Merge pull request #158 from diagrams/issue155

Exclude extra segment when joining loops in offset. Fixes #155.

src/Diagrams/TwoD/Offset.hs

@@ -481,9 +481,9 @@ joinSegments _ _ _ _ _ [] = mempty `at` origin
 joinSegments _ _ _ _ [] _ = mempty `at` origin
 joinSegments j isLoop ml r es ts@(t:_) = t'
   where
-    t' | isLoop    = mapLoc (glueTrail . (<> mconcat (take (length ts) $ ss es (ts ++ [t])))) t
+    t' | isLoop    = mapLoc (glueTrail . (<> mconcat (take (length ts * 2 - 1) $ ss es (ts ++ [t])))) t
        | otherwise = mapLoc (<> mconcat (ss es ts)) t
-    ss es' ts' = [j ml r e a b <> unLoc b | (e,(a,b)) <- zip es' . (zip <*> tail) $ ts']
+    ss es' ts' = concat [[j ml r e a b, unLoc b] | (e,(a,b)) <- zip es' . (zip <*> tail) $ ts']
 
 -- | Take a join style and give the join function to be used by joinSegments.
 fromLineJoin