Directed graph with custom Vertex widthxheight shifts arrow wrong

[mfe-]

When setting a custom width and height >40 on the VertexControl on a directed graph the arrow is underneath the control. Therefore it looks like that the arrow isn't displayed. The ShiftConverter is currently using hardcoded +-7.

To fix this:

• Pass additonal parameter with width and height of control to ShiftConverter
• Calculate a reasonable value which can be used to shift the arrow