Relative to the start point
This is needed because some twisted edges may have
unusual forms that do not fall in the rectangle determined by the
start end end points
Each canvas can have a status manager that can be used to represent
various pieces of information pertaining to outcomes of various actions
performed on the canvas or its descendants.
Notifies the canvas about changes in its sub-components that may require
the re-evaluation of the state of the canvas object, most notably a
re-rendering of the canvas.
This method takes a graph and a Hashtable with the nodes that cannot be moved and
returns a Hashtable with the coordinates of the nodes after doing the layout.