no need for try here

whats blist ?

this could be a regular function

our API should be able to do this.

image names can be up to 64 characters now, does this size need updating?

Best use pythons tempfile - http://docs.python.org/3/library/tempfile.html

prefer filepath.lower().endswith((".svg", ".png"))

Much more efficient to simply do present.clear()

I think this is a bit confusing, why not import bmesh and call bmesh.new ?

a type similar to list, implemented using a search tree. It can insert at any position in O(log n). https://pypi.python.org/pypi/blist/1.3.4

sure, as v1.to_3d().cross(v2.to_3d()).z
I did some profiling and this appears to be faster. It is one of the most often called functions in the script.

I don't think that would work. There may be other unrelated items in the list present. Each vertex may have many instances in the flat net.
This code really needs to make sure that source is not in present, and that target is.

this way seemed to look more like Python to me, but I should better just conform with the API.
I'll change it to bmesh.new

Or perhaps I'll just remove this function for now. It's commented out from the UI.
I have this functionality in a branch, but it will take a few more weeks to finish.