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[docs] Update the "creating new behaviours" chapter

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The signature of the ::alpha_notify virtual function has been
changed with the switch to float ClutterAlpha.
This commit is contained in:
Emmanuele Bassi 2009-07-21 11:51:20 +01:00
parent c87fea6cf1
commit ed005685c9
1 changed files with 17 additions and 30 deletions
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47
doc/reference/clutter/creating-behaviours.xml
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@ -12,55 +12,45 @@
</chapterinfo>
<title>Creating You Own Behaviours</title>
<para>
Clutter comes with a number of fairly generic prebuilt behaviour
<para>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.
these behaviours sometimes they are not enough and a custom behaviour
is needed to create a spcific animation.</para>
</para>
<para>
In order to implement a new #ClutterBehaviour subclass the usual
<para>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
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.
</para>
modifications to any actors the behaviour is applied to.</para>
<example id="clutter-behaviour-alpha-notify-example">
<title>Implementing the alpha-notify virtual function<title>
<para>This example demonstrates a behaviour that produces a vertical
'wipe' like affect by modifying the actors clip region</para>
<programlisting>
static void
clutter_behaviour_foo_alpha_notify (ClutterBehaviour *behaviour,
guint32 alpha_value)
gdouble factor)
{
ClutterActor *actor
gint i, n;
gdouble factor;
/* Normalise alpha value */
factor = (gdouble) alpha_value / CLUTTER_ALPHA_MAX_ALPHA;
gint i, n;
n = clutter_behaviour_get_n_actors (behaviour);
/* Change clip height of each applied actor. Note usually better to use
* clutter_behaviour_actors_foreach () for performance reasons.
/* 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&lt;n; i++)
for (i = 0; i &lt; n; i++)
{
int clip_height;
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_get_height (actor) * factor);
clutter_actor_set_clip (actor,
0,
@ -72,10 +62,7 @@ clutter_behaviour_foo_alpha_notify (ClutterBehaviour *behaviour,
</programlisting>
</example>
<para>
If the new behaviour is meant to set an initial state on the
<para>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.
</para>
signal class handler should be overridden.</para>
</chapter>