[kepler-dev] handling layer events

[Edward A. Lee]

At 03:30 PM 10/18/2005 -0700, Chad Berkley wrote:
>Hi,
>
>I'm trying to enable the canvas to allow a user to drag an actor from
>the canvas back to the actor library.  I've got the drag n' drop
>working, except that I can't seem to figure out how to get a
>reference to the NamedObj that implements the diva Figure on the
>canvas.  I have a reference to the Figure and also a reference to the
>root model itself, but how do I get a reference to the NamedObj that
>the Figure represents?  I'm working within the confines of
>BasicGraphFrame and the LayerAdapter that is implemented there.  My
>question is, how do I reconcile a Figure with a NamedObj so that when
>I drop the actor (or director or whatever) onto the actor library, i
>can process the actual ptolemy object instead of the diva object?
>
>thanks,
>chad

The following method in ptolemy.vergil.basic.EditorDropTarget
illustrates what you need, I think:

         /** Return the object under the specified point, or null if there
          *  is none.
          *  @param point The point in the graph pane.
          *  @return The object under the specified point, or null if there
          *   is none or it is not a NamedObj.
          */
         private NamedObj _getObjectUnder(Point2D point) {
             Figure figureUnderMouse = _getFigureUnder(point);

             if (figureUnderMouse == null) {
                 return null;
             }

             Object objectUnderMouse = ((UserObjectContainer) figureUnderMouse)
                     .getUserObject();

             // Object might be a Location, in which case we want its 
container.
             if (objectUnderMouse instanceof Location) {
                 return (NamedObj) ((NamedObj) 
objectUnderMouse).getContainer();
             } else if (objectUnderMouse instanceof NamedObj) {
                 return (NamedObj) objectUnderMouse;
             }

             return null;
         }


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------------
Edward A. Lee
Professor, Chair of the EE Division, Associate Chair of EECS
231 Cory Hall, UC Berkeley, Berkeley, CA 94720
phone: 510-642-0253 or 510-642-0455, fax: 510-642-2845
eal at eecs.Berkeley.EDU, http://ptolemy.eecs.berkeley.edu/~eal