nsdraganddrop.js

用javascript实现拖拽功能的类

          const kDSContractID = "@mozilla.org/widget/dragservice;1";
          const kDSIID = Components.interfaces.nsIDragService;
          this._mDS = Components.classes[kDSContractID].getService(kDSIID);
        }
      return this._mDS;
    },

  /**
   * void startDrag (DOMEvent aEvent, Object aDragDropObserver) ;
   *
   * called when a drag on an element is started.
   *
   * @param DOMEvent aEvent
   *        the DOM event fired by the drag init
   * @param Object aDragDropObserver
   *        javascript object of format described above that specifies
   *        the way in which the element responds to drag events.
   **/  
  startDrag: function (aEvent, aDragDropObserver)
    {
      if (!("onDragStart" in aDragDropObserver))
        return;

      const kDSIID = Components.interfaces.nsIDragService;
      var dragAction = { action: kDSIID.DRAGDROP_ACTION_COPY + kDSIID.DRAGDROP_ACTION_MOVE + kDSIID.DRAGDROP_ACTION_LINK };

      var transferData = { data: null };
      try 
        {
          aDragDropObserver.onDragStart(aEvent, transferData, dragAction);
        }
      catch (e) 
        {
          return;  // not a draggable item, bail!
        }

      if (!transferData.data) return;
      transferData = transferData.data;
      
      var transArray = Components.classes["@mozilla.org/supports-array;1"]
                                 .createInstance(Components.interfaces.nsISupportsArray);

      var region = null;
      if (aEvent.originalTarget.localName == "treechildren") {
        // let's build the drag region
        var tree = aEvent.originalTarget.parentNode;
        try {
          region = Components.classes["@mozilla.org/gfx/region;1"].createInstance(Components.interfaces.nsIScriptableRegion);
          region.init();
          var obo = tree.treeBoxObject;
          var bo = obo.treeBody.boxObject;
          var sel= obo.view.selection;

          var rowX = bo.x;
          var rowY = bo.y;
          var rowHeight = obo.rowHeight;
          var rowWidth = bo.width;

          //add a rectangle for each visible selected row
          for (var i = obo.getFirstVisibleRow(); i <= obo.getLastVisibleRow(); i ++)
          {
            if (sel.isSelected(i))
              region.unionRect(rowX, rowY, rowWidth, rowHeight);
            rowY = rowY + rowHeight;
          }
      
          //and finally, clip the result to be sure we don't spill over...
          region.intersectRect(bo.x, bo.y, bo.width, bo.height);
        } catch(ex) {
          dump("Error while building selection region: " + ex + "\n");
          region = null;
        }
      }

      var count = 0;
      do 
        {
          var trans = nsTransferable.set(transferData._XferID == "TransferData" 
                                         ? transferData 
                                         : transferData.dataList[count++]);
          transArray.AppendElement(trans.QueryInterface(Components.interfaces.nsISupports));
        }
      while (transferData._XferID == "TransferDataSet" && 
             count < transferData.dataList.length);
      
      try {
        this.mDragService.invokeDragSessionWithImage(aEvent.target, transArray,
                                                     region, dragAction.action,
                                                     null, 0, 0, aEvent);
      }
      catch(ex) {
        // this could be because the user pressed escape to
        // cancel the drag. even if it's not, there's not much
        // we can do, so be silent.
      }
      aEvent.stopPropagation();
    },

  /** 
   * void dragOver (DOMEvent aEvent, Object aDragDropObserver) ;
   *
   * called when a drag passes over this element
   *
   * @param DOMEvent aEvent
   *        the DOM event fired by passing over the element
   * @param Object aDragDropObserver
   *        javascript object of format described above that specifies
   *        the way in which the element responds to drag events.
   **/
  dragOver: function (aEvent, aDragDropObserver)
    { 
      if (!("onDragOver" in aDragDropObserver)) 
        return;
      if (!this.checkCanDrop(aEvent, aDragDropObserver))
        return;
      var flavourSet = aDragDropObserver.getSupportedFlavours();
      for (var flavour in flavourSet.flavourTable)
        {
          if (this.mDragSession.isDataFlavorSupported(flavour))
            {
              aDragDropObserver.onDragOver(aEvent, 
                                           flavourSet.flavourTable[flavour], 
                                           this.mDragSession);
              aEvent.stopPropagation();
              break;
            }
        }
    },

  mDragSession: null,

  /** 
   * void drop (DOMEvent aEvent, Object aDragDropObserver) ;
   *
   * called when the user drops on the element
   *
   * @param DOMEvent aEvent
   *        the DOM event fired by the drop
   * @param Object aDragDropObserver
   *        javascript object of format described above that specifies
   *        the way in which the element responds to drag events.
   **/
  drop: function (aEvent, aDragDropObserver)
    {
    try{
      if (!("onDrop" in aDragDropObserver))
        return;
      if (!this.checkCanDrop(aEvent, aDragDropObserver))
        return;  
      if (this.mDragSession.canDrop) {
        var flavourSet = aDragDropObserver.getSupportedFlavours();
        var transferData = nsTransferable.get(flavourSet, this.getDragData, true);
        // hand over to the client to respond to dropped data
        var multiple = "canHandleMultipleItems" in aDragDropObserver && aDragDropObserver.canHandleMultipleItems;
        var dropData = multiple ? transferData : transferData.first.first;
        aDragDropObserver.onDrop(aEvent, dropData, this.mDragSession);
      }
      aEvent.stopPropagation();
      }
      catch(e){
        alert(e);
      }
    },

  /** 
   * void dragExit (DOMEvent aEvent, Object aDragDropObserver) ;
   *
   * called when a drag leaves this element
   *
   * @param DOMEvent aEvent
   *        the DOM event fired by leaving the element
   * @param Object aDragDropObserver
   *        javascript object of format described above that specifies
   *        the way in which the element responds to drag events.
   **/
  dragExit: function (aEvent, aDragDropObserver)
    {
      if (!this.checkCanDrop(aEvent, aDragDropObserver))
        return;
      if ("onDragExit" in aDragDropObserver)
        aDragDropObserver.onDragExit(aEvent, this.mDragSession);
    },  
    
  /** 
   * void dragEnter (DOMEvent aEvent, Object aDragDropObserver) ;
   *
   * called when a drag enters in this element
   *
   * @param DOMEvent aEvent
   *        the DOM event fired by entering in the element
   * @param Object aDragDropObserver
   *        javascript object of format described above that specifies
   *        the way in which the element responds to drag events.
   **/
  dragEnter: function (aEvent, aDragDropObserver)
    {
      if (!this.checkCanDrop(aEvent, aDragDropObserver))
        return;
      if ("onDragEnter" in aDragDropObserver)
        aDragDropObserver.onDragEnter(aEvent, this.mDragSession);
    },  
    
  /** 
   * nsISupportsArray getDragData (Object aFlavourList)
   *
   * Creates a nsISupportsArray of all droppable items for the given
   * set of supported flavours.
   * 
   * @param FlavourSet aFlavourSet
   *        formatted flavour list.
   **/  
  getDragData: function (aFlavourSet)
    {
      var supportsArray = Components.classes["@mozilla.org/supports-array;1"]
                                    .createInstance(Components.interfaces.nsISupportsArray);

      for (var i = 0; i < nsDragAndDrop.mDragSession.numDropItems; ++i)
        {
          var trans = nsTransferable.createTransferable();
          for (var j = 0; j < aFlavourSet.flavours.length; ++j)
            trans.addDataFlavor(aFlavourSet.flavours[j].contentType);
          nsDragAndDrop.mDragSession.getData(trans, i);
          supportsArray.AppendElement(trans);
        }
      return supportsArray;
    },

  /** 
   * Boolean checkCanDrop (DOMEvent aEvent, Object aDragDropObserver) ;
   *
   * Sets the canDrop attribute for the drag session.
   * returns false if there is no current drag session.
   *
   * @param DOMEvent aEvent
   *        the DOM event fired by the drop
   * @param Object aDragDropObserver
   *        javascript object of format described above that specifies
   *        the way in which the element responds to drag events.
   **/
  checkCanDrop: function (aEvent, aDragDropObserver)
    {
      if (!this.mDragSession) 
        this.mDragSession = this.mDragService.getCurrentSession();
      if (!this.mDragSession) 
        return false;
      this.mDragSession.canDrop = this.mDragSession.sourceNode != aEvent.target;
      if ("canDrop" in aDragDropObserver)
        this.mDragSession.canDrop &= aDragDropObserver.canDrop(aEvent, this.mDragSession);
      return true;
    },

  /**
   * Do a security check for drag n' drop. Make sure the source document
   * can load the dragged link.
   *
   * @param DOMEvent aEvent
   *        the DOM event fired by leaving the element
   * @param Object aDragDropObserver
   *        javascript object of format described above that specifies
   *        the way in which the element responds to drag events.
   * @param String aDraggedText
   *        the text being dragged
   **/
  dragDropSecurityCheck: function (aEvent, aDragSession, aDraggedText)
    {
      var sourceDoc = aDragSession.sourceDocument;
      if (!sourceDoc)
        return;

      // Strip leading and trailing whitespace, then try to create a
      // URI from the dropped string. If that succeeds, we're
      // dropping a URI and we need to do a security check to make
      // sure the source document can load the dropped URI. We don't
      // so much care about creating the real URI here
      // (i.e. encoding differences etc don't matter), we just want
      // to know if aDraggedText really is a URI.

      aDraggedText = aDraggedText.replace(/^\s*|\s*$/g, '');

      var uri;

      try {
        uri = Components.classes["@mozilla.org/network/io-service;1"]
                        .getService(Components.interfaces.nsIIOService)
                        .newURI(aDraggedText, null, null);
      } catch (e) {
      }

      if (!uri)
        return;

      // aDraggedText is a URI, do the security check.
      const nsIScriptSecurityManager = Components.interfaces
                                                 .nsIScriptSecurityManager;
      var secMan = Components.classes["@mozilla.org/scriptsecuritymanager;1"]
                             .getService(nsIScriptSecurityManager);

      try {
        secMan.checkLoadURIStr(sourceDoc.documentURI, aDraggedText,
                               nsIScriptSecurityManager.STANDARD);
      } catch (e) {
        // Stop event propagation right here.
        aEvent.stopPropagation();

        throw "Drop of " + aDraggedText + " denied.";
      }
    }
};