def setlayout(self, layout):
if self.viewer and getattr(self.viewer.graphlayout, 'key',
True) is not None:
self.viewers_history.append(self.viewer)
del self.forward_viewers_history[:]
self.layout = layout
self.viewer = GraphRenderer(self.screen, layout)
self.searchpos = 0
self.searchresults = []
self.zoom_to_fit()
