private Polygon createSafeTriangle() {
		return new Polygon(
			new int[] { mouseX, targetX, targetX },
			new int[] { mouseY, targetTopY, targetBottomY },
			3 );
	}
Improves usability of submenus by using a
<a href="https://height.app/blog/guide-to-build-context-menus#safe-triangle">safe triangle</a>
to avoid that the submenu closes while the user moves the mouse to it.

@author Karl Tauber
flatlaf-core/src/main/java/com/formdev/flatlaf/SubMenuUsabilityHelper.java