meta_keymap_x11_replace_keycode currently reports to the X server
that the key types data is changed when adding a key to the keymap.
It's not changed. The number of key types is the same, and none of
them are modified.
This has two bad side effects:
1) It sends all of the key types data into the request
2) It hits a bug in the X server leading to the request getting
rejected entirely. See:
https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/761
Furthmore, the changed structure used to report to the X server
that the key types data is changed doesn't actually need to modified
at all in the function. It's already prepped by libX11 with the
correct state for the changes mutter is doing when
XkbChangeTypesOfKey is called.
This commit addresses the above two problems by just removing the
lines causing the issues.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2039>
Keys in the reserved keycode list are always added for the first group.
Before the previous commit such keycodes were not found unless that was
the current group. But now that we can also find matching keycodes that
are not directly in the current group, this is not necessary anymore.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1955>
Some keys, such as enter or backspace are only bound to a single group,
even if multiple groups are configured. Because the code was previously
only looking for keysyms in the same group as the current one, no
matching keycodes for these would be found if the current group is not
the first group. This was causing those keys to not work on the X11 OSK.
To fix this use the correct action to convert an out of range group for
that key according to its group_info field.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1955>
This effectively changes meta_keymap_x11_get_entries_for_keyval() to
meta_keymap_x11_get_entry_for_keyval() and moves the check if the
keycode maps to the keyval in the current group there. This simplifies
the code a bit and will allow a followup fix.
As a side effect this now also causes the reserved kecodes to be
searched, if no keycodes were found, rather than just when only ones
matching the wrong groups.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1955>
The extra stage update we schedule in `apply_state()` is mainly
needed in two situations:
- a partial update happened only in obscurred or off-screen parts
of a surface
- a surface requests frame callbacks without having done damage,
notably the (in)famous Firefox vsync implementation.
Commit 0330ce1f15 limited the update to cases when the actor
was mapped, breaking it for Firefox in the overview.
Remove the mapped check again and get the stage from the backend,
restoring previous behaviour.
Fixes 0330ce1f15
Closes https://gitlab.gnome.org/GNOME/mutter/-/issues/1957
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2034>
Avoid having laptops suspend or lock as soon as the power cable is
unplugged as the timeout for those actions when on battery are smaller
than the timeouts when on AC.
- laptop is plugged in, and hasn't been used for X minutes
- laptop is unplugged
- the gnome-settings-daemon power plugin sets up its timeouts for
inactivity for the "on battery" case
- those X minutes of inactivity are still counting, and are above
the level of one of the timeouts (say, suspend or lock screen),
mutter fires the timeouts
- gsd-power activates the action associated with the timeout
Fixes: https://gitlab.gnome.org/GNOME/mutter/-/issues/1953
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2029>
If the ancestor a window is transient for has already been unmanaged
when the window is activated via meta_window_activate_full while its
transient_for property still points to that ancestor, this will cause
the already unmanaged ancestor to get added to the windows workspace.
This is after the ancestor had its workspace set to NULL when it was
unmanaged, causing this to look like an actual workspace change. Once
the window has been added to the workspace, it will never be removed
again, because the it has already been unmanaged. This confuses things
like the shell window tracker and leads to phantom windows being
considered present for apps that are not even running anymore.
Fixes: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/4184
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2003>
When a test failed, an exception would be raised. This meant that the
mocked service would stay alive, and the test case being run eventually
failing due to a timeout, not the failure itself.
Fix this by catching the exception during the test, ensuring that we
tear down properly, then re-raise the same exception again after having
teared down.
This avoids the dead lock, while still printing the appropriate error
message.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2008>
With the introduction of MetaContext, the responsibility for handling
signals was changed to the application (e.g. GNOME Shell) using
libmutter. What wasn't fixed was making the stand-alone mutter do the
equivalent as well. This commit fixes this.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2007>
When the native backend is paused we still process the udev events
even though this isn't needed and may just cause unneeded events to be
triggered afterwards.
Since we'll resume with full changes on such event, we can just block
the signal hander when paused and restore it afterwards.
As per this we can cleanup also a bit the device adding signal handling
given that now we don't have to disconnect/reconnect it again.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1964>
Resume happens after we may have received various events that we've
ignored, so at this point we need to just emit an hotplug event like if
everything changed so that user settings may be re-applied.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1964>
On hotplug events we may get informations about what CRTC or connector
changed a property (and the property itself), so in such case let's just
ignore the changes to the non-affected CRTCs/connectors, and let's read
only the affected one
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1964>
On hotplug events we may receive a "CRTC" or "CONNECTOR" property that
indicates which crtc/connector property ID has changed.
In such case, instead of update data for all the devices, only update the
device containing the relative connector.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1964>
Hotplug events may contain CRTC or CONNECTOR ids to notify a property
change to just one owner, so we need to find its parent device.
Also we may want to update properties directly without having to go through
all the devices, so expose a simple way to find them.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1964>
In case we have no devices, after a KMS update (both because they've
all have been removed or because there were none), we may need to behave
differently compared to the case in which nothing changed, so add a more
specific KMS update change type
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1964>
If only gamma changed on drm CRTC's we don't have to rebuild the whole
monitors, nor to inform the backed about, the only consumer could be the
DBus API, and so we still emit a signal, but nothing else is needed.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1964>
Since we cache already all the KMS parameters we care about let's check at
each device update if anything has really changed and only in such case
emit a resources-changed signal.
In this way we can also filter out the DRM parameters that when changed
don't require a full monitors rebuild.
Examples are the gamma settings or the privacy screen parameters, that
emits an udev "hotplug" event when changed, but we want to register those
only when we handle the changed property.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1964>
A client request for maximizing itself should always be handled by mutter
by emitting a configure event with the native maximized resolution,
regardless of the client's own set limits. This also aligns the behavior by
allowing fixed-sized windows to go into fullscreen or maximized state.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1997>
It works correctly with scanouts, in contrast to
clutter_stage_capture_into. Inspired by
meta_screen_cast_area_stream_src_record_to_buffer.
maybe_paint_cursor_sprite is now unused and thus removed.
v2:
* clutter_stage_paint_to_buffer requires switching to recording from an
idle callback as well. (Jonas Ådahl)
v3:
* Set human readable name for idle source. (Ivan Molodetskikh)
Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/1940
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1914>
The way wl_seat capabilities work, by notifying clients of capabilities
changes, and clients consequently requesting the relevant interface
objects (pointer, keyboard, touch) is inherently racy.
On quick VT changes for example, capabilities on the seat will be added
and removed, and by the time the client receives the capability change
notification and requests the relevant keyboard, pointer or touch,
another VT switch might have occurred and the wl_pointer, wl_keyboard or
wl_touch already destroyed, leading to a protocol error which kills the
client.
To avoid this, create the objects when requested regardless of the
capabilities.
Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/1797
Related: https://bugzilla.gnome.org/show_bug.cgi?id=790932
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/77>
Analogous to `get_image()` this returns a `ClutterContent` for a
given `MetaWindowActor`. This can be used to implement window
effects without a roundtrip from GPU to CPU memory.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1893>
In X11 when we switch to another tty all the the signals are blocked (as
the display fd is not replying back to polling, causing the main loop to
stop), and they are all handled once we switch back to the tty.
This is not a problem for most of external events, but in case of
accelerometer changes, once we reactivate a mutter session we'll get
them all together, causing lots of monitor reconfigurations leading to
black screen for some seconds and most of the times to a wrong
configuration being applied.
To avoid this, batch all these events using an idle to only apply the
last one we got in a loop.
Fixes: https://gitlab.gnome.org/GNOME/mutter/-/issues/1217
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1233>
Create a test system bus and use it to run all the tests, add a mock
SensorsProxy (via dbusmock template) server that implements the
net.hadess.SensorProxy interface.
To make testing easier, the service is created on request of a proxy for
it, whose lifetime controls the mock service lifetime as well.
This is done using a further mock service that is used to manage the
others, using python-dbusmock to simplify the handling.
Add basic tests for the orientation manager.
As per the usage dbusmock, we're now launching all the tests under such
wrapper, so that local dbus environment won't ever considered, and
there's no risk that it may affect the tests results both locally and in
CI.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1233>
When creating the configuration for the builtin monitor we try to get
the panel configuration for the builtin panel, but we don't proceed if
that monitor is currently inactive.
This is fine when adjusting an active configuration to the current
device rotation, but it isn't correct when we want to create a new
configuration based on another where the monitor is configured but not
yet enabled.
So, only find the panel configuration without looking the current state
but ensuring that the passed configuration will enable it.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1233>
When we get an orientation event we don't care about keeping track of the
configuration changes, but actually we can consider the new configuration
just a variant of the previous one, adapted to floating device hardware
events, so we only want to apply it if possible, but we don't want to keep
a record of it for reverting capabilities.
Doing that would in fact, break the ability of reverting back to an actual
temporary or persistent configuration.
For example when device orientation events happen while we're waiting for
an user resolution change confirmation, we would save our new rotated
configuration in the history, making then impossible to revert back to
the original persistent one.
So in such case, don't keep track of those configurations in the history,
but only keep track of the last one as current, checking whether the
new current is child or sibling of the previously one.
Fixes: https://gitlab.gnome.org/GNOME/mutter/-/issues/1221
Related to: https://gitlab.gnome.org/GNOME/mutter/-/issues/646
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1233>
When creating a configuration taking orientation into account we're using
the sensors orientation even if this is currently not used (for example
when an accelerator is available, but there's no touch screen).
This would cause to have a different behavior when configuration is
created and when we're loading a known configuration on startup.
So always honor whether the monitor's orientation is managed or not.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1233>
All the auto-rotation code is expecting to have a built-in panel, but we
still monitor accelerometer changes if we don't have one (uncommon, but
possible).
Thus manage the panel orientation in such case and update it on monitors
changes.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1233>
These are ClutterInputFocus subclasses, so this will trigger reset of
the input method. As the .done event is possibly deferred in the
zwp_text_input_v3 implementation, ensure the changes caused by the
reset are flushed immediately, before the button press is forwarded
to the client by MetaWaylandPointer.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1940>
This commit adds support to atomic KMS backend for optional plane property
prop_fb_damage_clips. Some drivers (e.g. EVDI) take advantage of this
property and process only updated regions of the screen instead of
processing the full frame. This can save system resources.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1879>
Added a function `meta_window_set_inactive_since` it sets
xattr on the cgroup directory for the given MetaWindow.
Resource management daemons can then monitor these changes on xattr
and make allocation decisions accordingly.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1960>
Currently the only way to get cgroup for a MetaWindow is to get it's
PID and perform a bunch of file accesses and string manipulations.
This is especially not feasible if we want to get the cgroup every
time a MetaWindow has gained or lost focus.
A solution to this is to cache the GFile for a cgroup path.
The creation and access of this GFile is handled by
`meta_window_get_unit_cgroup` function.
`meta_window_unit_cgroup_equal` is a utility function which allows
us to compare whether two MetaWindows belong to the same cgroup.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1960>
To utilize the API provided by libsystemd it would be better to
create a separate HAVE_LIBSYSTEMD configuration option instead of
having to rely on HAVE_NATIVE_BACKEND.
For now this will be utilized for getting the control group of a
MetaWindow.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1960>
and the subsurface was not previously detached from it using
`wl_subsurface_destroy()`.
Without 'window-actor/wayland: Remove subsurface actors on dispose' this
test would fail.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1958>
commit c4a73e7950 added
code to cleanup the renderer when the meta backend is
disposed. Unfortunately, this introduced a crash when
the window manager is replaced.
This is because cleaning up the renderer involves talking
to the X server over a display connection that's closed
two lines higher as part of the clutter_backend_destroy
call.
This commit fixes the crash by swapping their order.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1965>
There is very little point in sending an X11 client message to
gnome-panel in case gnome-shell isn't handling the binding. We
can just as well do nothing, so do exactly that.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1886>
We fetch a frame clock that we schedule update on when queuing
_NET_WM_FRAME_DRAWN events. In some situations this frame clock is the
one from the stage, and if there are multiple hotplugs in a row, we
failed to update it as there were no stage views changes on the window
actor itself. As an actor updates the stage views list on layout, When a
queue_frame_drawn() call was done (typically from an X11 event) after a
second hotplug, it'd attempt to schedule an update on the frame clock
from the previous hotplug, as it didn't get notified about any
stage-views changes since for itself there was none.
Fix this by not caching the frame clock at all and just fetch it every
time.
In the majority of cases, this fetching means iterating over a very
short list (most often a single entry, rarely more), so it's very
unlikely to be of any relevance. The only situations where it might be a
heavier operation is the short time between a hotplug and a layout, as
it will attempt to traverse up to the stage to find a clock, but that's
likely only a few levels, so even that is unlikely to be an issue.
Closes: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/4486
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1947>
This is more in line with the protocol, and allows us to remove some
awkward code that tries to "combine" different metadata from different
monitors into one, which sometimes meant picking an arbitrary "main"
monitor, or "and" metadata together to find a common ground.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1712>
Makes workspace transitions in gnome-shell look more seamless, since
both outgoing and incoming workspace have focused windows.
This is only done for click focus mode, since it's not known which
window would be focused for the other modes.
Track the state and recompute it when it changes, to avoid redrawing
the windows needlessly.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/850>
Each workspace has a window that will be focused when switching to that
workspace. Add a function to retrieve that window.
This is only relevant for click-to-focus focus mode, since with the two
other modes no window will be focused upon switching, and will only gain
focus when hovered.
This will be used in the next commit to make this window appear focused.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/850>
This was introduced by accident in commit 1467b6b02a
y-inverted textures in combination with shape masks appear to
be only commonly used with EGLstreams. However, as we draw the
shape mask ourselves, we don't want to apply the y-invert to it
as testified by the left over `cogl_pipeline_set_layer_matrix()`.
Note that we still allow to apply viemports and buffer transforms,
as the Xwayland mode setting emulation may use it (in fact only
the former, but it probably does not hurt to leave the later as well).
Closes https://gitlab.gnome.org/GNOME/mutter/-/issues/1792
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1937>
Monitor configuration check tests can be very complex and in case of
failures we can't easily catch where a failure happened without entering
in debug mode, something that isn't always an option in CI or external
builders.
So add more debug statements in configuration check functions and use
macros to ensure that we print the caller function and location on more
complex check functions.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/522>
Primary monitor is just the same of the other monitors, but it has a
primary monitor flag. Since the computation of the scaling isn't
dependent anymore on the computed configuration we can now generate the
primary monitor config together with the others.
However, we've to ensure that the primary monitor is the first of the
configs list in order to properly compute the positioning.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/522>
Compute the monitor scaling in a separated function using the primary
monitor (not its config) and pass it to the creation function instead.
This will allow removing the special logic for the primary monitor.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/522>
Factorize the creation of a configuration inside one function that looks for
the primary monitor and the other monitors using the matching rules and
dispose them according to the chosen policy (checking if the result is valid
when using the suggested positioning).
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/522>
Add a find_monitors function that allows to search for monitors that match
the MonitorMatchRule filter and use this to look for the primary monitor and
the other monitors that need to match the requested filter in order to be
configured.
Having just one function doing this kind of checks reduces the possibility
of unexpected results.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/522>
Verify that the suggested monitor configuration contains only adjacent monitors,
and that if this is not the case we fallback to the linear configuration.
This can happen in case of multi-DPI setup, so add a test checking this too.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/522>
It could happen that monitors suggest to use coordinates that don't take
in consideration the scaling applied to one monitor, and such the
generated configuration is not valid because not all the monitors are
adjacent.
So enforce this check before accepting a suggested configuration as it
is.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/522>
We may need to check if rectangles region has adjacent neighbors and
so if there are no gaps in between monitors.
This can be done by checking if each monitor is adjacent to any other in
the same region.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/522>
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>
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>
When a selection owner advertises a mime type, but does not provide the
content upon a request for the mime type content, the requesting side
might wait indefinitely on the content.
To avoid this situation, add a timeout source, which will cancel the
selection transfer request after a certain timeout (15 seconds) passed.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1874>
Currently, if g-r-d closes the read end of the pipe for a
SelectionRead() operation, due to realizing that the application, that
should provide the mime type content, does not provide any content,
mutter won't notice that and still assumes that the read() operation
on the pipe in g-r-d is still happening, as mutter never writes to the
pipe in that situation and therefore cannot realize that the pipe is
already closed.
The effect of this is, that if g-r-d aborts a read() operation and
requests a new read() operation via SelectionRead(), mutter will deny
the request since it assumes that the previous read() operation is
still ongoing.
Fix this behaviour by also checking the pipe fd in mutter before
denying a SelectionRead() request.
https://gitlab.gnome.org/GNOME/gnome-remote-desktop/-/issues/60
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1874>
With some resolutions (such as 4096x2160) we may compute duplicated
scale factors because we used a too wide threshold to check for an
applicable value.
In fact, while when we're at the first and last values it's fine to
search applicable values up to SCALE_FACTORS_STEP, on intermediate ones
we should stop in the middle of it, or we're end up overlapping the
previous scaling value domain.
In the said example in fact we were returning 2.666667 both when
looking to a scaling value close to 2.75 and 3.00 as the upper bound of
2.75 (3.0) was overlapping with the lower bound of 3.0 (2.75).
With the current code, the lower and upper bounds will be instead 2.875.
Adapt test to this, and this allows to also ensure that we're always
returning a sorted and unique list of scales (which is useful as also
g-c-c can ensure that this is true).
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1878>
We introduced META_MONITOR_SCALES_CONSTRAINT_NO_FRAC to get global scale
values however, this didn't work properly for some resolutions.
In fact it may happen that for some resolutions (such as 3200x1800) that
we did not compute some odd scaling levels (such as 3.0) but instead
its closest fractional value that allowed to get an integer resolution
(2.98507452 in this case).
Now this is something relevant when using fractional scaling because we
want to ensure that the returned value, when multiplied to the scaled
sizes, will produce an integer resolution, but it's not in global scale
mode where we don't use a scaled framebuffer.
So, take a short path when using no fractional mode and just return all
the applicable values without waste iterations on fractional values.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1878>
Scaling values computation code served us well in the past years but
it's quite delicate and it has some issues in edge cases, so add a test
that verifies that the computed scaling values for all the most common
resolutions (and some that may be common in future) are what we expect
to be.
This may also serve us in future when we'd define a better algorithm to
compute the preferred scale, but this not the day.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1878>
When deriving the global scale from current monitor, we were just checking the
supported value by the primary monitor, without considering weather the current
scale was supported by other monitors.
Resolve this by checking if the picked global scale is valid for all active
monitors, and if it's not the case, use a fallback strategy by just picking the
maximum scale level supported by every head.
Fixes https://gitlab.gnome.org/GNOME/mutter/issues/407
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/336>
In Xrandr we were caching the available scaling modes that were computed just
for the current mode, for each monitor, while we can actually reuse the
default implementation, by just passing the proper scaling constraint.
In monitor we need then to properly filter these values, by only accepting
integer scaling factors that would allow to have a minimal logical monitor
size.
Fixes https://gitlab.gnome.org/GNOME/mutter/issues/407
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/336>
This will require some symbol exporting, but the benefit is that have
better control of what external test cases can do in terms of creating
more testing specific contexts.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1861>
This makes it possible to declare the type in an installed header (so
that e.g. META_CONTEXT_TEST(context) works), but without having to
expose the MetaContextClass struct.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1861>
