# Yahoo! UI Library

### animation

Yahoo! UI Library > animation > Motion.js (source view)

    /**
     * Anim subclass for moving elements along a path defined by the "points"
     * member of "attributes".  All "points" are arrays with x, y coordinates.
     * <p>Usage: <code>var myAnim = new YAHOO.util.Motion(el, { points: { to: [800, 800] } }, 1, YAHOO.util.Easing.easeOut);</code></p>
     * @class Motion
     * @namespace YAHOO.util
     * @requires YAHOO.util.Anim
     * @requires YAHOO.util.AnimMgr
     * @requires YAHOO.util.Easing
     * @requires YAHOO.util.Bezier
     * @requires YAHOO.util.Dom
     * @requires YAHOO.util.Event
     * @requires YAHOO.util.CustomEvent
     * @constructor
     * @extends YAHOO.util.Anim
     * @param {String | HTMLElement} el Reference to the element that will be animated
     * @param {Object} attributes The attribute(s) to be animated.
     * Each attribute is an object with at minimum a "to" or "by" member defined.
     * Additional optional members are "from" (defaults to current value), "units" (defaults to "px").
     * All attribute names use camelCase.
     * @param {Number} duration (optional, defaults to 1 second) Length of animation (frames or seconds), defaults to time-based
     * @param {Function} method (optional, defaults to YAHOO.util.Easing.easeNone) Computes the values that are applied to the attributes per frame (generally a YAHOO.util.Easing method)
     */
    (function() {
       YAHOO.util.Motion = function(el, attributes, duration,  method) {
          if (el) { // dont break existing subclasses not using YAHOO.extend
             YAHOO.util.Motion.superclass.constructor.call(this, el, attributes, duration, method);
          }
       };

       YAHOO.extend(YAHOO.util.Motion, YAHOO.util.ColorAnim);

       // shorthand
       var Y = YAHOO.util;
       var superclass = Y.Motion.superclass;
       var proto = Y.Motion.prototype;

       proto.toString = function() {
          var el = this.getEl();
          var id = el.id || el.tagName;
          return ("Motion " + id);
       };

       proto.patterns.points = /^points$/i;

       proto.setAttribute = function(attr, val, unit) {
          if (  this.patterns.points.test(attr) ) {
             unit = unit || 'px';
             superclass.setAttribute.call(this, 'left', val[0], unit);
             superclass.setAttribute.call(this, 'top', val[1], unit);
          } else {
             superclass.setAttribute.call(this, attr, val, unit);
          }
       };

       proto.getAttribute = function(attr) {
          if (  this.patterns.points.test(attr) ) {
             var val = [
                superclass.getAttribute.call(this, 'left'),
                superclass.getAttribute.call(this, 'top')
             ];
          } else {
             val = superclass.getAttribute.call(this, attr);
          }

          return val;
       };

       proto.doMethod = function(attr, start, end) {
          var val = null;

          if ( this.patterns.points.test(attr) ) {
             var t = this.method(this.currentFrame, 0, 100, this.totalFrames) / 100;
             val = Y.Bezier.getPosition(this.runtimeAttributes[attr], t);
          } else {
             val = superclass.doMethod.call(this, attr, start, end);
          }
          return val;
       };

       proto.setRuntimeAttribute = function(attr) {
          if ( this.patterns.points.test(attr) ) {
             var el = this.getEl();
             var attributes = this.attributes;
             var start;
             var control = attributes['points']['control'] || [];
             var end;
             var i, len;

             if (control.length > 0 && !(control[0] instanceof Array) ) { // could be single point or array of points
                control = [control];
             } else { // break reference to attributes.points.control
                var tmp = [];
                for (i = 0, len = control.length; i< len; ++i) {
                   tmp[i] = control[i];
                }
                control = tmp;
             }

             if (Y.Dom.getStyle(el, 'position') == 'static') { // default to relative
                Y.Dom.setStyle(el, 'position', 'relative');
             }

             if ( isset(attributes['points']['from']) ) {
                Y.Dom.setXY(el, attributes['points']['from']); // set position to from point
             }
             else { Y.Dom.setXY( el, Y.Dom.getXY(el) ); } // set it to current position

             start = this.getAttribute('points'); // get actual top & left

             // TO beats BY, per SMIL 2.1 spec
             if ( isset(attributes['points']['to']) ) {
                end = translateValues.call(this, attributes['points']['to'], start);

                var pageXY = Y.Dom.getXY(this.getEl());
                for (i = 0, len = control.length; i < len; ++i) {
                   control[i] = translateValues.call(this, control[i], start);
                }

             } else if ( isset(attributes['points']['by']) ) {
                end = [ start[0] + attributes['points']['by'][0], start[1] + attributes['points']['by'][1] ];

                for (i = 0, len = control.length; i < len; ++i) {
                   control[i] = [ start[0] + control[i][0], start[1] + control[i][1] ];
                }
             }

             this.runtimeAttributes[attr] = [start];

             if (control.length > 0) {
                this.runtimeAttributes[attr] = this.runtimeAttributes[attr].concat(control);
             }

             this.runtimeAttributes[attr][this.runtimeAttributes[attr].length] = end;
          }
          else {
             superclass.setRuntimeAttribute.call(this, attr);
          }
       };

       var translateValues = function(val, start) {
          var pageXY = Y.Dom.getXY(this.getEl());
          val = [ val[0] - pageXY[0] + start[0], val[1] - pageXY[1] + start[1] ];

          return val;
       };

       var isset = function(prop) {
          return (typeof prop !== 'undefined');
       };
    })();

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