From ee9847a904ad984d13e5ecac112c54fff00a05b8 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Fri, 23 Dec 2022 13:26:41 +0300
Subject: [PATCH] Fix cg::delaunay for some weird circular cases

---
 libs/cg/include/psemek/cg/triangulation/delaunay.hpp | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/libs/cg/include/psemek/cg/triangulation/delaunay.hpp b/libs/cg/include/psemek/cg/triangulation/delaunay.hpp
index f5e46816..af204f2d 100644
--- a/libs/cg/include/psemek/cg/triangulation/delaunay.hpp
+++ b/libs/cg/include/psemek/cg/triangulation/delaunay.hpp
@@ -4,6 +4,7 @@
 #include <psemek/cg/triangulation/triangulation.hpp>
 
 #include <queue>
+#include <vector>
 
 namespace psemek::cg
 {
@@ -12,6 +13,7 @@ namespace psemek::cg
 	auto delaunay(RobustTag robust_tag, InputIterator begin, InputIterator end)
 	{
 		std::vector<Index> edge_queue;
+		std::vector<Index> flipped_set;
 
 		auto at = [&](Index i){ return *(begin + i); };
 
@@ -62,6 +64,8 @@ namespace psemek::cg
 				// decide if a flip is needed
 				if (in_circle(robust_tag, at(p0.index()), at(p1.index()), at(p2.index()), at(p3.index())) != geom::sign_t::positive) continue;
 
+				flipped_set.insert(std::lower_bound(flipped_set.begin(), flipped_set.end(), e.index()), e.index());
+
 				auto f0 = e.face();
 				auto f1 = twin.face();
 
@@ -81,15 +85,17 @@ namespace psemek::cg
 				tprev.face(f0);
 				tprev.next(next); next.prev(tprev);
 
+				p0.edge(prev);
 				p1.edge(tnext);
 				p2.edge(next);
+				p3.edge(tprev);
 
 				f0.edge(e);
 				f1.edge(twin);
 
 				auto push = [&](auto e)
 				{
-					if (e.twin().face() != outer_face)
+					if (e.twin().face() != outer_face && !std::binary_search(flipped_set.begin(), flipped_set.end(), e.index()))
 						edge_queue.push_back(e.index());
 				};
 
@@ -98,6 +104,8 @@ namespace psemek::cg
 				push(tnext);
 				push(tprev);
 			}
+
+			flipped_set.clear();
 		};
 		return detail::triangulate<Index>(robust_tag, begin, end, callback);
 	}