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<title>ClutterEffect: Clutter Reference Manual</title>
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<a href="#ClutterEffect.description" class="shortcut">Description</a></span><span id="nav_hierarchy"> <span class="dim">|</span>
<a href="#ClutterEffect.object-hierarchy" class="shortcut">Object Hierarchy</a></span>
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<div class="refentry">
<a name="ClutterEffect"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2><span class="refentrytitle"><a name="ClutterEffect.top_of_page"></a>ClutterEffect</span></h2>
<p>ClutterEffect — Base class for actor effects</p>
</td>
<td class="gallery_image" valign="top" align="right"></td>
</tr></table></div>
<div class="refsect1">
<a name="ClutterEffect.functions"></a><h2>Functions</h2>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="functions_return">
<col class="functions_name">
</colgroup>
<tbody><tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="ClutterEffect.html#clutter-effect-queue-repaint" title="clutter_effect_queue_repaint ()">clutter_effect_queue_repaint</a> <span class="c_punctuation">()</span>
</td>
</tr></tbody>
</table></div>
</div>
<div class="refsect1">
<a name="ClutterEffect.other"></a><h2>Types and Values</h2>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="name">
<col class="description">
</colgroup>
<tbody>
<tr>
<td class="datatype_keyword"> </td>
<td class="function_name"><a class="link" href="ClutterEffect.html#ClutterEffect-struct" title="ClutterEffect">ClutterEffect</a></td>
</tr>
<tr>
<td class="datatype_keyword">struct</td>
<td class="function_name"><a class="link" href="ClutterEffect.html#ClutterEffectClass" title="struct ClutterEffectClass">ClutterEffectClass</a></td>
</tr>
<tr>
<td class="datatype_keyword">enum</td>
<td class="function_name"><a class="link" href="ClutterEffect.html#ClutterEffectPaintFlags" title="enum ClutterEffectPaintFlags">ClutterEffectPaintFlags</a></td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect1">
<a name="ClutterEffect.object-hierarchy"></a><h2>Object Hierarchy</h2>
<pre class="screen"> GObject
<span class="lineart">╰──</span> GInitiallyUnowned
<span class="lineart">╰──</span> <a class="link" href="ClutterActorMeta.html" title="ClutterActorMeta">ClutterActorMeta</a>
<span class="lineart">╰──</span> ClutterEffect
<span class="lineart">╰──</span> <a class="link" href="ClutterOffscreenEffect.html" title="ClutterOffscreenEffect">ClutterOffscreenEffect</a>
</pre>
</div>
<div class="refsect1">
<a name="ClutterEffect.description"></a><h2>Description</h2>
<p>The <a class="link" href="ClutterEffect.html" title="ClutterEffect"><span class="type">ClutterEffect</span></a> class provides a default type and API for creating
effects for generic actors.</p>
<p>Effects are a <a class="link" href="ClutterActorMeta.html" title="ClutterActorMeta"><span class="type">ClutterActorMeta</span></a> sub-class that modify the way an actor
is painted in a way that is not part of the actor's implementation.</p>
<p>Effects should be the preferred way to affect the paint sequence of an
actor without sub-classing the actor itself and overriding the
<a class="link" href="ClutterActor.html#ClutterActorClass.paint"><code class="function">ClutterActorClass.paint()</code></a>_ virtual function.</p>
<div class="refsect3">
<a name="id-1.5.2.11.6.5"></a><h4>Implementing a ClutterEffect</h4>
<p>Creating a sub-class of <a class="link" href="ClutterEffect.html" title="ClutterEffect"><span class="type">ClutterEffect</span></a> requires overriding the
<a class="link" href="ClutterEffect.html#ClutterEffectClass.paint"><code class="function">ClutterEffectClass.paint()</code></a> method. The implementation of the function should look
something like this:</p>
<div class="informalexample"><pre class="programlisting">
void effect_paint (ClutterEffect *effect, ClutterEffectPaintFlags flags)
{
// Set up initialisation of the paint such as binding a
// CoglOffscreen or other operations
// Chain to the next item in the paint sequence. This will either call
// ‘paint’ on the next effect or just paint the actor if this is
// the last effect.
ClutterActor *actor =
clutter_actor_meta_get_actor (CLUTTER_ACTOR_META (effect));
clutter_actor_continue_paint (actor);
// perform any cleanup of state, such as popping the CoglOffscreen
}
</pre></div>
<p></p>
<p>The effect can optionally avoid calling <a class="link" href="ClutterActor.html#clutter-actor-continue-paint" title="clutter_actor_continue_paint ()"><code class="function">clutter_actor_continue_paint()</code></a> to skip any
further stages of the paint sequence. This is useful for example if the effect
contains a cached image of the actor. In that case it can optimise painting by
avoiding the actor paint and instead painting the cached image.</p>
<p>The <a class="link" href="ClutterEffect.html#CLUTTER-EFFECT-PAINT-ACTOR-DIRTY:CAPS"><code class="literal">CLUTTER_EFFECT_PAINT_ACTOR_DIRTY</code></a> flag is useful in this case. Clutter will set
this flag when a redraw has been queued on the actor since it was last painted. The
effect can use this information to decide if the cached image is still valid.</p>
</div>
<div class="refsect3">
<a name="id-1.5.2.11.6.6"></a><h4>A simple ClutterEffect implementation</h4>
<p>The example below creates two rectangles: one will be painted "behind" the actor,
while another will be painted "on top" of the actor.</p>
<p>The <a class="link" href="ClutterActorMeta.html#ClutterActorMetaClass.set-actor"><code class="function">ClutterActorMetaClass.set_actor()</code></a> implementation will create the two materials
used for the two different rectangles; the <a class="link" href="ClutterEffect.html#ClutterEffectClass.paint"><code class="function">ClutterEffectClass.paint()</code></a> implementation
will paint the first material using <code class="function">cogl_rectangle()</code>, before continuing and then it
will paint paint the second material after.</p>
<div class="informalexample"><pre class="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);
// Clear the previous state //
if (self->rect_1)
{
cogl_handle_unref (self->rect_1);
self->rect_1 = NULL;
}
if (self->rect_2)
{
cogl_handle_unref (self->rect_2);
self->rect_2 = NULL;
}
// Maintain a pointer to the actor
self->actor = actor;
// If we've been detached by the actor then we should just bail out here
if (self->actor == NULL)
return;
// Create a red material
self->rect_1 = cogl_material_new ();
cogl_material_set_color4f (self->rect_1, 1.0, 0.0, 0.0, 1.0);
// Create a green material
self->rect_2 = cogl_material_new ();
cogl_material_set_color4f (self->rect_2, 0.0, 1.0, 0.0, 1.0);
}
static gboolean
my_effect_paint (ClutterEffect *effect)
{
MyEffect *self = MY_EFFECT (effect);
gfloat width, height;
clutter_actor_get_size (self->actor, &width, &height);
// Paint the first rectangle in the upper left quadrant
cogl_set_source (self->rect_1);
cogl_rectangle (0, 0, width / 2, height / 2);
// Continue to the rest of the paint sequence
clutter_actor_continue_paint (self->actor);
// Paint the second rectangle in the lower right quadrant
cogl_set_source (self->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->set_actor = my_effect_set_actor;
klass->paint = my_effect_paint;
}
</pre></div>
<p></p>
<p><a class="link" href="ClutterEffect.html" title="ClutterEffect"><span class="type">ClutterEffect</span></a> is available since Clutter 1.4</p>
</div>
</div>
<div class="refsect1">
<a name="ClutterEffect.functions_details"></a><h2>Functions</h2>
<div class="refsect2">
<a name="clutter-effect-queue-repaint"></a><h3>clutter_effect_queue_repaint ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
clutter_effect_queue_repaint (<em class="parameter"><code><a class="link" href="ClutterEffect.html" title="ClutterEffect"><span class="type">ClutterEffect</span></a> *effect</code></em>);</pre>
<p>Queues a repaint of the effect. The effect can detect when the ‘paint’
method is called as a result of this function because it will not
have the <a class="link" href="ClutterEffect.html#CLUTTER-EFFECT-PAINT-ACTOR-DIRTY:CAPS"><code class="literal">CLUTTER_EFFECT_PAINT_ACTOR_DIRTY</code></a> flag set. In that case the
effect is free to assume that the actor has not changed its
appearance since the last time it was painted so it doesn't need to
call <a class="link" href="ClutterActor.html#clutter-actor-continue-paint" title="clutter_actor_continue_paint ()"><code class="function">clutter_actor_continue_paint()</code></a> if it can draw a cached
image. This is mostly intended for effects that are using a
<code class="literal">CoglOffscreen</code> to redirect the actor (such as
<a class="link" href="ClutterOffscreenEffect.html" title="ClutterOffscreenEffect"><code class="literal">ClutterOffscreenEffect</code></a>). In that case the effect can save a bit of
rendering time by painting the cached texture without causing the
entire actor to be painted.</p>
<p>This function can be used by effects that have their own animatable
parameters. For example, an effect which adds a varying degree of a
red tint to an actor by redirecting it through a CoglOffscreen
might have a property to specify the level of tint. When this value
changes, the underlying actor doesn't need to be redrawn so the
effect can call <a class="link" href="ClutterEffect.html#clutter-effect-queue-repaint" title="clutter_effect_queue_repaint ()"><code class="function">clutter_effect_queue_repaint()</code></a> to make sure the
effect is repainted.</p>
<p>Note however that modifying the position of the parent of an actor
may change the appearance of the actor because its transformation
matrix would change. In this case a redraw wouldn't be queued on
the actor itself so the <a class="link" href="ClutterEffect.html#CLUTTER-EFFECT-PAINT-ACTOR-DIRTY:CAPS"><code class="literal">CLUTTER_EFFECT_PAINT_ACTOR_DIRTY</code></a> would still
not be set. The effect can detect this case by keeping track of the
last modelview matrix that was used to render the actor and
veryifying that it remains the same in the next paint.</p>
<p>Any other effects that are layered on top of the passed in effect
will still be passed the <a class="link" href="ClutterEffect.html#CLUTTER-EFFECT-PAINT-ACTOR-DIRTY:CAPS"><code class="literal">CLUTTER_EFFECT_PAINT_ACTOR_DIRTY</code></a> flag. If
anything queues a redraw on the actor without specifying an effect
or with an effect that is lower in the chain of effects than this
one then that will override this call. In that case this effect
will instead be called with the <a class="link" href="ClutterEffect.html#CLUTTER-EFFECT-PAINT-ACTOR-DIRTY:CAPS"><code class="literal">CLUTTER_EFFECT_PAINT_ACTOR_DIRTY</code></a>
flag set.</p>
<div class="refsect3">
<a name="id-1.5.2.11.7.2.8"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>effect</p></td>
<td class="parameter_description"><p>A <a class="link" href="ClutterEffect.html" title="ClutterEffect"><span class="type">ClutterEffect</span></a> which needs redrawing</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<p class="since">Since: <a class="link" href="ix11.html#api-index-1.8">1.8</a></p>
</div>
</div>
<div class="refsect1">
<a name="ClutterEffect.other_details"></a><h2>Types and Values</h2>
<div class="refsect2">
<a name="ClutterEffect-struct"></a><h3>ClutterEffect</h3>
<pre class="programlisting">typedef struct _ClutterEffect ClutterEffect;</pre>
<p>The <a class="link" href="ClutterEffect.html" title="ClutterEffect"><span class="type">ClutterEffect</span></a> structure contains only private data and should
be accessed using the provided API</p>
<p class="since">Since: <a class="link" href="ix09.html#api-index-1.4">1.4</a></p>
</div>
<hr>
<div class="refsect2">
<a name="ClutterEffectClass"></a><h3>struct ClutterEffectClass</h3>
<pre class="programlisting">struct ClutterEffectClass {
gboolean (* pre_paint) (ClutterEffect *effect);
void (* post_paint) (ClutterEffect *effect);
gboolean (* get_paint_volume) (ClutterEffect *effect,
ClutterPaintVolume *volume);
void (* paint) (ClutterEffect *effect,
ClutterEffectPaintFlags flags);
void (* pick) (ClutterEffect *effect,
ClutterEffectPaintFlags flags);
};
</pre>
<p>The <a class="link" href="ClutterEffect.html#ClutterEffectClass" title="struct ClutterEffectClass"><span class="type">ClutterEffectClass</span></a> structure contains only private data</p>
<div class="refsect3">
<a name="id-1.5.2.11.8.3.5"></a><h4>Members</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="300px" class="struct_members_name">
<col class="struct_members_description">
<col width="200px" class="struct_members_annotations">
</colgroup>
<tbody>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="ClutterEffectClass.pre-paint"></a>pre_paint</code></em> ()</p></td>
<td class="struct_member_description"><p>virtual function</p></td>
<td class="struct_member_annotations"> </td>
</tr>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="ClutterEffectClass.post-paint"></a>post_paint</code></em> ()</p></td>
<td class="struct_member_description"><p>virtual function</p></td>
<td class="struct_member_annotations"> </td>
</tr>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="ClutterEffectClass.get-paint-volume"></a>get_paint_volume</code></em> ()</p></td>
<td class="struct_member_description"><p>virtual function</p></td>
<td class="struct_member_annotations"> </td>
</tr>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="ClutterEffectClass.paint"></a>paint</code></em> ()</p></td>
<td class="struct_member_description"><p>virtual function</p></td>
<td class="struct_member_annotations"> </td>
</tr>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="ClutterEffectClass.pick"></a>pick</code></em> ()</p></td>
<td class="struct_member_description"><p>virtual function</p></td>
<td class="struct_member_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<p class="since">Since: <a class="link" href="ix09.html#api-index-1.4">1.4</a></p>
</div>
<hr>
<div class="refsect2">
<a name="ClutterEffectPaintFlags"></a><h3>enum ClutterEffectPaintFlags</h3>
<p>Flags passed to the ‘paint’ or ‘pick’ method of <a class="link" href="ClutterEffect.html" title="ClutterEffect"><span class="type">ClutterEffect</span></a>.</p>
<div class="refsect3">
<a name="id-1.5.2.11.8.4.4"></a><h4>Members</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="300px" class="enum_members_name">
<col class="enum_members_description">
<col width="200px" class="enum_members_annotations">
</colgroup>
<tbody><tr>
<td class="enum_member_name"><p><a name="CLUTTER-EFFECT-PAINT-ACTOR-DIRTY:CAPS"></a>CLUTTER_EFFECT_PAINT_ACTOR_DIRTY</p></td>
<td class="enum_member_description">
<p>The actor or one of its children
has queued a redraw before this paint. This implies that the effect
should call <a class="link" href="ClutterActor.html#clutter-actor-continue-paint" title="clutter_actor_continue_paint ()"><code class="function">clutter_actor_continue_paint()</code></a> to chain to the next
effect and can not cache any results from a previous paint.</p>
</td>
<td class="enum_member_annotations"> </td>
</tr></tbody>
</table></div>
</div>
</div>
</div>
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