API: dragdrop DDProxy.js (YUI Library)

# Yahoo! UI Library

### Drag and Drop 2.8.1

Yahoo! UI Library > dragdrop > DDProxy.js (source view)
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    /**
     * A DragDrop implementation that inserts an empty, bordered div into
     * the document that follows the cursor during drag operations.  At the time of
     * the click, the frame div is resized to the dimensions of the linked html
     * element, and moved to the exact location of the linked element.
     *
     * References to the "frame" element refer to the single proxy element that
     * was created to be dragged in place of all DDProxy elements on the
     * page.
     *
     * @class DDProxy
     * @extends YAHOO.util.DD
     * @namespace YAHOO.util
     * @constructor
     * @param {String} id the id of the linked html element
     * @param {String} sGroup the group of related DragDrop objects
     * @param {object} config an object containing configurable attributes
     *                Valid properties for DDProxy in addition to those in DragDrop:
     *                   resizeFrame, centerFrame, dragElId
     */
    YAHOO.util.DDProxy = function(id, sGroup, config) {
        if (id) {
            this.init(id, sGroup, config);
            this.initFrame();
        }
    };

    /**
     * The default drag frame div id
     * @property YAHOO.util.DDProxy.dragElId
     * @type String
     * @static
     */
    YAHOO.util.DDProxy.dragElId = "ygddfdiv";

    YAHOO.extend(YAHOO.util.DDProxy, YAHOO.util.DD, {

        /**
         * By default we resize the drag frame to be the same size as the element
         * we want to drag (this is to get the frame effect).  We can turn it off
         * if we want a different behavior.
         * @property resizeFrame
         * @type boolean
         */
        resizeFrame: true,

        /**
         * By default the frame is positioned exactly where the drag element is, so
         * we use the cursor offset provided by YAHOO.util.DD.  Another option that works only if
         * you do not have constraints on the obj is to have the drag frame centered
         * around the cursor.  Set centerFrame to true for this effect.
         * @property centerFrame
         * @type boolean
         */
        centerFrame: false,

        /**
         * Creates the proxy element if it does not yet exist
         * @method createFrame
         */
        createFrame: function() {
            var self=this, body=document.body;

            if (!body || !body.firstChild) {
                setTimeout( function() { self.createFrame(); }, 50 );
                return;
            }

            var div=this.getDragEl(), Dom=YAHOO.util.Dom;

            if (!div) {
                div    = document.createElement("div");
                div.id = this.dragElId;
                var s  = div.style;

                s.position   = "absolute";
                s.visibility = "hidden";
                s.cursor     = "move";
                s.border     = "2px solid #aaa";
                s.zIndex     = 999;
                s.height     = "25px";
                s.width      = "25px";

                var _data = document.createElement('div');
                Dom.setStyle(_data, 'height', '100%');
                Dom.setStyle(_data, 'width', '100%');
                /**
                * If the proxy element has no background-color, then it is considered to the "transparent" by Internet Explorer.
                * Since it is "transparent" then the events pass through it to the iframe below.
                * So creating a "fake" div inside the proxy element and giving it a background-color, then setting it to an
                * opacity of 0, it appears to not be there, however IE still thinks that it is so the events never pass through.
                */
                Dom.setStyle(_data, 'background-color', '#ccc');
                Dom.setStyle(_data, 'opacity', '0');
                div.appendChild(_data);

                // appendChild can blow up IE if invoked prior to the window load event
                // while rendering a table.  It is possible there are other scenarios
                // that would cause this to happen as well.
                body.insertBefore(div, body.firstChild);
            }
        },

        /**
         * Initialization for the drag frame element.  Must be called in the
         * constructor of all subclasses
         * @method initFrame
         */
        initFrame: function() {
            this.createFrame();
        },

        applyConfig: function() {
            //this.logger.log("DDProxy applyConfig");
            YAHOO.util.DDProxy.superclass.applyConfig.call(this);

            this.resizeFrame = (this.config.resizeFrame !== false);
            this.centerFrame = (this.config.centerFrame);
            this.setDragElId(this.config.dragElId || YAHOO.util.DDProxy.dragElId);
        },

        /**
         * Resizes the drag frame to the dimensions of the clicked object, positions
         * it over the object, and finally displays it
         * @method showFrame
         * @param {int} iPageX X click position
         * @param {int} iPageY Y click position
         * @private
         */
        showFrame: function(iPageX, iPageY) {
            var el = this.getEl();
            var dragEl = this.getDragEl();
            var s = dragEl.style;

            this._resizeProxy();

            if (this.centerFrame) {
                this.setDelta( Math.round(parseInt(s.width,  10)/2),
                               Math.round(parseInt(s.height, 10)/2) );
            }

            this.setDragElPos(iPageX, iPageY);

            YAHOO.util.Dom.setStyle(dragEl, "visibility", "visible");
        },

        /**
         * The proxy is automatically resized to the dimensions of the linked
         * element when a drag is initiated, unless resizeFrame is set to false
         * @method _resizeProxy
         * @private
         */
        _resizeProxy: function() {
            if (this.resizeFrame) {
                var DOM    = YAHOO.util.Dom;
                var el     = this.getEl();
                var dragEl = this.getDragEl();

                var bt = parseInt( DOM.getStyle(dragEl, "borderTopWidth"    ), 10);
                var br = parseInt( DOM.getStyle(dragEl, "borderRightWidth"  ), 10);
                var bb = parseInt( DOM.getStyle(dragEl, "borderBottomWidth" ), 10);
                var bl = parseInt( DOM.getStyle(dragEl, "borderLeftWidth"   ), 10);

                if (isNaN(bt)) { bt = 0; }
                if (isNaN(br)) { br = 0; }
                if (isNaN(bb)) { bb = 0; }
                if (isNaN(bl)) { bl = 0; }

                this.logger.log("proxy size: " + bt + "  " + br + " " + bb + " " + bl);

                var newWidth  = Math.max(0, el.offsetWidth  - br - bl);
                var newHeight = Math.max(0, el.offsetHeight - bt - bb);

                this.logger.log("Resizing proxy element");

                DOM.setStyle( dragEl, "width",  newWidth  + "px" );
                DOM.setStyle( dragEl, "height", newHeight + "px" );
            }
        },

        // overrides YAHOO.util.DragDrop
        b4MouseDown: function(e) {
            this.setStartPosition();
            var x = YAHOO.util.Event.getPageX(e);
            var y = YAHOO.util.Event.getPageY(e);
            this.autoOffset(x, y);

            // This causes the autoscroll code to kick off, which means autoscroll can
            // happen prior to the check for a valid drag handle.
            // this.setDragElPos(x, y);
        },

        // overrides YAHOO.util.DragDrop
        b4StartDrag: function(x, y) {
            // show the drag frame
            this.logger.log("start drag show frame, x: " + x + ", y: " + y);
            this.showFrame(x, y);
        },

        // overrides YAHOO.util.DragDrop
        b4EndDrag: function(e) {
            this.logger.log(this.id + " b4EndDrag");
            YAHOO.util.Dom.setStyle(this.getDragEl(), "visibility", "hidden");
        },

        // overrides YAHOO.util.DragDrop
        // By default we try to move the element to the last location of the frame.
        // This is so that the default behavior mirrors that of YAHOO.util.DD.
        endDrag: function(e) {
            var DOM = YAHOO.util.Dom;
            this.logger.log(this.id + " endDrag");
            var lel = this.getEl();
            var del = this.getDragEl();

            // Show the drag frame briefly so we can get its position
            // del.style.visibility = "";
            DOM.setStyle(del, "visibility", "");

            // Hide the linked element before the move to get around a Safari
            // rendering bug.
            //lel.style.visibility = "hidden";
            DOM.setStyle(lel, "visibility", "hidden");
            YAHOO.util.DDM.moveToEl(lel, del);
            //del.style.visibility = "hidden";
            DOM.setStyle(del, "visibility", "hidden");
            //lel.style.visibility = "";
            DOM.setStyle(lel, "visibility", "");
        },

        toString: function() {
            return ("DDProxy " + this.id);
        }
    /**
    * @event mouseDownEvent
    * @description Provides access to the mousedown event. The mousedown does not always result in a drag operation.
    * @type YAHOO.util.CustomEvent See <a href="YAHOO.util.Element.html#addListener">Element.addListener</a> for more information on listening for this event.
    */

    /**
    * @event b4MouseDownEvent
    * @description Provides access to the mousedown event, before the mouseDownEvent gets fired. Returning false will cancel the drag.
    * @type YAHOO.util.CustomEvent See <a href="YAHOO.util.Element.html#addListener">Element.addListener</a> for more information on listening for this event.
    */

    /**
    * @event mouseUpEvent
    * @description Fired from inside DragDropMgr when the drag operation is finished.
    * @type YAHOO.util.CustomEvent See <a href="YAHOO.util.Element.html#addListener">Element.addListener</a> for more information on listening for this event.
    */

    /**
    * @event b4StartDragEvent
    * @description Fires before the startDragEvent, returning false will cancel the startDrag Event.
    * @type YAHOO.util.CustomEvent See <a href="YAHOO.util.Element.html#addListener">Element.addListener</a> for more information on listening for this event.
    */

    /**
    * @event startDragEvent
    * @description Occurs after a mouse down and the drag threshold has been met. The drag threshold default is either 3 pixels of mouse movement or 1 full second of holding the mousedown.
    * @type YAHOO.util.CustomEvent See <a href="YAHOO.util.Element.html#addListener">Element.addListener</a> for more information on listening for this event.
    */

    /**
    * @event b4EndDragEvent
    * @description Fires before the endDragEvent. Returning false will cancel.
    * @type YAHOO.util.CustomEvent See <a href="YAHOO.util.Element.html#addListener">Element.addListener</a> for more information on listening for this event.
    */

    /**
    * @event endDragEvent
    * @description Fires on the mouseup event after a drag has been initiated (startDrag fired).
    * @type YAHOO.util.CustomEvent See <a href="YAHOO.util.Element.html#addListener">Element.addListener</a> for more information on listening for this event.
    */

    /**
    * @event dragEvent
    * @description Occurs every mousemove event while dragging.
    * @type YAHOO.util.CustomEvent See <a href="YAHOO.util.Element.html#addListener">Element.addListener</a> for more information on listening for this event.
    */
    /**
    * @event b4DragEvent
    * @description Fires before the dragEvent.
    * @type YAHOO.util.CustomEvent See <a href="YAHOO.util.Element.html#addListener">Element.addListener</a> for more information on listening for this event.
    */
    /**
    * @event invalidDropEvent
    * @description Fires when the dragged objects is dropped in a location that contains no drop targets.
    * @type YAHOO.util.CustomEvent See <a href="YAHOO.util.Element.html#addListener">Element.addListener</a> for more information on listening for this event.
    */
    /**
    * @event b4DragOutEvent
    * @description Fires before the dragOutEvent
    * @type YAHOO.util.CustomEvent See <a href="YAHOO.util.Element.html#addListener">Element.addListener</a> for more information on listening for this event.
    */
    /**
    * @event dragOutEvent
    * @description Fires when a dragged object is no longer over an object that had the onDragEnter fire.
    * @type YAHOO.util.CustomEvent See <a href="YAHOO.util.Element.html#addListener">Element.addListener</a> for more information on listening for this event.
    */
    /**
    * @event dragEnterEvent
    * @description Occurs when the dragged object first interacts with another targettable drag and drop object.
    * @type YAHOO.util.CustomEvent See <a href="YAHOO.util.Element.html#addListener">Element.addListener</a> for more information on listening for this event.
    */
    /**
    * @event b4DragOverEvent
    * @description Fires before the dragOverEvent.
    * @type YAHOO.util.CustomEvent See <a href="YAHOO.util.Element.html#addListener">Element.addListener</a> for more information on listening for this event.
    */
    /**
    * @event dragOverEvent
    * @description Fires every mousemove event while over a drag and drop object.
    * @type YAHOO.util.CustomEvent See <a href="YAHOO.util.Element.html#addListener">Element.addListener</a> for more information on listening for this event.
    */
    /**
    * @event b4DragDropEvent
    * @description Fires before the dragDropEvent
    * @type YAHOO.util.CustomEvent See <a href="YAHOO.util.Element.html#addListener">Element.addListener</a> for more information on listening for this event.
    */
    /**
    * @event dragDropEvent
    * @description Fires when the dragged objects is dropped on another.
    * @type YAHOO.util.CustomEvent See <a href="YAHOO.util.Element.html#addListener">Element.addListener</a> for more information on listening for this event.
    */

    });

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