Get the 'Pinned' UV-Verts

I am intenting to make my own UV-Unwrapper, something like the fabuleous ‘smart unwrap’, but it should obey seams and pinned uv-coordinates.

At the moment i am stuck with the somehow pinned-property of an UV-coordinate, how can i archieve if a vert is pinned to an uv-coordinate ?

the script will unscrample by a mean-least-square-algorithm, which obeys angles between edges, distances of edges and z-coordinate, after a proper approximation the script will detect verts under ‘stress’ - which means, the square error at this vert is higher than a certain given amount, and break the edge at this point.
I am experimenting already with different parameters to decide, which edge will be broken up, but i can’t avoid at this point to overlap the uv-faces, with pinned points i have a relevant influence on the unwrapping which could avoid overlapping

The pinned state of an UV node might not be accessible from Python yet. I had a quick look and couldn’t find anything about it in the Python API docs. If so, you could try to request inclusion fo this property via the bug tracker.