sdk/samples/WPFSamples/CompositionTargetRenderingAnimations/csharp/followexample/followexample.xaml.cs

   1 using System;
   2 using System.Windows;
   3 using System.Windows.Controls;
   4 using System.Windows.Data;
   5 using System.Windows.Documents;
   6 using System.Windows.Media;
   7 using System.Windows.Navigation;
   8 using System.Windows.Shapes;
   9
  10 namespace Microsoft.Samples.PerFrameAnimations
  11 {
  12     /// <summary>
  13     /// Interaction logic for FollowExample.xaml
  14     /// </summary>
  15
  16     public partial class FollowExample : Page
  17     {
  18         private Vector _rectangleVelocity = new Vector(0,0);
  19         private Point _lastMousePosition = new Point(0, 0);
  20
  21         public FollowExample()
  22             : base()
  23         {
  24             CompositionTarget.Rendering += UpdateRectangle;
  25             this.PreviewMouseMove += UpdateLastMousePosition;
  26         }
  27
  28         private void UpdateRectangle(object sender, EventArgs e)
  29         {
  30             Point location = new Point(Canvas.GetLeft(followRectangle), Canvas.GetTop(followRectangle));
  31
  32             //find vector toward mouse location
  33             Vector toMouse = _lastMousePosition - location;
  34
  35             //add a force toward the mouse to the rectangles velocity
  36             double followForce = 0.01;
  37             _rectangleVelocity += toMouse * followForce;
  38
  39             //dampen the velocity to add stability
  40             double drag = 0.8;
  41             _rectangleVelocity *= drag;
  42
  43             //update the new location from the velocity
  44             location += _rectangleVelocity;
  45
  46             //set new position
  47             Canvas.SetLeft(followRectangle, location.X);
  48             Canvas.SetTop(followRectangle, location.Y);
  49         }
  50
  51         void UpdateLastMousePosition(object sender, System.Windows.Input.MouseEventArgs e)
  52         {
  53             _lastMousePosition = e.GetPosition(containerCanvas);
  54         }
  55     }
  56 }