When does a JPanel paint (or repaint) its child components?

Question

I\'ve got a JButton which is painted using a custom UI delegate (CustomButtonUI extends BasicButtonUI). The CustomButtonUI\'s paint() method draws the button with rounded \"

Answer 1

For antialiasing to work consistently, your component needs to return false for isOpaque. Otherwise, the RepaintManager is free to skip painting the region behind your component.

I suspect that if you use a screen magnifier to look at the "unaliased" edges, you will find they really are antialiased. But it was done against against a black, unpainted background, not the parent's background.