[gef-dev] Can't use DirectedGraphLayout re-Layout view

[刘建峰 <liu-jf@xxxxxxxxxxx>]

When using DirectedGraphLayout to layout view containing nodes(subclasses of node) once , DirectedGraphLayout  will write many position messages into the node ,  so call visit() will go wrong .

if the class DirectedGraphLayout have a methed to clear out all additional messages attaching the nodes ,DirectedGraphLayout will can always make Layout for views.