From a3f75133c8baead6f8d7bb01722a6bfcdc2e9038 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Luk=C3=A1=C5=A1=20Hejl?= <hejl.lukas@gmail.com>
Date: Mon, 24 Feb 2025 01:48:23 +0100
Subject: [PATCH] SPE-2698: Fix crash during regions expansion.

---
 src/libslic3r/Algorithm/RegionExpansion.cpp |  5 ++++
 tests/libslic3r/test_region_expansion.cpp   | 28 +++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/src/libslic3r/Algorithm/RegionExpansion.cpp b/src/libslic3r/Algorithm/RegionExpansion.cpp
index 8cd0ff0f54..e719a8c249 100644
--- a/src/libslic3r/Algorithm/RegionExpansion.cpp
+++ b/src/libslic3r/Algorithm/RegionExpansion.cpp
@@ -283,6 +283,11 @@ std::vector<WaveSeed> wave_seeds(
             // Hope that at least one end of an open polyline is clipped by the boundary, thus an intersection point is created.
             (front.z() < 0 || back.z() < 0));
 
+        if (front != back && front.z() >= 0 && back.z() >= 0) {
+            // Very rare case when both endpoints intersect boundary ExPolygons in existing points.
+            // So the ZFillFunction callback hasn't been called.
+            continue;
+        } else
         if (front == back && (front.z() < idx_boundary_end)) {
             // This should be a very rare exception.
             // See https://github.com/prusa3d/PrusaSlicer/issues/12469.
diff --git a/tests/libslic3r/test_region_expansion.cpp b/tests/libslic3r/test_region_expansion.cpp
index 4da6c19ce6..7f8903737f 100644
--- a/tests/libslic3r/test_region_expansion.cpp
+++ b/tests/libslic3r/test_region_expansion.cpp
@@ -284,3 +284,31 @@ SCENARIO("Region expansion basics", "[RegionExpansion]") {
         }
     }
 }
+
+TEST_CASE("WaveSeed - ZFillFunction - SPE-2698", "[WaveSeedZFillFunctionSPE2698]")
+{
+    const ExPolygons boundary = {{
+        Point(-5900000, -20000000),
+        Point(-6518889, -22009467),
+        Point(-5779768, -22315621),
+        Point(-5662934, -22033558),
+        Point(-5615689, -21919501),
+        Point(-5779767, -22315622),
+        Point(-5040682, -22621761),
+        Point(-4000000, -20000000),
+    }};
+
+    const ExPolygons src = {{
+        Point(-5615689, -21919501),
+        Point(-5662934, -22033558),
+        Point(-5779768, -22315621),
+        Point(-5779767, -22315622),
+    }};
+
+    std::vector<Slic3r::Algorithm::WaveSeed> wave_seeds = Slic3r::Algorithm::wave_seeds(src, boundary, 83561.8046, true);
+    for (const Slic3r::Algorithm::WaveSeed &wave_seed : wave_seeds) {
+        REQUIRE(wave_seed.src < src.size());
+        REQUIRE(wave_seed.boundary < boundary.size());
+    }
+}
+