Canvas.onContextMenu Method
        
 Fires when the user does a context click on the canvas.
 
         
        Parameters
        
            - callback
            
 
            - 
                
Type: Function
The event handler to subscribe with. 
            - e
            
 
            - 
                
Type: jQuery.Event
The event from jQuery. 
        
        Return Value
        
Type: String
        
GUID of the event handler registered.