if (availableItemsCount == 0 && isFocusControl ()) redraw ();
void onResize (Event event) {	clientArea = getClientArea ();	/* vertical scrollbar */	ScrollBar vBar = getVerticalBar ();	int clientHeight = (clientArea.height - getHeaderHeight ()) / itemHeight;	int thumb = Math.min (clientHeight, availableItemsCount);	vBar.setThumb (thumb);	vBar.setPageIncrement (thumb);	int index = vBar.getSelection ();	if (index != topIndex) {		topIndex = index;		redraw ();	}	boolean visible = clientHeight < availableItemsCount;	if (visible != vBar.getVisible ()) {		vBar.setVisible (visible);		clientArea = getClientArea ();	}	/* horizontal scrollbar */ 	ScrollBar hBar = getHorizontalBar ();	int hBarMaximum = hBar.getMaximum ();	thumb = Math.min (clientArea.width, hBarMaximum);	hBar.setThumb (thumb);	hBar.setPageIncrement (thumb);	horizontalOffset = hBar.getSelection ();	visible = clientArea.width < hBarMaximum;	if (visible != hBar.getVisible ()) {		hBar.setVisible (visible);		clientArea = getClientArea ();	}	/* header */	int headerHeight = Math.max (fontHeight, headerImageHeight) + 2 * getHeaderPadding ();	header.setSize (clientArea.width, headerHeight);}