The helper doesn't do anything that makes it worth
to be exposed as public API. End-users, such as GNOME Shell could have
an in-tree helper if they end up using it that much.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3086>
These functions ends-up calling gdk-pixbuf for loading textures/bitmaps
from a file and they don't seem to be used anywhere.
These changes are only useful with the following up commit.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3097>
Create a fake monitor region right of the right-most monitor and if a
horizontal barrier extends into that region, fail the barrier. Barriers
are aligned on the top/left edge of the pixel so the most natural
barrier of (e.g. 0-1024) is also wrong - it's one pixel into the next
monitor.
Check this for nonexisting screens on the right too to avoid clients
suddenly failing when multiple monitors are present.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3319>
Assuming two 1920x1080 screens next to each other: a horizontal barrier
starting at 1920 going east is always outside the left screen.
Assuming two 1920x1080 screens on top of each other: a vertical barrier
starting at 1080 going south is always outside the top screen.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3319>
`clutter_actor_destroy()` queues a stage update. Under certain
circumstances - i.e. when run in a very slow container - this can race
with the stage update triggered by the following
`clutter_virtual_input_device_notify_button()`, occasionally resulting in
`wait_stage_updated()` to return before the
`on_event_return_propagate()` callbacks ran, making the test fail.
This notably became more common since
8f27ebf87e (clutter/frame-clock: Start next update ASAP after idle period)
landed.
Thus wait for a stage update to happen after `clutter_actor_destroy()`,
preventing the race.
Fixes: f6da583d06 (tests/clutter/event-delivery: Add tests for implicit grabbing)
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3332>
Instead of g_get_monotonic_time. This makes sure last_presentation_time_us
advances by refresh_interval_us.
Doesn't affect test results at this point, but it will with the next
commit.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3174>
The virtual stream source with CURSOR_MODE_EMBEDDED uses
META_STAGE_WATCH_AFTER_PAINT as the callback for recording its frame. In
this stage of the paint though, there is no ClutterPaintContext anymore
(there only is a paint context during the paint, not afterwards).
The callback (actors_painted()) tries to get the redraw clip from the paint
context, and we end up with a NULL pointer crash.
We actually do still have a redraw clip at this point, so because everyone
uses the paint context to get the redraw clip anyway, just pass the redraw
clip to the stage watches directly.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3283>
Realizing a cursor will assume view related state objects are valid so
they can mark them as dirty. This assumption broke when there were a
scale changed that happened with multiple CRTCs, as we'd create view
object by view object as we realized the texture. Realizing the texture
would trigger a signal that had the handler assuming the validity of all
view objects, but if we only had gotten to the first, the second view
would not be there yet, thus we'd be doing a NULL pointer dereference.
Creating the view objects first, then handling the updating avoids this
problem by making the already done assumption valid on hotplugs.
The test case added tests exactly this series of events, and uses a
virtual monitor as a cheap trick to make the KMS CRTC based view the
first one, and an arbitrary view the second that previously had its view
object initialized too late.
Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/3012
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3262>
We need to trigger a mode set when power-save changes to 'on' if it's
purely about power saving, but when they arrive as part of a hotplug
event, we'll handle all that later, in the monitors-changed handling,
that contains the new configuration.
This avoids a crash that happens due to the mode set being queued on now
disabled connectors.
Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/2985
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3233>
Currently, Meta/Cogl/Clutter makes use of cairo_rectangle_int_t despite
the existance of MetaRectangle.
In order to make MetaRectangle usable in Cogl/Clutter as well, Mtk would
provide such base types that are shared across the various private
libraries
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3128>
Dropped obsolete Free Software Foundation address pointing
to the FSF website instead as suggested by
https://www.gnu.org/licenses/gpl-howto.html
keeping intact the important part of the historical notice
as requested by the license.
Resolving rpmlint reported issue E: incorrect-fsf-address.
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3155>
This fixes the following
1. Minimize window; minimize animation starts
2. Do something that immediately destroys the animated actor (e.g. terminate)
3. This triggered the timeline of the animation to emit a "stopped"
signal while all transitions of the actor were destroyed
Previously we'd implicitly animate the scale again (set_scale(..)) which
created a new transition The hash table iterator didn't like this and
abort():ed
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3213>
Except for the tests that launches `mutter`, use a custom shell
implementation. It's roughly a copy of default.c with some cleanups on
top. A custom shell allows for a bit more freedom when doing testy
things.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3185>
With the ClutterEvent subtype structs sealed, this remains the only useful
struct type that is now usable on the Javascript side. Make all
ClutterActorClass event vmethods use ClutterEvent, and update all users
to this change.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3163>
The default cogl blend string is
`RGBA = ADD (SRC_COLOR, DST_COLOR*(1-SRC_COLOR[A]))` which is alpha
blending with premult fragment results. We do not clear the src
framebuffer and even if we did set alpha to 1 in the src fb, the
resulting alpha would be 1 and we want to check the alpha of the
fragment color.
Just turn off any kind of blending instead and write out the fragment
color to the fb.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3065>
To obtain a float between 0 and 1 we have to devide the integer by the
highest possible value instead of the number of values.
Fixes off by one errors in the tests on some hardware/driver
combinations.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3065>
So we can properly handle matching DRM and WL_SHM formats in a unified
manner.
Add extensive testing between these and existing pre-multiplied alpha
formats, i.e. all formats we support on Wayland.
Note that unfortunately for some format combinations the value in the
alpha channel is not cleared as expected, likely because of fast-paths
in Cogl. If both source and destination format is opaque, it always
works, however. This thereby includes all cases where they are the same.
Co-Authored-By: Jonas Ådahl <jadahl@gmail.com>
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3065>
We can schedule an update from the cursor manager, but that doesn't mean
there will be an actual plane assignment changed at the time of the
update processing, since for example we might have "touched" a CRTC, but
already left it before the processing started, meaning we have nothing
to change after all.
Add a test case that checks that this works properly.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2777>
It can be quite slow to set up the test environment inside the VM, as
well as outside, leaving very little time for the test itself. While
it'd be nice to not run the mock env etc outside the VM, let's just bump
the timeout for now, to avoid unnecessary timeout failures.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2777>
If we turn of a CRTC, we might have invalidated the cursor manager for
the same CRTC, but that should not mean a cursor plane is assigned when
turning off the CRTC.
Add a test case for this.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2777>
Real time scheduling is needed for better control of when we commit
updates to the kernel, so add a property to MetaThread that, if the
thread implementation uses a kernel thread and not a user thread, RTKit
is asked to make the thread real time scheduled using the maximum
priority allowed.
Currently RTKit doesn't support the GetAll() D-Bus properties method, so
some fall back code is added, as GDBusProxy depends on GetAll() working
to make the cached properties up to date. Once
https://github.com/heftig/rtkit/pull/30 lands and becomes widely
available in distributions, the work around can be dropped.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2777>
Also add an API to inhibit the kernel thread from being used, and make
MetaRenderDeviceEglStream inhibit the kernel thread from being used if
it's active.
The reason for this is that the MetaRenderDeviceEGlStream is used when
using EGLStreams instead of KMS for page flipping. This means the actual
page flipping happens as a side effect of using EGL/OpenGL, which can't
easily be done off thread.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2777>
This will be necessary in order to default to 'kernel' and then switch
to 'user' if the thread instance can no longer be properly multi
threaded.
To avoid having the same thread impl creating and destroying
GMainContext's, this also means always creating a GMainContext for the
thread-impl. When running in user-thread mode, the GMainContext is
wrapped in a wrapper source and dispatched as part of the real main
thread GMainContext, and when in kernel-thread mode, it runs
independently in the dedicated thread.
This has the consequence that the wrapper source will always have the
priority of the highest impl context GSource, but only after it has
dispatched once. Would we need it earlier than that, we either need a
way to introspect existing sources in a GMainContext and their
priorities, or manually track known sources in MetaThreadImpl.
The wrapper source will never be below 0, as that'd mean it could reach
INT_MAX priority if it had no more sources attached to it, meaning it'd
never be dispatched again.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2777>
While the default when passing NULL will be the main context of the main
thread, make it possible to specify another main context, so that
result handlers can be invoked on the right thread.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2777>
Callbacks could be queued to be invoked either on the impl side or the
main thread side of the thread; change this to take a GMainContext,
which effectively means a callback can be queued to be invoked on any
thread that has a GMainLoop running on its own GMainContext.
Flushing is made to handle flushing callbacks synchronously on all
threads. This works by keeping a hash table of queued callbacks per
thread (GMainContext); when flushing (from the main thread), callbacks
on the main thread context is flushed, followed by synchronization with
all the other threads.
meta_thread_flush_callbacks() is changed to no longer return the number
of dispatched callbacks; it becomes much harder when there are N queues
spread across multiple threads. Since it wasn't used for anything, just
drop the counting, making life slightly easier.
Feedback to thread tasks are however always queued on the callers
thread.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2777>
This means each test is run 4 times:
* with atomic mode setting using a kernel thread,
* with atomic mode setting using a user thread,
* with legacy mode setting using a kernel thread, and
* with legacy mode setting using a user thread.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2777>
This isn't a problem for user space threads, as there are no race
conditions, but when kernel thread support is introduced, we must make
sure that e.g. the main loop is actually running before quitting it.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2777>
This uses the queue that was introduced when migrating impl task
management from MetaThread to MetaThreadImpl, with the exception that
it's now fully used as an actual queue. It now has a GSource that sits
on the right GMainContext that is dispatched whenever there are tasks to
execute.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2777>
It's the impl side that wants to add impl side idle sources, or fd
sources, etc, so make it part of MetaThreadImpl.
This changes things to be GAsyncQueue based. While things are still
technically single threaded, the GAsyncQueue type is used as later we'll
introduce queuing tasks asynchronously, then eventually queuing across
thread barriers.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2777>
Accessibility should be handled on the receiving end, if needed. Make
sure this is the case by listening on some signals, verifying they are
only triggered if we're not capturing input.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2628>
This adds the actual input capturing rerouting that takes events and
first hands them to the input capture session, would it be active.
Events are right now not actually processed in any way, but will
eventually be passed to a libei client using libeis.
A key binding for allowing cancelling the capture session is added
(defaults to <Super><Shift>Escape) to avoid getting stuck in case the client
doesn't even terminate the session.
The added test case makes sure that the pointer moves again after
pressing the keybinding.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2628>
An input only grab is a ClutterGrab on the stage that doesn't have an
explicit actor associated with it. This is useful for cases where event
should be captured as if focus was stolen to some mysterious place that
doesn't have anything in the scene graph that represents it.
Internally, it's implemented using a 0x0 sized actor attached directly
to the stage, and a clutter action that consumes the events. An
input-only grab takes a handler, user data and a destroy function for
the user data. These are handed to the ClutterAction, which handles the
actual event handling.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2628>
Adding a barrier and later enabling the input capture session will
create MetaBarrier instances for each added input capture barrier.
The barriers are created as "sticky" which means that when a pointer
hits the barrier, it'll stick to the point of entry, until it's
released.
The input capture session is also turned into a state machine with
explicit state, to more easily track things.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2628>
This API aims to provide a way for users to capture input devices under
certain conditions, for example when a pointer crosses a specified
barrier.
So far only part of the API is implemented, specifially the session
management as well as zone advertisement, where a zone refers to a
region in the compositor which edges will eventually be made available
for barrier placement.
So far the remote access handle is created while the session is enable,
despite the input capturing isn't actually active yet. This will change
in the future once it can actually become active.
v2: Remove absolute/relative pointer, keep only pointer (ofourdan)
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2628>
We'd get a re-entry like scenario when destroying the PipeWire stream
object, where PipeWire would call the stream process vfunc. When this
happened, we had already destroyed the stream, so don't try to dequeue
or anything, just do an early exit. Fixes the following crash in the
test case client:
#0 pw_stream_dequeue_buffer() in /usr/lib64/libpipewire-0.3.so.0.367.0
#1 on_stream_process() at ../src/tests/screen-cast-client.c:348
#2 do_call_process() in /usr/lib64/libpipewire-0.3.so.0.367.0
#3 flush_items() in /usr/lib64/spa-0.2/support/libspa-support.so
#4 loop_invoke() in /usr/lib64/spa-0.2/support/libspa-support.so
#5 impl_send_command.lto_priv.0() in /usr/lib64/libpipewire-0.3.so.0.367.0
#6 suspend_node.lto_priv.0() in /usr/lib64/libpipewire-0.3.so.0.367.0
#7 pw_impl_node_set_state() in /usr/lib64/libpipewire-0.3.so.0.367.0
#8 client_node_removed() in /usr/lib64/pipewire-0.3/libpipewire-module-client-node.so
#9 pw_proxy_destroy() in /usr/lib64/libpipewire-0.3.so.0.367.0
#10 pw_stream_disconnect() in /usr/lib64/libpipewire-0.3.so.0.367.0
#11 pw_stream_destroy() in /usr/lib64/libpipewire-0.3.so.0.367.0
#12 stream_free() at ../src/tests/screen-cast-client.c:530
#13 main() at ../src/tests/screen-cast-client.c:803
#14 __libc_start_call_main() at ../sysdeps/nptl/libc_start_call_main.h:58
#15 __libc_start_main() at ../csu/libc-start.c:360
#16 _start() in /home/jonas/Dev/gnome/mutter/build/src/tests/mutter-screen-cast-client
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3095>
If the timelines don't get destroyed they keep references to frame
clocks. Later tests check for the destruction of those frame clocks and
then can fail if the frame clock is implemented slightly differenty.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3084>
The stage already maintains its own list of stage-views via
clutter_stage_peek_stage_views(), it's a bit superfluous to copy that list
around all the time into priv->stage_views of ClutterActor. Let's deal with
that by returning clutter_stage_peek_stage_views() when
clutter_actor_peek_stage_views() gets called for the stage.
In order to make sure ClutterActor::stage-views-changed still gets emitted
correctly for the stage, always emit that signal on the ClutterStage when
the stage views get invalidated. This now depends on the backend only
actually invalidating the views and calling
clutter_stage_clear_stage_views() when things have actually changed, but
that should be the case.
This needs a change in one of the stage-views tests, namely the one which
tests stage-view-changed emission on the stage: Here we now see an emission
of stage-views-changed, but that signal emission actually seems correct.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2679>
Under X11 hiding the backend implies also unmapping the stage window, if
we do that after that we've closed the display we may end up in a
BadWindow error because such window seems to be destroyed together with
the compositor output parent (even though we are not notified about), so
to prevent this, reparent the backend window during compositor unmanage,
setting it back as a root window child.
Fixes: https://gitlab.gnome.org/GNOME/mutter/-/issues/2835
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3020>
Hides libdisplay-info under a build time default-off flag,
provides provision to parse essential edid parameters with
APIs provided by libdisplay-info. This implementaion increases
readibility, avoids code duplication and decreases complexity
of edid parsing.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2642>
This ATM triggers missed .commit events for the window in question,
to be addressed in Xwayland. Since the test does not seem to specifically
rely on this window being CSD, make it a regular window instead.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2975>
This will be used to extract the resolution and refresh rate from
strings like "1920x1080@60.0" or "1280x720". This aims to replace the
use of the locale dependent sscanf() function.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2902>
Otherwise we'll have a cursor sprite backed by a surface that no longer
exist. This usually doesn't happen, but can happen in rare situations
related to pointer capability changes Wayland client cursor changes and
hotplugs.
Fixes the following crash:
#0 meta_wayland_buffer_get_resource() at ../src/wayland/meta-wayland-buffer.c:128
#1 realize_cursor_sprite_from_wl_buffer_for_gpu() at ../src/backends/native/meta-cursor-renderer-native.c:1649
#2 realize_cursor_sprite_for_gpu() at ../src/backends/native/meta-cursor-renderer-native.c:1869
#3 realize_cursor_sprite() at ../src/backends/native/meta-cursor-renderer-native.c:1887
#4 meta_cursor_renderer_native_update_cursor() at ../src/backends/native/meta-cursor-renderer-native.c:1100
#5 meta_cursor_renderer_update_cursor() at ../src/backends/meta-cursor-renderer.c:414
#6 meta_cursor_renderer_force_update() at ../src/backends/meta-cursor-renderer.c:449
#7 update_cursors() at ../src/backends/meta-backend.c:328
#8 meta_backend_monitors_changed() at ../src/backends/meta-backend.c:338
#9 meta_monitor_manager_notify_monitors_changed() at ../src/backends/meta-monitor-manager.c:3590
#10 meta_monitor_manager_rebuild() at ../src/backends/meta-monitor-manager.c:3678
#11 meta_monitor_manager_native_apply_monitors_config() at ../src/backends/native/meta-monitor-manager-native.c:343
#12 meta_monitor_manager_apply_monitors_config() at ../src/backends/meta-monitor-manager.c:706
#13 meta_monitor_manager_ensure_configured() at ../src/backends/meta-monitor-manager.c:779
#14 meta_monitor_manager_reconfigure() at ../src/backends/meta-monitor-manager.c:3738
#15 meta_monitor_manager_reload() at ../src/backends/meta-monitor-manager.c:3745
or the following on gnome-43:
#0 meta_wayland_surface_get_buffer at ../src/wayland/meta-wayland-surface.c:441
#1 meta_cursor_sprite_wayland_get_buffer at ../src/wayland/meta-cursor-sprite-wayland.c:83
#2 realize_cursor_sprite_from_wl_buffer_for_gpu at ../src/backends/native/meta-cursor-renderer-native.c:1612
#3 realize_cursor_sprite_for_gpu at ../src/backends/native/meta-cursor-renderer-native.c:1836
#4 realize_cursor_sprite at ../src/backends/native/meta-cursor-renderer-native.c:1854
#5 meta_cursor_renderer_native_update_cursor at ../src/backends/native/meta-cursor-renderer-native.c:1087
#6 meta_cursor_renderer_update_cursor at ../src/backends/meta-cursor-renderer.c:413
#7 meta_cursor_renderer_force_update at ../src/backends/meta-cursor-renderer.c:448
#8 update_cursors at ../src/backends/meta-backend.c:344
#9 meta_backend_monitors_changed at ../src/backends/meta-backend.c:354
Related: https://bugzilla.redhat.com/show_bug.cgi?id=2185113
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2968>
We have the drm/InfoFrame encoding and our MetaOutputHdrMetadata
encoding. Check that we can correctly convert between each other by
doing a encode/decode and decode/encode roundtrip and then checking for
equality.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2879>
We relied on them being valid longer to keep track of used GPUs. If we
don't have the CRTC (or output) we don't have a way to fetch the pointer
to the MetaGpu that drives the associated monitor.
This avoids a crash when trying to fetch said pointer from what would be
the NULL MetaCrtc pointer.
Fixes: 08593ea872 ("onscreen/native: Hold ref to the output and CRTC until detached")
Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/2667
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2887>
We want to avoid using too high scales too easily, which started to
happen 2f1dd049bf ("monitor-manager: Rework default scale factor
selection"). Instead of using the closest non-fractional scale, which
effectively is what we'd do, only round upwards if we're closer than
0.25 (25%).
Since there are some wiggle room for scales to make the logical
resolution on the integer pixel grid, make sure to compensate. This
compensation is done by adding an extra 0.2 to scale difference.
For example the following fractional scales will get these corresponding
integer scales:
* 1.25 -> 1.0
* 1.5 -> 1.0
* 1.75 -> 2.0
* 2.0 -> 2.0
* 2.50 -> 2.0
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2880>
Instead of testing headless start using the dummy backend, do so with
the real native backend, and use the drm-mock library instead to emulate
monitors being disconnected at startup.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2821>
This new filter allows test cases to manipulate what the kernel reports,
e.g. mark connected connectors as disconnected to emulate monitors
connecting and disconnecting.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2821>
In order to make things more and more asynchronus and to each time we
paint be an isolated event, that can be potentially be applied
individually or together with other updates, make it so that each time
we draw, we use the transient MetaFrameNative (ClutterFrame) instance to
carry a KMS update for us.
For this to work, we also need to restructure how we apply mode sets.
Previously we'd amend the same KMS update each frame during mode set,
then after the last CRTC was composited, we'd apply the update that
contained updates for all CRTC.
Now each CRTC has its own KMS update, and instead we put them in a per
device table, and whenever we finished painting, we'll merge the new
update into any existing one, and then finally once all CRTCs have been
composited, we'll apply an update that contains all the mode sets for all
relevant CRTCs on a device.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2855>
Add a tiny library that sabotages errors in drmMode*() API calls. This
will be used to artificially trigger arbitrary errors, e.g. cause the
next commit to fail with EBUSY.
The three mocked methods are added as they will be used in a future
commit.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2854>
At first it was called seal(), but then updates could be amended after
being posted, given a flag. That flag has been removed, so we can go
back to sealing, since it's once again acts more as a seal.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2854>
