private boolean onVertex(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;
			}

			return true;
		}
Sets the given vertex to be the focused vertex.  This will be the only focused vertex.

@param vertex the vertex
Ghidra/Framework/Graph/src/main/java/ghidra/graph/viewer/GraphComponent.java