# Yahoo! UI Library

### Drag and Drop 2.8.2r1

Yahoo! UI Library > dragdrop > DragDropMgr.js (source view)
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    /**
     * The drag and drop utility provides a framework for building drag and drop
     * applications.  In addition to enabling drag and drop for specific elements,
     * the drag and drop elements are tracked by the manager class, and the
     * interactions between the various elements are tracked during the drag and
     * the implementing code is notified about these important moments.
     * @module dragdrop
     * @title Drag and Drop
     * @requires yahoo,dom,event
     * @namespace YAHOO.util
     */

    // Only load the library once.  Rewriting the manager class would orphan
    // existing drag and drop instances.
    if (!YAHOO.util.DragDropMgr) {

    /**
     * DragDropMgr is a singleton that tracks the element interaction for
     * all DragDrop items in the window.  Generally, you will not call
     * this class directly, but it does have helper methods that could
     * be useful in your DragDrop implementations.
     * @class DragDropMgr
     * @static
     */
    YAHOO.util.DragDropMgr = function() {

        var Event = YAHOO.util.Event,
            Dom = YAHOO.util.Dom;

        return {
            /**
            * This property is used to turn on global use of the shim element on all DragDrop instances, defaults to false for backcompat. (Use: YAHOO.util.DDM.useShim = true)
            * @property useShim
            * @type Boolean
            * @static
            */
            useShim: false,
            /**
            * This property is used to determine if the shim is active over the screen, default false.
            * @private
            * @property _shimActive
            * @type Boolean
            * @static
            */
            _shimActive: false,
            /**
            * This property is used when useShim is set on a DragDrop object to store the current state of DDM.useShim so it can be reset when a drag operation is done.
            * @private
            * @property _shimState
            * @type Boolean
            * @static
            */
            _shimState: false,
            /**
            * This property is used when useShim is set to true, it will set the opacity on the shim to .5 for debugging. Use: (YAHOO.util.DDM._debugShim = true;)
            * @private
            * @property _debugShim
            * @type Boolean
            * @static
            */
            _debugShim: false,
            /**
            * This method will create a shim element (giving it the id of yui-ddm-shim), it also attaches the mousemove and mouseup listeners to it and attaches a scroll listener on the window
            * @private
            * @method _sizeShim
            * @static
            */
            _createShim: function() {
                YAHOO.log('Creating Shim Element', 'info', 'DragDropMgr');
                var s = document.createElement('div');
                s.id = 'yui-ddm-shim';
                if (document.body.firstChild) {
                    document.body.insertBefore(s, document.body.firstChild);
                } else {
                    document.body.appendChild(s);
                }
                s.style.display = 'none';
                s.style.backgroundColor = 'red';
                s.style.position = 'absolute';
                s.style.zIndex = '99999';
                Dom.setStyle(s, 'opacity', '0');
                this._shim = s;
                Event.on(s, "mouseup",   this.handleMouseUp, this, true);
                Event.on(s, "mousemove", this.handleMouseMove, this, true);
                Event.on(window, 'scroll', this._sizeShim, this, true);
            },
            /**
            * This method will size the shim, called from activate and on window scroll event
            * @private
            * @method _sizeShim
            * @static
            */
            _sizeShim: function() {
                if (this._shimActive) {
                    YAHOO.log('Sizing Shim', 'info', 'DragDropMgr');
                    var s = this._shim;
                    s.style.height = Dom.getDocumentHeight() + 'px';
                    s.style.width = Dom.getDocumentWidth() + 'px';
                    s.style.top = '0';
                    s.style.left = '0';
                }
            },
            /**
            * This method will create the shim element if needed, then show the shim element, size the element and set the _shimActive property to true
            * @private
            * @method _activateShim
            * @static
            */
            _activateShim: function() {
                if (this.useShim) {
                    YAHOO.log('Activating Shim', 'info', 'DragDropMgr');
                    if (!this._shim) {
                        this._createShim();
                    }
                    this._shimActive = true;
                    var s = this._shim,
                        o = '0';
                    if (this._debugShim) {
                        o = '.5';
                    }
                    Dom.setStyle(s, 'opacity', o);
                    this._sizeShim();
                    s.style.display = 'block';
                }
            },
            /**
            * This method will hide the shim element and set the _shimActive property to false
            * @private
            * @method _deactivateShim
            * @static
            */
            _deactivateShim: function() {
                YAHOO.log('Deactivating Shim', 'info', 'DragDropMgr');
                this._shim.style.display = 'none';
                this._shimActive = false;
            },
            /**
            * The HTML element created to use as a shim over the document to track mouse movements
            * @private
            * @property _shim
            * @type HTMLElement
            * @static
            */
            _shim: null,
            /**
             * Two dimensional Array of registered DragDrop objects.  The first
             * dimension is the DragDrop item group, the second the DragDrop
             * object.
             * @property ids
             * @type {string: string}
             * @private
             * @static
             */
            ids: {},

            /**
             * Array of element ids defined as drag handles.  Used to determine
             * if the element that generated the mousedown event is actually the
             * handle and not the html element itself.
             * @property handleIds
             * @type {string: string}
             * @private
             * @static
             */
            handleIds: {},

            /**
             * the DragDrop object that is currently being dragged
             * @property dragCurrent
             * @type DragDrop
             * @private
             * @static
             **/
            dragCurrent: null,

            /**
             * the DragDrop object(s) that are being hovered over
             * @property dragOvers
             * @type Array
             * @private
             * @static
             */
            dragOvers: {},

            /**
             * the X distance between the cursor and the object being dragged
             * @property deltaX
             * @type int
             * @private
             * @static
             */
            deltaX: 0,

            /**
             * the Y distance between the cursor and the object being dragged
             * @property deltaY
             * @type int
             * @private
             * @static
             */
            deltaY: 0,

            /**
             * Flag to determine if we should prevent the default behavior of the
             * events we define. By default this is true, but this can be set to
             * false if you need the default behavior (not recommended)
             * @property preventDefault
             * @type boolean
             * @static
             */
            preventDefault: true,

            /**
             * Flag to determine if we should stop the propagation of the events
             * we generate. This is true by default but you may want to set it to
             * false if the html element contains other features that require the
             * mouse click.
             * @property stopPropagation
             * @type boolean
             * @static
             */
            stopPropagation: true,

            /**
             * Internal flag that is set to true when drag and drop has been
             * initialized
             * @property initialized
             * @private
             * @static
             */
            initialized: false,

            /**
             * All drag and drop can be disabled.
             * @property locked
             * @private
             * @static
             */
            locked: false,

            /**
             * Provides additional information about the the current set of
             * interactions.  Can be accessed from the event handlers. It
             * contains the following properties:
             *
             *       out:       onDragOut interactions
             *       enter:     onDragEnter interactions
             *       over:      onDragOver interactions
             *       drop:      onDragDrop interactions
             *       point:     The location of the cursor
             *       draggedRegion: The location of dragged element at the time
             *                      of the interaction
             *       sourceRegion: The location of the source elemtn at the time
             *                     of the interaction
             *       validDrop: boolean
             * @property interactionInfo
             * @type object
             * @static
             */
            interactionInfo: null,

            /**
             * Called the first time an element is registered.
             * @method init
             * @private
             * @static
             */
            init: function() {
                this.initialized = true;
            },

            /**
             * In point mode, drag and drop interaction is defined by the
             * location of the cursor during the drag/drop
             * @property POINT
             * @type int
             * @static
             * @final
             */
            POINT: 0,

            /**
             * In intersect mode, drag and drop interaction is defined by the
             * cursor position or the amount of overlap of two or more drag and
             * drop objects.
             * @property INTERSECT
             * @type int
             * @static
             * @final
             */
            INTERSECT: 1,

            /**
             * In intersect mode, drag and drop interaction is defined only by the
             * overlap of two or more drag and drop objects.
             * @property STRICT_INTERSECT
             * @type int
             * @static
             * @final
             */
            STRICT_INTERSECT: 2,

            /**
             * The current drag and drop mode.  Default: POINT
             * @property mode
             * @type int
             * @static
             */
            mode: 0,

            /**
             * Runs method on all drag and drop objects
             * @method _execOnAll
             * @private
             * @static
             */
            _execOnAll: function(sMethod, args) {
                for (var i in this.ids) {
                    for (var j in this.ids[i]) {
                        var oDD = this.ids[i][j];
                        if (! this.isTypeOfDD(oDD)) {
                            continue;
                        }
                        oDD[sMethod].apply(oDD, args);
                    }
                }
            },

            /**
             * Drag and drop initialization.  Sets up the global event handlers
             * @method _onLoad
             * @private
             * @static
             */
            _onLoad: function() {

                this.init();

                YAHOO.log("DragDropMgr onload", "info", "DragDropMgr");
                Event.on(document, "mouseup",   this.handleMouseUp, this, true);
                Event.on(document, "mousemove", this.handleMouseMove, this, true);
                Event.on(window,   "unload",    this._onUnload, this, true);
                Event.on(window,   "resize",    this._onResize, this, true);
                // Event.on(window,   "mouseout",    this._test);

            },

            /**
             * Reset constraints on all drag and drop objs
             * @method _onResize
             * @private
             * @static
             */
            _onResize: function(e) {
                YAHOO.log("window resize", "info", "DragDropMgr");
                this._execOnAll("resetConstraints", []);
            },

            /**
             * Lock all drag and drop functionality
             * @method lock
             * @static
             */
            lock: function() { this.locked = true; },

            /**
             * Unlock all drag and drop functionality
             * @method unlock
             * @static
             */
            unlock: function() { this.locked = false; },

            /**
             * Is drag and drop locked?
             * @method isLocked
             * @return {boolean} True if drag and drop is locked, false otherwise.
             * @static
             */
            isLocked: function() { return this.locked; },

            /**
             * Location cache that is set for all drag drop objects when a drag is
             * initiated, cleared when the drag is finished.
             * @property locationCache
             * @private
             * @static
             */
            locationCache: {},

            /**
             * Set useCache to false if you want to force object the lookup of each
             * drag and drop linked element constantly during a drag.
             * @property useCache
             * @type boolean
             * @static
             */
            useCache: true,

            /**
             * The number of pixels that the mouse needs to move after the
             * mousedown before the drag is initiated.  Default=3;
             * @property clickPixelThresh
             * @type int
             * @static
             */
            clickPixelThresh: 3,

            /**
             * The number of milliseconds after the mousedown event to initiate the
             * drag if we don't get a mouseup event. Default=1000
             * @property clickTimeThresh
             * @type int
             * @static
             */
            clickTimeThresh: 1000,

            /**
             * Flag that indicates that either the drag pixel threshold or the
             * mousdown time threshold has been met
             * @property dragThreshMet
             * @type boolean
             * @private
             * @static
             */
            dragThreshMet: false,

            /**
             * Timeout used for the click time threshold
             * @property clickTimeout
             * @type Object
             * @private
             * @static
             */
            clickTimeout: null,

            /**
             * The X position of the mousedown event stored for later use when a
             * drag threshold is met.
             * @property startX
             * @type int
             * @private
             * @static
             */
            startX: 0,

            /**
             * The Y position of the mousedown event stored for later use when a
             * drag threshold is met.
             * @property startY
             * @type int
             * @private
             * @static
             */
            startY: 0,

            /**
             * Flag to determine if the drag event was fired from the click timeout and
             * not the mouse move threshold.
             * @property fromTimeout
             * @type boolean
             * @private
             * @static
             */
            fromTimeout: false,

            /**
             * Each DragDrop instance must be registered with the DragDropMgr.
             * This is executed in DragDrop.init()
             * @method regDragDrop
             * @param {DragDrop} oDD the DragDrop object to register
             * @param {String} sGroup the name of the group this element belongs to
             * @static
             */
            regDragDrop: function(oDD, sGroup) {
                if (!this.initialized) { this.init(); }

                if (!this.ids[sGroup]) {
                    this.ids[sGroup] = {};
                }
                this.ids[sGroup][oDD.id] = oDD;
            },

            /**
             * Removes the supplied dd instance from the supplied group. Executed
             * by DragDrop.removeFromGroup, so don't call this function directly.
             * @method removeDDFromGroup
             * @private
             * @static
             */
            removeDDFromGroup: function(oDD, sGroup) {
                if (!this.ids[sGroup]) {
                    this.ids[sGroup] = {};
                }

                var obj = this.ids[sGroup];
                if (obj && obj[oDD.id]) {
                    delete obj[oDD.id];
                }
            },

            /**
             * Unregisters a drag and drop item.  This is executed in
             * DragDrop.unreg, use that method instead of calling this directly.
             * @method _remove
             * @private
             * @static
             */
            _remove: function(oDD) {
                for (var g in oDD.groups) {
                    if (g) {
                        var item = this.ids[g];
                        if (item && item[oDD.id]) {
                            delete item[oDD.id];
                        }
                    }

                }
                delete this.handleIds[oDD.id];
            },

            /**
             * Each DragDrop handle element must be registered.  This is done
             * automatically when executing DragDrop.setHandleElId()
             * @method regHandle
             * @param {String} sDDId the DragDrop id this element is a handle for
             * @param {String} sHandleId the id of the element that is the drag
             * handle
             * @static
             */
            regHandle: function(sDDId, sHandleId) {
                if (!this.handleIds[sDDId]) {
                    this.handleIds[sDDId] = {};
                }
                this.handleIds[sDDId][sHandleId] = sHandleId;
            },

            /**
             * Utility function to determine if a given element has been
             * registered as a drag drop item.
             * @method isDragDrop
             * @param {String} id the element id to check
             * @return {boolean} true if this element is a DragDrop item,
             * false otherwise
             * @static
             */
            isDragDrop: function(id) {
                return ( this.getDDById(id) ) ? true : false;
            },

            /**
             * Returns the drag and drop instances that are in all groups the
             * passed in instance belongs to.
             * @method getRelated
             * @param {DragDrop} p_oDD the obj to get related data for
             * @param {boolean} bTargetsOnly if true, only return targetable objs
             * @return {DragDrop[]} the related instances
             * @static
             */
            getRelated: function(p_oDD, bTargetsOnly) {
                var oDDs = [];
                for (var i in p_oDD.groups) {
                    for (var j in this.ids[i]) {
                        var dd = this.ids[i][j];
                        if (! this.isTypeOfDD(dd)) {
                            continue;
                        }
                        if (!bTargetsOnly || dd.isTarget) {
                            oDDs[oDDs.length] = dd;
                        }
                    }
                }

                return oDDs;
            },

            /**
             * Returns true if the specified dd target is a legal target for
             * the specifice drag obj
             * @method isLegalTarget
             * @param {DragDrop} the drag obj
             * @param {DragDrop} the target
             * @return {boolean} true if the target is a legal target for the
             * dd obj
             * @static
             */
            isLegalTarget: function (oDD, oTargetDD) {
                var targets = this.getRelated(oDD, true);
                for (var i=0, len=targets.length;i<len;++i) {
                    if (targets[i].id == oTargetDD.id) {
                        return true;
                    }
                }

                return false;
            },

            /**
             * My goal is to be able to transparently determine if an object is
             * typeof DragDrop, and the exact subclass of DragDrop.  typeof
             * returns "object", oDD.constructor.toString() always returns
             * "DragDrop" and not the name of the subclass.  So for now it just
             * evaluates a well-known variable in DragDrop.
             * @method isTypeOfDD
             * @param {Object} the object to evaluate
             * @return {boolean} true if typeof oDD = DragDrop
             * @static
             */
            isTypeOfDD: function (oDD) {
                return (oDD && oDD.__ygDragDrop);
            },

            /**
             * Utility function to determine if a given element has been
             * registered as a drag drop handle for the given Drag Drop object.
             * @method isHandle
             * @param {String} id the element id to check
             * @return {boolean} true if this element is a DragDrop handle, false
             * otherwise
             * @static
             */
            isHandle: function(sDDId, sHandleId) {
                return ( this.handleIds[sDDId] &&
                                this.handleIds[sDDId][sHandleId] );
            },

            /**
             * Returns the DragDrop instance for a given id
             * @method getDDById
             * @param {String} id the id of the DragDrop object
             * @return {DragDrop} the drag drop object, null if it is not found
             * @static
             */
            getDDById: function(id) {
                for (var i in this.ids) {
                    if (this.ids[i][id]) {
                        return this.ids[i][id];
                    }
                }
                return null;
            },

            /**
             * Fired after a registered DragDrop object gets the mousedown event.
             * Sets up the events required to track the object being dragged
             * @method handleMouseDown
             * @param {Event} e the event
             * @param oDD the DragDrop object being dragged
             * @private
             * @static
             */
            handleMouseDown: function(e, oDD) {
                //this._activateShim();

                this.currentTarget = YAHOO.util.Event.getTarget(e);

                this.dragCurrent = oDD;

                var el = oDD.getEl();

                // track start position
                this.startX = YAHOO.util.Event.getPageX(e);
                this.startY = YAHOO.util.Event.getPageY(e);

                this.deltaX = this.startX - el.offsetLeft;
                this.deltaY = this.startY - el.offsetTop;

                this.dragThreshMet = false;

                this.clickTimeout = setTimeout(
                        function() {
                            var DDM = YAHOO.util.DDM;
                            DDM.startDrag(DDM.startX, DDM.startY);
                            DDM.fromTimeout = true;
                        },
                        this.clickTimeThresh );
            },

            /**
             * Fired when either the drag pixel threshold or the mousedown hold
             * time threshold has been met.
             * @method startDrag
             * @param x {int} the X position of the original mousedown
             * @param y {int} the Y position of the original mousedown
             * @static
             */
            startDrag: function(x, y) {
                if (this.dragCurrent && this.dragCurrent.useShim) {
                    this._shimState = this.useShim;
                    this.useShim = true;
                }
                this._activateShim();
                YAHOO.log("firing drag start events", "info", "DragDropMgr");
                clearTimeout(this.clickTimeout);
                var dc = this.dragCurrent;
                if (dc && dc.events.b4StartDrag) {
                    dc.b4StartDrag(x, y);
                    dc.fireEvent('b4StartDragEvent', { x: x, y: y });
                }
                if (dc && dc.events.startDrag) {
                    dc.startDrag(x, y);
                    dc.fireEvent('startDragEvent', { x: x, y: y });
                }
                this.dragThreshMet = true;
            },

            /**
             * Internal function to handle the mouseup event.  Will be invoked
             * from the context of the document.
             * @method handleMouseUp
             * @param {Event} e the event
             * @private
             * @static
             */
            handleMouseUp: function(e) {
                if (this.dragCurrent) {
                    clearTimeout(this.clickTimeout);

                    if (this.dragThreshMet) {
                        YAHOO.log("mouseup detected - completing drag", "info", "DragDropMgr");
                        if (this.fromTimeout) {
                            YAHOO.log('fromTimeout is true (mouse didn\'t move), call handleMouseMove so we can get the dragOver event', 'info', 'DragDropMgr');
                            this.fromTimeout = false;
                            this.handleMouseMove(e);
                        }
                        this.fromTimeout = false;
                        this.fireEvents(e, true);
                    } else {
                        YAHOO.log("drag threshold not met", "info", "DragDropMgr");
                    }

                    this.stopDrag(e);

                    this.stopEvent(e);
                }
            },

            /**
             * Utility to stop event propagation and event default, if these
             * features are turned on.
             * @method stopEvent
             * @param {Event} e the event as returned by this.getEvent()
             * @static
             */
            stopEvent: function(e) {
                if (this.stopPropagation) {
                    YAHOO.util.Event.stopPropagation(e);
                }

                if (this.preventDefault) {
                    YAHOO.util.Event.preventDefault(e);
                }
            },

            /**
             * Ends the current drag, cleans up the state, and fires the endDrag
             * and mouseUp events.  Called internally when a mouseup is detected
             * during the drag.  Can be fired manually during the drag by passing
             * either another event (such as the mousemove event received in onDrag)
             * or a fake event with pageX and pageY defined (so that endDrag and
             * onMouseUp have usable position data.).  Alternatively, pass true
             * for the silent parameter so that the endDrag and onMouseUp events
             * are skipped (so no event data is needed.)
             *
             * @method stopDrag
             * @param {Event} e the mouseup event, another event (or a fake event)
             *                  with pageX and pageY defined, or nothing if the
             *                  silent parameter is true
             * @param {boolean} silent skips the enddrag and mouseup events if true
             * @static
             */
            stopDrag: function(e, silent) {
                // YAHOO.log("mouseup - removing event handlers");
                var dc = this.dragCurrent;
                // Fire the drag end event for the item that was dragged
                if (dc && !silent) {
                    if (this.dragThreshMet) {
                        YAHOO.log("firing endDrag events", "info", "DragDropMgr");
                        if (dc.events.b4EndDrag) {
                            dc.b4EndDrag(e);
                            dc.fireEvent('b4EndDragEvent', { e: e });
                        }
                        if (dc.events.endDrag) {
                            dc.endDrag(e);
                            dc.fireEvent('endDragEvent', { e: e });
                        }
                    }
                    if (dc.events.mouseUp) {
                        YAHOO.log("firing dragdrop onMouseUp event", "info", "DragDropMgr");
                        dc.onMouseUp(e);
                        dc.fireEvent('mouseUpEvent', { e: e });
                    }
                }

                if (this._shimActive) {
                    this._deactivateShim();
                    if (this.dragCurrent && this.dragCurrent.useShim) {
                        this.useShim = this._shimState;
                        this._shimState = false;
                    }
                }

                this.dragCurrent = null;
                this.dragOvers = {};
            },

            /**
             * Internal function to handle the mousemove event.  Will be invoked
             * from the context of the html element.
             *
             * @TODO figure out what we can do about mouse events lost when the
             * user drags objects beyond the window boundary.  Currently we can
             * detect this in internet explorer by verifying that the mouse is
             * down during the mousemove event.  Firefox doesn't give us the
             * button state on the mousemove event.
             * @method handleMouseMove
             * @param {Event} e the event
             * @private
             * @static
             */
            handleMouseMove: function(e) {
                //YAHOO.log("handlemousemove");

                var dc = this.dragCurrent;
                if (dc) {
                    // YAHOO.log("no current drag obj");

                    // var button = e.which || e.button;
                    // YAHOO.log("which: " + e.which + ", button: "+ e.button);

                    // check for IE mouseup outside of page boundary
                    if (YAHOO.util.Event.isIE && !e.button) {
                        YAHOO.log("button failure", "info", "DragDropMgr");
                        this.stopEvent(e);
                        return this.handleMouseUp(e);
                    } else {
                        if (e.clientX < 0 || e.clientY < 0) {
                            //This will stop the element from leaving the viewport in FF, Opera & Safari
                            //Not turned on yet
                            //YAHOO.log("Either clientX or clientY is negative, stop the event.", "info", "DragDropMgr");
                            //this.stopEvent(e);
                            //return false;
                        }
                    }

                    if (!this.dragThreshMet) {
                        var diffX = Math.abs(this.startX - YAHOO.util.Event.getPageX(e));
                        var diffY = Math.abs(this.startY - YAHOO.util.Event.getPageY(e));
                        // YAHOO.log("diffX: " + diffX + "diffY: " + diffY);
                        if (diffX > this.clickPixelThresh ||
                                    diffY > this.clickPixelThresh) {
                            YAHOO.log("pixel threshold met", "info", "DragDropMgr");
                            this.startDrag(this.startX, this.startY);
                        }
                    }

                    if (this.dragThreshMet) {
                        if (dc && dc.events.b4Drag) {
                            dc.b4Drag(e);
                            dc.fireEvent('b4DragEvent', { e: e});
                        }
                        if (dc && dc.events.drag) {
                            dc.onDrag(e);
                            dc.fireEvent('dragEvent', { e: e});
                        }
                        if (dc) {
                            this.fireEvents(e, false);
                        }
                    }

                    this.stopEvent(e);
                }
            },

            /**
             * Iterates over all of the DragDrop elements to find ones we are
             * hovering over or dropping on
             * @method fireEvents
             * @param {Event} e the event
             * @param {boolean} isDrop is this a drop op or a mouseover op?
             * @private
             * @static
             */
            fireEvents: function(e, isDrop) {
                var dc = this.dragCurrent;

                // If the user did the mouse up outside of the window, we could
                // get here even though we have ended the drag.
                // If the config option dragOnly is true, bail out and don't fire the events
                if (!dc || dc.isLocked() || dc.dragOnly) {
                    return;
                }

                var x = YAHOO.util.Event.getPageX(e),
                    y = YAHOO.util.Event.getPageY(e),
                    pt = new YAHOO.util.Point(x,y),
                    pos = dc.getTargetCoord(pt.x, pt.y),
                    el = dc.getDragEl(),
                    events = ['out', 'over', 'drop', 'enter'],
                    curRegion = new YAHOO.util.Region( pos.y,
                                                   pos.x + el.offsetWidth,
                                                   pos.y + el.offsetHeight,
                                                   pos.x ),

                    oldOvers = [], // cache the previous dragOver array
                    inGroupsObj  = {},
                    inGroups  = [],
                    data = {
                        outEvts: [],
                        overEvts: [],
                        dropEvts: [],
                        enterEvts: []
                    };

                // Check to see if the object(s) we were hovering over is no longer
                // being hovered over so we can fire the onDragOut event
                for (var i in this.dragOvers) {

                    var ddo = this.dragOvers[i];

                    if (! this.isTypeOfDD(ddo)) {
                        continue;
                    }
                    if (! this.isOverTarget(pt, ddo, this.mode, curRegion)) {
                        data.outEvts.push( ddo );
                    }

                    oldOvers[i] = true;
                    delete this.dragOvers[i];
                }

                for (var sGroup in dc.groups) {
                    // YAHOO.log("Processing group " + sGroup);

                    if ("string" != typeof sGroup) {
                        continue;
                    }

                    for (i in this.ids[sGroup]) {
                        var oDD = this.ids[sGroup][i];
                        if (! this.isTypeOfDD(oDD)) {
                            continue;
                        }

                        if (oDD.isTarget && !oDD.isLocked() && oDD != dc) {
                            if (this.isOverTarget(pt, oDD, this.mode, curRegion)) {
                                inGroupsObj[sGroup] = true;
                                // look for drop interactions
                                if (isDrop) {
                                    data.dropEvts.push( oDD );
                                // look for drag enter and drag over interactions
                                } else {

                                    // initial drag over: dragEnter fires
                                    if (!oldOvers[oDD.id]) {
                                        data.enterEvts.push( oDD );
                                    // subsequent drag overs: dragOver fires
                                    } else {
                                        data.overEvts.push( oDD );
                                    }

                                    this.dragOvers[oDD.id] = oDD;
                                }
                            }
                        }
                    }
                }

                this.interactionInfo = {
                    out:       data.outEvts,
                    enter:     data.enterEvts,
                    over:      data.overEvts,
                    drop:      data.dropEvts,
                    point:     pt,
                    draggedRegion:    curRegion,
                    sourceRegion: this.locationCache[dc.id],
                    validDrop: isDrop
                };

                for (var inG in inGroupsObj) {
                    inGroups.push(inG);
                }

                // notify about a drop that did not find a target
                if (isDrop && !data.dropEvts.length) {
                    YAHOO.log(dc.id + " dropped, but not on a target", "info", "DragDropMgr");
                    this.interactionInfo.validDrop = false;
                    if (dc.events.invalidDrop) {
                        dc.onInvalidDrop(e);
                        dc.fireEvent('invalidDropEvent', { e: e });
                    }
                }
                for (i = 0; i < events.length; i++) {
                    var tmp = null;
                    if (data[events[i] + 'Evts']) {
                        tmp = data[events[i] + 'Evts'];
                    }
                    if (tmp && tmp.length) {
                        var type = events[i].charAt(0).toUpperCase() + events[i].substr(1),
                            ev = 'onDrag' + type,
                            b4 = 'b4Drag' + type,
                            cev = 'drag' + type + 'Event',
                            check = 'drag' + type;
                        if (this.mode) {
                            YAHOO.log(dc.id + ' ' + ev + ': ' + tmp, "info", "DragDropMgr");
                            if (dc.events[b4]) {
                                dc[b4](e, tmp, inGroups);
                                dc.fireEvent(b4 + 'Event', { event: e, info: tmp, group: inGroups });

                            }
                            if (dc.events[check]) {
                                dc[ev](e, tmp, inGroups);
                                dc.fireEvent(cev, { event: e, info: tmp, group: inGroups });
                            }
                        } else {
                            for (var b = 0, len = tmp.length; b < len; ++b) {
                                YAHOO.log(dc.id + ' ' + ev + ': ' + tmp[b].id, "info", "DragDropMgr");
                                if (dc.events[b4]) {
                                    dc[b4](e, tmp[b].id, inGroups[0]);
                                    dc.fireEvent(b4 + 'Event', { event: e, info: tmp[b].id, group: inGroups[0] });
                                }
                                if (dc.events[check]) {
                                    dc[ev](e, tmp[b].id, inGroups[0]);
                                    dc.fireEvent(cev, { event: e, info: tmp[b].id, group: inGroups[0] });
                                }
                            }
                        }
                    }
                }
            },

            /**
             * Helper function for getting the best match from the list of drag
             * and drop objects returned by the drag and drop events when we are
             * in INTERSECT mode.  It returns either the first object that the
             * cursor is over, or the object that has the greatest overlap with
             * the dragged element.
             * @method getBestMatch
             * @param  {DragDrop[]} dds The array of drag and drop objects
             * targeted
             * @return {DragDrop}       The best single match
             * @static
             */
            getBestMatch: function(dds) {
                var winner = null;

                var len = dds.length;

                if (len == 1) {
                    winner = dds[0];
                } else {
                    // Loop through the targeted items
                    for (var i=0; i<len; ++i) {
                        var dd = dds[i];
                        // If the cursor is over the object, it wins.  If the
                        // cursor is over multiple matches, the first one we come
                        // to wins.
                        if (this.mode == this.INTERSECT && dd.cursorIsOver) {
                            winner = dd;
                            break;
                        // Otherwise the object with the most overlap wins
                        } else {
                            if (!winner || !winner.overlap || (dd.overlap &&
                                winner.overlap.getArea() < dd.overlap.getArea())) {
                                winner = dd;
                            }
                        }
                    }
                }

                return winner;
            },

            /**
             * Refreshes the cache of the top-left and bottom-right points of the
             * drag and drop objects in the specified group(s).  This is in the
             * format that is stored in the drag and drop instance, so typical
             * usage is:
             * <code>
             * YAHOO.util.DragDropMgr.refreshCache(ddinstance.groups);
             * </code>
             * Alternatively:
             * <code>
             * YAHOO.util.DragDropMgr.refreshCache({group1:true, group2:true});
             * </code>
             * @TODO this really should be an indexed array.  Alternatively this
             * method could accept both.
             * @method refreshCache
             * @param {Object} groups an associative array of groups to refresh
             * @static
             */
            refreshCache: function(groups) {
                YAHOO.log("refreshing element location cache", "info", "DragDropMgr");

                // refresh everything if group array is not provided
                var g = groups || this.ids;

                for (var sGroup in g) {
                    if ("string" != typeof sGroup) {
                        continue;
                    }
                    for (var i in this.ids[sGroup]) {
                        var oDD = this.ids[sGroup][i];

                        if (this.isTypeOfDD(oDD)) {
                            var loc = this.getLocation(oDD);
                            if (loc) {
                                this.locationCache[oDD.id] = loc;
                            } else {
                                delete this.locationCache[oDD.id];
    YAHOO.log("Could not get the loc for " + oDD.id, "warn", "DragDropMgr");
                            }
                        }
                    }
                }
            },

            /**
             * This checks to make sure an element exists and is in the DOM.  The
             * main purpose is to handle cases where innerHTML is used to remove
             * drag and drop objects from the DOM.  IE provides an 'unspecified
             * error' when trying to access the offsetParent of such an element
             * @method verifyEl
             * @param {HTMLElement} el the element to check
             * @return {boolean} true if the element looks usable
             * @static
             */
            verifyEl: function(el) {
                try {
                    if (el) {
                        var parent = el.offsetParent;
                        if (parent) {
                            return true;
                        }
                    }
                } catch(e) {
                    YAHOO.log("detected problem with an element", "info", "DragDropMgr");
                }

                return false;
            },

            /**
             * Returns a Region object containing the drag and drop element's position
             * and size, including the padding configured for it
             * @method getLocation
             * @param {DragDrop} oDD the drag and drop object to get the
             *                       location for
             * @return {YAHOO.util.Region} a Region object representing the total area
             *                             the element occupies, including any padding
             *                             the instance is configured for.
             * @static
             */
            getLocation: function(oDD) {
                if (! this.isTypeOfDD(oDD)) {
                    YAHOO.log(oDD + " is not a DD obj", "info", "DragDropMgr");
                    return null;
                }

                var el = oDD.getEl(), pos, x1, x2, y1, y2, t, r, b, l;

                try {
                    pos= YAHOO.util.Dom.getXY(el);
                } catch (e) { }

                if (!pos) {
                    YAHOO.log("getXY failed", "info", "DragDropMgr");
                    return null;
                }

                x1 = pos[0];
                x2 = x1 + el.offsetWidth;
                y1 = pos[1];
                y2 = y1 + el.offsetHeight;

                t = y1 - oDD.padding[0];
                r = x2 + oDD.padding[1];
                b = y2 + oDD.padding[2];
                l = x1 - oDD.padding[3];

                return new YAHOO.util.Region( t, r, b, l );
            },

            /**
             * Checks the cursor location to see if it over the target
             * @method isOverTarget
             * @param {YAHOO.util.Point} pt The point to evaluate
             * @param {DragDrop} oTarget the DragDrop object we are inspecting
             * @param {boolean} intersect true if we are in intersect mode
             * @param {YAHOO.util.Region} pre-cached location of the dragged element
             * @return {boolean} true if the mouse is over the target
             * @private
             * @static
             */
            isOverTarget: function(pt, oTarget, intersect, curRegion) {
                // use cache if available
                var loc = this.locationCache[oTarget.id];
                if (!loc || !this.useCache) {
                    YAHOO.log("cache not populated", "info", "DragDropMgr");
                    loc = this.getLocation(oTarget);
                    this.locationCache[oTarget.id] = loc;

                    YAHOO.log("cache: " + loc, "info", "DragDropMgr");
                }

                if (!loc) {
                    YAHOO.log("could not get the location of the element", "info", "DragDropMgr");
                    return false;
                }

                //YAHOO.log("loc: " + loc + ", pt: " + pt);
                oTarget.cursorIsOver = loc.contains( pt );

                // DragDrop is using this as a sanity check for the initial mousedown
                // in this case we are done.  In POINT mode, if the drag obj has no
                // contraints, we are done. Otherwise we need to evaluate the
                // region the target as occupies to determine if the dragged element
                // overlaps with it.

                var dc = this.dragCurrent;
                if (!dc || (!intersect && !dc.constrainX && !dc.constrainY)) {

                    //if (oTarget.cursorIsOver) {
                        //YAHOO.log("over " + oTarget + ", " + loc + ", " + pt, "warn");
                    //}
                    return oTarget.cursorIsOver;
                }

                oTarget.overlap = null;

                // Get the current location of the drag element, this is the
                // location of the mouse event less the delta that represents
                // where the original mousedown happened on the element.  We
                // need to consider constraints and ticks as well.

                if (!curRegion) {
                    var pos = dc.getTargetCoord(pt.x, pt.y);
                    var el = dc.getDragEl();
                    curRegion = new YAHOO.util.Region( pos.y,
                                                       pos.x + el.offsetWidth,
                                                       pos.y + el.offsetHeight,
                                                       pos.x );
                }

                var overlap = curRegion.intersect(loc);

                if (overlap) {
                    oTarget.overlap = overlap;
                    return (intersect) ? true : oTarget.cursorIsOver;
                } else {
                    return false;
                }
            },

            /**
             * unload event handler
             * @method _onUnload
             * @private
             * @static
             */
            _onUnload: function(e, me) {
                this.unregAll();
            },

            /**
             * Cleans up the drag and drop events and objects.
             * @method unregAll
             * @private
             * @static
             */
            unregAll: function() {
                YAHOO.log("unregister all", "info", "DragDropMgr");

                if (this.dragCurrent) {
                    this.stopDrag();
                    this.dragCurrent = null;
                }

                this._execOnAll("unreg", []);

                //for (var i in this.elementCache) {
                    //delete this.elementCache[i];
                //}
                //this.elementCache = {};

                this.ids = {};
            },

            /**
             * A cache of DOM elements
             * @property elementCache
             * @private
             * @static
             * @deprecated elements are not cached now
             */
            elementCache: {},

            /**
             * Get the wrapper for the DOM element specified
             * @method getElWrapper
             * @param {String} id the id of the element to get
             * @return {YAHOO.util.DDM.ElementWrapper} the wrapped element
             * @private
             * @deprecated This wrapper isn't that useful
             * @static
             */
            getElWrapper: function(id) {
                var oWrapper = this.elementCache[id];
                if (!oWrapper || !oWrapper.el) {
                    oWrapper = this.elementCache[id] =
                        new this.ElementWrapper(YAHOO.util.Dom.get(id));
                }
                return oWrapper;
            },

            /**
             * Returns the actual DOM element
             * @method getElement
             * @param {String} id the id of the elment to get
             * @return {Object} The element
             * @deprecated use YAHOO.util.Dom.get instead
             * @static
             */
            getElement: function(id) {
                return YAHOO.util.Dom.get(id);
            },

            /**
             * Returns the style property for the DOM element (i.e.,
             * document.getElById(id).style)
             * @method getCss
             * @param {String} id the id of the elment to get
             * @return {Object} The style property of the element
             * @deprecated use YAHOO.util.Dom instead
             * @static
             */
            getCss: function(id) {
                var el = YAHOO.util.Dom.get(id);
                return (el) ? el.style : null;
            },

            /**
             * Inner class for cached elements
             * @class DragDropMgr.ElementWrapper
             * @for DragDropMgr
             * @private
             * @deprecated
             */
            ElementWrapper: function(el) {
                    /**
                     * The element
                     * @property el
                     */
                    this.el = el || null;
                    /**
                     * The element id
                     * @property id
                     */
                    this.id = this.el && el.id;
                    /**
                     * A reference to the style property
                     * @property css
                     */
                    this.css = this.el && el.style;
                },

            /**
             * Returns the X position of an html element
             * @method getPosX
             * @param el the element for which to get the position
             * @return {int} the X coordinate
             * @for DragDropMgr
             * @deprecated use YAHOO.util.Dom.getX instead
             * @static
             */
            getPosX: function(el) {
                return YAHOO.util.Dom.getX(el);
            },

            /**
             * Returns the Y position of an html element
             * @method getPosY
             * @param el the element for which to get the position
             * @return {int} the Y coordinate
             * @deprecated use YAHOO.util.Dom.getY instead
             * @static
             */
            getPosY: function(el) {
                return YAHOO.util.Dom.getY(el);
            },

            /**
             * Swap two nodes.  In IE, we use the native method, for others we
             * emulate the IE behavior
             * @method swapNode
             * @param n1 the first node to swap
             * @param n2 the other node to swap
             * @static
             */
            swapNode: function(n1, n2) {
                if (n1.swapNode) {
                    n1.swapNode(n2);
                } else {
                    var p = n2.parentNode;
                    var s = n2.nextSibling;

                    if (s == n1) {
                        p.insertBefore(n1, n2);
                    } else if (n2 == n1.nextSibling) {
                        p.insertBefore(n2, n1);
                    } else {
                        n1.parentNode.replaceChild(n2, n1);
                        p.insertBefore(n1, s);
                    }
                }
            },

            /**
             * Returns the current scroll position
             * @method getScroll
             * @private
             * @static
             */
            getScroll: function () {
                var t, l, dde=document.documentElement, db=document.body;
                if (dde && (dde.scrollTop || dde.scrollLeft)) {
                    t = dde.scrollTop;
                    l = dde.scrollLeft;
                } else if (db) {
                    t = db.scrollTop;
                    l = db.scrollLeft;
                } else {
                    YAHOO.log("could not get scroll property", "info", "DragDropMgr");
                }
                return { top: t, left: l };
            },

            /**
             * Returns the specified element style property
             * @method getStyle
             * @param {HTMLElement} el          the element
             * @param {string}      styleProp   the style property
             * @return {string} The value of the style property
             * @deprecated use YAHOO.util.Dom.getStyle
             * @static
             */
            getStyle: function(el, styleProp) {
                return YAHOO.util.Dom.getStyle(el, styleProp);
            },

            /**
             * Gets the scrollTop
             * @method getScrollTop
             * @return {int} the document's scrollTop
             * @static
             */
            getScrollTop: function () { return this.getScroll().top; },

            /**
             * Gets the scrollLeft
             * @method getScrollLeft
             * @return {int} the document's scrollTop
             * @static
             */
            getScrollLeft: function () { return this.getScroll().left; },

            /**
             * Sets the x/y position of an element to the location of the
             * target element.
             * @method moveToEl
             * @param {HTMLElement} moveEl      The element to move
             * @param {HTMLElement} targetEl    The position reference element
             * @static
             */
            moveToEl: function (moveEl, targetEl) {
                var aCoord = YAHOO.util.Dom.getXY(targetEl);
                YAHOO.log("moveToEl: " + aCoord, "info", "DragDropMgr");
                YAHOO.util.Dom.setXY(moveEl, aCoord);
            },

            /**
             * Gets the client height
             * @method getClientHeight
             * @return {int} client height in px
             * @deprecated use YAHOO.util.Dom.getViewportHeight instead
             * @static
             */
            getClientHeight: function() {
                return YAHOO.util.Dom.getViewportHeight();
            },

            /**
             * Gets the client width
             * @method getClientWidth
             * @return {int} client width in px
             * @deprecated use YAHOO.util.Dom.getViewportWidth instead
             * @static
             */
            getClientWidth: function() {
                return YAHOO.util.Dom.getViewportWidth();
            },

            /**
             * Numeric array sort function
             * @method numericSort
             * @static
             */
            numericSort: function(a, b) { return (a - b); },

            /**
             * Internal counter
             * @property _timeoutCount
             * @private
             * @static
             */
            _timeoutCount: 0,

            /**
             * Trying to make the load order less important.  Without this we get
             * an error if this file is loaded before the Event Utility.
             * @method _addListeners
             * @private
             * @static
             */
            _addListeners: function() {
                var DDM = YAHOO.util.DDM;
                if ( YAHOO.util.Event && document ) {
                    DDM._onLoad();
                } else {
                    if (DDM._timeoutCount > 2000) {
                        YAHOO.log("DragDrop requires the Event Utility", "error", "DragDropMgr");
                    } else {
                        setTimeout(DDM._addListeners, 10);
                        if (document && document.body) {
                            DDM._timeoutCount += 1;
                        }
                    }
                }
            },

            /**
             * Recursively searches the immediate parent and all child nodes for
             * the handle element in order to determine wheter or not it was
             * clicked.
             * @method handleWasClicked
             * @param node the html element to inspect
             * @static
             */
            handleWasClicked: function(node, id) {
                if (this.isHandle(id, node.id)) {
                    YAHOO.log("clicked node is a handle", "info", "DragDropMgr");
                    return true;
                } else {
                    // check to see if this is a text node child of the one we want
                    var p = node.parentNode;
                    // YAHOO.log("p: " + p);

                    while (p) {
                        if (this.isHandle(id, p.id)) {
                            return true;
                        } else {
                            YAHOO.log(p.id + " is not a handle", "info", "DragDropMgr");
                            p = p.parentNode;
                        }
                    }
                }

                return false;
            }

        };

    }();

    // shorter alias, save a few bytes
    YAHOO.util.DDM = YAHOO.util.DragDropMgr;
    YAHOO.util.DDM._addListeners();

    }

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