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docs: Clean up ClutterActor's long description
The Actor's long description is a bit cluttered; it contains a section on the actor's box semantics, on the transformation order and on the event handling. We should use <refsect2> tags to divide the Actor's description into logically separated sections. We should also add a section about the custom Scriptable properties that ClutterActor defines, and the special handling of unit-based properties.
This commit is contained in:
Emmanuele Bassi
parent
2d4ddc1b11
commit
15ef549207
@ -36,97 +36,125 @@
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* it parent with the childs origin being its anchor point (also top
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* left by default).
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*
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* The actors 2D surface is contained inside its bounding box,
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* described by the #ClutterActorBox structure:
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* <refsect2 id="ClutterActor-box">
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* <title>Actor bounding box and transformations</title>
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* <para>Any actor's 2D surface is contained inside its bounding box,
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* as described by the #ClutterActorBox structure:</para>
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* <figure id="actor-box">
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* <title>Bounding box of an Actor</title>
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* <graphic fileref="actor-box.png" format="PNG"/>
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* </figure>
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* <para>The actor box represents the untransformed area occupied by an
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* actor. Each visible actor that has been put on a #ClutterStage also
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* has a transformed area, depending on the actual transformations
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* applied to it by the developer (scale, rotation). Tranforms will
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* also be applied to any child actors. Also applied to all actors by
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* the #ClutterStage is a perspective transformation. API is provided
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* for both tranformed and untransformed actor geometry information.</para>
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* <para>The GL 'modelview' transform matrix for the actor is constructed
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* from the actor settings by the following order of operations:</para>
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* <orderedlist>
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* <listitem><para>Translation by actor x, y coords,</para></listitem>
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* <listitem><para>Translation by actor depth (z),</para></listitem>
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* <listitem><para>Scaling by scale_x, scale_y,</para></listitem>
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* <listitem><para>Rotation around z axis,</para></listitem>
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* <listitem><para>Rotation around y axis,</para></listitem>
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* <listitem><para>Rotation around x axis,</para></listitem>
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* <listitem><para>Negative translation by anchor point x,
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* y,</para></listitem>
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* <listitem><para>Rectangular Clip is applied (this is not an operation
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* on the matrix as such, but it is done as part of the transform set
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* up).</para></listitem>
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* </orderedlist>
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* <para>An actor can either be explicitly sized and positioned, using the
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* various size and position accessors, like clutter_actor_set_x() or
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* clutter_actor_set_width(); or it can have a preferred width and
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* height, which then allows a layout manager to implicitly size and
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* position it by "allocating" an area for an actor. This allows for
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* actors to be manipulated in both a fixed (or static) parent container
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* (i.e. children of #ClutterGroup) and a more automatic (or dynamic)
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* layout based parent container.</para>
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* <para>When accessing the position and size of an actor, the simple
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* accessors like clutter_actor_get_width() and clutter_actor_get_x()
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* will return a value depending on whether the actor has been explicitly
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* sized and positioned by the developer or implicitly by the layout
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* manager.</para>
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* <para>Depending on whether you are querying an actor or implementing a
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* layout manager, you should either use the simple accessors or use the
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* size negotiation API.</para>
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* </refsect2>
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*
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* <figure id="actor-box">
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* <title>Bounding box of an Actor</title>
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* <graphic fileref="actor-box.png" format="PNG"/>
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* </figure>
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* <refsect2 id="ClutterActor-event-handling">
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* <title>Event Handling</title>
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* <para>Clutter actors are also able to receive input events and react to
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* them. Events are handled in the following ways:</para>
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* <orderedlist>
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* <listitem><para>Actors emit pointer events if set reactive, see
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* clutter_actor_set_reactive()</para></listitem>
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* <listitem><para>The stage is always reactive</para></listitem>
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* <listitem><para>Events are handled by connecting signal handlers to
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* the numerous event signal types.</para></listitem>
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* <listitem><para>Event handlers must return %TRUE if they handled
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* the event and wish to block the event emission chain, or %FALSE
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* if the emission chain must continue</para></listitem>
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* <listitem><para>Keyboard events are emitted if actor has focus, see
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* clutter_stage_set_key_focus()</para></listitem>
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* <listitem><para>Motion events (motion, enter, leave) are not emitted
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* if clutter_set_motion_events_enabled() is called with %FALSE.
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* See clutter_set_motion_events_enabled() documentation for more
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* information.</para></listitem>
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* <listitem><para>Once emitted, an event emission chain has two
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* phases: capture and bubble. An emitted event starts in the capture
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* phase (see ClutterActor::captured-event) beginning at the stage and
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* traversing every child actor until the event source actor is reached.
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* The emission then enters the bubble phase, traversing back up the
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* chain via parents until it reaches the stage. Any event handler can
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* abort this chain by returning %TRUE (meaning "event handled").
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* </para></listitem>
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* <listitem><para>Pointer events will 'pass through' non reactive
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* overlapping actors.</para></listitem>
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* </orderedlist>
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* <figure id="event-flow">
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* <title>Event flow in Clutter</title>
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* <graphic fileref="event-flow.png" format="PNG"/>
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* </figure>
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* <para>Every '?' box in the diagram above is an entry point for
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* application code.</para>
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* </refsect2>
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*
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* The actor box represents the untransformed area occupied by an
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* actor. Each visible actor that has been put on a #ClutterStage also
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* has a transformed area, depending on the actual transformations
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* applied to it by the developer (scale, rotation). Tranforms will
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* also be applied to any child actors. Also applied to all actors by
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* the #ClutterStage is a perspective transformation. API is provided
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* for both tranformed and untransformed actor geometry information.
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* <refsect2 id="ClutterActor-subclassing">
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* <title>Implementing a ClutterActor</title>
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* <para>For implementing a new custom actor class, please read <link
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* linkend="clutter-subclassing-ClutterActor">the corresponding
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* section</link> of the API reference.</para>
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* </refsect2>
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*
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* The 'modelview' transform matrix for the actor is constructed from
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* the actor settings by the following order of operations:
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* <orderedlist>
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* <listitem><para>Translation by actor x, y coords,</para></listitem>
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* <listitem><para>Translation by actor depth (z),</para></listitem>
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* <listitem><para>Scaling by scale_x, scale_y,</para></listitem>
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* <listitem><para>Rotation around z axis,</para></listitem>
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* <listitem><para>Rotation around y axis,</para></listitem>
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* <listitem><para>Rotation around x axis,</para></listitem>
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* <listitem><para>Negative translation by anchor point x,
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* y,</para></listitem>
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* <listitem><para>Rectangular Clip is applied (this is not an operation on
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* the matrix as such, but it is done as part of the transform set
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* up).</para></listitem>
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* </orderedlist>
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*
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* An actor can either be explicitly sized and positioned, using the
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* various size and position accessors, like clutter_actor_set_x() or
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* clutter_actor_set_width(); or it can have a preferred width and
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* height, which then allows a layout manager to implicitly size and
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* position it by "allocating" an area for an actor. This allows for
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* actors to be manipulated in both a fixed (or static) parent container
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* (i.e. children of #ClutterGroup) and a more automatic (or dynamic)
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* layout based parent container.
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*
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* When accessing the position and size of an actor, the simple accessors
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* like clutter_actor_get_width() and clutter_actor_get_x() will return
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* a value depending on whether the actor has been explicitly sized and
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* positioned by the developer or implicitly by the layout manager.
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*
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* Depending on whether you are querying an actor or implementing a
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* layout manager, you should either use the simple accessors or use the
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* size negotiation API.
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*
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* Clutter actors are also able to receive input events and react to
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* them. Events are handled in the following ways:
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*
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* <orderedlist>
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* <listitem><para>Actors emit pointer events if set reactive, see
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* clutter_actor_set_reactive()</para></listitem>
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* <listitem><para>The stage is always reactive</para></listitem>
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* <listitem><para>Events are handled by connecting signal handlers to
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* the numerous event signal types.</para></listitem>
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* <listitem><para>Event handlers must return %TRUE if they handled
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* the event and wish to block the event emission chain, or %FALSE
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* if the emission chain must continue</para></listitem>
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* <listitem><para>Keyboard events are emitted if actor has focus, see
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* clutter_stage_set_key_focus()</para></listitem>
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* <listitem><para>Motion events (motion, enter, leave) are not emitted
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* if clutter_set_motion_events_enabled() is called with %FALSE.
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* See clutter_set_motion_events_enabled() documentation for more
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* information.</para></listitem>
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* <listitem><para>Once emitted, an event emission chain has two
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* phases: capture and bubble. An emitted event starts in the capture
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* phase (see ClutterActor::captured-event) beginning at the stage and
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* traversing every child actor until the event source actor is reached.
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* The emission then enters the bubble phase, traversing back up the
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* chain via parents until it reaches the stage. Any event handler can
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* abort this chain by returning %TRUE (meaning "event handled").
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* </para></listitem>
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* <listitem><para>Pointer events will 'pass through' non reactive
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* overlapping actors.</para></listitem>
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* </orderedlist>
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*
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* <figure id="event-flow">
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* <title>Event flow in Clutter</title>
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* <graphic fileref="event-flow.png" format="PNG"/>
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* </figure>
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*
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* Every '?' box in the diagram above is an entry point for application
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* code.
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*
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* For implementing a new custom actor class, please read <link
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* linkend="clutter-subclassing-ClutterActor">the corresponding section</link>
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* of the API reference.
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* <refsect2 id="ClutterActor-script">
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* <title>ClutterActor custom properties for #ClutterScript</title>
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* <para>#ClutterActor defines a custom "rotation" property which
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* allows a short-hand description of the rotations to be applied
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* to an actor.</para>
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* <para>The syntax of the "rotation" property is the following:</para>
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* <informalexample>
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* <programlisting>
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* "rotation" : [
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* { "<axis>" : [ <angle>, [ <center> ] ] }
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* ]
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* </programlisting>
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* </informalexample>
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* <para>where the <emphasis>axis</emphasis> is the name of an enumeration
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* value of type #ClutterRotateAxis and <emphasis>angle</emphasis> is a
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* floating point value representing the rotation angle on the given axis,
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* in degrees.</para>
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* <para>The <emphasis>center</emphasis> array is optional, and if present
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* it must contain the center of rotation as described by two coordinates:
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* Y and Z for "x-axis"; X and Z for "y-axis"; and X and Y for
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* "z-axis".</para>
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* <para>#ClutterActor will also parse every positional and dimensional
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* property defined as a string through clutter_units_from_string(); you
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* should read the documentation for the #ClutterUnits parser format for
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* the valid units and syntax.</para>
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* </refsect2>
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*/
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/**
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