Which is used for Wayland popup grabs.
The issue here is that we don't want the code that raises or focuses
windows based on mouse ops to run while a client has a grab.
We still keep the "old" grab infrastructure in place for now, but
ideally we'd replace it eventually with a better grab-op infrastructure.
... and individually. It turns out that updating the opaque region
was causing the shape region to be updated, which was causing a new
shape mask to be generated and uploaded to the GPU. Considering
GTK+ regenerates the opaque region on pretty much any focus change,
this is not good.
We need a MetaWaylandSurface to build a MetaSurfaceActor, but
we don't have one until we get the set_window_xid() call from
XWayland. On the other hand, plugins expect to see the window
actor right from when the window is created, so we need this
empty state.
Based on a patch by Jasper St. Pierre.
The input region was set on the shaped texture, but the shaped texture
was never picked properly, as it was never set to be reactive. Move the
pick implementation and reactivity to the MetaSurfaceActor, and update
the code everywhere else to expect a MetaSurfaceActor.
Traditionally, WMs unmap windows when minimizing them, and map them
when restoring them or wanting to show them for other reasons, like
upon creation.
However, as metacity morphed into mutter, we optionally chose to keep
windows mapped for the lifetime of the window under the user option
"live-window-previews", which makes the code keep windows mapped so it
can show window preview for minimized windows in other places, like
Alt-Tab and Expose.
I removed this preference two years ago mechanically, by removing all
the if statements, but never went through and cleaned up the code so
that windows are simply mapped for the lifetime of the window -- the
"architecture" of the old code that maps and unmaps on show/hide was
still there.
Remove this now.
The one case we still need to be careful of is shaded windows, in which
we do still unmap the client window. In the future, we might want to
show previews of shaded windows in the overview and Alt-Tab. In that
we'd also keep shaded windows mapped, and could remove all unmap logic,
but we'd need a more complex method of showing the shaded titlebar, such
as using a different actor.
At the same time, simplify the compositor interface by removing
meta_compositor_window_[un]mapped API, and instead adding/removing the
window on-demand.
https://bugzilla.gnome.org/show_bug.cgi?id=720631
We want to remove a bunch of auxilliary duties from the MetaWindowActor
and MetaSurfaceActor, including some details of how culling is done.
Move the unobscured region culling code to the MetaShapedTexture, which
helps the actor become "more independent".
https://bugzilla.gnome.org/show_bug.cgi?id=720631
We no longer unmap the toplevel windows during normal operation. The
toplevel state is tied to the window's lifetime.
Call meta_compositor_add_window / meta_compositor_remove_window instead...
Traditionally, WMs unmap windows when minimizing them, and map them
when restoring them or wanting to show them for other reasons, like
upon creation.
However, as metacity morphed into mutter, we optionally chose to keep
windows mapped for the lifetime of the window under the user option
"live-window-previews", which makes the code keep windows mapped so it
can show window preview for minimized windows in other places, like
Alt-Tab and Expose.
I removed this preference two years ago mechanically, by removing all
the if statements, but never went through and cleaned up the code so
that windows are simply mapped for the lifetime of the window -- the
"architecture" of the old code that maps and unmaps on show/hide was
still there.
Remove this now.
The one case we still need to be careful of is shaded windows, in which
we do still unmap the client window. Theoretically, we might want to
show previews of shaded windows in the overview and Alt-Tab, so we remove
the complex unmap tracking for this later.
Currently the only way to move a window to another monitor via
keyboard is to start a move operation and move it manually using
arrow keys. We do have all the bits of a dedicated keybinding in
place already, so offer it as a more comfortable alternative.
https://bugzilla.gnome.org/show_bug.cgi?id=671054
Make MetaWindowActor chain up to the generic default MetaCullable
implementation, and remove the helper methods for MetaSurfaceActor
and MetaShapedTexture.
For clarity, rename meta_window_get_outer_rect() to match terminology
we use elsewhere. The old function is left as a deprecated
compatibility wrapper.
There are extensive places in the code where we convert between the client
rectangle and the frame rectangle. Instead of manually doing it use
new helper functions on MetaWindow and the existing meta_window_get_outer_rect().
This fixes a number of bugs where the computation was being done incorrectly,
most of these bugs are with the recently added custom frame extents, but
some relate to invisible borders or even simply to confusion between the
window and frame rectangle.
Switch the placement code to place the frame rectangle rather
than the client window - this simplifies things considerably.
https://bugzilla.gnome.org/show_bug.cgi?id=707194
Use the "hotplug_mode_update" connector property indicating that the
screen settings should be updated: get a new preferred mode on hotplug
events to handle dynamic guest resizing (where you resize the host
window and the guest resizes with it).
https://bugzilla.gnome.org/show_bug.cgi?id=711216
When X clients change the keyboard map, the also update a property
on the root window. We can notice that and rebuild our data structures
with the new values, as well as inform the wayland clients.
This is a terrible hack, and it's not how we want to implement things
in 3.12, but it's enough to have the same keyboard layout in the
shell, in X clients and in wayland clients in 3.10, until we decide
on the fate of the keyboard g-s-d plugin.
https://bugzilla.gnome.org/show_bug.cgi?id=707446
Switching meta/util.h to gi18n.h was wrong, mutter is a library
and needs gi18n-lib.h, but that cannot be included from a public
header (since it depends on config.h or command line options),
so split util.h into a public and a private part.
https://bugzilla.gnome.org/show_bug.cgi?id=707897
clutter_stage_show_cursor()/hide_cursor() only works in the X11
backend (where someone else is in charge of showing the cursor),
and even then, it has confusing effects when running nested wayland,
so an abstraction layer is needed.
https://bugzilla.gnome.org/show_bug.cgi?id=707474
When we get a damage event we update the window by calling
meta_shaped_texture_update_area which queues a redraw on the actor.
We can avoid that for obscured regions by comparing the damage area to
our visible area.
This patch causes _NET_WM_FRAME_DRAWN messages to be not sent in some cases
where they should be sent; they will be added back in a later commit.
https://bugzilla.gnome.org/show_bug.cgi?id=703332
When drawing entirely opaque regions, we traditionally kept blending on
simply because it made the code more convenient and obvious to handle.
However, this can cause lots of performance issues on GPUs that aren't
too powerful, as they have to readback the buffer underneath.
Keep track of the opaque region set by windows (through _NET_WM_OPAQUE_REGION,
Wayland opaque_region hints, standard RGB32 frame masks or similar), and draw
those rectangles separately through a different path with blending turned off.
https://bugzilla.gnome.org/show_bug.cgi?id=707019
When running as a wayland compositor, we can't use the xserver's
IDLETIME, because that's updated only in response to X events.
But we have all the events ourselves, so we can just run the timer
in process.
https://bugzilla.gnome.org/show_bug.cgi?id=706005
Remove grab window and cursor from the API, and just grab always
on the stage window with no cursor.
This is mainly to remove the X11 usage in the public API, in preparation
for implementing this in wayland.
https://bugzilla.gnome.org/show_bug.cgi?id=705917
Under X, we need to use XFixes to watch the cursor changing, while
on wayland, we're in charge of setting and painting the cursor.
MetaCursorTracker provides the abstraction layer for gnome-shell,
which can thus drop ShellXFixesCursor. In the future, it may grow
the ability to watch for pointer position too, especially if
CursorEvents are added to the next version of XInput2, and thus
it would also replace the PointerWatcher we use for gnome-shell's
magnifier.
https://bugzilla.gnome.org/show_bug.cgi?id=705911
We want to show a dialog when a display change happens from the
control center. To do so, add a new vfunc to MetaPlugin and
call it when a configuration change is requested via DBus.
https://bugzilla.gnome.org/show_bug.cgi?id=705670
GnomeRR needs that too.
The backlight is exported as a normalized 0-100 value, or -1 if not
supported. Clamping to HW limits is handled by the backend.
Changing backlight uses a different method call, to avoid recomputing
the full display configuration every time the user presses the
backlight keys.
https://bugzilla.gnome.org/show_bug.cgi?id=705670
Use a private output property to store if the output is in
presentation mode or not, so that this information is not lost
after the configuration read back from the server.
https://bugzilla.gnome.org/show_bug.cgi?id=705670
This new interface will be used by the control center and possibly
the settings daemon to configure the screens. It is designed to
resemble a simplified XRandR, while still exposing all the quirks
of the hardware, so that the panel can limit the user choices
appropriately.
To do so, MetaMonitorMode needs to track CRTCs, outputs and modes,
so the low level objects have been decoupled from the high-level
MetaMonitorInfo, which is used by core and API and offers a simplified
view of HW, that hides away the details of what is cloned and how.
This is still not efficient as it should be, because on every
HW change we drop all data structures and rebuild them from scratch
(which is not expensive because there aren't many of them, but
at least in the XRandR path it involves a few sync X calls)
https://bugzilla.gnome.org/show_bug.cgi?id=705670
This breaks down the assumptions in stack-tracker.c and stack.c that
Mutter is only stacking X windows.
The stack tracker now tracks windows using a MetaStackWindow structure
which is a union with a type member so that X windows can be
distinguished from Wayland windows.
Some notable changes are:
Queued stack tracker operations that affect Wayland windows will not be
associated with an X serial number.
If an operation only affects a Wayland window and there are no queued
stack tracker operations ("unvalidated predictions") then the operation
is applied immediately since there is no server involved with changing
the stacking for Wayland windows.
The stack tracker can no longer respond to X events by turning them into
stack operations and discarding the predicted operations made prior to
that event because operations based on X events don't know anything
about the stacking of Wayland windows.
Instead of discarding old predictions the new approach is to trust the
predictions but whenever we receive an event from the server that
affects stacking we cross-reference with the predicted stack and check
for consistency. So e.g. if we have an event that says ADD window A then
we apply the predictions (up to the serial for that event) and verify
the predicted state includes a window A. Similarly if an event says
RAISE_ABOVE(B, C) we can apply the predictions (up to the serial for
that event) and verify that window B is above C.
If we ever receive spurious stacking events (with a serial older than we
would expect) or find an inconsistency (some things aren't possible to
predict from the compositor) then we hit a re-synchronization code-path
that will query the X server for the full stacking order and then use
that stack to walk through our combined stack and force the X windows to
match the just queried stack but avoiding disrupting the relative
stacking of Wayland windows. This will be relatively expensive but
shouldn't be hit for compositor initiated restacking operations where
our predictions should be accurate.
The code in core/stack.c that deals with synchronizing the window stack
with the X server had to be updated quite heavily. In general the patch
avoids changing the fundamental approach being used but most of the code
did need some amount of re-factoring to consider what re-stacking
operations actually involve X or not and when we need to restack X
windows we sometimes need to search for a suitable X sibling to restack
relative too since the closest siblings may be Wayland windows.
This adds support for running mutter as a hybrid X and Wayland
compositor. It runs a headless XWayland server for X applications
that presents wayland surfaces back to mutter which mutter can then
composite.
This aims to not break Mutter's existing support for the traditional X
compositing model which means a single build of Mutter can be
distributed supporting the traditional model and the new Wayland based
compositing model.
TODO: although building with --disable-wayland has at least been tested,
I still haven't actually verified that running as a traditional
compositor isn't broken currently.
Note: At this point no input is supported
Note: multiple authors have contributed to this patch:
Authored-by: Robert Bragg <robert@linux.intel.com>
Authored-by: Neil Roberts <neil@linux.intel.com>
Authored-by: Rico Tzschichholz.
Authored-by: Giovanni Campagna <gcampagna@src.gnome.org>
This adds a --nested option to request that mutter no longer run as a
classic X compositor with an output window mapped on the X Composite
Overlay Window and also not assume it is running directly under X.
The intention is that in this mode Mutter will itself launch a headless
X server and display output will be handled by Clutter and Cogl. This
will enable running Mutter nested as an application within an X session.
This patch introduces an internal meta_is_wayland_compositor() function
as a means to condition the way mutter operates when running as a
traditional X compositor vs running as a wayland compositor where the
compositor and display server are combined into a single process.
Later we also expect to add a --kms option as another way of enabling
this wayland compositor mode that will assume full control of the
display hardware instead of running as a nested application.
We now track whether a window has an input shape specified via the X
Shape extension. Intersecting that with the bounding shape (as required
by the X Shape extension) we use the resulting rectangles to paint
window silhouettes when picking. As well as improving the correctness of
picking this should also be much more efficient because typically when
only picking solid rectangles then the need to actually render and issue
a read_pixels request can be optimized away and instead the picking is
done on the cpu.
Add new api (meta_screen_get_current_monitor_for_pos and
meta_screen_get_current_monitor_info_for_pos) that allow querying the monitor
without a roundtrip by reusing the passed in cursor position.
gnome-shell needs to know whether the stage window is focused so
it can synchronize between stage window focus and Clutter key actor
focus. Track all X windows, even those without MetaWindows, when
tracking the focus window, and add a compositor-level API to determine
when the stage is focused.
https://bugzilla.gnome.org/show_bug.cgi?id=700735
When we set the input focus, we first set the predicted window,
and then try to process focus events. But as XI_FocusOut on the
existing window comes before XI_FocusIn on the new window, we'll
see the focus out on the old window and think the focus is going
to nothing, which makes mutter think the prediction failed.
This didn't really matter as nothing paid attention to the focus
window changing, but with gnome-shell's focus rework, we'll try
and drop keyboard focus in events like these.
Fix this by making sure that we ignore focus window changes of our
own cause when updating the focus window field, by ignoring all
focus events that have a serial the same as the focus request or
lower. Note that if mutter doens't make any requests after the
focus request, this could be racy, as another client could steal
the focus, but mutter would ignore it as the serial was the same.
Bump the serial by making a dummy ChangeProperty request to a
mutter-controlled window in this case.
https://bugzilla.gnome.org/show_bug.cgi?id=701017
We'll use this in gnome-shell to freeze the keyboard right before
switching input source and unfreeze it after that's finished so that
we don't lose any key events to the wrong input source.
https://bugzilla.gnome.org/show_bug.cgi?id=697001
gnome-shell has traditionally just called XSetInputFocus when wanting to
set the input focus to the stage window, but this might cause strange,
hard-to-reproduce bugs because of an interference with mutter's focus
prediction. Add API to allow gnome-shell to focus the stage window that
also updates mutter's internal focus prediction state.
https://bugzilla.gnome.org/show_bug.cgi?id=700735
Mutter previously defined display->focus_window as the window that the
server says is focused, but kept display->expected_focus_window to
indicate the window that we have requested to be focused. But it turns
out that "expected_focus_window" was almost always what we wanted.
Make MetaDisplay do a better job of tracking focus-related requests
and events, and change display->focus_window to be our best guess of
the "currently" focused window (ie, the window that will be focused at
the time when the server processes the next request we send it).
https://bugzilla.gnome.org/show_bug.cgi?id=647706
The hierarchy handling is handled in the shell by adding stuff
directly to the uiGroup, and we have a dedicated actor for
the overview there, so we don't need this anymore.
https://bugzilla.gnome.org/show_bug.cgi?id=700735
Trying to track the fullscreen status outside of Mutter, as GNOME Shell
was doing previously, was very prone to errors, because Mutter has a
very tricky definition of when a window is set to be fullscreen and
*actually* acting like a fullscreen window.
* Add meta_screen_get_monitor_in_fullscreen() and an
::in-fullscreen-changed signal. This allows an application to
track when there are fullscreen windows on a monitor.
* Do the computation of fullscreen status in a "later" function that
runs after showing, so we properly take focus into account.
* To get ordering of different phases right, add more values
to MetaLaterType.
* Add auto-minimization, similar to what was added to GNOME Shell
earlier in this cycle - if a window is set to be fullscreen, but
not actually fullscreen, minimize.
https://bugzilla.gnome.org/show_bug.cgi?id=649748
gnome-shell shouldn't announce to the session manager it's
"ready" until it's fully initialized. It currently tells
the session manager it's ready as soon as it hits the main
loop. This causes nautilus in classic mode to start before
we have workspaces initialized.
https://bugzilla.gnome.org/show_bug.cgi?id=694876
During compositor grabs, all global keybindings that don't go
through mutter's keybinding system are blocked. To allow other
processes to make use of it, gnome-shell will expose a simple
grab API on DBus; for this, add API to grab key combos directly
instead of parsing accelerators stored in GSettings.
https://bugzilla.gnome.org/show_bug.cgi?id=643111
Background handling in GNOME is very roundabout at the moment.
gnome-settings-daemon uses gnome-desktop to read the background from
disk into a screen-sized pixmap. It then sets the XID of that pixmap
on the _XROOTPMAP_ID root window property.
mutter puts that pixmap into a texture/actor which gnome-shell then
uses.
Having the gnome-settings-daemon detour from disk to screen means we
can't easily let the compositor handle transition effects when
switching backgrounds. Also, having the background actor be
per-screen instead of per-monitor means we may have oversized
textures in certain multihead setups.
This commit changes mutter to read backgrounds from disk itself, and
it changes backgrounds to be per-monitor.
This way background handling/compositing is left to the compositor.
https://bugzilla.gnome.org/show_bug.cgi?id=682427
We do, in fact, need freezing to affect window geometry, so that
move-resize operations (such as an interactive resize from the
left, or a resize of a popup centered by the application) occur
atomically.
So to make map effects work properly, only exclude the initial
placement of a window from freezing. (In the future, we may want
to consider whether pure moves of a window being done in response
to a user drag should also be excluded from freezing.)
Rename meta_window_sync_actor_position() to
meta_window_sync_actor_geometry() for clarity.
https://bugzilla.gnome.org/show_bug.cgi?id=693922
The WM spec requires _NET_WM_FRAME_DRAWN to *always* be sent when
there is an appropriate update to the sync counter value. We were
potentially missing _NET_WM_FRAME_DRAWN when an application did a
spontaneous update during an interactive resize and during effects.
Refactor the code to always send _NET_WM_FRAME_DRAWN, even when
a window is frozen.
https://bugzilla.gnome.org/show_bug.cgi?id=693833
Put override redirect windows such as menus into a separate window group
stacked above everything else. This will allow us to visually put these
above other compositior chrome.
Based on a patch from Muffin.
https://bugzilla.gnome.org/show_bug.cgi?id=633620
We previously had timestamp information stubbed out in
_NET_WM_FRAME_DRAWN. Instead of this, add a high-resolution timestamp
in _NET_WM_FRAME_DRAWN then send a _NET_WM_FRAME_TIMINGS message
after when we have complete frame timing information, representing
the "presentation time" of the frame as an offset from the timestamp
in _NET_WM_FRAME_DRAWN.
To provide maximum space in the messages,_NET_WM_FRAME_DRAWN and
_NET_WM_FRAME_TIMINGS are not done as WM_PROTOCOLS messages but
have their own message types.
https://bugzilla.gnome.org/show_bug.cgi?id=685463
When the application provides the extended second counter for
_NET_WM_SYNC_REQUEST, send a client message with completion
information after the next redraw after each counter update
by the application.
https://bugzilla.gnome.org/show_bug.cgi?id=685463
Replace the unused meta_compositor_set_updates() with
a reversed-meaning meta_compositor_set_updates_frozen(), and use
it to implement freezing application window updates during
interactive resizing. This avoids drawing new areas of the window
with blank content before the application has a chance to repaint.
https://bugzilla.gnome.org/show_bug.cgi?id=685463
XInput 2.3 adds support for "barrier events", which let us know when
a pointer barrier has been hit, and when the pointer has stopped
hitting the barrier, and lets us "release" the barrier, temporarily
letting the pointer pass through the barrier. These features can be
combined to allow for certain pointer gestures, such as "pushing"
against the bottom of the screen, or stopping the pointer on monitor
edges while dragging slowly for increased edge precision.
This commit should allow graceful fallback if servers with
XInput 2.3 aren't supported.
https://bugzilla.gnome.org/show_bug.cgi?id=677215
Currently, we have a few function wrappers in the shell for pointer
barriers. If we want to implement interactive features on barriers,
we need some sort of signal to be notified of the interactivity.
In that case, we need to make a more sophisticated object-based wrapper
for a pointer barrier. Add one, and stick it in mutter.
https://bugzilla.gnome.org/show_bug.cgi?id=677215
This new hint allows compositors to know what portions of a window
will be obscured, as a region above them is opaque. For an RGB window,
possible to glean this information from the bounding shape region of
a client window, but not for an ARGB32 window. This new hint allows
clients that use ARGB32 windows to say which part of the window is
opaque, allowing this sort of optimization.
https://bugzilla.gnome.org/show_bug.cgi?id=679901
Using a public method for setting the (cached) icon geometry rather
than accessing the struct members directly allows setting the icon
geometry from extensions.
https://bugzilla.gnome.org/show_bug.cgi?id=692997
We have some code in gnome-shell that does the equivalent of:
window.get_workspace() == workspace || window.is_on_all_workspaces();
which is a bit unwieldy. We already have a method in mutter,
so use that and document it.
https://bugzilla.gnome.org/show_bug.cgi?id=691744
Add meta_window_check_alive(), which is a simple wrapper over
meta_display_ping_window(), and takes care of showing the "Application
is not responding dialog" if needed.
https://bugzilla.gnome.org/show_bug.cgi?id=684340
Mechanically transform the event processing of mutter to care
about XI2 events instead of Core Events. Core Events will be left
in the dust soon, and removed entirely.
https://bugzilla.gnome.org/show_bug.cgi?id=688779
Since we want nice alt-tab applications for gnome-shell, we should up the
limit to 96. In the future, we probably want to get rid of the icon-cache,
and allow looking up a correctly sized icon directly from the window.
To prevent app breakage, set the legacy WM_HINTS pixmap size directly to
32x32.
https://bugzilla.gnome.org/show_bug.cgi?id=689651
Add an additional "switcher" keybinding for switching between
applications rather than windows (like the existing 'switch-windows'
and 'switch-group' bindings).
The purpose of the new keybinding is to be taken over by gnome-shell's
application-based alt-tab popup, so rather than actually implementing
an application switcher in mutter, let it duplicate the normal window
switcher when run standalone.
https://bugzilla.gnome.org/show_bug.cgi?id=688913
Currently keybindings are blocked while the compositor holds a grab; if
we want a keybinding to be available anyway, we use captured ClutterEvents
to determine the KeyBindingAction the event would have triggered and
run our own handlers (ugh).
Instead, provide a hook to allow the compositor to filter out keybindings
before processing them normally, regardless of whether the compositor
holds a grab or not.
https://bugzilla.gnome.org/show_bug.cgi?id=688202
Using ClutterEffect is not pratical on MetaBackgroundActor, as the FBO
redirection has a noticeable performance impact. Instead, allow adding
GLSL code directly to the pipeline used to draw the background texture.
At the same time, port MetaBackgroundActor to modern Cogl API.
https://bugzilla.gnome.org/show_bug.cgi?id=669798
Moving focus immediately on crossing events as we currently do
in focus-follows-mouse mode may trigger a lot of unwanted focus
changes when moving over unrelated windows on the way to a target.
Those accidental focus changes prevent features like GNOME Shell's
application menu from working properly and are visually expensive
since we now use a very distinct style for unfocused windows.
Instead, delay the actual focus change until the pointer has stopped
moving.
https://bugzilla.gnome.org/show_bug.cgi?id=678169
Add a type annotation on the xevent_filter vfunc. This is sufficient
to remove the skip annotation on MetaPlugin and MetaPluginClass
without triggering scan errors.
https://bugzilla.gnome.org/show_bug.cgi?id=671098
As plugins can now define their own keyboard shortcuts via
meta_display_add_keybinding(), it makes sense for them to
expose those shortcuts to System Settings, so add some API
to set the properties gnome-control-center uses to pick up
wm keybinding settings.
https://bugzilla.gnome.org/show_bug.cgi?id=671010
Similar to meta_screen_get_primary_monitor, this returns a monitor index.
The monitor that the pointer is on. The previous private implementation
has been renamed to meta_screen_get_current_monitor_info.
https://bugzilla.gnome.org/show_bug.cgi?id=642591
The "multiple plugins loaded at once" strategy was always a big fiction:
while it may be viable if you're super careful, it's fragile and requires
a bit of infrastructure that we would be better off without.
Note that for simplicity, we're keeping the MetaPluginManager, but it only
manages one plugin. A possible future cleanup would be to remove it entirely.
https://bugzilla.gnome.org/show_bug.cgi?id=676855
We already check that the plugin has the appropriate vfunc in the klass
structure, so we shouldn't need to check for the same data again with
a "features" long.
https://bugzilla.gnome.org/show_bug.cgi?id=676855
We may not show the backtrace, but it's prohibitly expensive to generate,
so don't. If someone wants a backtrace they can use the appropriate G_DEBUG
environment variable plus GDB.
https://bugzilla.gnome.org/show_bug.cgi?id=676855
This effectively makes MetaShapedTexture not a MetaShapedTexture, but a simple
and dumb MetaMaskedTexture, with an optimization for clipped regions.
We're doing this as the mask may need to be more complicated than made of
a cairo path -- we eventually want GTK+ to draw the entire frame background,
which we'll then scan.
https://bugzilla.gnome.org/show_bug.cgi?id=676052
