How to track mouse EXIT/ENTER/HOVER over composite?

Question

The code below shows, that:

1) HOVER is totally ignored with composite. How to enable?

2) ENTER/EXIT are tracked, but when mouse entered child control region, parent composite receives EXIT event. How to make that entre area of a composite would serve as belonging to composite?

public class TryHover {

    public static void main(String[] args) {

        Display display = new Display();

        Shell shell = new Shell(display);
        shell.setLayout(new FillLayout());

        Composite composite = new Composite(shell, SWT.BORDER);
        composite.setLayout(new GridLayout(1, false));

        Label label1 = new Label(composite, SWT.BORDER);
        label1.setText("Label 1");

        Label label2 = new Label(composite, SWT.BORDER);
        label2.setText("Label 2");

        composite.addListener(SWT.MouseEnter, new Listener() {

            @Override
            public void handleEvent(Event event) {
                System.out.println("ENTER");

            }
        });

        composite.addListener(SWT.MouseExit, new Listener() {

            @Override
            public void handleEvent(Event event) {
                System.out.println("EXIT");

            }
        });

        composite.addListener(SWT.MouseHover, new Listener() {

            @Override
            public void handleEvent(Event event) {
                System.out.println("HOVER");

            }
        });

        shell.pack();
        shell.open();
        while (!shell.isDisposed()) {
            if (!display.readAndDispatch())
                display.sleep();
        }

    }
}

UPDATE

Yes, agree, if mouse is slow, it produces HOVER too.

Then the question is about ENTER/EXIT only: how to turn EXITs of on child controls?

Answer 1

SWT.MouseHover is only triggered when the mouse is located over the Composite and doesn't move for a fraction of a second.

SWT.MouseMove is triggered on each movement of the mouse over the Composite.

So it really depends on what you want to achieve here.

---

As for the second part of your question: SWT does not propagate events up the widget hierarchy (with some exceptions).

You can however implement your own logic to determine when to listen to the events.

• For SWT.MouseExit: Get the coordinates of the mouse and check if any of the children contains the mouse. If so, do nothing, if not, you left the Composite.
• For SWT.MouseEnter: This is a bit more tricky. I came up with a solution that keeps track of the current Widget the mouse is moving over using a filter on the display. When you enter the Composite, you can check if the previous widget was a child. If so, do nothing.

---

private static Widget mouseControl = null;

public static void main(String[] args)
{
    Display display = new Display();

    /* Overall, keep track of the Widget the mouse is moving over */
    display.addFilter(SWT.MouseMove, new Listener()
    {
        @Override
        public void handleEvent(Event e)
        {
            mouseControl = e.widget;
        }
    });

    Shell shell = new Shell(display);
    shell.setLayout(new FillLayout());

    final Composite composite = new Composite(shell, SWT.BORDER);
    composite.setLayout(new GridLayout(1, false));

    Label label1 = new Label(composite, SWT.BORDER);
    label1.setText("Label 1");

    Label label2 = new Label(composite, SWT.BORDER);
    label2.setText("Label 2");

    composite.addListener(SWT.MouseEnter, new Listener()
    {
        @Override
        public void handleEvent(Event event)
        {
            /* Check if the mouse was previously moving over a child (you could
             * even do recursive search here) */
            for (Control child : composite.getChildren())
            {
                if (child.equals(mouseControl))
                    return;
            }
            System.out.println("ENTER");
        }
    });

    composite.addListener(SWT.MouseExit, new Listener()
    {
        @Override
        public void handleEvent(Event event)
        {
            /* Check if the mouse is now located over a child (you could
             * even do recursive search here) */
            for (Control child : composite.getChildren())
            {
                if (child.getBounds().contains(new Point(event.x, event.y)))
                    return;
            }
            System.out.println("EXIT");
        }
    });

    composite.addListener(SWT.MouseHover, new Listener()
    {

        @Override
        public void handleEvent(Event event)
        {
            System.out.println("HOVER");
        }
    });

    shell.pack();
    shell.open();
    while (!shell.isDisposed())
    {
        if (!display.readAndDispatch())
            display.sleep();
    }
}