Description of Mouse enter/exit handling is not specific enough

[Tom Schindl]

Hi,

I've been looking at how the mouse enter/exit is handled in JavaFX -
which is different in how it works in Swing/SWT and so I looked at the
documentation on MouseEvent which says the following:

---------8<---------
When mouse enters a node, the node gets MOUSE_ENTERED event, when it
leaves, it gets MOUSE_EXITED event. These events are delivered only to
the entered/exited node and seemingly don't go through the
capturing/bubbling phases. This is the most common use-case.
---------8<---------

In JavaFX leave means of if the mouse leaves the nodes bounds completely
you get an EXIT. Or if you flip the sides: If you move the mouse above a
node which is a child of the parent you won't see an EXIT on the
parent-node, nor you see an ENTER if you move from the sub-node once
more to the parent.

So IMHO while the current strategy of mouse enter/exit makes sense from
a SceneGraph point of view e.g. when you have graphic primitives but
reacts a bit out of order for Swing/SWT convertibles. So the
documentation needs to be a bit more specific.

To understand the difference you can run these 2 snippets:

Swing:
> 		JFrame f = new JFrame();
> 		
> 		JPanel p = new JPanel();
> 		p.setLayout(new BorderLayout());
> 		MouseAdapter a = new MouseAdapter() {
> 			
> 			@Override
> 			public void mouseExited(MouseEvent e) {
> 				System.err.println("EXITED: " + e.getSource());
> 			}
> 			
> 			@Override
> 			public void mouseEntered(MouseEvent e) {
> 				System.err.println("ENTERED: " + e.getSource());
> 			}			
> 		};
> 		p.addMouseListener(a);
> 		
> 		JButton jl = new JButton("Hello World!!!");
> 		jl.addMouseListener(a);
> 		p.add(jl,BorderLayout.WEST);
> 		f.getContentPane().add(p);
> 		f.pack();
> 		
> 		f.setVisible(true);

FX:
> 		BorderPane p = new BorderPane();
> 		EventHandler<MouseEvent> h = new EventHandler<MouseEvent>() {
> 
> 			@Override
> 			public void handle(MouseEvent event) {
> 				if( event.getEventType() == MouseEvent.MOUSE_ENTERED ) {
> 					System.err.println("ENTERED: " + event.getTarget());	
> 				} else {
> 					System.err.println("EXIT: " + event.getTarget());
> 				}				
> 			}
> 		};
> 		p.addEventHandler(MouseEvent.MOUSE_ENTERED, h);
> 		p.addEventHandler(MouseEvent.MOUSE_EXITED, h);
> 		Button b = new Button("Hello World");
> 		b.addEventHandler(MouseEvent.MOUSE_ENTERED, h);
> 		b.addEventHandler(MouseEvent.MOUSE_EXITED, h);
> 		p.setCenter(b);
> 		
> 		Scene s = new Scene(p,400,400);
> 		primaryStage.setScene(s);
> 		primaryStage.show();


Tom