From 9298ac2a2cc5f72d10313af954e09a77886b40fd Mon Sep 17 00:00:00 2001
From: Barend Gehrels <barend@xs4all.nl>
Date: Wed, 17 Sep 2014 16:30:03 +0200
Subject: [PATCH] [buffer] fix intersection points on border, equal points
 should not be checked and correct order in call to side strategy This fixes
 case rt_u10

---
 .../detail/buffer/turn_in_piece_visitor.hpp     | 17 ++++++++++++-----
 test/algorithms/buffer/multi_polygon_buffer.cpp |  4 +---
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/include/boost/geometry/algorithms/detail/buffer/turn_in_piece_visitor.hpp b/include/boost/geometry/algorithms/detail/buffer/turn_in_piece_visitor.hpp
index 97463cacd..1f2513a00 100644
--- a/include/boost/geometry/algorithms/detail/buffer/turn_in_piece_visitor.hpp
+++ b/include/boost/geometry/algorithms/detail/buffer/turn_in_piece_visitor.hpp
@@ -17,6 +17,7 @@
 #include <boost/geometry/algorithms/detail/disjoint/point_box.hpp>
 #include <boost/geometry/algorithms/detail/overlay/segment_identifier.hpp>
 #include <boost/geometry/algorithms/detail/overlay/get_turn_info.hpp>
+#include <boost/geometry/policies/compare.hpp>
 #include <boost/geometry/strategies/buffer.hpp>
 
 #include <boost/geometry/geometries/linestring.hpp>
@@ -95,18 +96,24 @@ class turn_in_piece_visitor
             <
                 typename cs_tag<Point>::type
             >::type side_strategy;
+        geometry::equal_to<Point> comparator;
 
         for (int i = 1; i < piece.offsetted_count; i++)
         {
             Point const& previous = piece.robust_ring[i - 1];
             Point const& current = piece.robust_ring[i];
-            int const side = side_strategy::apply(point, previous, current);
-            if (side == 0)
+
+            // The robust ring contains duplicates, avoid applying side on them (will be 0)
+            if (! comparator(previous, current))
             {
-                // Collinear, check if projection falls on it
-                if (projection_on_segment(point, previous, current))
+                int const side = side_strategy::apply(previous, current, point);
+                if (side == 0)
                 {
-                    return true;
+                    // Collinear, check if projection falls on it
+                    if (projection_on_segment(point, previous, current))
+                    {
+                        return true;
+                    }
                 }
             }
         }
diff --git a/test/algorithms/buffer/multi_polygon_buffer.cpp b/test/algorithms/buffer/multi_polygon_buffer.cpp
index 9cecc6290..c75ea82bf 100644
--- a/test/algorithms/buffer/multi_polygon_buffer.cpp
+++ b/test/algorithms/buffer/multi_polygon_buffer.cpp
@@ -373,9 +373,7 @@ void test_all()
 
     test_one<multi_polygon_type, polygon_type>("rt_u8", rt_u8, join_miter, end_flat, 70.9142, 1.0);
     test_one<multi_polygon_type, polygon_type>("rt_u9", rt_u9, join_miter, end_flat, 59.3063, 1.0);
-#if defined(BOOST_GEOMETRY_BUFFER_INCLUDE_FAILING_TESTS)
-    test_one<multi_polygon_type, polygon_type>("rt_u10", rt_u10, join_miter, end_flat, 999, 1.0);
-#endif
+    test_one<multi_polygon_type, polygon_type>("rt_u10", rt_u10, join_miter, end_flat, 144.0858, 1.0);
 }
 
 int test_main(int, char* [])