protected boolean checkForVertex(MouseEvent e) {
		if (!checkModifiers(e)) {
			selectedVertex = null;
			return false;
		}

		VisualizationViewer<V, E> vv = getViewer(e);
		GraphElementAccessor<V, E> pickSupport = vv.getPickSupport();
		Layout<V, E> layout = vv.getGraphLayout();
		if (pickSupport == null) {
			return false;
		}

		// p is the screen point for the mouse event
		Point2D p = e.getPoint();
		selectedVertex = pickSupport.getVertex(layout, p.getX(), p.getY());
		if (selectedVertex == null) {
			return false;
		}

		e.consume();
		return true;
	}
Usage Notes:
<ul>
		<li>We clear state on mouseReleased() and mouseExited(), since we will get 
			at least one of those calls</li>
</ul>

@param <V> the vertex type
@param <E> the edge type
Ghidra/Framework/Graph/src/main/java/ghidra/graph/viewer/event/mouse/VisualGraphAbstractGraphMousePlugin.java