From bb92d788eff757279da496409bd5a06b857d56dd Mon Sep 17 00:00:00 2001
From: Revar Desmera <revarbat@gmail.com>
Date: Sun, 17 Nov 2019 18:19:55 -0800
Subject: [PATCH] Added reverse_polygon() and improved ccw_polygon() and
 clockwise_polygon()

---
 geometry.scad            | 13 +++++++++++--
 tests/test_geometry.scad | 17 ++++++++++++++---
 version.scad             |  2 +-
 3 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/geometry.scad b/geometry.scad
index c4eb861..1504eea 100644
--- a/geometry.scad
+++ b/geometry.scad
@@ -1230,7 +1230,7 @@ function polygon_is_clockwise(path) =
 // Description:
 //   Given a polygon path, returns the clockwise winding version of that path.
 function clockwise_polygon(path) =
-	polygon_is_clockwise(path)? path : reverse(path);
+	polygon_is_clockwise(path)? path : reverse_polygon(path);
 
 
 // Function: ccw_polygon()
@@ -1239,7 +1239,16 @@ function clockwise_polygon(path) =
 // Description:
 //   Given a polygon path, returns the counter-clockwise winding version of that path.
 function ccw_polygon(path) =
-	polygon_is_clockwise(path)? reverse(path) : path;
+	polygon_is_clockwise(path)? reverse_polygon(path) : path;
+
+
+// Function: reverse_polygon()
+// Usage:
+//   reverse_polygon(poly)
+// Description:
+//   Reverses a polygon's winding direction, while still using the same start point.
+function reverse_polygon(poly) =
+	let(lp=len(poly)) [for (i=idx(poly)) poly[(lp-i)%lp]];
 
 
 
diff --git a/tests/test_geometry.scad b/tests/test_geometry.scad
index c762503..2b8f3ce 100644
--- a/tests/test_geometry.scad
+++ b/tests/test_geometry.scad
@@ -655,20 +655,31 @@ test_polygon_is_clockwise();
 
 module test_clockwise_polygon() {
 	path = circle(d=100);
+	rpath = concat([path[0]], reverse(select(path,1,-1)));
 	assert(clockwise_polygon(path) == path);
-	assert(clockwise_polygon(reverse(path)) == path);
+	assert(clockwise_polygon(rpath) == path);
 }
 test_clockwise_polygon();
 
 
 module test_ccw_polygon() {
 	path = circle(d=100);
-	assert(ccw_polygon(path) == reverse(path));
-	assert(ccw_polygon(reverse(path)) == reverse(path));
+	rpath = concat([path[0]], reverse(select(path,1,-1)));
+	assert(ccw_polygon(path) == rpath);
+	assert(ccw_polygon(rpath) == rpath);
 }
 test_ccw_polygon();
 
 
+module test_reverse_polygon() {
+	path = circle(d=100);
+	rpath = concat([path[0]], reverse(select(path,1,-1)));
+	assert(reverse_polygon(path) == rpath);
+	assert(reverse_polygon(rpath) == path);
+}
+test_reverse_polygon();
+
+
 module test_is_region() {
 	assert(is_region([circle(d=10),square(10)]));
 	assert(is_region([circle(d=10),square(10),circle(d=50)]));
diff --git a/version.scad b/version.scad
index ede42f6..f418189 100644
--- a/version.scad
+++ b/version.scad
@@ -8,7 +8,7 @@
 //////////////////////////////////////////////////////////////////////
 
 
-BOSL_VERSION = [2,0,41];
+BOSL_VERSION = [2,0,42];
 
 
 // Section: BOSL Library Version Functions