# Yahoo! UI Library

### animation 2.3.1

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

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    (function() {
    /**
     * 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)
     */
        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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