Defines a function that, given some vertex, can provide the x/y location of the vertex on the canvas. During a group layout, the second
argument will contain the group that is being laid out, but when running the layout for the main canvas, parentGroup will not be provided.
Defines a function that, given some vertex, can provide the x/y location of the vertex on the canvas. During a group layout, the second argument will contain the group that is being laid out, but when running the layout for the main canvas,
parentGroupwill not be provided.