Class

ClutterEffect

Description [src]

abstract class Clutter.Effect : Clutter.ActorMeta
{
  /* No available fields */
}

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 Clutter.ActorClass.paint virtual function.

Implementing a ClutterEffect

Creating a sub-class of ClutterEffect requires overriding the Clutter.EffectClass.paint method. The implementation of the function should look something like this:

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
}

The effect can optionally avoid calling clutter_actor_continue_paint() 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.

The CLUTTER_EFFECT_PAINT_ACTOR_DIRTY 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.

A simple ClutterEffect implementation

The example below creates two rectangles: one will be painted “behind” the actor, while another will be painted “on top” of the actor.

The ClutterActorMetaClass.set_actor() implementation will create the two materials used for the two different rectangles; the ClutterEffectClass.paint() implementation will paint the first material using cogl_rectangle(), before continuing and then it will paint paint the second material after.

 typedef struct {
   ClutterEffect parent_instance;

   CoglPipeline *rect_1;
   CoglPipeline *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);
   CoglColor color;

   // Clear the previous state //
   if (self->rect_1)
     {
       g_object_unref (self->rect_1);
       self->rect_1 = NULL;
     }

   if (self->rect_2)
     {
       g_object_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_pipeline_new ();
   cogl_color_init_from_4f (&color, 1.0, 1.0, 1.0, 1.0);
   cogl_pipeline_set_color (self->rect_1, &color);

   // Create a green material
   self->rect_2 = cogl_pipeline_new ();
   cogl_color_init_from_4f (&color, 0.0, 1.0, 0.0, 1.0);
   cogl_pipeline_set_color (self->rect_2, &color);
 }

 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)
 {
   ClutterActorMetaClass *meta_class = CLUTTER_ACTOR_META_CLASS (klass);

   meta_class->set_actor = my_effect_set_actor;

   klass->paint = my_effect_paint;
 }

Hierarchy

hierarchy this ClutterEffect ancestor_0 ClutterActorMeta ancestor_0--this ancestor_1 GInitiallyUnowned ancestor_1--ancestor_0 ancestor_2 GObject ancestor_2--ancestor_1

Instance methods

clutter_effect_queue_repaint

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 CLUTTER_EFFECT_PAINT_ACTOR_DIRTY 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 clutter_actor_continue_paint() if it can draw a cached image. This is mostly intended for effects that are using a %CoglOffscreen to redirect the actor (such as %ClutterOffscreenEffect). 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.

Methods inherited from ClutterActorMeta (5)
clutter_actor_meta_get_actor

Retrieves a pointer to the ClutterActor that owns meta.

clutter_actor_meta_get_enabled

Retrieves whether meta is enabled.

clutter_actor_meta_get_name

Retrieves the name set using clutter_actor_meta_set_name()

clutter_actor_meta_set_enabled

Sets whether meta should be enabled or not.

clutter_actor_meta_set_name

Sets the name of meta.

Methods inherited from GObject (43)

Please see GObject for a full list of methods.

Properties

Properties inherited from ClutterActorMeta (3)
Clutter.ActorMeta:actor

The ClutterActor attached to the ClutterActorMeta instance.

Clutter.ActorMeta:enabled

Whether or not the ClutterActorMeta is enabled.

Clutter.ActorMeta:name

The unique name to access the ClutterActorMeta.

Signals

Signals inherited from GObject (1)
GObject::notify

The notify signal is emitted on an object when one of its properties has its value set through g_object_set_property(), g_object_set(), et al.

Class structure

struct ClutterEffectClass {
  gboolean (* pre_paint) (
    ClutterEffect* effect,
    ClutterPaintNode* node,
    ClutterPaintContext* paint_context
  );
  void (* post_paint) (
    ClutterEffect* effect,
    ClutterPaintNode* node,
    ClutterPaintContext* paint_context
  );
  gboolean (* modify_paint_volume) (
    ClutterEffect* effect,
    ClutterPaintVolume* volume
  );
  void (* paint) (
    ClutterEffect* effect,
    ClutterPaintNode* node,
    ClutterPaintContext* paint_context,
    ClutterEffectPaintFlags flags
  );
  void (* paint_node) (
    ClutterEffect* effect,
    ClutterPaintNode* node,
    ClutterPaintContext* paint_context,
    ClutterEffectPaintFlags flags
  );
  void (* pick) (
    ClutterEffect* effect,
    ClutterPickContext* pick_context
  );
  
}

The ClutterEffectClass structure contains only private data.

Class members
pre_paint: gboolean (* pre_paint) ( ClutterEffect* effect, ClutterPaintNode* node, ClutterPaintContext* paint_context )

No description available.

post_paint: void (* post_paint) ( ClutterEffect* effect, ClutterPaintNode* node, ClutterPaintContext* paint_context )

No description available.

modify_paint_volume: gboolean (* modify_paint_volume) ( ClutterEffect* effect, ClutterPaintVolume* volume )

No description available.

paint: void (* paint) ( ClutterEffect* effect, ClutterPaintNode* node, ClutterPaintContext* paint_context, ClutterEffectPaintFlags flags )

No description available.

paint_node: void (* paint_node) ( ClutterEffect* effect, ClutterPaintNode* node, ClutterPaintContext* paint_context, ClutterEffectPaintFlags flags )

No description available.

pick: void (* pick) ( ClutterEffect* effect, ClutterPickContext* pick_context )

No description available.

Virtual methods

Clutter.EffectClass.modify_paint_volume
No description available.

Clutter.EffectClass.paint
No description available.

Clutter.EffectClass.paint_node
No description available.

Clutter.EffectClass.pick
No description available.

Clutter.EffectClass.post_paint
No description available.

Clutter.EffectClass.pre_paint
No description available.