[geos-commits] [SCM] GEOS branch main updated. 00648624efd1b4a3650b6c7a473fcd3647957406

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- Log -----------------------------------------------------------------
commit 00648624efd1b4a3650b6c7a473fcd3647957406
Author: Daniel Baston <dbaston at gmail.com>
Date:   Tue Oct 20 10:31:30 2026 -0400

    CircularArcIntesector: check for common points before excluding based on distance (#1559)

diff --git a/src/algorithm/CircularArcIntersector.cpp b/src/algorithm/CircularArcIntersector.cpp
index d503fb384..a41265367 100644
--- a/src/algorithm/CircularArcIntersector.cpp
+++ b/src/algorithm/CircularArcIntersector.cpp
@@ -182,6 +182,30 @@ CircularArcIntersector::intersects(const CircularArc& arc, const CoordinateSeque
     }
 }
 
+static std::vector<CoordinateXY>
+getCommonPoints(const CircularArc& arc1, const CircularArc& arc2)
+{
+    std::vector<CoordinateXY> ret;
+    const CoordinateXY& ap0 = arc1.p0();
+    const CoordinateXY& ap1 = arc1.p1();
+    const CoordinateXY& ap2 = arc1.p2();
+    const CoordinateXY& bp0 = arc2.p0();
+    const CoordinateXY& bp1 = arc2.p1();
+    const CoordinateXY& bp2 = arc2.p2();
+
+    if (ap0 == bp0 || ap0 == bp1 || ap0 == bp2) {
+        ret.push_back(ap0);
+    }
+    if (ap1 == bp0 || ap1 == bp1 || ap1 == bp2) {
+        ret.push_back(ap1);
+    }
+    if (ap2 == bp0 || ap2 == bp1 || ap2 == bp2) {
+        ret.push_back(ap2);
+    }
+
+    return ret;
+}
+
 void
 CircularArcIntersector::intersects(const CircularArc& arc1, const CircularArc& arc2)
 {
@@ -217,16 +241,20 @@ CircularArcIntersector::intersects(const CircularArc& arc1, const CircularArc& a
 
     const auto d = c1.distance(c2);
 
-    if (d > r1 + r2) {
-        // Circles are disjoint
-        result = NO_INTERSECTION;
-        return;
-    }
+    auto commonPoints = getCommonPoints(arc1, arc2);
 
-    if (d < std::abs(r1-r2)) {
-        // One circle contained within the other; arcs cannot intersect
-        result = NO_INTERSECTION;
-        return;
+    if (commonPoints.empty()) {
+        if (d > r1 + r2) {
+            // Circles are disjoint
+            result = NO_INTERSECTION;
+            return;
+        }
+
+        if (d < std::abs(r1-r2)) {
+            // One circle contained within the other; arcs cannot intersect
+            result = NO_INTERSECTION;
+            return;
+        }
     }
 
     // TODO because the circle center calculation is inexact we need some kind of tolerance here.
@@ -253,22 +281,8 @@ CircularArcIntersector::intersects(const CircularArc& arc1, const CircularArc& a
         CoordinateXY isect0{p.x + h* dy/d, p.y - h* dx/d };
         CoordinateXY isect1{p.x - h* dy/d, p.y + h* dx/d };
 
-        // Check to see if computed intersection points are inexact versions of an endpoint intersection
-        const CoordinateXY& ap0 = arc1.p0();
-        const CoordinateXY& ap1 = arc1.p1();
-        const CoordinateXY& ap2 = arc1.p2();
-        const CoordinateXY& bp0 = arc2.p0();
-        const CoordinateXY& bp1 = arc2.p1();
-        const CoordinateXY& bp2 = arc2.p2();
-
-        if (ap0 == bp0 || ap0 == bp1 || ap0 == bp2) {
-            closestPoint(isect0, isect1, 2, ap0) = ap0;
-        }
-        if (ap1 == bp0 || ap1 == bp1 || ap1 == bp2) {
-            closestPoint(isect0, isect1, 2, ap1) = ap1;
-        }
-        if (ap2 == bp0 || ap2 == bp1 || ap2 == bp2) {
-            closestPoint(isect0, isect1, 2, ap2) = ap2;
+        for (const auto& pt : commonPoints) {
+            closestPoint(isect0, isect1, 2 , pt) = pt;
         }
 
         if (arc1.containsPointOnCircle(isect0) && arc2.containsPointOnCircle(isect0)) {
diff --git a/tests/unit/algorithm/CircularArcIntersectorTest.cpp b/tests/unit/algorithm/CircularArcIntersectorTest.cpp
index 63695fb9b..518de55e2 100644
--- a/tests/unit/algorithm/CircularArcIntersectorTest.cpp
+++ b/tests/unit/algorithm/CircularArcIntersectorTest.cpp
@@ -1823,6 +1823,18 @@ void object::test<91>()
                       XY{-3, 4});
 }
 
+template<>
+template<>
+void object::test<92>()
+{
+    set_test_name("arcs intersect at shared vertex when inexact distance calculation says they cannot");
+
+    checkIntersection(XY{5, 0}, XY{6.530331962423936, 32.9099081287533}, XY{39.1383458646334, 37.61324718856101},
+                      XY{5, 0}, XY{-13.013189892510923, 476.4218618845866}, XY{426.8482396243887, 660.3353967726679},
+                      CircularArcIntersector::ONE_POINT_INTERSECTION,
+                      XY{5, 0});
+}
+
 // TODO: check Z values of arc result centerpoints
 // TODO: add tests for seg/seg
 

-----------------------------------------------------------------------

Summary of changes:
 src/algorithm/CircularArcIntersector.cpp           | 64 +++++++++++++---------
 .../unit/algorithm/CircularArcIntersectorTest.cpp  | 12 ++++
 2 files changed, 51 insertions(+), 25 deletions(-)


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