Rambox-CE/ext/src/dd/DragDrop.js

/*
 * This is a derivative of the similarly named class in the YUI Library.
 * The original license:
 * Copyright (c) 2006, Yahoo! Inc. All rights reserved.
 * Code licensed under the BSD License:
 * http://developer.yahoo.net/yui/license.txt
 */


/**
 * Defines the interface and base operation of items that that can be
 * dragged or can be drop targets.  It was designed to be extended, overriding
 * the event handlers for startDrag, onDrag, onDragOver and onDragOut.
 * Up to three html elements can be associated with a DragDrop instance:
 *
 * - linked element: the element that is passed into the constructor.
 *   This is the element which defines the boundaries for interaction with
 *   other DragDrop objects.
 *
 * - handle element(s): The drag operation only occurs if the element that
 *   was clicked matches a handle element.  By default this is the linked
 *   element, but there are times that you will want only a portion of the
 *   linked element to initiate the drag operation, and the setHandleElId()
 *   method provides a way to define this.
 *
 * - drag element: this represents the element that would be moved along
 *   with the cursor during a drag operation.  By default, this is the linked
 *   element itself as in {@link Ext.dd.DD}.  setDragElId() lets you define
 *   a separate element that would be moved, as in {@link Ext.dd.DDProxy}.
 *
 * This class should not be instantiated until the onload event to ensure that
 * the associated elements are available.
 * The following would define a DragDrop obj that would interact with any
 * other DragDrop obj in the "group1" group:
 *
 *     dd = new Ext.dd.DragDrop("div1", "group1");
 *
 * Since none of the event handlers have been implemented, nothing would
 * actually happen if you were to run the code above.  Normally you would
 * override this class or one of the default implementations, but you can
 * also override the methods you want on an instance of the class...
 *
 *     dd.onDragDrop = function(e, id) {
 *         alert("dd was dropped on " + id);
 *     }
 *
 */
Ext.define('Ext.dd.DragDrop', {
    requires: ['Ext.dd.DragDropManager'],

    /**
     * Creates new DragDrop.
     * @param {String} id of the element that is linked to this instance
     * @param {String} sGroup the group of related DragDrop objects
     * @param {Object} config an object containing configurable attributes.
     * Valid properties for DragDrop:
     *
     * - padding
     * - isTarget
     * - maintainOffset
     * - primaryButtonOnly
     */
    constructor: function(id, sGroup, config) {
        if(id) {
            this.init(id, sGroup, config);
        }
    },

    /**
     * @property {Boolean} ignoreSelf
     * Set to false to enable a DragDrop object to fire drag events while dragging
     * over its own Element. Defaults to true - DragDrop objects do not by default
     * fire drag events to themselves.
     */

    /**
     * @property {String} id
     * The id of the element associated with this object.  This is what we
     * refer to as the "linked element" because the size and position of
     * this element is used to determine when the drag and drop objects have
     * interacted.
     */
    id: null,

    /**
     * @property {Object} config
     * Configuration attributes passed into the constructor
     */
    config: null,

    /**
     * @property {String} dragElId
     * The id of the element that will be dragged.  By default this is same
     * as the linked element, but could be changed to another element. Ex:
     * Ext.dd.DDProxy
     * @private
     */
    dragElId: null,

    /**
     * @property {String} handleElId
     * The ID of the element that initiates the drag operation.  By default
     * this is the linked element, but could be changed to be a child of this
     * element.  This lets us do things like only starting the drag when the
     * header element within the linked html element is clicked.
     * @private
     */
    handleElId: null,

    /**
     * @property {Object} invalidHandleTypes
     * An object who's property names identify HTML tags to be considered invalid as drag handles.
     * A non-null property value identifies the tag as invalid. Defaults to the
     * following value which prevents drag operations from being initiated by `<a>` elements:
     *
     *     {
     *         A: "A"
     *     }
     */
    invalidHandleTypes: null,

    /**
     * @property {Object} invalidHandleIds
     * An object who's property names identify the IDs of elements to be considered invalid as drag handles.
     * A non-null property value identifies the ID as invalid. For example, to prevent
     * dragging from being initiated on element ID "foo", use:
     *
     *     {
     *         foo: true
     *     }
     */
    invalidHandleIds: null,

    /**
     * @property {String[]} invalidHandleClasses
     * An Array of CSS class names for elements to be considered in valid as drag handles.
     */
    invalidHandleClasses: null,

    /**
     * @property {Number} startPageX
     * The linked element's absolute X position at the time the drag was
     * started
     * @private
     */
    startPageX: 0,

    /**
     * @property {Number} startPageY
     * The linked element's absolute X position at the time the drag was
     * started
     * @private
     */
    startPageY: 0,

    /**
     * @property {Object} groups
     * The group defines a logical collection of DragDrop objects that are
     * related.  Instances only get events when interacting with other
     * DragDrop object in the same group.  This lets us define multiple
     * groups using a single DragDrop subclass if we want.
     *
     * An object in the format {'group1':true, 'group2':true}
     */
    groups: null,

    /**
     * @property {Boolean} locked
     * Individual drag/drop instances can be locked.  This will prevent
     * onmousedown start drag.
     * @private
     */
    locked: false,

    /**
     * Locks this instance
     */
    lock: function() {
        this.locked = true;
    },

    /**
     * @property {Boolean} moveOnly
     * When set to true, other DD objects in cooperating DDGroups do not receive
     * notification events when this DD object is dragged over them.
     */
    moveOnly: false,

    /**
     * Unlocks this instace
     */
    unlock: function() {
        this.locked = false;
    },

    /**
     * @property {Boolean} isTarget
     * By default, all instances can be a drop target.  This can be disabled by
     * setting isTarget to false.
     */
    isTarget: true,

    /**
     * @property {Number[]} padding
     * The padding configured for this drag and drop object for calculating
     * the drop zone intersection with this object.
     * An array containing the 4 padding values: [top, right, bottom, left]
     */
    padding: null,

    /**
     * @property _domRef
     * Cached reference to the linked element
     * @private
     */
    _domRef: null,

    /**
     * @property __ygDragDrop
     * Internal typeof flag
     * @private
     */
    __ygDragDrop: true,

    /**
     * @property {Boolean} constrainX
     * Set to true when horizontal contraints are applied
     * @private
     */
    constrainX: false,

    /**
     * @property {Boolean} constrainY
     * Set to true when vertical contraints are applied
     * @private
     */
    constrainY: false,

    /**
     * @property {Number} minX
     * The left constraint
     * @private
     */
    minX: 0,

    /**
     * @property {Number} maxX
     * The right constraint
     * @private
     */
    maxX: 0,

    /**
     * @property {Number} minY
     * The up constraint
     * @private
     */
    minY: 0,

    /**
     * @property {Number} maxY
     * The down constraint
     * @private
     */
    maxY: 0,

    /**
     * @property {Boolean} maintainOffset
     * Maintain offsets when we resetconstraints.  Set to true when you want
     * the position of the element relative to its parent to stay the same
     * when the page changes
     */
    maintainOffset: false,

    /**
     * @property {Number[]} xTicks
     * Array of pixel locations the element will snap to if we specified a
     * horizontal graduation/interval.  This array is generated automatically
     * when you define a tick interval.
     */
    xTicks: null,

    /**
     * @property {Number[]} yTicks
     * Array of pixel locations the element will snap to if we specified a
     * vertical graduation/interval.  This array is generated automatically
     * when you define a tick interval.
     */
    yTicks: null,

    /**
     * @property {Boolean} primaryButtonOnly
     * By default the drag and drop instance will only respond to the primary
     * button click (left button for a right-handed mouse).  Set to true to
     * allow drag and drop to start with any mouse click that is propogated
     * by the browser
     */
    primaryButtonOnly: true,

    /**
     * @property {Boolean} available
     * The available property is false until the linked dom element is accessible.
     */
    available: false,

    /**
     * @property {Boolean} hasOuterHandles
     * By default, drags can only be initiated if the mousedown occurs in the
     * region the linked element is.  This is done in part to work around a
     * bug in some browsers that mis-report the mousedown if the previous
     * mouseup happened outside of the window.  This property is set to true
     * if outer handles are defined. Defaults to false.
     */
    hasOuterHandles: false,

    triggerEvent: 'mousedown',

    /**
     * Code that executes immediately before the startDrag event
     * @private
     */
    b4StartDrag: function(x, y) { },

    /**
     * Abstract method called after a drag/drop object is clicked
     * and the drag or mousedown time thresholds have beeen met.
     * @param {Number} x X click location
     * @param {Number} y Y click location
     */
    startDrag: function(x, y) { /* override this */ },

    /**
     * Code that executes immediately before the onDrag event
     * @private
     */
    b4Drag: function(e) { },

    /**
     * Abstract method called during the onMouseMove event while dragging an
     * object.
     * @param {Event} e the mousemove event
     */
    onDrag: function(e) { /* override this */ },

    /**
     * Abstract method called when this element fist begins hovering over
     * another DragDrop obj
     * @param {Event} e the mousemove event
     * @param {String/Ext.dd.DragDrop[]} id In POINT mode, the element
     * id this is hovering over.  In INTERSECT mode, an array of one or more
     * dragdrop items being hovered over.
     */
    onDragEnter: function(e, id) { /* override this */ },

    /**
     * Code that executes immediately before the onDragOver event
     * @private
     */
    b4DragOver: function(e) { },

    /**
     * Abstract method called when this element is hovering over another
     * DragDrop obj
     * @param {Event} e the mousemove event
     * @param {String/Ext.dd.DragDrop[]} id In POINT mode, the element
     * id this is hovering over.  In INTERSECT mode, an array of dd items
     * being hovered over.
     */
    onDragOver: function(e, id) { /* override this */ },

    /**
     * Code that executes immediately before the onDragOut event
     * @private
     */
    b4DragOut: function(e) { },

    /**
     * Abstract method called when we are no longer hovering over an element
     * @param {Event} e the mousemove event
     * @param {String/Ext.dd.DragDrop[]} id In POINT mode, the element
     * id this was hovering over.  In INTERSECT mode, an array of dd items
     * that the mouse is no longer over.
     */
    onDragOut: function(e, id) { /* override this */ },

    /**
     * Code that executes immediately before the onDragDrop event
     * @private
     */
    b4DragDrop: function(e) { },

    /**
     * Abstract method called when this item is dropped on another DragDrop
     * obj
     * @param {Event} e the mouseup event
     * @param {String/Ext.dd.DragDrop[]} id In POINT mode, the element
     * id this was dropped on.  In INTERSECT mode, an array of dd items this
     * was dropped on.
     */
    onDragDrop: function(e, id) { /* override this */ },

    /**
     * Abstract method called when this item is dropped on an area with no
     * drop target
     * @param {Event} e the mouseup event
     */
    onInvalidDrop: function(e) { /* override this */ },

    /**
     * Code that executes immediately before the endDrag event
     * @private
     */
    b4EndDrag: function(e) { },

    /**
     * Called when we are done dragging the object
     * @param {Event} e the mouseup event
     */
    endDrag: function(e) { /* override this */ },

    /**
     * Code executed immediately before the onMouseDown event
     * @param {Event} e the mousedown event
     * @private
     */
    b4MouseDown: function(e) {  },

    /**
     * Called when a drag/drop obj gets a mousedown
     * @param {Event} e the mousedown event
     */
    onMouseDown: function(e) { /* override this */ },

    /**
     * Called when a drag/drop obj gets a mouseup
     * @param {Event} e the mouseup event
     */
    onMouseUp: function(e) { /* override this */ },

    /**
     * Override the onAvailable method to do what is needed after the initial
     * position was determined.
     */
    onAvailable: function () {
    },

    /**
     * @property {Object} defaultPadding
     * Provides default constraint padding to "constrainTo" elements.
     */
    defaultPadding: {
        left: 0,
        right: 0,
        top: 0,
        bottom: 0
    },

    /**
     * Initializes the drag drop object's constraints to restrict movement to a certain element.
     *
     * Usage:
     *
     *     var dd = new Ext.dd.DDProxy("dragDiv1", "proxytest",
     *                    { dragElId: "existingProxyDiv" });
     *     dd.startDrag = function(){
     *         this.constrainTo("parent-id");
     *     };
     *
     * Or you can initalize it using the {@link Ext.dom.Element} object:
     *
     *     Ext.get("dragDiv1").initDDProxy("proxytest", {dragElId: "existingProxyDiv"}, {
     *         startDrag : function(){
     *             this.constrainTo("parent-id");
     *         }
     *     });
     *
     * @param {String/HTMLElement/Ext.dom.Element} constrainTo The element or element ID to constrain to.
     * @param {Object/Number} pad (optional) Pad provides a way to specify "padding" of the constraints,
     * and can be either a number for symmetrical padding (4 would be equal to `{left:4, right:4, top:4, bottom:4}`) or
     * an object containing the sides to pad. For example: `{right:10, bottom:10}`
     * @param {Boolean} inContent (optional) Constrain the draggable in the content box of the element (inside padding and borders)
     */
    constrainTo : function(constrainTo, pad, inContent){
        if (Ext.isNumber(pad)) {
            pad = {left: pad, right:pad, top:pad, bottom:pad};
        }
        pad = pad || this.defaultPadding;
        var ddBox = Ext.get(this.getEl()).getBox(),
            constrainEl = Ext.get(constrainTo),
            s = constrainEl.getScroll(),
            c,
            constrainDom = constrainEl.dom,
            xy,
            topSpace,
            leftSpace;

        if (constrainDom === document.body) {
            c = {
                x: s.left,
                y: s.top,
                width: Ext.Element.getViewportWidth(),
                height: Ext.Element.getViewportHeight()
            };
        } else {
            xy = constrainEl.getXY();
            c = {
                x : xy[0],
                y: xy[1],
                width: constrainDom.clientWidth,
                height: constrainDom.clientHeight
            };
        }

        topSpace = ddBox.y - c.y;
        leftSpace = ddBox.x - c.x;

        this.resetConstraints();
        this.setXConstraint(leftSpace - (pad.left||0), // left
            c.width - leftSpace - ddBox.width - (pad.right||0), //right
            this.xTickSize
        );
        this.setYConstraint(topSpace - (pad.top||0), //top
            c.height - topSpace - ddBox.height - (pad.bottom||0), //bottom
            this.yTickSize
        );
    },

    /**
     * Returns a reference to the linked element
     * @return {HTMLElement} the html element
     */
    getEl: function() {
        if (!this._domRef) {
            this._domRef = Ext.getDom(this.id);
        }

        return this._domRef;
    },

    /**
     * Returns a reference to the actual element to drag.  By default this is
     * the same as the html element, but it can be assigned to another
     * element. An example of this can be found in Ext.dd.DDProxy
     * @return {HTMLElement} the html element
     */
    getDragEl: function() {
        return Ext.getDom(this.dragElId);
    },

    /**
     * Sets up the DragDrop object.  Must be called in the constructor of any
     * Ext.dd.DragDrop subclass
     * @param {String} id the id of the linked element
     * @param {String} sGroup the group of related items
     * @param {Object} config configuration attributes
     */
    init: function(id, sGroup, config) {
        var me = this;

        me.el = me.el || Ext.get(id); // subclass may have already set "el"

        me.initTarget(id, sGroup, config);
        Ext.get(me.id).on(me.triggerEvent, me.handleMouseDown, me);
    },

    /**
     * Initializes Targeting functionality only... the object does not
     * get a mousedown handler.
     * @param {String} id the id of the linked element
     * @param {String} sGroup the group of related items
     * @param {Object} config configuration attributes
     */
    initTarget: function(id, sGroup, config) {
        // configuration attributes
        this.config = config || {};

        // create a local reference to the drag and drop manager
        this.DDMInstance = Ext.dd.DragDropManager;
        // initialize the groups array
        this.groups = {};

        // assume that we have an element reference instead of an id if the
        // parameter is not a string
        if (typeof id !== "string") {
            id = Ext.id(id);
        }

        // set the id
        this.id = id;

        // add to an interaction group
        this.addToGroup((sGroup) ? sGroup : "default");

        // We don't want to register this as the handle with the manager
        // so we just set the id rather than calling the setter.
        this.handleElId = id;

        // the linked element is the element that gets dragged by default
        this.setDragElId(id);

        // by default, clicked anchors will not start drag operations.
        this.invalidHandleTypes = { A: "A" };
        this.invalidHandleIds = {};
        this.invalidHandleClasses = [];

        this.applyConfig();

        this.handleOnAvailable();
    },

    /**
     * Applies the configuration parameters that were passed into the constructor.
     * This is supposed to happen at each level through the inheritance chain.  So
     * a DDProxy implentation will execute apply config on DDProxy, DD, and
     * DragDrop in order to get all of the parameters that are available in
     * each object.
     */
    applyConfig: function() {

        // configurable properties:
        //    padding, isTarget, maintainOffset, primaryButtonOnly
        this.padding           = this.config.padding || [0, 0, 0, 0];
        this.isTarget          = (this.config.isTarget !== false);
        this.maintainOffset    = (this.config.maintainOffset);
        this.primaryButtonOnly = (this.config.primaryButtonOnly !== false);
    },
    
    /**
     * Executed when the linked element is available
     * @private
     */
    handleOnAvailable: function() {
        this.available = true;
        this.resetConstraints();
        this.onAvailable();
    },
    
    /**
     * Configures the padding for the target zone in px.  Effectively expands
     * (or reduces) the virtual object size for targeting calculations.
     * Supports css-style shorthand; if only one parameter is passed, all sides
     * will have that padding, and if only two are passed, the top and bottom
     * will have the first param, the left and right the second.
     * @param {Number} iTop    Top pad
     * @param {Number} iRight  Right pad
     * @param {Number} iBot    Bot pad
     * @param {Number} iLeft   Left pad
     */
    setPadding: function(iTop, iRight, iBot, iLeft) {
        // this.padding = [iLeft, iRight, iTop, iBot];
        if (!iRight && 0 !== iRight) {
            this.padding = [iTop, iTop, iTop, iTop];
        } else if (!iBot && 0 !== iBot) {
            this.padding = [iTop, iRight, iTop, iRight];
        } else {
            this.padding = [iTop, iRight, iBot, iLeft];
        }
    },

    /**
     * Stores the initial placement of the linked element.
     * @param {Number} diffX   the X offset, default 0
     * @param {Number} diffY   the Y offset, default 0
     */
    setInitPosition: function(diffX, diffY) {
        var el = this.getEl(),
            dx, dy, p;

        if (!this.DDMInstance.verifyEl(el)) {
            return;
        }

        dx = diffX || 0;
        dy = diffY || 0;

        p = Ext.fly(el).getXY();

        this.initPageX = p[0] - dx;
        this.initPageY = p[1] - dy;

        this.lastPageX = p[0];
        this.lastPageY = p[1];

        this.setStartPosition(p);
    },

    /**
     * Sets the start position of the element.  This is set when the obj
     * is initialized, the reset when a drag is started.
     * @param pos current position (from previous lookup)
     * @private
     */
    setStartPosition: function(pos) {
        var p = pos || Ext.fly(this.getEl()).getXY();
        this.deltaSetXY = null;

        this.startPageX = p[0];
        this.startPageY = p[1];
    },

    /**
     * Adds this instance to a group of related drag/drop objects.  All
     * instances belong to at least one group, and can belong to as many
     * groups as needed.
     * @param {String} sGroup the name of the group
     */
    addToGroup: function(sGroup) {
        this.groups[sGroup] = true;
        this.DDMInstance.regDragDrop(this, sGroup);
    },

    /**
     * Removes this instance from the supplied interaction group
     * @param {String} sGroup  The group to drop
     */
    removeFromGroup: function(sGroup) {
        if (this.groups[sGroup]) {
            delete this.groups[sGroup];
        }

        this.DDMInstance.removeDDFromGroup(this, sGroup);
    },

    /**
     * Allows you to specify that an element other than the linked element
     * will be moved with the cursor during a drag
     * @param {String} id the id of the element that will be used to initiate the drag
     */
    setDragElId: function(id) {
        this.dragElId = id;
    },

    /**
     * Allows you to specify a child of the linked element that should be
     * used to initiate the drag operation.  An example of this would be if
     * you have a content div with text and links.  Clicking anywhere in the
     * content area would normally start the drag operation.  Use this method
     * to specify that an element inside of the content div is the element
     * that starts the drag operation.
     * @param {String} id the id of the element that will be used to
     * initiate the drag.
     */
    setHandleElId: function(id) {
        if (typeof id !== "string") {
            id = Ext.id(id);
        }
        this.handleElId = id;
        this.DDMInstance.regHandle(this.id, id);
    },

    /**
     * Allows you to set an element outside of the linked element as a drag
     * handle
     * @param {String} id the id of the element that will be used to initiate the drag
     */
    setOuterHandleElId: function(id) {
        if (typeof id !== "string") {
            id = Ext.id(id);
        }
        Ext.get(id).on(this.triggerEvent, this.handleMouseDown, this);
        this.setHandleElId(id);

        this.hasOuterHandles = true;
    },

    /**
     * Removes all drag and drop hooks for this element
     */
    unreg: function() {
        var me = this,
            el;
        
        if (me._domRef) {
            el = Ext.fly(me.id);
            if (el) {
                el.un(me.triggerEvent, me.handleMouseDown, me);
            }
        }
        me._domRef = null;
        me.DDMInstance._remove(me, me.autoGroup);
    },

    /**
     * Destroy this DragDrop instance
     */
    destroy: function() {
        this.unreg();
        this.isDestroyed = true;
    },

    /**
     * Returns true if this instance is locked, or the drag drop mgr is locked
     * (meaning that all drag/drop is disabled on the page.)
     * @return {Boolean} true if this obj or all drag/drop is locked, else
     * false
     */
    isLocked: function() {
        return (this.DDMInstance.isLocked() || this.locked);
    },

    /**
     * Called when this object is clicked
     * @param {Event} e
     * @param {Ext.dd.DragDrop} oDD the clicked dd object (this dd obj)
     * @private
     */
    handleMouseDown: function(e, oDD){
        var me = this;

        if ((me.primaryButtonOnly && e.button) || me.isLocked()) {
            return;
        }

        me.DDMInstance.refreshCache(me.groups);

        if (me.hasOuterHandles || me.DDMInstance.isOverTarget(e.getPoint(), me))  {
            if (me.clickValidator(e)) {
                // set the initial element position
                me.setStartPosition();
                me.b4MouseDown(e);
                me.onMouseDown(e);

                me.DDMInstance.handleMouseDown(e, me);

                me.DDMInstance.stopEvent(e);
            }
        }
    },

    clickValidator: function(e) {
        var target = e.getTarget();
        return ( this.isValidHandleChild(target) &&
                    (this.id === this.handleElId ||
                        this.DDMInstance.handleWasClicked(target, this.id)) );
    },

    /**
     * Allows you to specify a tag name that should not start a drag operation
     * when clicked.  This is designed to facilitate embedding links within a
     * drag handle that do something other than start the drag.
     * @method addInvalidHandleType
     * @param {String} tagName the type of element to exclude
     */
    addInvalidHandleType: function(tagName) {
        var type = tagName.toUpperCase();
        this.invalidHandleTypes[type] = type;
    },

    /**
     * Lets you to specify an element id for a child of a drag handle
     * that should not initiate a drag
     * @method addInvalidHandleId
     * @param {String} id the element id of the element you wish to ignore
     */
    addInvalidHandleId: function(id) {
        if (typeof id !== "string") {
            id = Ext.id(id);
        }
        this.invalidHandleIds[id] = id;
    },

    /**
     * Lets you specify a css class of elements that will not initiate a drag
     * @param {String} cssClass the class of the elements you wish to ignore
     */
    addInvalidHandleClass: function(cssClass) {
        this.invalidHandleClasses.push(cssClass);
    },

    /**
     * Unsets an excluded tag name set by addInvalidHandleType
     * @param {String} tagName the type of element to unexclude
     */
    removeInvalidHandleType: function(tagName) {
        var type = tagName.toUpperCase();
        // this.invalidHandleTypes[type] = null;
        delete this.invalidHandleTypes[type];
    },

    /**
     * Unsets an invalid handle id
     * @param {String} id the id of the element to re-enable
     */
    removeInvalidHandleId: function(id) {
        if (typeof id !== "string") {
            id = Ext.id(id);
        }
        delete this.invalidHandleIds[id];
    },

    /**
     * Unsets an invalid css class
     * @param {String} cssClass the class of the element(s) you wish to
     * re-enable
     */
    removeInvalidHandleClass: function(cssClass) {
        var invalidHandleClasses = this.invalidHandleClasses,
            len = invalidHandleClasses.length,
            i;

        for (i = 0; i < len; ++i) {
            if (invalidHandleClasses[i] === cssClass) {
                delete invalidHandleClasses[i];
            }
        }
    },

    /**
     * Checks the tag exclusion list to see if this click should be ignored
     * @param {HTMLElement} node the HTMLElement to evaluate
     * @return {Boolean} true if this is a valid tag type, false if not
     */
    isValidHandleChild: function(node) {

        var valid = true,
            nodeName,
            i, len;
        // var n = (node.nodeName == "#text") ? node.parentNode : node;
        try {
            nodeName = node.nodeName.toUpperCase();
        } catch(e) {
            nodeName = node.nodeName;
        }
        valid = valid && !this.invalidHandleTypes[nodeName];
        valid = valid && !this.invalidHandleIds[node.id];

        for (i=0, len=this.invalidHandleClasses.length; valid && i<len; ++i) {
            valid = !Ext.fly(node).hasCls(this.invalidHandleClasses[i]);
        }


        return valid;

    },

    /**
     * Creates the array of horizontal tick marks if an interval was specified
     * in setXConstraint().
     * @private
     */
    setXTicks: function(iStartX, iTickSize) {
        this.xTicks = [];
        this.xTickSize = iTickSize;

        var tickMap = {},
            i;

        for (i = this.initPageX; i >= this.minX; i = i - iTickSize) {
            if (!tickMap[i]) {
                this.xTicks[this.xTicks.length] = i;
                tickMap[i] = true;
            }
        }

        for (i = this.initPageX; i <= this.maxX; i = i + iTickSize) {
            if (!tickMap[i]) {
                this.xTicks[this.xTicks.length] = i;
                tickMap[i] = true;
            }
        }

        Ext.Array.sort(this.xTicks, this.DDMInstance.numericSort);
    },

    /**
     * Creates the array of vertical tick marks if an interval was specified in
     * setYConstraint().
     * @private
     */
    setYTicks: function(iStartY, iTickSize) {
        this.yTicks = [];
        this.yTickSize = iTickSize;

        var tickMap = {},
            i;

        for (i = this.initPageY; i >= this.minY; i = i - iTickSize) {
            if (!tickMap[i]) {
                this.yTicks[this.yTicks.length] = i;
                tickMap[i] = true;
            }
        }

        for (i = this.initPageY; i <= this.maxY; i = i + iTickSize) {
            if (!tickMap[i]) {
                this.yTicks[this.yTicks.length] = i;
                tickMap[i] = true;
            }
        }

        Ext.Array.sort(this.yTicks, this.DDMInstance.numericSort);
    },

    /**
     * By default, the element can be dragged any place on the screen.  Use
     * this method to limit the horizontal travel of the element.  Pass in
     * 0,0 for the parameters if you want to lock the drag to the y axis.
     * @param {Number} iLeft the number of pixels the element can move to the left
     * @param {Number} iRight the number of pixels the element can move to the
     * right
     * @param {Number} iTickSize (optional) parameter for specifying that the
     * element should move iTickSize pixels at a time.
     */
    setXConstraint: function(iLeft, iRight, iTickSize) {
        this.leftConstraint = iLeft;
        this.rightConstraint = iRight;

        this.minX = this.initPageX - iLeft;
        this.maxX = this.initPageX + iRight;
        if (iTickSize) { this.setXTicks(this.initPageX, iTickSize); }

        this.constrainX = true;
    },

    /**
     * Clears any constraints applied to this instance.  Also clears ticks
     * since they can't exist independent of a constraint at this time.
     */
    clearConstraints: function() {
        this.constrainX = false;
        this.constrainY = false;
        this.clearTicks();
    },

    /**
     * Clears any tick interval defined for this instance
     */
    clearTicks: function() {
        this.xTicks = null;
        this.yTicks = null;
        this.xTickSize = 0;
        this.yTickSize = 0;
    },

    /**
     * By default, the element can be dragged any place on the screen.  Set
     * this to limit the vertical travel of the element.  Pass in 0,0 for the
     * parameters if you want to lock the drag to the x axis.
     * @param {Number} iUp the number of pixels the element can move up
     * @param {Number} iDown the number of pixels the element can move down
     * @param {Number} iTickSize (optional) parameter for specifying that the
     * element should move iTickSize pixels at a time.
     */
    setYConstraint: function(iUp, iDown, iTickSize) {
        this.topConstraint = iUp;
        this.bottomConstraint = iDown;

        this.minY = this.initPageY - iUp;
        this.maxY = this.initPageY + iDown;
        if (iTickSize) { this.setYTicks(this.initPageY, iTickSize); }

        this.constrainY = true;

    },

    /**
     * Must be called if you manually reposition a dd element.
     * @param {Boolean} maintainOffset
     */
    resetConstraints: function() {
        // Maintain offsets if necessary
        if (this.initPageX || this.initPageX === 0) {
            // figure out how much this thing has moved
            var dx = (this.maintainOffset) ? this.lastPageX - this.initPageX : 0,
                dy = (this.maintainOffset) ? this.lastPageY - this.initPageY : 0;

            this.setInitPosition(dx, dy);

        // This is the first time we have detected the element's position
        } else {
            this.setInitPosition();
        }

        if (this.constrainX) {
            this.setXConstraint( this.leftConstraint,
                                 this.rightConstraint,
                                 this.xTickSize        );
        }

        if (this.constrainY) {
            this.setYConstraint( this.topConstraint,
                                 this.bottomConstraint,
                                 this.yTickSize         );
        }
    },

    /**
     * Normally the drag element is moved pixel by pixel, but we can specify
     * that it move a number of pixels at a time.  This method resolves the
     * location when we have it set up like this.
     * @param {Number} val where we want to place the object
     * @param {Number[]} tickArray sorted array of valid points
     * @return {Number} the closest tick
     * @private
     */
    getTick: function(val, tickArray) {
        if (!tickArray) {
            // If tick interval is not defined, it is effectively 1 pixel,
            // so we return the value passed to us.
            return val;
        } else if (tickArray[0] >= val) {
            // The value is lower than the first tick, so we return the first
            // tick.
            return tickArray[0];
        } else {
            var i, len, next, diff1, diff2;
            for (i=0, len=tickArray.length; i<len; ++i) {
                next = i + 1;
                if (tickArray[next] && tickArray[next] >= val) {
                    diff1 = val - tickArray[i];
                    diff2 = tickArray[next] - val;
                    return (diff2 > diff1) ? tickArray[i] : tickArray[next];
                }
            }

            // The value is larger than the last tick, so we return the last
            // tick.
            return tickArray[tickArray.length - 1];
        }
    },

    /**
     * toString method
     * @return {String} string representation of the dd obj
     */
    toString: function() {
        return ("DragDrop " + this.id);
    }

});