rightMargin, renderHeight);
rightMargin, renderHeight + topMargin);
void clearMargin(GC gc, Color background, Rectangle clientArea, int renderHeight) {	// clear the margin background	gc.setBackground(background);	gc.fillRectangle(0, 0, clientArea.width, topMargin);	gc.fillRectangle(0, 0, leftMargin, renderHeight);		gc.fillRectangle(		0, clientArea.height - bottomMargin, 		clientArea.width, bottomMargin);	gc.fillRectangle(		clientArea.width - rightMargin, 0, 		rightMargin, renderHeight);}