The test-easing interactive demo for the high-level animation API
is a bit "flat". Instead of using a Rectangle actor we should
probably be using something more "interesting" -- like a CairoTexture
with a gradient.
In order to chain up animations using clutter_actor_animate() and
friends you have to use an idle handler that guarantees that the
main loop spins at least once after the animation pointer has been
detached from the actor.
This has several drawbacks, first and foremost the fact that the
slice of the main loop for the idle handler might be starved by
other operations, like redrawing. This inevitably leads to tricks
with priorities and the like, contributing to the overall complexity.
Instead, we should guarantee that the animation instance created by
clutter_actor_animate() is valid for the ::completed signal until
it reaches its default handler; after that, the animation is detached
from the actor and destroyed. This means that it's possible to
create a new animation after the first is complete by simply using
g_signal_connect_after().
This unfortunately makes it impossible to keep a reference to the
animation pointer attached to the actor by using g_object_ref(); a
way to "fix" this would be to have a clutter_animation_attach()
and a clutter_animation_detach() pair of methods that allow attaching
any animation to an actor. This might overcomplicate what it is
the simple animation API, though, so it's currently not implemented
and left for future versions.
The test-easing interactive demo has been modified to show how
the animation queuing works by adding a command line switch that
recenters the animated actor once the first animation has ended.
All the underlying implementation and the public entry points have
been switched to floats; the only missing bits are the Actor properties
that deal with positioning and sizing.
This usually means a major pain when dealing with GValues and varargs
functions. While GValue will warn you when dealing with the wrong
conversions, varags will simply die an horrible (and hard to debug)
death via segfault. Nothing much to do here, except warn people in the
release notes and hope for the best.
With the recent change to internal floating point values, ClutterUnit
has become a redundant type, defined to be a float. All integer entry
points are being internally converted to floating point values to be
passed to the GL pipeline with the least amount of conversion.
ClutterUnit is thus exposed as just a "pixel with fractionary bits",
and not -- as users might think -- as generic, resolution and device
independent units. not that it was the case, but a definitive amount
of people was convinced it did provide this "feature", and was flummoxed
about the mere existence of this type.
So, having ClutterUnit exposed in the public API doubles the entry
points and has the following disadvantages:
- we have to maintain twice the amount of entry points in ClutterActor
- we still do an integer-to-float implicit conversion
- we introduce a weird impedance between pixels and "pixels with
fractionary bits"
- language bindings will have to choose what to bind, and resort
to manually overriding the API
+ *except* for language bindings based on GObject-Introspection, as
they cannot do manual overrides, thus will replicate the entire
set of entry points
For these reason, we should coalesces every Actor entry point for
pixels and for ClutterUnit into a single entry point taking a float,
like:
void clutter_actor_set_x (ClutterActor *self,
gfloat x);
void clutter_actor_get_size (ClutterActor *self,
gfloat *width,
gfloat *height);
gfloat clutter_actor_get_height (ClutterActor *self);
etc.
The issues I have identified are:
- we'll have a two cases of compiler warnings:
- printf() format of the return values from %d to %f
- clutter_actor_get_size() taking floats instead of unsigned ints
- we'll have a problem with varargs when passing an integer instead
of a floating point value, except on 64bit platforms where the
size of a float is the same as the size of an int
To be clear: the *intent* of the API should not change -- we still use
pixels everywhere -- but:
- we remove ambiguity in the API with regard to pixels and units
- we remove entry points we get to maintain for the whole 1.0
version of the API
- we make things simpler to bind for both manual language bindings
and automatic (gobject-introspection based) ones
- we have the simplest API possible while still exposing the
capabilities of the underlying GL implementation
Instead of using our own homegrown alpha functions, we should
use the easing functions also shared by other animation frameworks,
like jQuery and Tween, in the interests of code portability.
The easing functions have been defined by Robert Penner and
are divided into three categories:
In Out InOut
Each category has a particular curve:
Quadratic
Cubic
Quartic
Quintic
Sinusoidal
Exponential
Circular
In addition, there are "physical" curves:
Elastic
Back (overshooting cubic)
Bounce (exponentially decaying parabolic)
Finally, the Linear curve is also provided as a reference.
The functions are private, and are meant to be used only
through their logical id as provided by the AnimationMode
enumeration.
The tests should be updated as well to match the new
easing functions.
* tests/interactive/test-pixmap.c (create_pixmap): Use a format
string instead of passing the error message directly to g_error.
* tests/interactive/test-easing.c (test_easing_main)
(on_button_press):
* tests/interactive/test-animation.c (on_button_press): Use
unsigned variables for the results from clutter_actor_get_size
otherwise it complains about the pointer signedness being
different.
* clutter/clutter-script.c (clutter_script_add_search_paths): Use
G_GSIZE_FORMAT instead of %d for a gsize parameter otherwise it
gets upset on 64-bit.
* clutter/clutter-alpha.h:
* clutter/clutter-alpha.c:
(clutter_alpha_set_mode): Use a lookup table to find the alpha
function given the animation mode.
(clutter_exp_in_func),
(clutter_exp_out_func),
(clutter_exp_in_out_func): Add new exponential functions.
* clutter/clutter-script.c: Update the lookup table with the
new animation modes; match "linear" to the ramp-inc alpha
function.
* clutter/clutter-types.h: Add new AnimationMode values.
* tests/interactive/test-easing.c: Update the easing functions
test.
Bug 1014 - Clutter Animation API Improvements
* clutter/Makefile.am:
* clutter/clutter.h: Update the build
* clutter/clutter-types.h: Add AnimationMode, an enumeration
for easing functions.
* clutter/clutter-alpha.[ch]: Add the :mode property to
control the function bound to an Alpha instance using an
enumeration value. Also add six new alpha functions:
- ease-in, ease-out, ease-in-out
- sine-in, sine-out, sine-in-out
* clutter/clutter-deprecated.h: Deprecate the #defines for
the alpha functions. They will be replaced by entries in the
ClutterAnimationMode.
* clutter/clutter-interval.[ch]: Add ClutterInterval, an
object for defining, validating and computing an interval
between two values.
* clutter/clutter-animation.[ch]: Add ClutterAnimation, an
object responsible for animation the properties of a single
actor along an interval of values. ClutterAnimation memory
management is automatic. A simple wrapper method for
ClutterActor is provided:
clutter_actor_animate()
which will create, or update, an animation for the passed
actor.
* clutter/clutter-debug.h:
* clutter/clutter-main.c: Add a new 'animation' debug note.
* clutter/clutter-script.c: Clean up the alpha functions
whitelist, and add the new functions.
* doc/reference/clutter/Makefile.am:
* doc/reference/clutter/clutter-sections.txt: Update the
API reference.
* doc/reference/clutter/clutter-animation.xml: Renamed to
doc/reference/clutter/clutter-animation-tutorial.xml to
avoid clashes with the ClutterAnimation section.
* doc/reference/clutter/clutter-docs.sgml: Renamed to
doc/reference/clutter/clutter-docs.xml, as it was an XML
file and not a SGML file.
* tests/Makefile.am:
* tests/interactive/Makefile.am:
* tests/interactive/test-animation.c:
* tests/interactive/test-easing.c: Add two tests for the
new simple animation API and the easing functions.
* tests/interactive/test-actors.c:
* tests/interactive/test-behave.c:
* tests/interactive/test-depth.c:
* tests/interactive/test-effects.c:
* tests/interactive/test-layout.c:
* tests/interactive/test-multistage.c:
* tests/interactive/test-paint-wrapper.c:
* tests/interactive/test-rotate.c:
* tests/interactive/test-scale.c:
* tests/interactive/test-texture-quality.c:
* tests/interactive/test-threads.c:
* tests/interactive/test-viewport.c: Update interactive tests
to the deprecations and new alpha API.
