[union] handle clusters with uu/ux combined

include/boost/geometry/algorithms/detail/overlay/traverse.hpp

@@ -259,16 +259,21 @@ struct traversal
 
         sbs_type sbs;
         bool has_subject = false;
-        bool only_uu = true;
+        bool only_uu_or_ux = true;
 
         for (typename std::set<signed_size_type>::const_iterator sit = ids.begin();
              sit != ids.end(); ++sit)
         {
             signed_size_type turn_index = *sit;
             turn_type const& cturn = m_turns[turn_index];
-            if (only_uu && ! cturn.both(operation_union))
+            if (only_uu_or_ux)
             {
-                only_uu = false;
+                if (! (cturn.both(operation_union)
+                        || (cturn.has(operation_union) && cturn.has(operation_blocked))))
+                {
+                    // not a u-turn and not a ux turn
+                    only_uu_or_ux = false;
+                }
             }
             for (int i = 0; i < 2; i++)
             {
@@ -292,12 +297,13 @@ struct traversal
         }
         sbs.apply(turn.point);
 
-        if (only_uu)
+        if (only_uu_or_ux)
         {
             sbs.reverse();
         }
 
         bool result = false;
+        std::size_t target_main_rank = 1;
         for (std::size_t i = 0; i < sbs.m_ranked_points.size(); i++)
         {
             const typename sbs_type::rp& ranked_point = sbs.m_ranked_points[i];
@@ -309,14 +315,21 @@ struct traversal
                 return false;
             }
 
-            if (ranked_point.main_rank == 1
+            if (ranked_point.main_rank == target_main_rank
                     && ranked_point.index == sort_by_side::index_to
                     && ranked_point.operation == operation_blocked)
             {
+                if (only_uu_or_ux)
+                {
+                    // Turns are reversed and ux is allowed, now aim for
+                    // the next main_rank
+                    target_main_rank++;
+                    continue;
+                }
                 return false;
             }
 
-            if (ranked_point.main_rank == 1
+            if (ranked_point.main_rank == target_main_rank
                     && ranked_point.index == sort_by_side::index_to
                     && (ranked_point.operation == OperationType
                         || ranked_point.operation == operation_continue))
@@ -351,7 +364,7 @@ struct traversal
                 result = true;
                 // Don't return yet, maybe there is a blocked
             }
-            if (ranked_point.main_rank > 1)
+            if (ranked_point.main_rank > target_main_rank)
             {
                 return result;
             }

test/algorithms/overlay/multi_overlay_cases.hpp

@@ -522,11 +522,18 @@ static std::string case_recursive_boxes_17[2] =
 
 static std::string case_recursive_boxes_18[2] =
 {
-    // Very simple case having two colocated uu turns
+    // Simple case having two colocated uu turns
     "MULTIPOLYGON(((2 1,3 0,2 0,2 1)),((2 1,1 1,1 2,2 1)))",
     "MULTIPOLYGON(((2 2,2 3,3 3,3 2,2 1,2 2)))"
 };
 
+static std::string case_recursive_boxes_19[2] =
+{
+    // Simple case having two colocated uu and ux turns
+    "MULTIPOLYGON(((1 4,2 3,1 3,1 4)),((1 4,0 4,0 5,1 4)))",
+    "MULTIPOLYGON(((3 4,1 4,2 5,3 4)),((1 4,1 3,0 3,1 4)))"
+};
+
 static std::string pie_21_7_21_0_3[2] =
 {
     "MULTIPOLYGON(((2500 2500,2500 3875,2855 3828,3187 3690,3472 3472,3690 3187,3828 2855,3875 2500,3828 2144,3690 1812,3472 1527,3187 1309,2855 1171,2499 1125,2144 1171,1812 1309,1527 1527,1309 1812,1171 2144,1125 2499,1171 2855,1309 3187,2500 2500)))",

test/algorithms/set_operations/intersection/intersection_multi.cpp

@@ -180,6 +180,9 @@ void test_areal()
     test_one<Polygon, MultiPolygon, MultiPolygon>("case_recursive_boxes_18",
         case_recursive_boxes_18[0], case_recursive_boxes_18[1],
         0, 0, 0.0);
+    test_one<Polygon, MultiPolygon, MultiPolygon>("case_recursive_boxes_19",
+        case_recursive_boxes_19[0], case_recursive_boxes_19[1],
+        0, 0, 0.0);
 
     test_one<Polygon, MultiPolygon, MultiPolygon>("ggl_list_20120915_h2_a",
         ggl_list_20120915_h2[0], ggl_list_20120915_h2[1],

test/algorithms/set_operations/union/union_multi.cpp

@@ -171,6 +171,9 @@ void test_areal()
     test_one<Polygon, MultiPolygon, MultiPolygon>("case_recursive_boxes_18",
         case_recursive_boxes_18[0], case_recursive_boxes_18[1],
             3, 0, -1, 2.5);
+    test_one<Polygon, MultiPolygon, MultiPolygon>("case_recursive_boxes_19",
+        case_recursive_boxes_19[0], case_recursive_boxes_19[1],
+            3, 0, -1, 2.5);
 
     test_one<Polygon, MultiPolygon, MultiPolygon>("ggl_list_20120915_h2_a",
          ggl_list_20120915_h2[0], ggl_list_20120915_h2[1],