mutter/clutter/clutter-effect.c

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/*
* Clutter.
*
* An OpenGL based 'interactive canvas' library.
*
* Copyright (C) 2010 Intel Corporation.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see <http://www.gnu.org/licenses/>.
*
* Author:
* Emmanuele Bassi <ebassi@linux.intel.com>
*/
/**
* SECTION:clutter-effect
* @short_description: Base class for actor effects
*
* The #ClutterEffect class provides a default type and API for creating
* effects for generic actors.
*
* Effects are a #ClutterActorMeta sub-class that modify the way an actor
* is painted in a way that is not part of the actor's implementation.
*
* Effects should be the preferred way to affect the paint sequence of an
* actor without sub-classing the actor itself and overriding the
* #ClutterActor::paint virtual function.
*
* <refsect2 id="ClutterEffect-implementation">
* <title>Implementing a ClutterEffect</title>
* <para>Creating a sub-class of #ClutterEffect requires the implementation
* of three virtual functions:</para>
* <itemizedlist>
* <listitem><simpara><function>prepare()</function>, which is called when
* attaching the #ClutterEffect to a #ClutterActor through the
* clutter_actor_add_effect() function or when the actor is being
* painted;</simpara></listitem>
* <listitem><simpara><function>pre_paint()</function>, which is called
* before painting the #ClutterActor.</simpara></listitem>
* <listitem><simpara><function>post_paint()</function>, which is called
* after painting the #ClutterActor.</simpara></listitem>
* </itemizedlist>
* <para>The <function>prepare()</function> function receives the
* #ClutterActor to which the effect has been attached to, and it should be
* used to set up the initial state of the effect, for instance depending on
* the actor that has been passed. The function returns a boolean value,
* which is used to determine whether the #ClutterEffect has been prepared or
* not. An unprepared shader will be asked to prepare itself again during the
* actor's paint sequence, and if it fails again it will be ignored.</para>
* <para>The <function>pre_paint()</function> function should be used to set
* up the #ClutterEffect right before the #ClutterActor's paint
* sequence. This function, like <function>prepare()</function> can fail, and
* return %FALSE; in that case, no <function>post_paint()</function>
* invocation will follow.</para>
* <para>The <function>post_paint()</function> function is called after the
* #ClutterActor's paint sequence.</para>
* <para>The <function>pre_paint()</function> phase could be seen as a custom
* handler to the #ClutterActor::paint signal, while the
* <function>post_paint()</function> phase could be seen as a custom handler
* to the #ClutterActor::paint signal connected using
* g_signal_connect_after().</para>
* <example id="ClutterEffect-example">
* <title>A simple ClutterEffect implementation</title>
* <para>The example below creates two rectangles: one will be painted
* "behind" the actor, while another will be painted "on top" of the actor.
* The <function>prepare()</function> phase will create the two materials
* used for the two different rectangles; the
* <function>pre_paint()</function> function will paint the first material
* using cogl_rectangle(), while the <function>post_paint()</function>
* phase will paint the second material.</para>
* <programlisting>
* typedef struct {
* ClutterEffect parent_instance;
*
* CoglHandle rect_1;
* CoglHandle rect_2;
* } MyEffect;
*
* typedef struct _ClutterEffectClass MyEffectClass;
*
* G_DEFINE_TYPE (MyEffect, my_effect, CLUTTER_TYPE_EFFECT);
*
* static void
* my_effect_set_actor (ClutterActorMeta *meta,
* ClutterActor *actor)
* {
* MyEffect *self = MY_EFFECT (meta);
*
* /&ast; Clear the previous state &ast;/
* if (self-&gt;rect_1)
* {
* cogl_handle_unref (self-&gt;rect_1);
* self-&gt;rect_1 = NULL;
* }
*
* if (self-&gt;rect_2)
* {
* cogl_handle_unref (self-&gt;rect_2);
* self-&gt;rect_2 = NULL;
* }
*
* /&ast; Maintain a pointer to the actor &ast;
* self-&gt;actor = actor;
*
* /&ast; If we've been detached by the actor then we should
* &ast; just bail out here
* &ast;/
* if (self-&gt;actor == NULL)
* return;
*
* /&ast; Create a red material &ast;/
* self-&gt;rect_1 = cogl_material_new ();
* cogl_material_set_color4f (self-&gt;rect_1, 1.0, 0.0, 0.0, 1.0);
*
* /&ast; Create a green material &ast;/
* self-&gt;rect_2 = cogl_material_new ();
* cogl_material_set_color4f (self-&gt;rect_2, 0.0, 1.0, 0.0, 1.0);
* }
*
* static gboolean
* my_effect_pre_paint (ClutterEffect *effect)
* {
* MyEffect *self = MY_EFFECT (effect);
* gfloat width, height;
*
* /&ast; If we were disabled we don't need to paint anything &ast;/
* if (!clutter_actor_meta_get_enabled (CLUTTER_ACTOR_META (effect)))
* return FALSE;
*
* clutter_actor_get_size (self-&gt;actor, &amp;width, &amp;height);
*
* /&ast; Paint the first rectangle in the upper left quadrant &ast;/
* cogl_set_source (self-&gt;rect_1);
* cogl_rectangle (0, 0, width / 2, height / 2);
*
* return TRUE;
* }
*
* static void
* my_effect_post_paint (ClutterEffect *effect)
* {
* MyEffect *self = MY_EFFECT (effect);
* gfloat width, height;
*
* clutter_actor_get_size (self-&gt;actor, &amp;width, &amp;height);
*
* /&ast; Paint the second rectangle in the lower right quadrant &ast;/
* cogl_set_source (self-&gt;rect_2);
* cogl_rectangle (width / 2, height / 2, width, height);
* }
*
* static void
* my_effect_class_init (MyEffectClass *klass)
* {
* ClutterActorMetaClas *meta_class = CLUTTER_ACTOR_META_CLASS (klass);
*
* meta_class-&gt;set_actor = my_effect_set_actor;
*
* klass-&gt;pre_paint = my_effect_pre_paint;
* klass-&gt;post_paint = my_effect_post_paint;
* }
* </programlisting>
* </example>
* </refsect2>
*
* #ClutterEffect is available since Clutter 1.4
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "clutter-effect.h"
#include "clutter-actor-meta-private.h"
#include "clutter-debug.h"
#include "clutter-enum-types.h"
#include "clutter-marshal.h"
#include "clutter-private.h"
G_DEFINE_ABSTRACT_TYPE (ClutterEffect,
clutter_effect,
CLUTTER_TYPE_ACTOR_META);
static gboolean
clutter_effect_real_pre_paint (ClutterEffect *effect)
{
return TRUE;
}
static void
clutter_effect_real_post_paint (ClutterEffect *effect)
{
}
static void
clutter_effect_class_init (ClutterEffectClass *klass)
{
klass->pre_paint = clutter_effect_real_pre_paint;
klass->post_paint = clutter_effect_real_post_paint;
}
static void
clutter_effect_init (ClutterEffect *self)
{
}
gboolean
_clutter_effect_pre_paint (ClutterEffect *effect)
{
g_return_val_if_fail (CLUTTER_IS_EFFECT (effect), FALSE);
return CLUTTER_EFFECT_GET_CLASS (effect)->pre_paint (effect);
}
void
_clutter_effect_post_paint (ClutterEffect *effect)
{
g_return_if_fail (CLUTTER_IS_EFFECT (effect));
CLUTTER_EFFECT_GET_CLASS (effect)->post_paint (effect);
}