Overriding the MouseWheelListener in Swing

Question

I want to override the mouse wheel listener in Swing but only if they have the Control button pressed. The listener will be attached to a JPanel so that when they scroll the wheel it will scroll the JScrollPane and when they have the control button pressed and scroll the wheel it will zoom in. The default scroll of JScrollPane works (obviously) before I override it with my own listener. Here is my code:

mainPanel.addMouseWheelListener(new MouseWheelListener(){
    @Override
    public void mouseWheelMoved(MouseWheelEvent e) {
        if ((e.getModifiers() & InputEvent.CTRL_MASK) == InputEvent.CTRL_MASK) {
            int notches = e.getWheelRotation();

            if (notches < 0) {
                redrawOnZoom(true);
            } else {
                redrawOnZoom(false);
            }
        }
    }
});

Is there a way of saying something like "If mouse is scrolled on its own then do default JScrollPane scrolling behaviour but If Ctrl is pressed then zoom"?

Answer 1

you can dispatch the event to its parent if you don't want to handle it:

final MouseWheelListener wheel = new MouseWheelListener() {

    @Override
    public void mouseWheelMoved(MouseWheelEvent e) {
        // handle some events here and dispatch others
        if (shouldHandleHere(e)) {
            LOG.info("do-my-own-stuff");
        } else {
            LOG.info("dispatch-to-parent");
            e.getComponent().getParent().dispatchEvent(e);
        } 
    }

    public boolean shouldHandleHere(MouseWheelEvent e) {
        return (e.getModifiersEx() & InputEvent.CTRL_DOWN_MASK) != 0;
    }
};