Function tweakShape

tweak the layout by truncating edges early

This tweak truncates edges at the extent of a node shape sized by a bounding box. After applying this tweak, edge endings like arrows can be easily rendered in the appropriate place.

There are three built in Shapes:

• shapeRect - a simple rectangle
• shapeEllipse - an ellipse (circle for square node sizes)
• shapeTopBottom - to center edges into the top or bottom of a node