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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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43
doc/reference/clutter/creating-behaviours.xml
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@ -12,50 +12,40 @@
</chapterinfo> </chapterinfo>
<title>Creating You Own Behaviours</title> <title>Creating You Own Behaviours</title>
<para> <para>Clutter comes with a number of fairly generic prebuilt behaviour
Clutter comes with a number of fairly generic prebuilt behaviour
classes which provide a basis for transitions, animations and other classes which provide a basis for transitions, animations and other
visual effects. However even with the ability to combine a number of visual effects. However even with the ability to combine a number of
these behaviours sometimes they are not enough and a custom these behaviours sometimes they are not enough and a custom behaviour
behaviour is needed to create a spcific animation. 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 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 method is passed an alpha value which is then used to compute
modifications to any actors the behaviour is applied to. modifications to any actors the behaviour is applied to.</para>
</para>
<example id="clutter-behaviour-alpha-notify-example"> <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 <para>This example demonstrates a behaviour that produces a vertical
'wipe' like affect by modifying the actors clip region</para> 'wipe' like affect by modifying the actors clip region</para>
<programlisting> <programlisting>
static void static void
clutter_behaviour_foo_alpha_notify (ClutterBehaviour *behaviour, clutter_behaviour_foo_alpha_notify (ClutterBehaviour *behaviour,
guint32 alpha_value) gdouble factor)
{ {
ClutterActor *actor ClutterActor *actor
gint i, n; gint i, n;
gdouble factor;
/* Normalise alpha value */
factor = (gdouble) alpha_value / CLUTTER_ALPHA_MAX_ALPHA;
n = clutter_behaviour_get_n_actors (behaviour); n = clutter_behaviour_get_n_actors (behaviour);
/* Change clip height of each applied actor. Note usually better to use /* Change clip height of each applied actor. Note that it is
* clutter_behaviour_actors_foreach () for performance reasons. * 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); actor = clutter_behaviour_get_nth_actor (behaviour, i);
@ -72,10 +62,7 @@ clutter_behaviour_foo_alpha_notify (ClutterBehaviour *behaviour,
</programlisting> </programlisting>
</example> </example>
<para> <para>If the new behaviour is meant to set an initial state on the
If the new behaviour is meant to set an initial state on the
actors to which its applied to, then the ClutterBehaviour::applied actors to which its applied to, then the ClutterBehaviour::applied
signal class handler should be overridden. signal class handler should be overridden.</para>
</para>
</chapter> </chapter>