From aef9a07d2a63eca3d2d3fd0587bed8f2696bb006 Mon Sep 17 00:00:00 2001
From: Andreas Fabri <andreas.fabri@geometryfactory.com>
Date: Tue, 10 Jun 2025 14:37:06 +0100
Subject: [PATCH] Add that for join() and intersect() the input must have
 correct orientation

---
 Polygon_repair/include/CGAL/Polygon_repair/repair.h | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/Polygon_repair/include/CGAL/Polygon_repair/repair.h b/Polygon_repair/include/CGAL/Polygon_repair/repair.h
index 871bf75ff71..d60519226b8 100644
--- a/Polygon_repair/include/CGAL/Polygon_repair/repair.h
+++ b/Polygon_repair/include/CGAL/Polygon_repair/repair.h
@@ -104,7 +104,8 @@ Multipolygon_with_holes_2<Kernel, Container> repair(const Polygon_with_holes_2<K
 /// \tparam Kernel parameter of the input and output polygons. Must be model of `ConstrainedDelaunayTriangulationTraits_2 `
 /// \tparam Container parameter of the input and output polygons
 /// \tparam Rule may be any \ref PkgPolygonRepairRules
-/// \pre If the rule is the `Union_rule` or `Non_zero_rule`, each polygon with hole must be free of self-intersections
+/// \pre If the rule is the `Union_rule` or `Non_zero_rule`, each polygon with hole must be free of self-intersections,
+///      the outer boundary of each polygon with holes must be counterclockwise  and the  holes clockwise oriented.
 template <class Kernel, class Container, class Rule = Even_odd_rule>
 Multipolygon_with_holes_2<Kernel, Container> repair(const Multipolygon_with_holes_2<Kernel, Container>& p, Rule = Rule())
 {
@@ -813,7 +814,8 @@ protected:
 /// computes the union of all polygons with holes in `p`
 /// \tparam Kernel parameter of the input and output polygons. Must be model of `ConstrainedDelaunayTriangulationTraits_2 `
 /// \tparam Container parameter of the input and output polygons
-/// \pre Each polygon with hole must be free of self-intersections
+/// \pre Each polygon with holes must be free of self-intersections,
+///      the outer boundaries must be counterclockwise and the holes clockwise oriented.
 template <typename Kernel, typename Container>
 Multipolygon_with_holes_2<Kernel,Container>
 join(const Multipolygon_with_holes_2<Kernel,Container>& pa)
@@ -838,7 +840,8 @@ join(const Multipolygon_with_holes_2<Kernel,Container>& pa)
 /// \tparam Container parameter of the input and output polygons
 /// \tparam PA must be `Polygon_2<Kernel, Container>`, or `Polygon_with_holes_2<Kernel, Container>`, or `Multipolygon_with_holes_2<Kernel, Container>`
 /// \tparam PB must be `Polygon_2<Kernel, Container>`, or `Polygon_with_holes_2<Kernel, Container>`, or `Multipolygon_with_holes_2<Kernel, Container>`
-/// \pre The polygons `pa` and `pb` must be free of self-intersections
+/// \pre The polygons `pa` and `pb` must be free of self-intersections,
+///      the outer boundaries must be counterclockwise  and the holes clockwise oriented.
 template <typename PA, typename PB, typename Kernel = Default, typename Container = Default>
 #ifdef DOXYGEN_RUNNING
 Multipolygon_with_holes_2<Kernel,Container>
@@ -870,7 +873,8 @@ join(const PA& pa, const PB& pb, const Kernel& = Default(), const Container& = D
 /// computes the intersection of all polygons with holes in `p`
 /// \tparam Kernel parameter of the input and output polygons. Must be model of `ConstrainedDelaunayTriangulationTraits_2 `
 /// \tparam Container parameter of the input and output polygons
-/// \pre Each polygon with hole must be free of self-intersections
+/// \pre Each polygon with holes must be free of self-intersections
+///      the outer boundaries must be counterclockwise and the holes clockwise oriented.
 template <typename Kernel, typename Container>
 Multipolygon_with_holes_2<Kernel,Container>
 intersect(const Multipolygon_with_holes_2<Kernel,Container>& p)
@@ -902,6 +906,7 @@ intersect(const Multipolygon_with_holes_2<Kernel,Container>& p)
 /// \tparam PA must be `Polygon_2<Kernel, Container>`, or `Polygon_with_holes_2<Kernel, Container>`, or `Multipolygon_with_holes_2<Kernel, Container>`
 /// \tparam PB must be `Polygon_2<Kernel, Container>`, or `Polygon_with_holes_2<Kernel, Container>`, or `Multipolygon_with_holes_2<Kernel, Container>`
 /// \pre The polygons `pa` and `pb` must be free of self-intersections
+///      the outer boundaries must be counterclockwise and the holes clockwise oriented.
 template <typename PA, typename PB, typename Kernel = Default, typename Container = Default>
 #ifdef DOXYGEN_RUNNING
 Multipolygon_with_holes_2<Kernel, Container>