Implements the `MetaScreenCastWindow` interface for screen-cast
`RecordWindow` mode.
`meta_window_actor_capture_into()` implementation is still pretty crude
and doesn't take into account subsurfaces and O-R windows so menus,
popups and other tooltips won't show in the capture.
This is left as a future improvement for now.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/306
The shader used for computing a vignette currently has two
problems:
* The math is wrong such that the vignette isn't stretched
across the whole actor and so ends abruptly
* There is noticeable banding in its gradient
This commit corrects both problems by fixing the computing
and introducing noise dithering.
This adds the necessary bits to support Wayland buffer transforms.
The main part here is to properly setup the Cogl pipeline
and to recalculate the size of the painted area accordingly,
so culling etc. still works.
The choosen approach additionally lays groundwork for Wayland
wp_viewporter support.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/322
It cuts out some of the GObject boilerplate, and gives us g_autoptr()
support for free.
Since this changes the ABI, we also need to bump the libmutter API
version.
Following up last commit, this commit adds a CoglFramebuffer
argument to meta_shadow_paint(), and stops using the draw
framebuffer internally.
The only consumer of this API, MetaWindowActor, still passes
the draw framebuffer though.
MetaShadow.paint() uses Cogl implicit APIs (cogl_rectangle* ones, in
this case) to paint shadows with the shadow pipeline.
Replace those calls by cogl_framebuffer_draw_textured_rectangle()
calls, that achieve the exact same result but with the non-deprecated
API.
This commit adds meson build support to mutter. It takes a step away
from the three separate code bases with three different autotools setups
into a single meson build system. There are still places that can be
unified better, for example by removing various "config.h" style files
from cogl and clutter, centralizing debug C flags and other configurable
macros, and similar artifacts that are there only because they were once
separate code bases.
There are some differences between the autotools setup and the new
meson. Here are a few:
The meson setup doesn't generate wrapper scripts for various cogl and
clutter test cases. What these tests did was more or less generate a
tiny script that called an executable with a test name as the argument.
To run particular tests, just run the test executable with the name of
the test as the argument.
The meson setup doesn't install test files anymore. The autotools test
suite was designed towards working with installed tests, but it didn't
really still, and now with meson, it doesn't install anything at all,
but instead makes sure that everything runs with the uninstalled input
files, binaries and libraries when running the test suite. Installable
tests may come later.
Tests from cogl, clutter and mutter are run on 'meson test'. In
autotools, only cogl and clutter tests were run on 'make check'.
Install include files in
$prefix/include/mutter-$apiversion/[clutter,cogl,...,meta]/, and
datafiles in /usr/share/mutter-$apiversion/.... We still would conflict
e.g. given that our gettext name is "mutter", and how keybindings are
installed, but it's a step in the right direction.
This is the filename convention you get when you define a shared module
in meson, and since there is no particular reason to not include the
"lib" prefix, lets make it easier to port it over. While at it,
de-duplicate the retrieval of the plugin name.
The order and way include macros were structured was chaotic, with no
real common thread between files. Try to tidy up the mess with some
common scheme, to make things look less messy.
The clip and opaque region are both in a translated stage coordinate
space, where the origin is in the top left corner of the painted
texture. The painting, however, is in the texture coordinate space,
so when the texture is scaled, the coordinate spaces differ.
Handle this by transforming the clip and opaque region to texture
coordinate space before computing the blend region and the opaque region
to paint.
Closes: https://gitlab.gnome.org/GNOME/mutter/issues/300
They were int before entering MetaShapedTexture, used as ints in the
cairo regions and rectangles, so there is no reason they should be
stored as unsigned.
Related: https://gitlab.gnome.org/GNOME/mutter/issues/300
The compositor will automatically unredirect the top most window which
is fully visible on screen. When unredirecting windows, it also shapes
the compositor overlay window (COW) so that other redirected windows
still shows correctly.
The function `get_top_visible_window_actor()` however will simply walks
down the window list, so if a window is placed on a layer above and
unredirected, then iconified by the client, it will still be picked up
by `get_top_visible_window_actor()` and he compositor will reckon it's
still unredirected while not in a visible state anymore, thus leaving a
black area on screen.
Make sure we skip the windows not known to the compositor while picking
the top visible window actor to avoid this issue.
Closes: https://gitlab.gnome.org/GNOME/mutter/issues/306
The function is intentionally provided as macro to not require a
cast. Recently the macro was improved to check that the passed in
pointer matches the free function, so the cast to GDestroyNotify
is now even harmful.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/176
The special ::pick implementation there makes clutter fall into paths
that do require a get_paint_volume() implementation, or an infinite
area will be used.
Providing a paint volume here is easier on the invalidation mechanism.
This optimization was presumably added before Clutter was able to
invalidate selected regions of an actor. Paint volumes are supposed
to be invariable as long as the actor conditions don't change.
Stacking of other actors shouldn't affect the paint volume, so it's
actually wrong to optimize those areas away here.
- Stop using CurrentTime, introduce META_CURRENT_TIME
- Use g_get_monotonic_time () instead of relying on an
X server running and making roundtrip to it
https://bugzilla.gnome.org/show_bug.cgi?id=759538
Split X11 specific parts into MetaX11Display. This also required
changing MetaScreen to stop listening to any signals by itself, but
instead relying on MetaDisplay forwarding them. This was to ensure the
ordering. MetaDisplay listens to both the internal and external
monitors-changed signal so that it can pass the external one via the
redundant MetaDisplay(prev MetaScreen)::monitors-changed.
https://bugzilla.gnome.org/show_bug.cgi?id=759538
They are X11 specific functions, used for X11 code. They have been
improved per jadahl's suggestion to use gdk_x11_lookup_xdisplay and
gdk_x11_display_error_trap_* functions, instead of current code.
https://bugzilla.gnome.org/show_bug.cgi?id=759538
- Moved xdisplay, name and various atoms from MetaDisplay
- Moved xroot, screen_name, default_depth and default_xvisual
from MetaScreen
- Moved some X11 specific functions from screen.c and display.c
to meta-x11-display.c
https://bugzilla.gnome.org/show_bug.cgi?id=759538
This avoids overwhelming the GPU with trying to update mipmaps at a high
rate. Because doing so could easily cause a reduction in the compositor
frame rate and thus actually reduce visual quality.
In the case of a window that is constantly animating in the overview,
this reduces mutter's render time by around 20%-30%.
While MetaStage, MetaWindowGroup and MetaDBusDisplayConfigSkeleton don't
appear explicitly in the public API, their gtypes are still exposed via
meta_get_stage_for_screen(), meta_get_*window_group_for_screen() and
MetaMonitorManager's parent type. Newer versions of gjs will warn about
undefined properties if it encounters a gtype without introspection
information, so expose those types to shut up the warnings.
https://bugzilla.gnome.org/show_bug.cgi?id=781471
When using plugins, the effects will affect the MetaWindowActor size
and position.
Add a new signal "effects-completed" wired to the corresponding
MetaWindowActor which is emitted when all effects are completed so that
derived objects can be notified when all effects are completed and use
the actual size and position.
Closes: https://gitlab.gnome.org/GNOME/mutter/issues/104
Make the Wayland objects push the state relevant to their role to the
MetaSurfaceActor instead of MetaSurfaceActorWayland pulling the state
from the associated surface.
This makes the relationship between the actor and the objects that
constructs it more clear; the actor is a drawable that the protocol
objects control, not the other way around.
This will make it easier to "detach" a surface actor from a surface,
which is necessary when unmapping a window while the underlying surface
is yet to be destroyed and potentially reused.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/5https://bugzilla.gnome.org/show_bug.cgi?id=791938
When the top window actor is destroyed, we need to make sure that
all its references are removed or it could be picked again in next
windows sync, causing crashes.
Since the window might or might not be destroyed when removed (depending
weather animations are in progress over it or not), it's just safer
to wait it to be destroyed before cleaning up any of its reference.
https://bugzilla.gnome.org/show_bug.cgi?id=791006
We must emit ::dnd-leave to pair the ::dnd-enter that shall be
emitted whenever the plugin grab begins, otherwise we leave
listeners unable to clean up if the plugin begins and ends a
grab while there is an ongoing DnD operation.
https://bugzilla.gnome.org/show_bug.cgi?id=784545
This is not a leak per se, but it seems too easy to make valgrind
SIGSEGV due to MetaBackground disconnecting signals from an already
destroyed MetaScreen when trying to SIGTERM gnome-shell. Keeping a
reference fixes this.
https://bugzilla.gnome.org/show_bug.cgi?id=789984
It looks that there are some extensions that run a Mainloop on startup,
causing to dispatch a clutter paint before the compositor is even available.
In such scenario a MetaWindow could try to start a simple effect
using a compositor plugin which is not there yet.
Then in order to catch these bugs we can now assert that the expected
conditions are valid, so that gnome-shell will provide a dumpstack to
debug the real offending JS code.
https://bugzilla.gnome.org/show_bug.cgi?id=789223
There are cases when no compositor is available (yet) but a MetaWindow tries
to start a simple effect using a compositor plugin which is not available.
In that case we should just ignore any request and protect ourselves from
crashes.
https://bugzilla.gnome.org/show_bug.cgi?id=789223
This function might be called by components with invalid plugin manager
(as it might happen to MetaWindow when the compositor isn't initialized
properly), so we need to protect ourselves from crashes.
https://bugzilla.gnome.org/show_bug.cgi?id=789223
When determining whether we should unredirect a window or not, ignore
offscreen windows, and just check the top most visible window.
Previously this was not an issue, but since 'stack-tracker: Keep
override redirect windows on top' we started sorting the UI frames
window, which is an offscreen override redirect window, on top, causing
the unredirect checking code to always check whether to unredirect the
UI frames window. This effectively disabled the compositor bypass
functionality.
https://bugzilla.gnome.org/show_bug.cgi?id=788493
Turn MetaOutput into a GObject and move it to a separate file. This
changes the storage format, resulting in changing the API for accessing
MetaOutputs from using an array, to using a GList.
https://bugzilla.gnome.org/show_bug.cgi?id=785381
The brightness is about the vignette. Add a 'vignette_' prefix in order
to give more context. Keep the property name as it is, doing so we don't
break any plugin (e.g., gnome-shell).
https://bugzilla.gnome.org/show_bug.cgi?id=786618
Add the word 'vignette' in order to give some context on what the
snippets do. This will be useful later when we land other snippets
for the gradient effect.
https://bugzilla.gnome.org/show_bug.cgi?id=786618
This commit adds support for rendering onto enlarged per logical
monitor framebuffers, using the scaled clutter stage views, for HiDPI
enabled logical monitors.
This works by scaling the mode of the monitors in a logical monitors by
the scale, no longer relying on scaling the window actors and window
geometry for making windows have the correct size on HiDPI monitors.
It is disabled by default, as in automatically created configurations
will still use the old mode. This is partly because Xwayland clients
will not yet work good enough to make it feasible.
To enable, add the 'scale-monitor-framebuffer' keyword to the
org.gnome.mutter.experimental-features gsettings array.
It is still possible to specify the mode via the new D-Bus API, which
has been adapted.
The adaptations to the D-Bus API means the caller need to be aware of
how to position logical monitors on the stage grid. This depends on the
'layout-mode' property that is used (see the DisplayConfig D-Bus
documentation).
https://bugzilla.gnome.org/show_bug.cgi?id=777732
No XDnD events which notify DnD status change comes in Wayland. To emulate XDnD
behavior, MetaDnd checks whether there is a grab or not when the modal window
starts showing. When there is a grab, it processes the raw events from
compositor, and emits DnD signals for plugin.
https://bugzilla.gnome.org/show_bug.cgi?id=765003
Implement MetaDnd for emitting DnD signals to plugins such as gnome-shell. The
xdnd handling code comes from gnome-shell, and it is hidden behind MetaDnd now.
https://bugzilla.gnome.org/show_bug.cgi?id=765003
We currently don't have any shadow class for combo box popups,
which means the default shadow of normal windows is used. That's
clearly odd given that the two are very different, and isn't
consistent with GTK+-3's client-side shadows for popups. While
we could add a dedicated shadow class, the designers are fine
with reusing the existing shadow for dropdown-menus, so let's
do that.
https://bugzilla.gnome.org/show_bug.cgi?id=744667
If the meta_window_actor_effect_completed() triggers inconsistent
accounting, there's also high chances that the thaw call will be
unexpected at this time too, which will lead to a g_error().
This makes mutter more lenient to effect_completed() calls of the
right type (i.e. those triggering freeze/thaw) being performed more
times than necessary in the upper parts. A warning will be issued,
but the process won't abort.
https://bugzilla.gnome.org/show_bug.cgi?id=777691
In preparation for further refactorizations, rename the MetaMonitorInfo
struct to MetaLogicalMonitor. Eventually, part of MetaLogicalMonitor
will be split into a MetaMonitor type.
https://bugzilla.gnome.org/show_bug.cgi?id=777732
In order for the compositor plugin to be able to animate window size
changes properly we need to let it know of the starting and final
window sizes.
For X clients this can be done synchronously and thus with a single
call into the compositor plugin since it's us (the window manager)
who's in charge of the final window size.
Wayland clients though, have the final say over their window size
since it's determined from the client allocated buffer.
This patch moves the meta_compositor_size_change_window() calls before
move_resize_internal() which lets the compositor plugin know the old
window size and freezes the MetaWindowActor.
Then we get rid of the META_MOVE_RESIZE_DONT_SYNC_COMPOSITOR flag
since it's not needed anymore as the window actor is frozen and that
means we can use meta_compositor_sync_window_geometry() as the point
where we inform the compositor plugin of the final window size.
https://bugzilla.gnome.org/show_bug.cgi?id=770345
This will be used to let plugins know when a previous size change
actually becomes effective. This is needed to handle wayland client
resizing properly since, unlike X, it's async.
https://bugzilla.gnome.org/show_bug.cgi?id=770345
Normally textures in OpenGL are inverted on the Y axis, and we only
apply our rotation transform when it is not. To make the common case
work as normal, default to assuming textures are Y inverted.
https://bugzilla.gnome.org/show_bug.cgi?id=773629
Add support for inverted Y Wayland buffers. OpenGL textures are by
default inverted, so adding support for EGL_WAYLAND_Y_INVERTED_WL
effectively means adding support for non-inverted, which makes the
MetaShapedTexture apply a transformation when drawing only when querying
EGL_WAYLAND_Y_INVERTED_WL resulted in the response "EGL_FALSE".
https://bugzilla.gnome.org/show_bug.cgi?id=773629
Wayland popup grabs, unlike other grab types, can be safely cancelled
so there's no reason to deny compositor grab requests if a wayland
popup is on.
In particular, this allows entering the overview via a keybinding or
locking the screen while a wayland popup has a grab which is something
that's been advertised as a wayland improvement over X.
https://bugzilla.gnome.org/show_bug.cgi?id=771235
When we mess with a window actor's visibility from the shell side
(yes, I know :-( ), we should at least restore the proper visibility
when we're done with it ...
https://bugzilla.gnome.org/show_bug.cgi?id=771536
Not having a surface actor would cause the window actor state to be
considered frozen, thus causing various state (such as geometry, shape
etc) synchronization to be delayed until thawed. If the window actor
was "thawed" due to having a surface set, not all state would be
properly synchronized, causing the thawed window actor to be displayed
incorrectly.
This patch fixes this by putting state synchronization after thawing in
a common function, calling it both from frozen count decreasing and
surface setting.
This fixes for example misplaced menus in Steam.
https://bugzilla.gnome.org/show_bug.cgi?id=770991
CoglFrameInfo is a frame info container associated with a single
onscreen framebuffer. The clutter stage will eventually support drawing
a stage frame with multiple onscreen framebuffers, thus needs its own
frame info container.
This patch introduces a new stage signal 'presented' and a accompaning
ClutterFrameInfo and adapts the stage windows and past onscreen frame
callbacks users to use the signal and new info container.
https://bugzilla.gnome.org/show_bug.cgi?id=768976
We were compensating for a clone paint viewport offset even when we
were not in clone paniting mode. This would break painting if we offset
the viewport for some other reason for example as in the future stage
view painting.
https://bugzilla.gnome.org/show_bug.cgi?id=768976
Instead of assuming there is a single onscreen framebuffer, use the
helper functions for setting the frame callback and getting the frame
counter.
https://bugzilla.gnome.org/show_bug.cgi?id=768976
Use the correct pointer types for cogl objects. This avoids warnings
when including the cogl headers doesn't result in all the cogl types
being typedefs to void.
https://bugzilla.gnome.org/show_bug.cgi?id=768976
Emit a signal so that interested parties can recreate their FBOs and
queue a full scene graph redraw to ensure we don't end up showing
graphical artifacts.
This relies on the GL driver supporting the
NV_robustness_video_memory_purge extension and cogl creating a
suitable GL context. For now we only make use of it with the X backend
since the only driver with which this is useful is NVIDIA.
https://bugzilla.gnome.org/show_bug.cgi?id=739178
We ignore all damage while a surface is frozen and queue a full
update instead once it's thawed. While not super efficient, this
isn't overly bad for the intended case of catching up with any
updates that happened during a compositor effect. However when
extended frame sync is used, surfaces are also frozen while the
client is drawing a frame, in which case the current behavior is
pretty damaging (pun intended), as we end up redrawing the entire
window each frame. To address this, keep track of the actual damage
we ignore and apply it when the surface is thawed.
https://bugzilla.gnome.org/show_bug.cgi?id=767798
The only time the surface pointer (priv->surface) may be NULL is when
the surface is unmanaged but still painting, possibly due to a unmap
animation or the like, so only guard handle this situation in the entry
points that may come from the stage painting.
https://bugzilla.gnome.org/show_bug.cgi?id=763431
Before this commit, on Wayland, the buffer rect would have the size of
the attached Wayland buffer, no matter the scale. The scale would then
be applied ad-hoc by callers when a sane rectangle was needed. This
commit changes buffer_rect to rather represent the surface rect (i.e.
what is drawn on the stage, including client side shadow). The users of
buffer_rect will no longer need to scale the buffer_rect themself to
get a usable rectangle.
https://bugzilla.gnome.org/show_bug.cgi?id=763431
While CoglError is a define to GError, it doesn't follow the convention
of ignoring errors when NULL is passed, but rather treats the error as
fatal :-(
That's clearly unwanted for a compositor, so make sure to always pass
an error parameter where a runtime error is possible (i.e. any CoglError
that is not a malformed blend string).
https://bugzilla.gnome.org/show_bug.cgi?id=765058
Each wl_surface.commit with a newly attached buffer should result in
one wl_buffer.release for the attached buffer. For example attaching
the same buffer to two different surfaces must always result in two
wl_buffer.release events being emitted by the server. The client is
responsible for counting the wl_buffer.release events and be sure to
have received as many release events as it has attached and committed
the buffer, before reusing it.
https://bugzilla.gnome.org/show_bug.cgi?id=762828
We can detect that these windows are already fully opaque, so allow them
to unredirect. Allows unredirecting Totem during video playback, giving
a significant speed boost.
We currently rely only on MetaWindowActor to update the mask
texture. This isn't good enough since we might get asked to use the
mask (e.g. via meta_shaped_texture_get_image() ) after having a new
texture size but before MetaWindowActor decides to update the mask in
which case we might crash since cogl_texture_new_from_sub_texture()
might fail with an early return such as
Cogl-CRITICAL **: cogl_sub_texture_new: assertion 'sub_x + sub_width
<= next_width' failed
https://bugzilla.gnome.org/show_bug.cgi?id=762639
CSD X11 clients and Wayland clients don't have a window frame drawn by
the compositor to flash. So instead of flashing the whole screen when
configured to just flash the window, flash just the window region.
https://bugzilla.gnome.org/show_bug.cgi?id=763284
Some windows, like Chromium and Steam, are technically CSD in that they
don't want a system titlebar and draw their own, but we should still
provide them with a shadow.
If a queued event is being processed after the surface is
destroyed, trying to access the window associated with the surface
will lead to a segmentation fault.
This patch avoids the crash by first checking if the surface is not null.
https://bugzilla.gnome.org/show_bug.cgi?id=754715
Some backgrounds don't fully fill the screen. For those backgrounds
it's important to paint a color behind them to fill in the gaps.
This commit checks whether or not the background image textures take
up the entire monitor, and in the event they don't, draws a color
behind them (such as it would do if the background were
translucent).
https://bugzilla.gnome.org/show_bug.cgi?id=754476
meta_background_get_texture only draws the bottom image texture
if
1) the blend factor leaves the top image translucent
or
2) the top image is translucent from alpha
The latter case doesn't actually matter since we're using REPLACE
on the top image texture.
This commit drops the unnecessary check for the second case and
applies demorgans law to the conditional for clarity.
https://bugzilla.gnome.org/show_bug.cgi?id=754476
Since mutter has two X connections and does damage handling on the
frontend while fence triggering is done on the backend, we have a race
between XDamageSubtract() and XSyncFenceTrigger() causing missed
redraws in the GL_EXT_X11_sync_object path.
If the fence trigger gets processed first by the server, any client
drawing that happens between that and the damage subtract being
processed and is completely contained in the last damage event box
that mutter got, won't be included in the current frame nor will it
cause a new damage event.
A simple fix for this would be XSync()ing on the frontend connection
after doing all the damage subtracts but that would add a round trip
on every frame again which defeats the asynchronous design of X
fences.
Instead, if we move fence handling to the frontend we automatically
get the right ordering between damage subtracts and fence triggers.
https://bugzilla.gnome.org/show_bug.cgi?id=728464
The spec says:
"A server should avoid signalling the frame callbacks if the surface is not
visible in any way, e.g. the surface is off-screen, or completely obscured
by other opaque surfaces."
We actually do have the information to do that but we are always calling
the frame callbacks in after_stage_paint. So fix that to only call when
when the surface gets drawn on screen.
https://bugzilla.gnome.org/show_bug.cgi?id=739163
The compositor maintains a ring of shared fences with the X server in order to
properly synchronize rendering between the X server and the compositor's GPU
channel. When all of the fences have been used, the compositor needs to reset
one so that it can be reused. It does this by first waiting on the CPU for the
fence to become triggered, and then sending a request to the X server to reset
the fence.
If the compositor's GPU channel is busy processing other work (e.g. the desktop
switcher animation), then the X server may process the reset request before the
GPU has consumed the fence. This causes the GPU channel to hang.
Fix the problem by having the compositor's GPU channel trigger its own fence
after waiting for the X server's fence. Wait for that fence on the CPU before
sending the reset request to the X server. This ensures that the GPU has
consumed the X11 fence before the server resets it.
Signed-off-by: Aaron Plattner <aplattner@nvidia.com>
https://bugzilla.gnome.org/show_bug.cgi?id=728464
If GL advertises this extension we'll use it to synchronize X with GL
rendering instead of relying on the XSync() behavior with open source
drivers.
Some driver bugs were uncovered while working on this so if we have
had to reboot the ring a few times, something is probably wrong and
we're likely to just make things worse by continuing to try. Let's
err on the side of caution, disable ourselves and fallback to the
XSync() path in the compositor.
https://bugzilla.gnome.org/show_bug.cgi?id=728464
When a client sets an input region or a opaque region to NULL, it
should still be considered a change to the corresponding region on the
actor. This patch makes sure this state is properly forwarded.
https://bugzilla.gnome.org/show_bug.cgi?id=753222
Keep the active position state in its original coordinate space, and
synchronize the surface actor with it when it changes and when
synchronizing the rest of the surface state, in case the surface scale
had changed.
https://bugzilla.gnome.org/show_bug.cgi?id=745655
Whenever a MetaSurfaceActor is painted, update the list of what outputs
the surface is being drawed upon. Since we do this on paint, we
effectively avoids this whenever the surface is not drawn, for example
being minimized, on a non-active workspace, or simply outside of the
damage region of a frame.
DND icons and cursors are not affected by this patch, since they are not
drawn as MetaSurfaceActors. If a MetaSurfaceActor or a parent is cloned,
then we'll check the position of the original actor again when the clone is
drawn, which is slightly expensive, but harmless. If the MetaShapedTexture
instead is cloned, as GNOME Shell does in many cases, then these clones
will not cause duplicate position checks.
https://bugzilla.gnome.org/show_bug.cgi?id=744453
We may access it during painting even if it has been freed. For now,
manually unset it during the MetaWaylandSurface cleanup; in the future
make MetaWaylandSurface a GObject and make the surface pointer a weak
reference.
https://bugzilla.gnome.org/show_bug.cgi?id=744453
The elementary guys would like this as an API, and I don't see any
reason to refuse -- this is quite nice shadow painting code :)
For some reason, gobject-introspection can't seem to cope with
MetaWindowShape. I'll look into it a bit later, but for now, mark
the function it has trouble with as (skip).
It seems that when translated, paint_offset and actor_offset will always
be the same, so our translation of the clip group won't work. For now,
until I figure out what's going on here, just use the painting offset,
since that what seems to make sense to me.
I didn't write this code, though, so I don't know why the actor's
allocation was involved in this computation at all.
I tested briefly with clones (magnifier, manual cloning through the
looking glass) and couldn't find any other artifacts, so I'm going to do
this for now.
A much less hacky version of maximize / unmaximize is reimplemented
in terms of this, but it could also eventually be used for fullscreen /
unfullscreen, and tile / untile.
