public void setVertexClickListener(VertexClickListener<V, E> l) {
		clientVertexClickListener = Optional.ofNullable(l);
	}
Sets a listener that allows clients to be notified of vertex double-clicks.  Normal
mouse processing is handled by the {@link VisualGraphMousePlugin} class.  This is a
convenience method so that clients do not have to deal with the mouse plugin.

@param l the listener
Ghidra/Framework/Graph/src/main/java/ghidra/graph/viewer/VisualGraphView.java