cookbook: Added "animated scaling" recipe skeleton
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@ -2703,4 +2703,136 @@ timeline_completed_cb (ClutterTimeline *timeline,
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</section>
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<section id="animations-scaling">
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<title>Animated scaling</title>
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<section>
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<title>Problem</title>
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<para>You want to animate scaling of an actor.</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 <varname>scale-x</varname> and
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<varname>scale-y</varname> properties to change the scaling on
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the x and y axes respectively.</para>
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<para>For example, to animate an actor to twice its initial scale
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with implicit animations:</para>
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<informalexample>
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<programlisting>
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<![CDATA[
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/* get the actor's current scale */
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gdouble scale_x;
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gdouble scale_y;
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clutter_actor_get_scale (actor, &scale_x, &scale_y);
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/* animate to twice current scale on both axes */
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clutter_actor_animate (actor, CLUTTER_LINEAR, 1000,
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"scale-x", scale_x * 2,
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"scale-y", scale_y * 2);
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]]>
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</programlisting>
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</informalexample>
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<para>Alternatively, <type>ClutterAnimator</type> or
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<type>ClutterState</type> can be used to animate an actor's scale
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properties. See <link linkend="animations-scaling-example-1">this
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example</link> for details.</para>
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</section>
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<section>
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<title>Discussion</title>
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<!--
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<para>The scale value is a double. Values less than 1.0 will reduce the apparent size of the actor; values greater than 1.0 will increase the apparent size.</para>
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When you scale an actor, you aren't changing the actor's real size: you are applying a transform which changes its <emphasis>apparent</emphasis> size. Changing the scale will also transform the actor's position (i.e. it will appear to be at a different position within its container, although it will actually report its original position if you call clutter_actor_get_position(), clutter_actor_get_x() or clutter_actor_get_y()).
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You can get the transformed (apparent) position and size for an actor with <function>clutter_actor_get_transformed_position()</function> and <function>clutter_actor_get_transformed_size()</function> respectively.
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Because an actor is at a different apparent size when scaled, mouse clicks need translating into actor coordinates before you can use them.
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You can scale on both axes by the same amount (uniform scaling), or by a different amount on each axis (differential scaling).
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clutter_actor_is_scaled() tells you whether scaling has been applied to the actor: it returns FALSE if both scale-x and scale-y are 1.0.
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Scaling a container scales all actors inside the container.
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-->
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<section>
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<title>Setting the scale center</title>
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<!--
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You can change the center of the scaling, using either gravity or actor-relative coordinates. Note that setting the scale gravity on an actor sets the scale-center-x and scale-center-y values behind the scenes.
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When you scale the actor, it will "shrink" into (if scale < 1.0) or "expand" out of (if scale > 1.0) the center.
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You can't really change the scaling center as part of the animation: you should do it before scaling an actor with an animation.
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Once you've scaled an actor, it's not a great idea to change the scale center: if you do, it probably won't do what you expect.
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animations-scaling.c shows all the scale gravities
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What if you set scale centers and scale gravity? which gets precedence - I think scale center
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For example, you have a square actor size 200x200 at x=100, y=100.
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You scale it to half scale, setting the scale center to x=100, y=0 (middle of the top of the square)
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(the scale center is relative to the actor)
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The center of the top of the square stays where it is
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The part of the line either side of the center "shrinks" in towards the center of the line
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The top of the square stays still; the rest of the square "shrinks" up towards the top
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The square now appears at half its original size, and with an _transformed_ position of x=150, y=0
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Note that the scale center is relative to the actor's actual size, not its transformed size.
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-->
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</section>
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</section>
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<section id="animations-scaling-examples">
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<title>Full examples</title>
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<example id="animations-scaling-example-1">
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<title>Animated scaling of an actor using each of the
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scale gravities. Press any key to start the animation.</title>
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<programlisting>
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<xi:include href="examples/animations-scaling.c" parse="text">
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<xi:fallback>a code sample should be here... but isn't</xi:fallback>
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</xi:include>
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</programlisting>
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</example>
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</section>
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</section>
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</chapter>
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