Transparent UI (+UIManager) artifacts

Question

I've got an application which draws a background image on a panel, but to achieve the optimal UI, I need to set Component backgrounds Transparent:

I made every component transparent by using the UI Manager: uimanager.put(Button, background(new color(0, 0, 0, 0); <- something like that, this works perfectly, except..

onMouseOver the component redraws itself (I guess) and causes Artifacts.. How can I avoid this in the UIManager?

(I created a class: uidefaults.java with all the UIManager settings)

Thanks in advance!!

Answer 1

Well, that is pretty simple - DO NOT use transparent background colors with components (any JComponent ancestor to be exact) that are OPAQUE.

To remove component background you don't need to set transparent color - just use this method:

component.setOpaque ( false );

This will hide component background and will also change component repaint strategy so it won't create any artifacts on repaint calls.

Also, if you still want to have semi-transparent background behind your component you can override paintComponent method like this:

    JLabel label = new JLabel ( "Transparent background" )
    {
        protected void paintComponent ( Graphics g )
        {
            g.setColor ( getBackground () );
            g.fillRect ( 0, 0, getWidth (), getHeight () );
            super.paintComponent ( g );
        }
    };
    label.setOpaque ( false );
    label.setBackground ( new Color ( 255, 0, 0, 128 ) );

This will force label to hide its default background and also paint your own background (that depends on component's background property).