noticed
because the relevant singletons were initialized on demand via their
"getters".
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2002>
This one is a trivial wrapper around clutter_actor_get_children(), so just
use that in the two places where clutter_container_get_children() is used,
and remove clutter_container_get_children().
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2057>
Right now we damage the stage even if an actor is not mapped, for
example in the overview.
Stop doing so, reducing over-paint significantly in some situations.
Clones will still do stage damage on their own.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2035>
ClutterText implements its own get_paint_volume() with its own cache,
but was not invalidating the actor paint volume when when it has
changed. This sometimes could result in labels, especially quickly
changing ones, using the old paint volume which either would cut off the
label or leave parts of the old label on screen.
Fixes: https://gitlab.gnome.org/GNOME/mutter/-/issues/1943
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2006>
This mode is passed along by the ClutterInputMethod, the
ClutterInputFocus will preserve it and ensure it is honored
whenever the IM is being reset.
This mode is immediate. The ClutterInputFocus commits the
text directly without queueing a CLUTTER_IM_COMMIT event.
This is important so events are serialized in the right order
in the wayland implementations (i.e. commit before wl_pointer.press).
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1940>
In line with GTK, the input method context should be reset when clicks
are handled by the ClutterInputFocus user. The reset action can then
either clear or commit the preedit text, as configured by the IM module.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1940>
Make sure that when we've recreated views that we'll actually paint a
new frame for it. This was very rarely a problem, as views tend to
result in getting damage etc being queued as side effects of various
things, like layout, but e.g. when running certain tests, this might not
happen. There is no situation where we want to create a new view that
should remain unpainted, so just make sure we initialize it to become up
to date.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1947>
This code sneaked unconditionally, even though we can disable
tracing code with -Dprofiler=false. Add some COGL_HAS_TRACING
checks so that this code is also optionally built.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1951>
Will be used to trace a lot more, and with more details, and thus may
have a larger impact on what is actually measured. This potential impact
is the reason for enabling only when needed.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1700>
The failure to allocate was not properly handled, causing crashes later
on due to the offscreen being NULL.
#0 cogl_gl_framebuffer_bind (target=36160, gl_framebuffer=0x0)
#1 _cogl_driver_gl_flush_framebuffer_state (...)
#2 cogl_context_flush_framebuffer_state (read_buffer=0x55f48f386780, draw_buffer=0x55f48f386780, ...)
#3 cogl_framebuffer_clear4f (framebuffer=0x55f48f386780, ...)
#4 clutter_layer_node_pre_draw (...)
#5 clutter_paint_node_paint (...)
...
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1942>
We only listen to it for 2 settings (drag threshold, double click
time), and we already have the stock ClutterSettings object tracking
the source of these. This code is redundant.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1862>
Not sure how to update the damage or redraw clip or something; at least
this works properly when under a constantly-redrawing window, which is
ok for debugging purposes.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1762>
Max render time shows how early the frame clock needs to be dispatched
to make it to the predicted next presentation time. Before this commit
it was set to refresh interval minus 2 ms. This means Mutter would
always start compositing 14.7 ms before a display refresh on a 60 Hz
screen or 4.9 ms before a display refresh on a 144 Hz screen. However,
Mutter frequently does not need as much time to finish compositing and
submit buffer to KMS:
max render time
/------------\
---|---------------|---------------|---> presentations
D----S D--S
D - frame clock dispatch
S - buffer submission
This commit aims to automatically compute a shorter max render time to
make Mutter start compositing as late as possible (but still making it
in time for the presentation):
max render time
/-----\
---|---------------|---------------|---> presentations
D----S D--S
Why is this better? First of all, Mutter gets application contents to
draw at the time when compositing starts. If new application buffer
arrives after the compositing has started, but before the next
presentation, it won't make it on screen:
---|---------------|---------------|---> presentations
D----S D--S
A-------------X----------->
^ doesn't make it for this presentation
A - application buffer commit
X - application buffer sampled by Mutter
Here the application committed just a few ms too late and didn't make on
screen until the next presentation. If compositing starts later in the
frame cycle, applications can commit buffers closer to the presentation.
These buffers will be more up-to-date thereby reducing input latency.
---|---------------|---------------|---> presentations
D----S D--S
A----X---->
^ made it!
Moreover, applications are recommended to render their frames on frame
callbacks, which Mutter sends right after compositing is done. Since
this commit delays the compositing, it also reduces the latency for
applications drawing on frame callbacks. Compare:
---|---------------|---------------|---> presentations
D----S D--S
F--A-------X----------->
\____________________/
latency
---|---------------|---------------|---> presentations
D----S D--S
F--A-------X---->
\_____________/
less latency
F - frame callback received, application starts rendering
So how do we actually estimate max render time? We want it to be as low
as possible, but still large enough so as not to miss any frames by
accident:
max render time
/-----\
---|---------------|---------------|---> presentations
D------S------------->
oops, took a little too long
For a successful presentation, the frame needs to be submitted to KMS
and the GPU work must be completed before the vblank. This deadline can
be computed by subtracting the vblank duration (calculated from display
mode) from the predicted next presentation time.
We don't know how long compositing will take, and we also don't know how
long the GPU work will take, since clients can submit buffers with
unfinished GPU work. So we measure and estimate these values.
The frame clock dispatch can be split into two phases:
1. From start of the dispatch to all GPU commands being submitted (but
not finished)—until the call to eglSwapBuffers().
2. From eglSwapBuffers() to submitting the buffer to KMS and to GPU
work completing. These happen in parallel, and we want the latest of
the two to be done before the vblank.
We measure these three durations and store them for the last 16 frames.
The estimate for each duration is a maximum of these last 16 durations.
Usually even taking just the last frame's durations as the estimates
works well enough, but I found that screen-capturing with OBS Studio
increases duration variability enough to cause frequent missed frames
when using that method. Taking a maximum of the last 16 frames smoothes
out this variability.
The durations are naturally quite variable and the estimates aren't
perfect. To take this into account, an additional constant 2 ms is added
to the max render time.
How does it perform in practice? On my desktop with 144 Hz monitors I
get a max render time of 4–5 ms instead of the default 4.9 ms (I had
1 ms manually configured in sway) and on my laptop with a 60 Hz screen I
get a max render time of 4.8–5.5 ms instead of the default 14.7 ms (I
had 5–6 ms manually configured in sway). Weston [1] went with a 7 ms
default.
The main downside is that if there's a sudden heavy batch of work in the
compositing, which would've made it in default 14.7 ms, but doesn't make
it in reduced 6 ms, there is a delayed frame which would otherwise not
be there. Arguably, this happens rarely enough to be a good trade-off
for reduced latency. One possible solution is a "next frame is expected
to be heavy" function which manually increases max render time for the
next frame. This would avoid this single dropped frame at the start of
complex animations.
[1]: https://www.collabora.com/about-us/blog/2015/02/12/weston-repaint-scheduling/
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1762>
This fixes a warning/error:
In function 'parse_settings',
inlined from 'read_settings' at ../clutter/clutter/x11/xsettings/xsettings-client.c:398:25:
../clutter/clutter/x11/xsettings/xsettings-client.c:202:13: error: 'buffer.byte_order' may be used uninitialized [-Werror=maybe-uninitialized]
202 | if (buffer.byte_order != MSBFirst &&
| ~~~~~~^~~~~~~~~~~
This is needed to bump the CI image from F33 to F34, which includes a
upgraded compiler.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1865>
A simply wrapper around `CoglTexture`, making it easy to reuse
content without roundtrip from GPU to CPU memory and back.
It optionally takes a clip rectangle which is implemented by
creating a `CoglSubTexture`. A limitation here is that floating
point clips are not supported.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1888>
When using `CLUTTER_PAINT=damage-region` highlighting was conspicuously
absent during fullscreen animations like entering or leaving the
overview. That was because `queued_redraw_clip` was empty, because it
had been initialized from `redraw_clip == NULL` (full stage redraw).
Now we paint the damage region as the full view (which it is) instead
of nothing at all.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1890>
This commit adds scaling support to clutter_stage_capture_into, which
is currently used when screencasting monitors. This is supposed to
fix graphical issues that arise when using fractional scaling.
Fixes#1131
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1855>
All pointer a11y is a fabrication of Clutter backend-independent
code, with the help of a ClutterVirtualInputDevice and with some
UI on top.
On the other hand, MetaInputSettings is a backend implementation
detail, this has 2 gotchas:
- In the native backend, the MetaInputSettings (and pointer a11y
with it) are initialized early, before the ClutterSeat core
pointer is set up.
- Doing this from the MetaInputSettings also means another dubious
access from the input thread into main thread territory.
Move the pointer a11y into ClutterSettings, making this effectively
backend-independent business, invariably done from the main thread
and ensured to happen after seat initialization.
Fixes: https://gitlab.gnome.org/GNOME/mutter/-/issues/1765
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1849>
Since commit d2f8a30625 we use Graphene to union paint volumes, it
turns out a quite severe issue snuck in during review of that MR though:
Unioned paint volumes (so paint volumes of any actors with children) now
have negative heights. Once projected to 2d coordinates they luckily are
correct again, which is why everything is still working.
The problem is that obvious once looking closer: For the y coordinates
of the unioned paint volume we confused the maximum and the minimum
points and simply used the wrong coordinates to create the unioned paint
volume.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1827>
The graphene functions used by clutter for picking assume that boxes are
inclusive in both there start and end coordinates, so picking at y
coordinate 32 for an actor with the height 32 placed at y coordinate 0
would still be considered a hit. This however is wrong as 32 is the
first position that is not in the actor anymore.
Usually this would not be much of a problem, because motion events are
rarely ever at exactly these borders and even if they are there will be
another motion event soon after. But since actors in gnome-shell usually
are aligned with the pixel grid and on X11 enter/leave events are
generated by the X server at integer coordinates, this case is much
more likely for those.
This can cause issues with Firefox which when using client side
decorations, still requests MWM_DECOR_BORDER via _MOTIF_WM_HINTS to have
mutter draw a border + shadow. This means that the Firefox window even
when using CSD is still reparented. For such windows we receive among
others XI_RawMotion and XI_Enter events, but no XI_Motion events. And
the raw motion events are discarded after an enter event, because that
sets has_pointer_focus to TRUE in MetaSeatX11. So when moving the cursor
from the panel to a maximized Firefox window the last event clutter
receives is the enter event at exactly integer coordinates. Since the
panel is 32px tall and the generated enter event is at y position 32,
the picking code will pick a panel actor and the focus will remain on it
as long as the cursor does not leave the Firefox window.
Fix this by excluding the bottom and right border of a box when picking.
Fixes https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/4041
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1842>
Turns out ClutterClones need a bit of extra handling as always, there's
currently nothing that invalidates a clones paint volume when the source
actors paint volume changes.
Since ClutterClones get_paint_volume() implementation simply takes the
source actors paint volume and returns that, we should make sure they
are kept in sync and invalidate the clones paint volume as soon as the
source actor gets its PV invalidated.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1829>
Updating the last_paint_volume while painting has proven itself to be
quite prone to issues: First we had to make sure actors painted by
offscreen effects get their last_paint_volumes updated correctly (see
0320649a1c), and now a new issue turned up
where we don't update the paint volumes while a fullscreen unredirect is
happening.
To stop those issues from happening and to lay the foundation for using
the last_paint_volume for other things, update the last_paint_volume in
a separate step before painting instead of doing it in
clutter_actor_paint().
To save some resources, avoid introducing another traversal of the
scenegraph and add that step into the existing step of updating the
stage_views lists of actors. To properly update the paint volumes, we
need to do that after finishing the queued redraws, which is why we move
clutter_stage_maybe_finish_queue_redraws() to happen before the new
clutter_stage_finish_layout().
Fixes https://gitlab.gnome.org/GNOME/mutter/-/issues/1699
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1773>
The priv->paint_volume field of ClutterActor stores the cached paint
volume in the actors local coordinate system. It consist of the actors
paint volume itself and the union of all children paint volumes.
We want to invalidate those cached paint volumes according to the
following rules:
- If an actors transformation matrix changes, all paint volumes of the
parent-tree need to be invalidated (that's because the parent-volumes
have unioned the actors paint volume). Our own paint volume does not
need invalidation since the transformation matrix is not applied to it.
- If an actors allocation-size changes, its own paint volume and all the
volumes of the parent-tree need to be invalidated. That's because the
allocation-size is used as the size of the paint volume.
- If a clip gets set or clip_to_allocation gets enabled for an actor,
its own paint volume and all the volumes of the parent-tree need to be
invalidated. That's because the clip is factored in when creating the
paint volume.
So far we did this invalidation in various places and the invalidation
up the parent-tree happened inside clutter_actor_real_queue_relayout().
We did not invalidate on changes to the actors transformation matrices
and the invalidation in clutter_actor_real_queue_relayout() was more
like a "big hammer" that probably invalidated unnecessarily a few times.
So introduce proper infrastructure to invalidate those cached paint
volumes of actors only in the cases where they actually need to be
invalidated. To do that, we reuse the transform_changed() function and
introduce a new function queue_update_paint_volume() that invalidates
the paint volumes up the actor tree.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1773>
ClutterActors can override the get_paint_volume() vfunc in case they
draw outside the allocation. That's used by a bunch of actors, for
example ClutterText or StViewport in gnome-shell.
In case of StViewport, the paint volume returned depends on the value of
the StAdjustment, which means when we start to cache paint volumes more
agressively in ClutterActor, we'll need to add API that allows
StViewport to invalidate the paint volume. So introduce
clutter_actor_invalidate_paint_volume() to invalidate the cached paint
volume.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1773>
The action might not have been triggered yet, as per its trigger
threshold. This doesn't mean we shouldn't reset the point(s) accumulated
so far.
This fixes those touchpoints persisting after disable/enable, thus
making gesture recognition fail from there on.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1791>
We might want to perform distance/threshold checks in the ::prepare
vfunc, but we didn't record the last motion event yet. This used to
give a delta of 0/0 between the press and last motion coordinates,
despite the ClutterGestureAction having a trigger threshold. This
happens no longer.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1791>
The usage of clutter_actor_get_preferred_width/height() for building the
pick box can trigger Clutters size negotiation machinery in case the
allocation of the actor is invalidated, with commit 82f3bdd1 we worked
around that by excluding actors with invalidated allocations from
picking.
There's no need to do that though, when picking we always want to
operate on the last known allocation of the actor, since that is what's
actually painted on the screen.
So instead of not picking at all when an actors allocation is
invalidated, just use the size of the last allocation. We still have to
factor in one extra case, that's when an actor hasn't gotten any
allocation yet: In that case we want to exclude the actor from picking
since the actor is not on the screen yet.
This fixes a regression introduced by the commit mentioned above where
picking wouldn't work on windows that have just been resized.
https://gitlab.gnome.org/GNOME/mutter/-/issues/1674
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1784>
As documented in g_once_init_enter(): "While @location has a volatile qualifier,
this is a historical artifact and the pointer passed to it should not be
volatile.". And effectively this now warns with modern glibc.
Drop the "volatile" qualifier from these static variables as it's expected.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1785>
Some events such as the proximity one requires a device to be set before
we process them, so ensure we process the event details after we've
added the device to the seat.
This may lead to handle a device-removed signal before the clutter event
but it's anyways not different from what we did before commit 012c0a18
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1779>
The CallyStage objects lifetime is tied to the stage, so if we add a
weak pointer to it, we won't be able to remove it, as we would try to do
so not until the stage itself is being disposed, at which point removing
it fails. However, not removing it will make the stage try to clean up
the weak refs, and since it does this more or less directly after
freeing the cally stage, it ends up writing NULL to freed memory,
causing memory corruption.
Fix this by avoiding adding the weak pointer when that pointer is to the
stage.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1775>
This adds a test framework that makes it possible to compare the result
of painting a view against a reference image. Test reference as PNG
images are stored in src/tests/ref-tests/.
Reference images needs to be created for testing to be able to succeed.
Adding a test reference image is done using the
`MUTTER_REF_TEST_UPDATE` environment variable. See meta-ref-test.c for
details.
The image comparison code is largely based on the reference image test
framework in weston; see meta-ref-test.c for details.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1698>
Since commit 2ceac4a device-related X11 events aren't processed anymore,
causing the input settings not to handle the devices.
This is due to the fact that we may never call clutter_seat_handle_event_post()
for such events.
While this is always happening for the native backend, it doesn't happen in
X11 because the events are removed from the queue as part of
meta_x11_handle_event(), and thus no event was queued to the stage by the
backend events source.
This also makes sure that the event post handler is called after the
event is actually processed, and not before an event is queued.
Fixes: https://gitlab.gnome.org/GNOME/mutter/-/issues/1564
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1769>
To make the double buffered shadow buffer damaged tiles detection
feasable, a new EGL extension is needed for creating FBO's backed by
a custom CPU memory buffer, instead of DMA buffers, as DMA buffers can
be very slow to read, much slower than just painting the shadow buffer
directly.
Leave the code there, since such an EGL extension is intended to be
added, but hide it behind an env var so that it isn't enabled by
accident.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1724>
Regarding the sequence = 0 fallback: in some cases (moving a cursor
plane on atomic amdgpu) we get sequence = 0 in the page flip callback.
This seems like an amdgpu bug, so work around it by assuming a sequence
delta of 1 (it is equal to 1 because of the sequence != 0 check above).
Sequence can also legitimately be 0 if we're lucky during the 32-bit
overflow, in which case assuming a delta of 1 will give more or less
reasonable values on this and next presentation, after which it'll be
back to normal.
Sequence is also 0 on mode set fallback and when running nested, in
which case assuming a delta of 1 every frame is the best we can do.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1484>
This concerns only the cases when the presentation timestamp is received
directly from the device (from KMS or from GLX). In the majority of
cases this timestamp is already MONOTONIC. When it isn't, after this
commit, the current value of the MONOTONIC clock is sampled instead.
The alternative is to store the clock id alongside the timestamp, with
possible values of MONOTONIC, REALTIME (from KMS) and GETTIMEOFDAY (from
GLX; this might be the same as REALTIME, I'm not sure), and then
"convert" the timestamp to MONOTONIC when needed. An example of such a
conversion was done in compositor.c (removed in this commit). It would
also be needed for the presentation-time Wayland protocol. However, it
seems that the vast majority of up-to-date systems are using MONOTONIC
anyway, making this effort not justified.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1484>
KMS and GLX device timestamps have microsecond precision, and whenever
we sample the time ourselves it's not the real presentation time anyway,
so nanosecond precision for that case is unnecessary.
The presentation timestamp in ClutterFrameInfo is in microseconds, too,
so this commit makes them have the same precision.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1484>
A flag indicating whether the presentation timestamp was provided by
the display hardware (rather than sampled in user space).
It will be used for the presentation-time Wayland protocol.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1484>
ClutterText has a bit of a mess around its signalling of changes to the
cursor position: There's the position (deprecated) and cursor-position
property, and there's the cursor-changed and cursor-event (deprecated)
signal. The two properties are supposed to be notified when the cursor
position changes, and the two signals are notified when the cursor
position or size changes.
Now the properties notifications and the signals get fired in two very
different places: The two properties are notified in
clutter_text_set_cursor_position(), while the signals are fired during
the paint cycle when we figured out the final cursor position. The
latter is a pretty bad idea, nobody expects such a signal to be fired
during painting, and also changes to the text that are done in the
signal handler will only be applied on the next paint.
Now StEntry listens to cursor position changes via cursor-changed and
invalidates its text shadow, but since the signal is only notified
during the paint, the old text shadow will still get applied. To fix
this, also emit the cursor-changed signal when we notify the
cursor-position property.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1757>
This removes the responsibility of tracking these from the backend to
the base object. The backends are instead responsible for calling the
function to update the values.
For the native backend, it's important that this happens on the correct
thread, so each time either of these states may change, post a idle
callback on the main thread that sets the, at the time of queuing said
callback, up to date state. This means that things on the main thread
will always be able to get a "new enough but not too new" state when
listening on the 'notify::' signals and getting the property value
after.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1739>
In an x11 session, we don't receive motion events from X when the
pointer is above a window. Since commit 734a1859 we only do picking on
motion events though, which means when clicking the mouse to focus a
window, we don't repick and might still think the pointer is hovering
above another window or actor, ending up not focussing the window.
Fix this by always repicking on BUTTON_PRESS events. While this is not
necessary in the wayland session, button presses happen rarely compared
to motion events, so it's not a performance regression to do it in
Wayland sessions, too.
Fixes https://gitlab.gnome.org/GNOME/mutter/-/issues/1660
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1752>
ClutterText allows setting a custom PangoAttrList, and St uses that to
set the text style it's reading from CSS. One style St enforces using
this mechanism is the text color and setting the text color should
obviously not affect the size of the layout. ClutterText does queue a
relayout in that case though because it unconditionally queues a
relayout when updating the PangoAttrList.
We can avoid this relayout by reusing an optimization ClutterText has:
clutter_text_queue_redraw_or_relayout() will only queue a relayout if
the requested size of the layout changed.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1750>
With 734a185915 an optimization was
introduced to only pick on events which can actually cause the pointer
to move. In case of touch events, the first event (TOUCH_BEGIN) will
already move the touchpoint though, and we'll send our crossing
CLUTTER_ENTER event to the actor this TOUCH_BEGIN happened on.
So fix this embarrassing bug that caused touch input to break by also
picking to find an event-actor on TOUCH_BEGIN events.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1733>
Aside from ENTER/LEAVE, there are only two kinds of events that can move
the pointer, motion events and touch update events. Everything else
keeps the pointer at it's current position.
The reason we pick inside _clutter_process_event_details() is that we
want to set the event actor. Now if an event can't move the pointer, it
also can't change the event actor (well, it can subsequently by
triggering changes to the scenegraph, but that's handled elsewhere), so
there's no need to pick a new event actor when we get those events.
Instead, simply reuse the actor that's already associated with the
current input device as the event actor for non MOTION/TOUCH_UPDATE
events.
Events where a device or a touchpoint goes away (like DEVICE_REMOVED or
TOUCH_END/CANCEL) also affect picking, they don't need a repick, but
instead the actor associated with the device/touchpoint needs to be
unassociated. This is ensured by invoking remove_device_for_event() on
those events and will not be affected by this change.
This should improve performance while scrolling quite a bit, since
scroll events come in unthrottled and we now no longer do a repick on
each one of those.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1729>
We might have a stage view listener attached to the stage itself if the
actor didn't have a suitable frame clock when the actor was associated
with the timeline. We'd then listen to stage-views-changed signals on
the stage itself to be able to attach to a frame clock when one
appeared.
What went wrong is that if an actor that didn't have a frameclock was
associated with a timeline, but then destroyed, the timeline would
disassociate itself from the actor, but it'd still listen on the
stage-views-changed signal on the stage. This would be in itself
harmless, until the timeline itself is destroyed, as at this point, it
wouldn't clean up the stage-views-changed listener on the stage, as it's
assumed to only be valid when there is an actor attached.
Fix this issue by cleaning up the stage's stage-views-changed listener
when the actor is destroyed, as we wouldn't be able to make use of it by
then anyway.
Closes: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3323
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1719>
Before this commit, next presentation time could end up behind now_us or
ahead of now_us depending on how presentation times happened to be
aligned relative to integer multiples of refresh_interval_us. It's not
clear whether this was originally intended because even if it the next
presentation time ends up behind now_us, it is moved ahead by a while
loop down below in this function.
Even though this difference in behavior didn't really matter, it made
reasoning about the subsequent branches more complex. It would also
potentially introduce bugs if the logic was to be modified. So this
commit makes it so next presentation time is always ahead of now_us.
It also adds a comment with a graph detailing the computations, and
adjusts the variable names to drop unfortunate terminology mistakes.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1707>
Last presentation time is mainly used to make sure predicted
presentation time is aligned with display refreshes. Even if it went
back in time, there will be no issue as next presentation time takes
current time into account. Synthetic presentation time is not exactly
aligned with display refreshes, so using it would only result in
inconsistent animations.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1707>
When a transfer request is done to the MetaSelectionSourceRemote source,
it's translated to a SelectionTransfer signal, which the remote desktop
server is supposed to respond to with SelectionWrite.
A timeout (set to 15 seconds) is added to handle too long timeouts,
which cancels the transfer request.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1552>
Previously we were setting the FBO's viewport to be the same dimensions as
the stage itself for compatibility. This works for most cases, but not if
the actor is larger than the stage. In that case it could cause excessive
clipping if the actor's transformed screen position was negative, which
is seen in https://gitlab.gnome.org/GNOME/gnome-shell/issues/2087
Also if a small actor paints to its negative dimensions (like a box-shadow)
then we might be missing those pixels on the left or top, even though
they're inside the paint volume.
Now we set the viewport dimensions to match the area we're actually
rendering so the FBO contents are never over or under clipped.
Fixes: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3068
Although if you try using shadows larger than that (like in
gnome-shell#1090) then you will also need gnome-shell!1417.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1053>
We had been doing it backwards as far back as e3966882e8 which meant
that we were translating by `fbo_offset / resource_scale` stage units
instead of just `fbo_offset`.
Because `fbo_offset` is in stage units already, it's not scaled and so
needs to be applied after the unscaling from texels to stage units.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1053>
We've inherited, and still keep in place, code that reads ini files
at ~/.config/clutter-1.0/settings.ini and /etc/clutter-1.0/settings.ini
to tweak different aspects of Clutter.
Some of these should use GSettings instead, some others are exposed
nowadays differently for our purposes (e.g. envvars, looking glass, ...).
Overall seems like an unexpected entry point nowadays, so remove the
parsing of these .ini files altogether.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1693>
If we are about to replace `redraw_clip` with a clamped version of itself
then we may as well do the same for `queued_redraw_clip`, so you can see
more precisely what the damage of the current frame is.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1554>
Initially we generate the new part of fb_clip_region from the new part
of redraw_clip, scale it up and clamp. But the clamping means the new
part of fb_clip_region might now represent a slightly larger area than
the new part of redraw_clip, by one pixel.
In some rare cases where a foreground actor honours redraw_clip, but
the background actor does not (meaning it might fill all fb_clip_region),
you could find 1px rendering glitches in that gap as the background
actor paints there but the foreground actor does not.
To ensure such glitches can never happen we now regenerate the final
redraw_clip as a clamped superset of the final fb_clip_region. That's
the minimum area we must paint to ensure no gaps appear inside
fb_clip_region.
Although the fix here sounds like the intent of the old code, the old
code forgot to include the new part of fb_clip_region in the clamping
of the final redraw_clip. So the new part of redraw_clip was sometimes
kept too small for the new part of fb_clip_region.
We also move the code to the main path because technically it's also
needed when `has_buffer_age == FALSE`.
Fixes: https://gitlab.gnome.org/GNOME/mutter/-/issues/1500
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1554>
Before each frame is maybe redrawn, push any new cursor KMS state to the
pending update. It'll then either be posted during the next page flip,
or when the same frame finishes, in case nothing was redrawn.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1488>
This makes it possible to post a symbolic page flip and frame callback,
meant to be used by immediate symbolic page flip reply when emulating
cursor plane changes using legacy drmMode* functions.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1488>
Just as with the frame clock, add an API to communicate that a frame did
not result in a presentation. This can't happen yet but will when we
emulate atomic cursor plane changes using legacy drmMode API.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1488>
In constrast to notify_presented(), notify_ready() also returns the
state machine to the idle state, but without providing new frame
information, as no frame was actually presented.
This will happen for example with the simple KMS impl backend will do a
cursor movement, which will trigger a symbolic "page flip" reply in
order to emulate atomic KMS behavior. When this happen, we should just
try to reschedule again.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1488>
Don't mode set each CRTC in separate KMS updates, as reconfiguring one
CRTC might cause other CRTCs to be implicitly reset thus as well,
causing KMS return EBUSY if using atomic modesetting.
Prepare for this by compositing each CRTC first including adding steps
to the KMS update, but wait until all views has rendered at least once
before posting the initial update. After this each CRTC is posted
separately.
Using EGLStreams instead of normal page flipping seems to fail when
doing this though, so handle that the old way for the EGLStream case,
i.e. eglSwapBuffers() -> mode set with dumb buffer -> eglStream
"acquire" (resulting in page flip under the hood).
For this we also introduce a new error code so that we don't use client
buffers when doing mode sets, which could accidentally configure the
CRTC in a way that is incompatible with the primary plane buffers.
Do the same also when we're in power save mode, to only have one special
case path for this scenario in the regular swap-buffer path.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1488>
Instead of setting the frame result in the most generic layer, have the
backends do it themselves. This is necessary to communicate that a
swap-buffer call didn't really succeed completely to present the swapped
buffer, e.g. errors from KMS.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1488>
