fletcher.paths.offset-vertex()

Offset a vertex to make a miter joint, given the angles of the incoming and outgoing legs.

     offset vertex ↓
───────────────────* ┐
     vertex ↓     /  │ offset
─[i-angle]──@    /   ┘
           /    /
    [o-angle]  /
         /    /

fletcher.paths.offset-vertex(
  vertex,
  i-angle,
  o-angle,
  offset,
)