src/src/fx/easing/Momentum.js

   1 /**
   2  * @private
   3  */
   4 Ext.define('Ext.fx.easing.Momentum', {
   5
   6     extend: 'Ext.fx.easing.Abstract',
   7
   8     config: {
   9         acceleration: 30,
  10         friction: 0,
  11         startVelocity: 0
  12     },
  13
  14     alpha: 0,
  15
  16     updateFriction: function(friction) {
  17         var theta = Math.log(1 - (friction / 10));
  18
  19         this.theta = theta;
  20
  21         this.alpha = theta / this.getAcceleration();
  22     },
  23
  24     updateStartVelocity: function(velocity) {
  25         this.velocity = velocity * this.getAcceleration();
  26     },
  27
  28     updateAcceleration: function(acceleration) {
  29         this.velocity = this.getStartVelocity() * acceleration;
  30
  31         this.alpha = this.theta / acceleration;
  32     },
  33
  34     getValue: function() {
  35         return this.getStartValue() - this.velocity * (1 - this.getFrictionFactor()) / this.theta;
  36     },
  37
  38     getFrictionFactor: function() {
  39         var deltaTime = Ext.Date.now() - this.getStartTime();
  40
  41         return Math.exp(deltaTime * this.alpha);
  42     },
  43
  44     getVelocity: function() {
  45         return this.getFrictionFactor() * this.velocity;
  46     }
  47 });