/** * @private */Ext.define('Ext.fx.easing.Momentum', { extend: 'Ext.fx.easing.Abstract', config: { acceleration: 30, friction: 0, startVelocity: 0 }, alpha: 0, updateFriction: function(friction) { var theta = Math.log(1 - (friction / 10)); this.theta = theta; this.alpha = theta / this.getAcceleration(); }, updateStartVelocity: function(velocity) { this.velocity = velocity * this.getAcceleration(); }, updateAcceleration: function(acceleration) { this.velocity = this.getStartVelocity() * acceleration; this.alpha = this.theta / acceleration; }, getValue: function() { return this.getStartValue() - this.velocity * (1 - this.getFrictionFactor()) / this.theta; }, getFrictionFactor: function() { var deltaTime = Ext.Date.now() - this.getStartTime(); return Math.exp(deltaTime * this.alpha); }, getVelocity: function() { return this.getFrictionFactor() * this.velocity; }});