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Merge remote branch 'elliot/cookbook-animation-fading'
* elliot/cookbook-animation-fading: cookbook: Minor modification to wording to improve clarity cookbook: Added recipe for fading actors in/out
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@ -28,6 +28,10 @@ XSL_XHTML_URI = $(XSL_BASE_URI)/xhtml/docbook.xsl
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HTML_FILES = html/*.html
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CSS_FILES = html/*.css
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IMAGE_FILES = images/clutter-logo.png
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VIDEO_FILES = \
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videos/animations-fading-out.ogv \
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videos/animations-fading-in-then-out.ogv \
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$(NULL)
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EXTRA_DIST = clutter-cookbook.xml.in $(IMAGE_FILES) $(XML_FILES)
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@ -88,7 +88,7 @@
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</itemizedlist>
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</section>
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<section>
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<section id="animations-introduction-alphas">
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<title>Alphas</title>
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<para>An alpha is generated for each frame of the animation.
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@ -379,4 +379,130 @@ _on_click_cb (ClutterActor *actor,
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</section>
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<section id="animations-fading">
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<title>Fading an actor out of or into view</title>
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<section>
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<title>Problem</title>
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<para>You want to animate an actor so that it fades out of or into
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view.</para>
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</section>
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<section>
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<title>Solution</title>
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<para>Animate the actor's opacity property.</para>
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<para>You can do this using any of the approaches provided
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by the animation API. Here's how to fade out an actor (until it's
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completely transparent) using implicit animations:</para>
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<informalexample>
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<programlisting>
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<![CDATA[
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/* fade out actor over 4000 milliseconds */
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clutter_actor_animate (actor,
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CLUTTER_EASE_OUT_CUBIC,
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4000,
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"opacity", 0,
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NULL);
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]]>
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</programlisting>
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</informalexample>
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<para>Here's an example of a rectangle fading out using this
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animation:</para>
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<inlinemediaobject>
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<videoobject>
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<videodata fileref="videos/animations-fading-out.ogv"/>
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</videoobject>
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<alt>
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<para>Video showing an actor fading out using implicit
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animations</para>
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</alt>
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</inlinemediaobject>
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<para><constant>CLUTTER_EASE_OUT_CUBIC</constant> is one of the
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Clutter easing modes; see
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<link linkend="animations-introduction-alphas">the introduction</link>
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for more details about what these are and how to choose one.</para>
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<para>Here's an example of the transitions you could use to
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fade an actor in and out using <type>ClutterState</type>:</para>
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<informalexample>
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<programlisting>
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<![CDATA[
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ClutterState *transitions = clutter_state_new ();
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/* all transitions last for 2000 milliseconds */
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clutter_state_set_duration (transitions, NULL, NULL, 2000);
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/* transition from any state to "fade-out" state */
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clutter_state_set (transitions,
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NULL, /* from state (NULL means "any") */
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"fade-out", /* to state */
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actor, "opacity", CLUTTER_EASE_OUT_QUAD, 0,
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NULL);
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/* transition from any state to "fade-in" state */
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clutter_state_set (transitions, NULL, "fade-in",
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actor, "opacity", CLUTTER_EASE_OUT_QUAD, 255,
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NULL);
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/* put the actor into the "fade-out" state with no animation */
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clutter_state_warp_to_state (transitions, "fade-out");
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]]>
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</programlisting>
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</informalexample>
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<para>You would then trigger an animated state change as events
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occur in the application (e.g. mouse button clicks):</para>
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<informalexample>
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<programlisting>
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<![CDATA[
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clutter_state_set_state (transitions, "fade-in");
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]]>
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</programlisting>
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</informalexample>
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<para>Here's an example of this animation fading in then out again:</para>
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<inlinemediaobject>
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<videoobject>
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<videodata fileref="videos/animations-fading-in-then-out.ogv"/>
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</videoobject>
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<alt>
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<para>Video showing an actor fading in then out using
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<type>ClutterState</type></para>
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</alt>
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</inlinemediaobject>
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<note>
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<para><type>ClutterState</type> is most useful where you
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need to animate an actor backwards and forwards between multiple
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states (e.g. fade an actor in and out of view). Where you just
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want to fade an actor in or out once,
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<function>clutter_actor_animate()</function> is adequate.</para>
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</note>
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</section>
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<section>
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<title>Discussion</title>
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<para>Reducing an actor's transparency to zero does not make it
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inactive: the actor will still be reactive even if it's not
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visible (responding to key events, mouse clicks etc.).
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To make it really "disappear", you could use
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<function>clutter_actor_hide()</function> once you'd made the actor
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fully transparent.</para>
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</section>
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</section>
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</chapter>
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doc/cookbook/videos/animations-fading-in-then-out.ogv
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doc/cookbook/videos/animations-fading-in-then-out.ogv
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doc/cookbook/videos/animations-fading-out.ogv
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doc/cookbook/videos/animations-fading-out.ogv
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