The clutter-stage.h header still has a bunch of macros that have, for
reasons unknown[*], survived the 1.0 API cut and have long since been
deprecated. Let's hide them under the deprecated/ carpet and let us
never speak of them ever again.
[*] pretty sure alcohol or other psychotropic substances were involved
but I take the 5th on that.
Instead of defining new symbols for the windowing systems enabled at
configure time, we can reuse the same symbols for both the compile time
and run time checks, e.g.:
#ifdef CLUTTER_WINDOWING_X11
if (clutter_check_windowing_backend (CLUTTER_WINDOWING_X11))
/* use the clutter_x11_* API */
else
#endif
#ifdef CLUTTER_WINDOWING_WIN32
if (clutter_check_windowing_backend (CLUTTER_WINDOWING_WIN32))
/* use the clutter_win32_* API */
#endif
This scheme allows us to ensure that the input system namespace is free
for us to use and select at run time in later versions of Clutter.
We need debugging notes, to see what's happening when handling events.
We need to queue a (clipped) redraw when receiving a GDK_EXPOSE event.
We need to check the device (both master and source) of the event using
the GdkEvent API, and pass them to the ClutterEvent using the
corresponding Clutter API.
The code is generally wrong, and does not work. We need to skip the
GdkWindow creation when we have a foreing window, but we still need to
create the Cogl onscreen buffer and connect it to the GdkWindow's native
resource.
Just like the other backends can disable the internal event handling,
and use clutter_<backend>_handle_event() to do the native → Clutter
event translation.
Portable code should be allowed to check type backend currently being
used, so that it can use platform-specific API (not just Clutter's).
We don't want to go down the GDK route, with public types for
ClutterBackend and ClutterStageWindow implementations, and use the type
system, e.g.:
#ifdef GDK_WINDOWING_X11
if (GDK_IS_WINDOW_X11 (window))
use_x11_api (window);
else
#endif
#ifdef GDK_WINDOWING_WIN32
if (GDK_IS_WINDOW_WIN32 (window))
use_win32_api (window);
else
#endif
g_critical ("Unsupported backend");
This system would make us expose the backend system, and we want to
still reserve us the option to change the backend system to increase its
granularity — e.g. choosing different input event systems regardless of
the windowing system.
This commit adds a simple function that checks the backend type against
a symbolic constant — the same constant string that can be used to
select the backend at run-time through the CLUTTER_BACKEND environment
variable.
The Clutter backend split is opaque enough that should allow us to just
build all possible backends inside the same shared object, and select
the wanted backend at initialization time.
This requires some work in the build system, as well as the
initialization code, to remove duplicate functions that might cause
conflicts at build and link time. We also need to defer all the checks
of the internal state of the platform-specific API to run-time type
checks.
Previously, the Cogl backend was at times a subclass of the X11
backend, and at times a standalone one. Now it is the other way
round, with GDK and X11 backends providing the concrete classes,
layered on top of the generic Cogl backend. A new EglNative backend
was introduced for direct to framebuffer rendering. This greatly
simplifies the API design (at the expense of some casts needed)
and reduces the amount of #ifdefs, without duplicating code.
https://bugzilla.gnome.org/show_bug.cgi?id=657434
This commit introduces a new flavour for Clutter, that uses GDK
for handling all window system specific interactions (except for
creating the cogl context, as cogl does not know about GDK), including
in particular events. This is not compatible with the X11 (glx)
flavour, and this is reflected by the different soname (libclutter-gdk-1.0.so),
as all X11 specific functions and classes are not available. If you
wish to be compatible, you should check for CLUTTER_WINDOWING_X11.
Other than that, this backend should be on feature parity with X11,
including XInput 2, XSettings and EMWH (with much, much less code)
https://bugzilla.gnome.org/show_bug.cgi?id=657434
If our check of the CoglOnscreenTemplate during initialization fails
then we disable the request for an alpha component in the swap chain and
try the check again.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
Reviewed-by: Emmanuele Bassi <ebassi@linux.intel.com>
Avoid double argument checking, and a deprecation warning when
implementing create() as a wrapper around create_region(), by using
a simple internal function.
The number of deprecations in clutter-main.h makes the header harder to
parse, and more confusing. We can use a separate header under the
deprecated subdirectory to hold all the deprecated symbols.
Since Xlib.h is such a terrible citizen when it comes to symbol
namespacing it's not desirable to include Xlib.h if it is not absolutely
required. Cogl now has a standalone cogl-xlib.h that should be included
whenever any xlib specific symbols are required.
This patch updates clutter to include <cogl/cogl-xlib.h> wherever
clutter needs to use xlib specific cogl apis.
Acked-by: Emmanuele Bassi <ebassi@linux.intel.com>
We use an atexit() handler to print out the profile report coming from
Uprof. The g_atexit() call has been deprecated by GLib, but since this
use case is pretty specific and it's not meant to be turned on by
default (or distributed) then we can safely disable the deprecation
warnings inside clutter-profile.c.
The g_atexit() function has been deprecated in GLib as it is a fairly
bad idea in basically all cases.
We could probably use a GCC destructor if we didn't care about
portability, but for the time being we just remove the atexit() handler
that disposed the backend.
There are a couple of gotchas in the 'mapped' flag that are not properly
documented, or are documented only in the actor_invariants.txt file; we
should have a proper description in the API reference as well, to avoid
confusion.
Since the Windows GUI system is assuming multithreadedness, initializing
locks after entering the GUI portion on Windows is likely to cause
problems[1][2], which results many Clutter programs to crash due to
releasing resources that they did not own.
[1]: Multi-threaded use of GTK+ on Win32 in README.win32 of GTK+
source package
[2]: Explanation of Windows GUI system regarding its multithreadness
assumptions-
http://mail.gnome.org/archives/gtk-list/2011-June/msg00005.html
Since the Windows GUI system is assuming multithreadedness, initializing
locks after entering the GUI portion on Windows is likely to cause
problems[1][2], which results many Clutter programs to crash due to
releasing resources that they did not own.
[1]: Multi-threaded use of GTK+ on Win32 in README.win32 of GTK+
source package
[2]: Explanation of Windows GUI system regarding its multithreadness
assumptions-
http://mail.gnome.org/archives/gtk-list/2011-June/msg00005.html
Since the Windows GUI system is assuming multithreadedness, initializing
locks after entering the GUI portion on Windows is likely to cause
problems[1][2], which results many Clutter programs to crash due to
releasing resources that they did not own.
[1]: Multi-threaded use of GTK+ on Win32 in README.win32 of GTK+ source package
[2]: Explanation of Windows GUI system regarding its multithreadness
assumtopns-http://lists-archives.org/gtk/12724-compiling-a-gtk-application-on-windows.html
Or, better, the fact that the behaviour of any Clutter function will be
undefined in case the initialization fails.
The value returned by clutter_init() and friends has to be handled
properly.
This removes the create_texture implementation for ClutterBlurEffect
because we already account for padding in the get_paint_volume
implementation so we were creating textures larger than necessary.
Reviewed-by: Emmanuele Bassi <ebassi@linux.intel.com>
Just like ClutterBindConstraint has two shorthand enumerations for binding
position and size and avoid using multiple instances, ClutterAlignConstraint
should have a way to align an actor with the same alignment factor on both
axis at the same time; this is especially useful for centering actors.
The CLUTTER_DEBUG class of debugging flags is meant for debugging notes,
while the CLUTTER_PAINT debugging flags are for changing the output of
the paint cycle. Painting the DeformEffect tiles should go in the latter.
This function is called when the backend is being disposed - as a way
of releasing all ClutterShader. This doesn't take into account three
things:
- ClutterShader is deprecated
- the Backend is *never* disposed
- once the process terminates, all its resources are automatically
released by the OS
So the _clutter_shader_release_all() function is a pointless exercise
in futility.
For deprecation of APIs, in commits
522b8be3 (clutter_get_input_device_for_id())
6ef09dd1 (clutter_clear_glyph_cache())
01080dc5 (clutter_[sg]et_font_flags())
Just like GLIB_DEPRECATED and GLIB_DEPRECATED_FOR, Clutter should have
its own wrappers for G_DEPRECATED and G_DEPRECATED_FOR, to allow opting
out of deprecation warnings.
Deprecation warnings are enabled by default, now, even when building
Clutter.
This moves a couple of definitions to the common types header, and makes
sure that ClutterBehaviour subclasses include clutter-behaviour.h first,
so that their types can be fully expanded without necessarily have the
ClutterBehaviour header header included by their public headers. This is
the necessary prelude to have clutter-behaviour.[ch] moved to the
deprecated section.
The code that has been deprecated should live into its own directory,
both in the repository and when installed. This should make it clear
which functionality is actually maintained and which is not.
We start with an oldie: the frame source API.
On top of the existing "Settings" group in the settings.ini file we
should have two more groups:
Environment - contains all the configuration possible through
environment variables
Debug - contains all the possible debug variables
ClutterSettings should be able to load its initial state by using
configuration files in SYSCONFDIR and XDG_CONFIG_HOME. This allows
Clutter to have a system (and user) configuration on platforms that
do not have XSETTINGS bridges.
We already have two mechanisms for controlling the font rendering
quality on a per-application basis:
• ClutterSettings properties
• clutter_backend_set_font_options()
The font flags were always a stop-gap solution, and one that tried to
simplify a fairly complex issue beyond the point of actually being
useful.
https://bugzilla.gnome.org/show_bug.cgi?id=660786
The grab API is a relic of Clutter 0.6, and hasn't been through proper
vetting in a *long* time — mostly due to the fact that we don't really
like grabs, and point to the ::captured-event as a way to implement
"soft grabs" in toolkits and applications.
The implementation of full and device grabs uses weak references on
actors instead of using the ::destroy signal, which is meant exactly for
the case of releasing pointers to actors when they are disposed.
The API naming scheme is also fairly broken, especially for
device-related grabs.
Finally, keyboard device grabs are just not implemented.
We can, in one go, clean up this mess and deprecate a bunch of badly
named API by introducing generic device grab/ungrab methods on
ClutterInputDevice, and re-implement the current API on top of them.
GLib deprecated g_thread_init(), and threading support is initialized
by GObject, so Clutter already runs with threading support enabled. We
can drop the clutter_threads_init() call requirement, and initialize the
Big Clutter Lock™ on clutter_init(). This reduces the things that have
to be done when dealing with threads with Clutter, and the things that
can possibly go wrong.
The Big Clutter Lock™ can now be a static GMutex, since GLib supports
them. We can also drop a bunch of checks given the recent changes in
GLib threading API.
The static initializer for GMutex has been removed from GLib.
The g_thread_supported() call can also be removed: threading is always
enabled in GLib ≥ 2.31.
This commit introduces a unicode-to-keyval conversion function that
performs identical action as the gdk version of that function. Also
added is the necessary table holding all the conversion values.
https://bugzilla.gnome.org/show_bug.cgi?id=661015
If we do project() → get_bounding_box(), we'll try to complete the
volume twice, which whacks out all the lazily computed vertices.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
This is used as an alternative to calling
clutter_shader_effect_set_shader_source. A ClutterShaderEffect
subclass is now expected to implement this method to return the source
for the effect that will be used for all instances of this
subclass. It is only called once regardless of the number of instances
created. That way Clutter can avoid recompiling the shader source for
every new instance of the effect.
https://bugzilla.gnome.org/show_bug.cgi?id=660512
Reviewed-by: Emmanuele Bassi <ebassi@linux.intel.com>
The asynchronous loading code could do with some modernization.
First of all, we should drop the internal GMutex held when manipulating
the boolean flags: it's far too expensive for its role, and modern GLib
provides us with bitlocks that are quite a lot faster.
Then we should consolidate most of the implementation into something
smaller and more manageable.
The ClutterGeometry type is a poor substitute of cairo_rectangle_int_t,
with unsigned integers for width and height to complicate matters.
Let's remove the internal usage of ClutterGeometry and switch to the
rectangle type from Cairo.
https://bugzilla.gnome.org/show_bug.cgi?id=656663
When testing the performance of an application, it's often useful to
force it to continuously redraw instead of going idle to help measure
the frame rate. This just adds a CLUTTER_PAINT=continuous-redraw which
causes the master clock to queue a redraw on all of the stages
just before it prepares its source.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
Reviewed-by: Emmanuele Bassi <ebassi@linux.intel.com>
When the viewport gets expanded because the actor extends off the edge
of the screen, instead of applying the transformation to the root of
the modelview transformation it is now applied to the end of the
projection transformation. This should end up with the same
transformation. This fixes a problem when the offscreen effects are
nested and the inner effect would try to pick up the current modelview
transformation to rescale it to fit the new viewport size. In this
case the modelview would have already been scaled for the size of the
outer viewport so it would end up wrong.
https://bugzilla.gnome.org/show_bug.cgi?id=659601
Reviewed-by: Emmanuele Bassi <ebassi@linux.intel.com>
Reviewed-by: Robert Bragg <robert@linux.intel.com>
A ClutterText in password mode should have the ability to show the last
input character. This feature allows easier password entry on platforms
with unreliable keyboards, such as touchscreens or small devices.
https://bugzilla.gnome.org/show_bug.cgi?id=652588
Add a setting that controls whether ClutterText actors in password mode
should display the last input character for a defined time. This helps
on touch-based interfaces.
https://bugzilla.gnome.org/show_bug.cgi?id=652588
In _clutter_actor_set_default_paint_volume we were returning FALSE if an
actor has an empty allocation because we were claiming it doesn't have a
paint-volume. Actually an empty/degenerate pv is valid and has different
semantics to returning FALSE because FALSE means the pv is unknown and
so Clutter will have to assume the worst - that the pv is basically
un-bounded.
Reviewed-by: Emmanuele Bassi <ebassi@linux.intel.com>
This implicitly intersects any clip for redrawing with the stage window
bounds. Without this we were sometimes trying to set huge off screen
scissors leading to undefined clipping results.
Reviewed-by: Emmanuele Bassi <ebassi@linux.intel.com>
Out-of-band transforms are considered to be all actor transforms done
directly with the Cogl API instead of via ClutterActor::apply_transform.
By running with CLUTTER_DEBUG=oob-transform then Clutter will explicitly
try to detect when un-expected transforms have been applied to the
modelview matrix stack.
Out-of-band transforms can lead to awkward bugs in Clutter applications
because Clutter itself doesn't know about them and this can disrupt
Clutter's input handling and calculations of actor paint-volumes
which can lead to visual artifacts.
Reviewed-by: Emmanuele Bassi <ebassi@linux.intel.com>
For god-knows-what reason, at-spi is trying various formats
of strings when registering listeners, triggering an ugly
(gnome-shell:4411): Clutter-WARNING **: invalid object type create
warning in .xsession-errors. Stop doing that.
Also don't leak temporary string arrays that are a side-effect
of passing parameters around as formatted strings.
https://bugzilla.gnome.org/show_bug.cgi?id=658721
A bunch of private functions we use when parsing got exposed accidentaly
to the list of public symbols by virtue of not having the leading '_'
that we use to filter them out of the shared object — all the while the
header that declares them is a private, non installed one.
Let's rectify this situation with a bit of minor surgery on the code.
The priv->text field cannot ever be NULL, so we don't need to check for
that in a series of places. We also need to assert() that pre-condition
in the couple of places where we set the contents of the ClutterText
actor, namely in set_text_internal() and set_markup_internal().
Based on a patch by: Dan Winship <danw@gnome.org>
http://bugzilla.clutter-project.org/show_bug.cgi?id=2629
Setting :use-markup and :text is currently not idempotent, and it
depends on the ordering, e.g.:
g_object_set (actor, "use-markup", TRUE, "text", value, NULL);
does not yield the same results as:
g_object_set (actor, "text", value, "use-markup", TRUE, NULL);
This is particularly jarring when using ClutterText from ClutterScript,
but in general GObject properties should not rely on the order when used
from g_object_set().
The fix is to store the contents of the ClutterText as a separate string
from the displayed text, and use the contents, instead of the displayed
text, when toggling the :use-markup property.
Let's also add a unit test for good measure, to try and catch
regressions.
https://bugzilla.gnome.org/show_bug.cgi?id=651940
The easing test is a nice example of what ClutterAnimation and
clutter_actor_animate() can do. The "tween ball to the pointer
event coordinates" is a bit of a staple in animation libraries
and their documentation.
When we paint a ClutterText we ask the actor for a PangoLayout that fits
inside the actor's allocation - both width and height.
Sadly, whenever a height is set on a PangoLayout, Pango will wrap its
contents - regardless of whether the layout should actually wrap or not.
This means that in certain easy to exploit cases, Clutter will paint a
Text actor with its contents wrapping even if the :wrap property is set
to FALSE.
In order to fix this we need to encode some more cases inside the
::paint implementation of ClutterText, and ask the cache for a layout
that is sized as the allocation's width, but not as its height; we also
need to perform a clip if we detect that the PangoLayout's logical size
is going to overflow the allocated size. This clip might cause some
performance issue, given that clipping breaks batching in the Cogl
journal; hopefully all clips for text are going to be screen-aligned, so
at the end of the batch it'll just scissor them out.
http://bugzilla.clutter-project.org/show_bug.cgi?id=2339
Like commit d0439cfb586ca14282c89035119a4acbc0295df7 for
AlignConstraint, let's check that the BindConstraint source is not
a child or a grandchild of the actor attached to the Constraint.
AlignConstraint won't work if the source is a child or a grandchild of
the ClutterActorMeta:actor to which it has been attached to: the
allocation flows from the parent to its children, not the other way
around; in order to avoid weirdness, we better document and check
that when we set the actor and when we set the source.
The repaint functions list can (and should) be manipulated from
different threads, but it currently doesn't prevent multiple threads
from accessing it concurrently. We should have a simple lock and take it
when adding and removing elements from the list; the invocation is still
performed under the Big Clutter Lock™, so it doesn't require special
handling.
Because we have had several reports about significant performance
regressions since we enabled offscreen redirection by default for
handling correct opacity we are now turning this feature off by default.
We feel that clutter should prioritize performance over correctness in
this case. Correct opacity is still possible if required but the
overhead of the numerous offscreen allocations as well as the cost of
many render target switches per-frame seems too high relative the
improvement in quality for many cases.
On reviewing the offscreen_redirect property so we have a way to
disable redirection by default we realized that it makes more sense for
it to take a set of flags instead of an enum so we can potentially
extend the number of things that might result in offscreen redirection.
We removed the ability to say REDIRECT_ALWAYS_FOR_OPACITY, since it
seems that implies you don't trust the implementation of an actor's
has_overlaps() vfunc which doesn't seem right.
The default value if actor::redirect_offscreen is now 0 which
effectively means don't ever redirect the actor offscreen.
If an actor using a LayoutManager has attributes like margin or padding
then it'll have to shave them from the available allocation before
passing it to the LayoutManager::allocate() implementation. Layout
managers should, thus, not assume that the origin of the allocation is
in (0, 0), but take into account that the passed ActorBox might have a
different origin.
https://bugzilla.gnome.org/show_bug.cgi?id=649631
The actor is in charge of providing to the LayoutManager the available
allocation. ClutterBox should not just pass the box it got from its
parent: it should, instead, provide a normalized box, with an origin in
(0, 0) and the available size.
https://bugzilla.gnome.org/show_bug.cgi?id=649631
This adds experimental API to be able to get the CoglContext associated
with the ClutterBackend. The CoglContext is required to use some of the
experimental 2.0 Cogl API.
Note: Since CoglContext is itself experimental API this API should
considered experimental too. This patch introduces a
CLUTTER_ENABLE_EXPERIMENTAL_API #ifdef guard which anyone wanting to use
this API must define so it's explicitly clear to developers that they
are playing with experimental API.
Note: This API is not yet supported on OSX because OSX still uses the
stub Cogl winsys and the Clutter backend doesn't explicitly create a
CoglContext.
Note: even though this is experimental API we still promise that it
wont be changed during a stable release cycle. This means for example
that you can depend on this for the lifetime of the clutter-1.8 stable
release cycle.
The :fontconfig-timestamp is a write-only property that will get updated
by the underlying platform whenever the fontconfig configuration has
been changed — i.e. when the fontconfig caches should be rebuilt after
the user has installed a new font.
This makes ClutterText implement the Scriptable interface so that we can
have a custom property parser and setter for the font-description
property. This works by simply passing the string description through
to clutter_text_set_font_name.
Reviewed-by: Emmanuele Bassi <ebassi@linux.intel.com>
Actually this change has two notable effects; firstly we no longer
perform culling during picking and secondly we avoid updating the
last-paint-volume of an actor when picking.
We shouldn't perform culling during picking until clutter-stage.c is
updated to setup the clipping planes appropriately.
Since the last-paint-volume is intended to represent the visible region
of the actor the last time it was painted on screen it doesn't make
sense to update this during off screen pick renders since we are liable
to end up with a last-paint-volume that maps to an actors new position
when we next come to paint for real.
This fixes a bug in gnome-shell with dragging dash icons leaving a
messy trail on the screen.
Reviewed-by: Emmanuele Bassi <ebassi@linux.intel.com>
All 2D coordinate spaces in Cogl have their origin at the top-left so we
shouldn't be flipping the coordinates we pass to
cogl_framebuffer_swap_region to be relative to the bottom of the
framebuffer.
This bumps the Cogl version requirement to 1.7.5 since we've had to fix
a bug in the semantics of cogl_framebuffer_swap_region.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
Since commit 38b67e2884 of Cogl the naming scheme for winsys-specific
API has changed to be cogl_win32_onscreen_* instead of
cogl_onscreen_win32_* so it wouldn't build on Windows.
Added isHiding field to _ClutterStageOSX to allow windowDidResignKey
delegate to not order full screen window back whilst the full screen
window was being hidden. This caused other application windows to be
hidden. Also added code to keep hidden stage windows from being listed
in the application's Windows menu.
https://bugzilla.gnome.org/show_bug.cgi?id=655311
Added -windowDidChangeScreen: delegate to handle condition where moving
host window to a different screen would cause pick errors to be output.
The delegate just causes the stage to be redrawn which re-creates the
pick buffer.
https://bugzilla.gnome.org/show_bug.cgi?id=655306
The Animatable interface allows object classes to provide and animate
properties outside of the usual GObject property introspection API.
This change allows ClutterState to defer to the animatable objects the
property introspection and animation, just like ClutterAnimation does.
The animate_property() method of the Animatable interface is far less
than optimal:
• it has a direct reference to ClutterAnimation;
• it has an interval decomposed as two values.
These issues tie the Animatable interface with the Animation object,
even though it's neither necessary nor future-proof.
Let's introduce a new method, interpolate_value(), which does not
reference ClutterAnimation and uses a ClutterInterval to express the
initial and final states.
All ClutterModelIter virtual functions have a default implementation,
and G_TYPE_INSTANCE_GET_CLASS cannot return NULL unless in case of a
catastrophic event in the type system - which will most likely blow up
any application code way before you could call a ModelIter method.
Thus, the idiom:
klass = CLUTTER_MODEL_ITER_GET_CLASS (instance);
if (klass && klass->vfunc)
klass->vfunc (instance);
is utterly useless complication, and it can be perfectly replaced by:
CLUTTER_MODEL_ITER_GET_CLASS (instance)->vfunc (instance);
without any loss of safety.
Currently, only clutter_model_iter_set_valist() is in charge of emitting
the ClutterModel::row-changed signal. Both the set() and the
set_valist() functions can be called with multiple columns, so we
coalesce the signal emission at the end of the set_valist(), to have a
single ::row-changed emission per change.
The clutter_model_iter_set_value() function is just a thin wrapper
around the set_value() virtual function, but since it's called
internally we cannot add the signal emission there as well, as we'd
break the signal coalescing.
For this reason, we need some code refactoring inside the various set()
variants of ClutterModelIter:
- we only use the internal va_arg variant for both the set() and
set_valist() public functions, to avoid multiple type checks;
- the internal set_valist() calls an internal set_value() method
which calls the virtual function from the iterator vtable;
- a new internal emit_row_changed() method is needed to retrieve
the ClutterModel from the iterator, and emit the signal;
Now, all three variants of the value setter will call an internal
ClutterModelIter::set_value() wrapper, and emit the ::row-changed
signal.
To check that the intended behaviour has been implemented, and it's not
going to be broken, the test suite has grown a new unit which populates
a model and changes a random row.
Cally was initially created with Clutter 0.6 in mind. To check
recursively the visibility of a actor a custom method was added.
Since 0.8.4 clutter_actor_get_pain_visibility provides
the same functionality.
Also removed a dummy method. Lets add methods that provide a real
functionality.
Keeping the backing Cairo surface of a CairoTexture canvas in sync with
the actor's allocation is tedious and prone to mistakes. We can
definitely do better by simply exposing a property that does the surface
resize and invalidation automagically on ::allocate.
