@Override
	public void paintIcon(Component c, Graphics g, int x, int y) {
		g.setColor(bgColor);
		g.fillRect(x + 1, y + 1, width - 2, height - 2);
		g.drawLine(x + 1, y, x + width - 2, y);
		g.drawLine(x + width - 1, y + 1, x + width - 1, y + height - 2);
		g.drawLine(x + 1, y + height - 1, x + width - 2, y + height - 1);
		g.drawLine(x, y + 1, x, y + height - 2);
	}
An icon used by the data types tree to uniformly space all icons.  Clients of versioned objects
can signal that this icon can paint a custom background.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/datamgr/tree/DtBackgroundIcon.java