indicates that wheter the last time GraphSelectPointData fired, it was originally cleared or not (it was cleared by thid object)
the initially use was for AddVertex, because it only adds vertices on graphselectpoints and if the selection was empty,
so AddVertex and ClearSelection are both listening to GraphSelectPoint, so if
ClearSelection fired before AddVertex it clears the selection and then AddVertex adds the Vertex
but it shouldn't do that, because at the click time the selection wasn'nt clear
and it is a mistake (bug) from users point of view,....
lc -
Variable in class graphlab.gui.core.graph.edge.EdgeView
determines the color of the line(edge);
lc -
Variable in class graphlab.gui.core.graph.vertex.VertexView
Constructs a light(weight) Edge Iterator object which iterates through all the edges going to
or coming from (depending on the second parameter) the specified vertex v.