Dev Blog

Summary ​

Conclusions ​

WPF keeps a tree of visual objects and redraws it itself, so animation comes down to changing dependency properties over time. The basic DoubleAnimation, ColorAnimation, ThicknessAnimation, and PointAnimation animations move between the From, To, and By values over a Duration; the BeginTime, AutoReverse, RepeatBehavior, SpeedRatio, and FillBehavior parameters control timing. A Storyboard combines animations and specifies their targets; it is started by triggers in XAML or with the Begin, Pause, Resume, and Stop methods in code. Easing functions and keyframes make motion natural, RenderTransform transformations let you move, rotate, and scale elements without recalculating the layout, and the CompositionTarget.Rendering event provides frame-by-frame animation for games and physical models. For multimedia, WPF has Image and BitmapImage, SoundPlayer for WAV, MediaPlayer for sound without an interface, and MediaElement for video with control in Manual mode; media files are copied to the program folder as Content.

Self-check questions ​

  1. How does the WPF retained graphics mode differ from the GDI+ immediate mode?
  2. What shapes does WPF have? How do you write a path in the Path.Data mini-language?
  3. What kinds of transformations does WPF have? What is RenderTransformOrigin for?
  4. How does RenderTransform differ from LayoutTransform? Which is better to animate, and why?
  5. What conditions must a property meet to be animatable?
  6. How does an animation behave if only To, only By, or no value at all is set?
  7. What do Duration, BeginTime, AutoReverse, RepeatBehavior, and SpeedRatio mean?
  8. Why might assigning a property in code have no effect after an animation? How do you fix it?
  9. What is a Storyboard? How do you write the TargetProperty for the angle of a RotateTransform?
  10. How do you start a storyboard with an event in XAML and with a property trigger in a style?
  11. How do you control a storyboard from code? What is the isControllable parameter for?
  12. What are easing functions? How do the EaseIn, EaseOut, and EaseInOut modes differ?
  13. What kinds of keyframes are there? When are discrete frames needed?
  14. How does the CompositionTarget.Rendering event work? Why is the displacement calculated from the frame time?
  15. What techniques improve animation performance? What does Freeze() give?
  16. How do SoundPlayer, MediaPlayer, and MediaElement differ?
  17. How do you set up a media file in a project, and why can't it be added as a resource?