89 lines
3.4 KiB
C
89 lines
3.4 KiB
C
/**
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* SECTION:clutter-constraint
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* @Title: ClutterConstraint
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* @Short_Description: Abstract class for constraints on position or size
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* @See_Also: #ClutterAction
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*
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* #ClutterConstraint is a base abstract class for modifiers of a #ClutterActor
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* position or size.
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*
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* A #ClutterConstraint sub-class should contain the logic for modifying
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* the position or size of the #ClutterActor to which it is applied, by
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* updating the actor's allocation. Each #ClutterConstraint can change the
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* allocation of the actor to which they are applied by overriding the
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* <function>update_allocation()</function> virtual function.
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*
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* <refsect2 id="ClutterConstraint-implementation">
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* <title>Implemting a ClutterConstraint</title>
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* <para>Creating a sub-class of #ClutterConstraint requires the
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* implementation of the <function>update_allocation()</function>
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* virtual function.</para>
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* <para>The <function>update_allocation()</function> virtual function
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* is called during the allocation sequence of a #ClutterActor, and
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* allows any #ClutterConstraint attached to that actor to modify the
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* allocation before it is passed to the <function>allocate()</function>
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* implementation.</para>
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* <para>The #ClutterActorBox passed to the
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* <function>update_allocation()</function> implementation contains the
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* original allocation of the #ClutterActor, plus the eventual modifications
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* applied by the other #ClutterConstraint<!-- -->s.</para>
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* <note><para>Constraints are queried in the same order as they were
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* applied using clutter_actor_add_constraint() or
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* clutter_actor_add_constraint_with_name().</para></note>
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* <para>It is not necessary for a #ClutterConstraint sub-class to chain
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* up to the parent's implementation.</para>
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* <para>If a #ClutterConstraint is parametrized - i.e. if it contains
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* properties that affect the way the constraint is implemented - it should
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* call clutter_actor_queue_relayout() on the actor to which it is attached
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* to whenever any parameter is changed. The actor to which it is attached
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* can be recovered at any point using clutter_actor_meta_get_actor().</para>
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* </refsect2>
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*
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* #ClutterConstraint is available since Clutter 1.4
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include "clutter-constraint.h"
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#include "clutter-actor.h"
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#include "clutter-actor-meta-private.h"
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G_DEFINE_ABSTRACT_TYPE (ClutterConstraint,
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clutter_constraint,
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CLUTTER_TYPE_ACTOR_META);
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static void
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constraint_update_allocation (ClutterConstraint *constraint,
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ClutterActor *actor,
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ClutterActorBox *allocation)
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{
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}
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static void
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clutter_constraint_class_init (ClutterConstraintClass *klass)
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{
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klass->update_allocation = constraint_update_allocation;
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}
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static void
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clutter_constraint_init (ClutterConstraint *self)
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{
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}
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void
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_clutter_constraint_update_allocation (ClutterConstraint *constraint,
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ClutterActor *actor,
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ClutterActorBox *allocation)
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{
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g_return_if_fail (CLUTTER_IS_CONSTRAINT (constraint));
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g_return_if_fail (CLUTTER_IS_ACTOR (actor));
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g_return_if_fail (allocation != NULL);
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CLUTTER_CONSTRAINT_GET_CLASS (constraint)->update_allocation (constraint,
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actor,
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allocation);
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}
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