Programming WPF, 2nd Edition

Timelines

A timeline represents a stretch of time. It usually also describes one or more things that happen during that time. All timeline types derive from the Timeline base class, which defines various common properties. For example, the animation types described in the preceding section are timelines. Consider this DoubleAnimation:

<DoubleAnimation From="10" To="300" BeginTime="0:0:2" Duration="0:0:5" />

Timelines of all kinds have a start time and a duration identifying the particular stretch of time they describe. The Duration property indicates that this DoubleAnimation represents a five-second stint. As the BeginTime property indicates, it starts at an offset of two seconds. BeginTime is relative to the timeline's container. For example, if an animation is defined inside a storyboard, the start time is relative to when the storyboard begins. If the start time is not specified, it defaults to 0:0:0. BeginTime and Duration are just two of the standard properties available on every timeline. Table 16-3 shows the properties common to all timelines.

Table 16-3. Timeline properties

Property	Usage
AccelerationRatio	Causes the timeline to ramp up to speed at the start
AutoReverse	Makes the timeline run in reverse once it reaches the end
BeginTime	Start time, relative to parent
DecelerationRatio	Causes the timeline to slow down toward the end
Duration	The length of the timeline
FillBehavior	How the timeline behaves when it reaches its natural end
Name	An optional name
RepeatBehavior	Indicates whether ...