279 lines
9.9 KiB
Plaintext
279 lines
9.9 KiB
Plaintext
ClutterActor Invariants
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===============================================================================
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ClutterActor behaviour has invariants that will be kept with the same API and
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ABI guarantees as the whole Clutter library.
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This document refers to the 0.8 release of Clutter.
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Sections:
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i. Flags
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a. Public ClutterActor Flags
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b. Private ClutterActor Flags
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c. Private Pick Modes
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ii. Invariants
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iii. State changes
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iv. Responsibilities of a ClutterActor
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a. Adding to a container
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b. Removing from a container
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c. Initial state
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i. Flags
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-------------------------------------------------------------------------------
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This section describes the various flags and enumerations used by
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ClutterActor.
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a. Public ClutterActor Flags
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CLUTTER_ACTOR_REALIZED
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Means: the actor has GPU resources associated to its paint
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cycle. Note however that an actor is allowed to allocate Cogl
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resources before being realized because Clutter only ever uses
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one rendering context which is always current. An actor is
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free to create resources at any time.
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Set by clutter_actor_realize(), unset by
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clutter_actor_unrealize(). Generally set implicitly when the
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actor becomes MAPPED (see below).
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May only be set if one of the actor's ancestors is a toplevel.
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May only be set if all of the actor's ancestors are realized.
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Once realized an actor remains realized until removed from the
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toplevel. Hide, reparent will not unrealize; but unparent or
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destroy will unrealize since they remove the actor from the
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toplevel.
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CLUTTER_ACTOR_MAPPED
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Means: the actor will be painted if the stage is mapped.
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On non-toplevels, will be set if all of the following are
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true, and unset otherwise:
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* the actor's VISIBLE flag is set
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* all of the actor's non-toplevel ancestors have the MAPPED
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flag set
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* the actor has a toplevel ancestor
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* the toplevel ancestor's VISIBLE flag is set
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* the toplevel ancestor's REALIZED flag is set
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On toplevels, MAPPED is set asynchronously when the window
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system notifies Clutter that the toplevel has been made
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visible on the screen.
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The MAPPED flag requires that an actor is REALIZED. When
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Clutter sets the MAPPED flag, it forces realization; this is
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the "normal" way for realization to occur, though explicit
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realization with clutter_actor_realize() is permitted.
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Reparent may not change the MAPPED flag if the old and the
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new parent are both MAPPED.
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CLUTTER_ACTOR_VISIBLE
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Means: the actor's "visible" property was set to true by
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the application programmer.
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Set by clutter_actor_show(), unset by clutter_actor_hide().
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This is an application-controlled property, while MAPPED and
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REALIZED are usually managed by Clutter (with the exception
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that applications can "realize early" with
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clutter_actor_realize()).
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If VISIBLE is unset, the actor (and any children) must
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be immediately unmapped, to maintain the invariants for
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the MAPPED flag.
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CLUTTER_ACTOR_REACTIVE
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Set and unset by clutter_actor_set_reactive()
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Means: the actor is now reactive to events.
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Notes:
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* If parents need to be reactive for child its up to the
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parent implementation. In the case of ClutterGroup it
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being marked unreactive does not mark all children unreactive.
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* Clutter stage is always reactive.
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b. Private ClutterActor flags
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CLUTTER_ACTOR_IN_DESTRUCTION
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Set internally by clutter_actor_destroy().
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Used to avoid uneeded overhead when freeing GPU resources on unrealize
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CLUTTER_ACTOR_IS_TOPLEVEL
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Set internally by the initialization of ClutterStage
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CLUTTER_ACTOR_IN_REPARENT [DEPRECATED]
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Set internally by clutter_actor_reparent(). This flag
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optimizes the reparent process by avoiding the need
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to pass through an unrealized state when the actor is
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removed from the old parent.
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CLUTTER_ACTOR_IN_PAINT:
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Set internally by clutter_actor_paint()
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CLUTTER_ACTOR_IN_RELAYOUT
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Set internally by clutter_actor_allocate()
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c. Pick Modes
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CLUTTER_PICK_NONE
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No pick operation is performed during the paint
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CLUTTER_PICK_REACTIVE
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Only reactive actors will be picked
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CLUTTER_PICK_ALL
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All visible actors will be picked
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ii. Invariants
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-------------------------------------------------------------------------------
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This section describes the various constraints and invariants on ClutterActor.
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In the following
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A => B means if A is true then B is true
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A <=> B means A is true if and only if B is true
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(equivalent to A => B && A <= B)
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1) CLUTTER_ACTOR_IN_DESTRUCTION => !CLUTTER_ACTOR_IS_MAPPED (actor) &&
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!CLUTTER_ACTOR_IS_REALIZED (actor)
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clutter_actor_destroy() will cause an actor to be unparented,
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which means the actor must be unmapped and unrealized as
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well.
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2) CLUTTER_ACTOR_IS_MAPPED (actor) => CLUTTER_ACTOR_IS_REALIZED (actor)
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when an actor is mapped, it must first be realized.
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This is the most common way an actor becomes realized.
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3) if clutter_actor_add_child (parent, actor):
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((parent_is_not_toplevel && CLUTTER_ACTOR_IS_MAPPED (parent)) ||
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(parent_is_toplevel && CLUTTER_ACTOR_IS_VISIBLE(parent))) &&
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CLUTTER_ACTOR_IS_VISIBLE (actor)
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=> CLUTTER_ACTOR_IS_MAPPED (actor)
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calling clutter_actor_add_child() on an actor and a mapped
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parent will map the actor if it has been shown.
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4) if clutter_actor_remove_child (parent, actor):
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CLUTTER_ACTOR_IS_MAPPED (actor) <=> CLUTTER_ACTOR_IN_REPARENT
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calling clutter_actor_remove_child() on an actor will unmap and
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unrealize the actor since it no longer has a toplevel.
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calling clutter_actor_reparent() on an actor will leave the
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actor mapped and realized (if it was before) until it has a
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new parent, at which point the invariants implied by the new
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parent's state are applied. [DEPRECATED]
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5) CLUTTER_ACTOR_IS_REALIZED(actor) => CLUTTER_ACTOR_IS_REALIZED(parent)
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Actors may only be realized if their parent is realized.
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However, they may be unrealized even though their parent
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is realized.
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This implies that an actor may not be realized unless
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it has a parent, or is a toplevel.
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Since only toplevels can realize without a parent, no actor
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can be realized unless it either is a toplevel or has a
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toplevel ancestor.
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As long as they are unmapped, actors may be unrealized. This
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will force all children of the actor to be unrealized, since
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children may not be realized while parents are unrealized.
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6) CLUTTER_ACTOR_IS_MAPPED(actor) <=>
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( ( (CLUTTER_ACTOR_IS_VISIBLE(toplevel_parent) &&
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CLUTTER_ACTOR_IS_REALIZED(toplevel_parent)) ||
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CLUTTER_ACTOR_IS_MAPPED(non_toplevel_parent) ) ) &&
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CLUTTER_ACTOR_IS_VISIBLE(actor)
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Actors _must_ be mapped if and only if they are visible and
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their parent is mapped, or they are visible and their
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parent is a toplevel that's realized and visible.
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This invariant enables us to track whether an actor will
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be painted (whether it's MAPPED) without ever traversing
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the actor graph.
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iii. State changes
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-------------------------------------------------------------------------------
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clutter_actor_show:
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1. sets VISIBLE
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2. sets MAPPED if invariants are met; mapping in turn sets
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REALIZED
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clutter_actor_hide:
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1. sets !VISIBLE
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2. unsets MAPPED if actor was mapped previously
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3. does not affect REALIZED
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clutter_actor_destroy:
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1. sets CLUTTER_ACTOR_IN_DESTRUCTION
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2. unparents the actor, which in turn implies unmap and unrealize
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clutter_actor_realize:
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1. attempts to set REALIZED on all parents, failing if
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invariants are not met, e.g. not in a toplevel yet
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2. sets REALIZED on actor if parent was successfully realized
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clutter_actor_unrealize:
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1. sets !VISIBLE which forces !MAPPED
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2. sets !REALIZED
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3. !MAPPED and !REALIZED forces unmap and unrealize of all
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children
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clutter_actor_add_child:
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1. sets actor->parent
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2. if actor->show_on_set_parent is TRUE calls clutter_actor_show
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3. sets MAPPED if all prerequisites are now met for map
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4. if !CLUTTER_ACTOR_IN_REPARENT emits ::parent-set with
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old_parent set to NULL
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clutter_actor_remove_child:
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1. unsets actor->parent
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2. if !CLUTTER_ACTOR_IN_REPARENT, sets !MAPPED and !REALIZED
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since the invariants for those flags are no longer met
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3. if !CLUTTER_ACTOR_IN_REPARENT emits ::parent-set with
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old_parent set to the previous parent
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clutter_actor_reparent: [DEPRECATED]
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1. sets CLUTTER_ACTOR_IN_REPARENT
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2. emits ::parent-set with old_parent set to the previous parent
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equivalent to:
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clutter_actor_unparent
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clutter_actor_set_parent
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3. updates state of the actor to match invariants
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(may change MAPPED or REALIZED in either direction,
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depending on state of the new parent)
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iv. Responsibilities of a ClutterActor
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-------------------------------------------------------------------------------
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a. Adding to a container
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When adding an actor to a container, the container must:
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1. call clutter_actor_add_child (container, actor)
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b. Removing from a container
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When removing an actor from a container, the container must:
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1. call clutter_actor_remove_child (container, actor)
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c. Initial state
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When creating an actor, the initial state is:
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1. !CLUTTER_ACTOR_REALIZED
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2. !CLUTTER_ACTOR_MAPPED
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