# Yahoo! UI Library

### dd 3.0.0b1

Yahoo! UI Library > dd > drop.js (source view)
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        /**
         * The Drag & Drop Utility allows you to create a draggable interface efficiently, buffering you from browser-level abnormalities and enabling you to focus on the interesting logic surrounding your particular implementation. This component enables you to create a variety of standard draggable objects with just a few lines of code and then, using its extensive API, add your own specific implementation logic.
         * @module dd
         * @submodule dd-drop
         */
        /**
         * This class provides the ability to create a Drop Target.
         * @class Drop
         * @extends Base
         * @constructor
         * @namespace DD
         */

        var NODE = 'node',
            DDM = Y.DD.DDM,
            OFFSET_HEIGHT = 'offsetHeight',
            OFFSET_WIDTH = 'offsetWidth',
            /**
            * @event drop:over
            * @description Fires when a drag element is over this target.
            * @bubbles DDM
            * @type {Event.Custom}
            */
            EV_DROP_OVER = 'drop:over',
            /**
            * @event drop:enter
            * @description Fires when a drag element enters this target.
            * @bubbles DDM
            * @type {Event.Custom}
            */
            EV_DROP_ENTER = 'drop:enter',
            /**
            * @event drop:exit
            * @description Fires when a drag element exits this target.
            * @bubbles DDM
            * @type {Event.Custom}
            */
            EV_DROP_EXIT = 'drop:exit',

            /**
            * @event drop:hit
            * @description Fires when a draggable node is dropped on this Drop Target. (Fired from dd-ddm-drop)
            * @bubbles DDM
            * @type {Event.Custom}
            */

        Drop = function() {
            this._lazyAddAttrs = false;
            Drop.superclass.constructor.apply(this, arguments);

            //DD init speed up.
            Y.on('domready', Y.bind(function() {
                Y.later(100, this, this._createShim);
            }, this));
            DDM._regTarget(this);

            /* TODO
            if (Dom.getStyle(this.el, 'position') == 'fixed') {
                Event.on(window, 'scroll', function() {
                    this.activateShim();
                }, this, true);
            }
            */
        };

        Drop.NAME = 'drop';

        Drop.ATTRS = {
            /**
            * @attribute node
            * @description Y.Node instanace to use as the element to make a Drop Target
            * @type Node
            */
            node: {
                setter: function(node) {
                    var n = Y.Node.get(node);
                    if (!n) {
                        Y.error('DD.Drop: Invalid Node Given: ' + node);
                    }
                    return n;
                }
            },
            /**
            * @attribute groups
            * @description Array of groups to add this drop into.
            * @type Array
            */
            groups: {
                value: ['default'],
                setter: function(g) {
                    this._groups = {};
                    Y.each(g, function(v, k) {
                        this._groups[v] = true;
                    }, this);
                    return g;
                }
            },
            /**
            * @attribute padding
            * @description CSS style padding to make the Drop Target bigger than the node.
            * @type String
            */
            padding: {
                value: '0',
                setter: function(p) {
                    return DDM.cssSizestoObject(p);
                }
            },
            /**
            * @attribute lock
            * @description Set to lock this drop element.
            * @type Boolean
            */
            lock: {
                value: false,
                setter: function(lock) {
                    if (lock) {
                        this.get(NODE).addClass(DDM.CSS_PREFIX + '-drop-locked');
                    } else {
                        this.get(NODE).removeClass(DDM.CSS_PREFIX + '-drop-locked');
                    }
                    return lock;
                }
            },
            /**
            * @attribute bubbles
            * @description Controls the default bubble parent for this Drop instance. Default: Y.DD.DDM. Set to false to disable bubbling.
            * @type Object
            */
            bubbles: {
                writeOnce: true,
                value: Y.DD.DDM
            }
        };

        Y.extend(Drop, Y.Base, {
            /**
            * @private
            * @method _createEvents
            * @description This method creates all the events for this Event Target and publishes them so we get Event Bubbling.
            */
            _createEvents: function() {

                var ev = [
                    EV_DROP_OVER,
                    EV_DROP_ENTER,
                    EV_DROP_EXIT,
                    'drop:hit'
                ];

                Y.each(ev, function(v, k) {
                    this.publish(v, {
                        type: v,
                        emitFacade: true,
                        preventable: false,
                        bubbles: true,
                        queuable: false,
                        prefix: 'drop'
                    });
                }, this);

                if (this.get('bubbles')) {
                    this.addTarget(this.get('bubbles'));
                }

            },
            /**
            * @private
            * @property _valid
            * @description Flag for determining if the target is valid in this operation.
            * @type Boolean
            */
            _valid: null,
            /**
            * @private
            * @property _groups
            * @description The groups this target belongs to.
            * @type Array
            */
            _groups: null,
            /**
            * @property shim
            * @description Node reference to the targets shim
            * @type {Object}
            */
            shim: null,
            /**
            * @property region
            * @description A region object associated with this target, used for checking regions while dragging.
            * @type Object
            */
            region: null,
            /**
            * @property overTarget
            * @description This flag is tripped when a drag element is over this target.
            * @type Boolean
            */
            overTarget: null,
            /**
            * @method inGroup
            * @description Check if this target is in one of the supplied groups.
            * @param {Array} groups The groups to check against
            * @return Boolean
            */
            inGroup: function(groups) {
                this._valid = false;
                var ret = false;
                Y.each(groups, function(v, k) {
                    if (this._groups[v]) {
                        ret = true;
                        this._valid = true;
                    }
                }, this);
                return ret;
            },
            /**
            * @private
            * @method initializer
            * @description Private lifecycle method
            */
            initializer: function() {
                //this._createEvents();
                Y.later(100, this, this._createEvents);

                var node = this.get(NODE), id;
                if (!node.get('id')) {
                    id = Y.stamp(node);
                    node.set('id', id);
                }
                node.addClass(DDM.CSS_PREFIX + '-drop');
                //Shouldn't have to do this..
                this.set('groups', this.get('groups'));
            },
            /**
            * @private
            * @method destructor
            * @description Lifecycle destructor, unreg the drag from the DDM and remove listeners
            */
            destructor: function() {
                DDM._unregTarget(this);
                if (this.shim) {
                    this.shim.detachAll();
                    this.shim.get('parentNode').removeChild(this.shim);
                    this.shim = null;
                }
                this.get(NODE).removeClass(DDM.CSS_PREFIX + '-drop');
                this.detachAll();
            },
            /**
            * @private
            * @method _deactivateShim
            * @description Removes classes from the target, resets some flags and sets the shims deactive position [-999, -999]
            */
            _deactivateShim: function() {
                if (!this.shim) {
                    return false;
                }
                this.get(NODE).removeClass(DDM.CSS_PREFIX + '-drop-active-valid');
                this.get(NODE).removeClass(DDM.CSS_PREFIX + '-drop-active-invalid');
                this.get(NODE).removeClass(DDM.CSS_PREFIX + '-drop-over');
                this.shim.setStyles({
                    top: '-999px',
                    left: '-999px',
                    zIndex: '2'
                });
                this.overTarget = false;
            },
            /**
            * @private
            * @method _activateShim
            * @description Activates the shim and adds some interaction CSS classes
            */
            _activateShim: function() {
                if (!DDM.activeDrag) {
                    return false; //Nothing is dragging, no reason to activate.
                }
                if (this.get(NODE) === DDM.activeDrag.get(NODE)) {
                    return false;
                }
                if (this.get('lock')) {
                    return false;
                }
                var node = this.get(NODE);
                //TODO Visibility Check..
                //if (this.inGroup(DDM.activeDrag.get('groups')) && this.get(NODE).isVisible()) {
                if (this.inGroup(DDM.activeDrag.get('groups'))) {
                    node.removeClass(DDM.CSS_PREFIX + '-drop-active-invalid');
                    node.addClass(DDM.CSS_PREFIX + '-drop-active-valid');
                    DDM._addValid(this);
                    this.overTarget = false;
                    this.sizeShim();
                } else {
                    DDM._removeValid(this);
                    node.removeClass(DDM.CSS_PREFIX + '-drop-active-valid');
                    node.addClass(DDM.CSS_PREFIX + '-drop-active-invalid');
                }
            },
            /**
            * @method sizeShim
            * @description Positions and sizes the shim with the raw data from the node, this can be used to programatically adjust the Targets shim for Animation..
            */
            sizeShim: function() {
                if (!DDM.activeDrag) {
                    return false; //Nothing is dragging, no reason to activate.
                }
                if (this.get(NODE) === DDM.activeDrag.get(NODE)) {
                    return false;
                }
                if (this.get('lock')) {
                    return false;
                }
                if (!this.shim) {
                    Y.later(100, this, this.sizeShim);
                    return false;
                }
                var node = this.get(NODE),
                    nh = node.get(OFFSET_HEIGHT),
                    nw = node.get(OFFSET_WIDTH),
                    xy = node.getXY(),
                    p = this.get('padding'),
                    dd, dH, dW;

                //Apply padding
                nw = nw + p.left + p.right;
                nh = nh + p.top + p.bottom;
                xy[0] = xy[0] - p.left;
                xy[1] = xy[1] - p.top;

                if (DDM.activeDrag.get('dragMode') === DDM.INTERSECT) {
                    //Intersect Mode, make the shim bigger
                    dd = DDM.activeDrag;
                    dH = dd.get(NODE).get(OFFSET_HEIGHT);
                    dW = dd.get(NODE).get(OFFSET_WIDTH);

                    nh = (nh + dH);
                    nw = (nw + dW);
                    xy[0] = xy[0] - (dW - dd.deltaXY[0]);
                    xy[1] = xy[1] - (dH - dd.deltaXY[1]);

                }

                //Set the style on the shim
                this.shim.setStyles({
                    height: nh + 'px',
                    width: nw + 'px',
                    top: xy[1] + 'px',
                    left: xy[0] + 'px'
                });

                //Create the region to be used by intersect when a drag node is over us.
                this.region = {
                    '0': xy[0],
                    '1': xy[1],
                    area: 0,
                    top: xy[1],
                    right: xy[0] + nw,
                    bottom: xy[1] + nh,
                    left: xy[0]
                };
            },
            /**
            * @private
            * @method _createShim
            * @description Creates the Target shim and adds it to the DDM's playground..
            */
            _createShim: function() {
                //No playground, defer
                if (!DDM._pg) {
                    Y.later(10, this, this._createShim);
                    return;
                }
                //Shim already here, cancel
                if (this.shim) {
                    return;
                }
                var s = Y.Node.create('<div id="' + this.get(NODE).get('id') + '_shim"></div>');

                s.setStyles({
                    height: this.get(NODE).get(OFFSET_HEIGHT) + 'px',
                    width: this.get(NODE).get(OFFSET_WIDTH) + 'px',
                    backgroundColor: 'yellow',
                    opacity: '.5',
                    zIndex: '1',
                    overflow: 'hidden',
                    top: '-900px',
                    left: '-900px',
                    position:  'absolute'
                });
                DDM._pg.appendChild(s);
                this.shim = s;

                s.on('mouseover', Y.bind(this._handleOverEvent, this));
                s.on('mouseout', Y.bind(this._handleOutEvent, this));
            },
            /**
            * @private
            * @method _handleOverTarget
            * @description This handles the over target call made from this object or from the DDM
            */
            _handleTargetOver: function() {
                if (DDM.isOverTarget(this)) {
                    this.get(NODE).addClass(DDM.CSS_PREFIX + '-drop-over');
                    DDM.activeDrop = this;
                    DDM.otherDrops[this] = this;
                    if (this.overTarget) {
                        DDM.activeDrag.fire('drag:over', { drop: this, drag: DDM.activeDrag });
                        this.fire(EV_DROP_OVER, { drop: this, drag: DDM.activeDrag });
                    } else {
                        this.overTarget = true;
                        this.fire(EV_DROP_ENTER, { drop: this, drag: DDM.activeDrag });
                        DDM.activeDrag.fire('drag:enter', { drop: this, drag: DDM.activeDrag });
                        DDM.activeDrag.get(NODE).addClass(DDM.CSS_PREFIX + '-drag-over');
                        //TODO - Is this needed??
                        //DDM._handleTargetOver();
                    }
                } else {
                    this._handleOut();
                }
            },
            /**
            * @private
            * @method _handleOverEvent
            * @description Handles the mouseover DOM event on the Target Shim
            */
            _handleOverEvent: function() {
                this.shim.setStyle('zIndex', '999');
                DDM._addActiveShim(this);
            },
            /**
            * @private
            * @method _handleOutEvent
            * @description Handles the mouseout DOM event on the Target Shim
            */
            _handleOutEvent: function() {
                this.shim.setStyle('zIndex', '1');
                DDM._removeActiveShim(this);
            },
            /**
            * @private
            * @method _handleOut
            * @description Handles out of target calls/checks
            */
            _handleOut: function(force) {
                if (!DDM.isOverTarget(this) || force) {
                    if (this.overTarget) {
                        this.overTarget = false;
                        if (!force) {
                            DDM._removeActiveShim(this);
                        }
                        if (DDM.activeDrag) {
                            this.get(NODE).removeClass(DDM.CSS_PREFIX + '-drop-over');
                            DDM.activeDrag.get(NODE).removeClass(DDM.CSS_PREFIX + '-drag-over');
                            this.fire(EV_DROP_EXIT);
                            DDM.activeDrag.fire('drag:exit', { drop: this });
                            delete DDM.otherDrops[this];
                            //if (DDM.activeDrop === this) {
                            //    DDM.activeDrop = null;
                            //}
                        }
                    }
                }
            }
        });

        Y.DD.Drop = Drop;

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