private void updateDimension() {
		Rectangle2D newSize = getBounds();
		if(size == null
			|| newSize.getWidth() != size.getWidth()
			|| newSize.getHeight() != size.getHeight()
		) {
			size = newSize;
			insets = getInsets();
			interior = new Dimension(
				(int)size.getWidth() - insets.left - insets.right
				,(int)size.getHeight() - insets.top - insets.bottom
			);
			updateBarSize();
		}
	}