From db59c229b019128b1c4d46bcc9ad61f06e7f2be9 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sat, 30 Dec 2017 20:34:21 +0000
Subject: [PATCH] helixish: ensure s and t are >0

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---
 helixish.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/helixish.py b/helixish.py
index b1eac1c..bf8083f 100644
--- a/helixish.py
+++ b/helixish.py
@@ -161,6 +161,7 @@ class HelixishCurve():
         def railway_ST(C, start, end, railway_r):
           delta = atan2(*(end - C)[0:2]) - atan2(*(start - C)[0:2])
           dbg('railway_ST C', C, 'start', start, 'end', end, 'delta', delta)
+          if delta < 0: delta += tau
           s = delta * railway_r
           dbg('railway_ST delta', delta, 'r', railway_r, 's', s)
           return s
-- 
2.30.2