![]() |
![]() |
![]() |
Clutter Reference Manual | ![]() |
---|
Clutter comes with a number of fairly generic prebuilt behaviour classes which provide a basis for transitions, animations and other visual effects. However even with the ability to combine a number of these behaviours sometimes they are not enough and a custom behaviour is needed to create a spcific animation.
In order to implement a new ClutterBehaviour subclass the usual
machinery for subclassing a GObject should be used. The new subclass
then just overides the ClutterBehaviour::alpha_notify()
method. This
method is passed an alpha value which is then used to compute
modifications to any actors the behaviour is applied to.
Example 23. Implementing the alpha-notify virtual function
This example demonstrates a behaviour that produces a vertical 'wipe' like affect by modifying the actors clip region
static void clutter_behaviour_foo_alpha_notify (ClutterBehaviour *behaviour, gdouble factor) { ClutterActor *actor gint i, n; n = clutter_behaviour_get_n_actors (behaviour); /* Change clip height of each applied actor. Note that it is * usually better to use clutter_behaviour_actors_foreach() * to avoid iterating multiple times */ for (i = 0; i < n; i++) { gfloat clip_height; actor = clutter_behaviour_get_nth_actor (behaviour, i); clip_height = clutter_actor_get_height (actor) - (clutter_actor_get_height (actor) * factor); clutter_actor_set_clip (actor, 0, 0, clutter_actor_get_width (actor), clip_height); } }
If the new behaviour is meant to set an initial state on the actors to which its applied to, then the ClutterBehaviour::applied signal class handler should be overridden.