From 1db93f640ee46de9dec9051862df8a09fef44782 Mon Sep 17 00:00:00 2001
From: astromko <astromko@opencascade.com>
Date: Wed, 17 Apr 2024 10:46:06 +0100
Subject: [PATCH] 0033146: Modeling Algorithms - 2D Offset with arc-lin
 approximation fails on open B-spline edge

Added additional conditions to avoid crash.
Added a test case.
---
 src/BRepFill/BRepFill_OffsetWire.cxx |  8 ++++----
 tests/bugs/modalg_8/bug33146         | 10 ++++++++++
 2 files changed, 14 insertions(+), 4 deletions(-)
 create mode 100644 tests/bugs/modalg_8/bug33146

diff --git a/src/BRepFill/BRepFill_OffsetWire.cxx b/src/BRepFill/BRepFill_OffsetWire.cxx
index befe34193c..ee611c1f09 100644
--- a/src/BRepFill/BRepFill_OffsetWire.cxx
+++ b/src/BRepFill/BRepFill_OffsetWire.cxx
@@ -926,7 +926,7 @@ void BRepFill_OffsetWire::PerformWithBiLo
     if (StartOnEdge) {
       Standard_Boolean Start = 1;
       Trim.AddOrConfuse(Start, E[0], E[1], Params);
-      if (Params.Length() == Vertices.Length()) 
+      if (Params.Length() == Vertices.Length() && Params.Length() != 0)
         Vertices.SetValue(1,VS);
       
       else
@@ -936,7 +936,7 @@ void BRepFill_OffsetWire::PerformWithBiLo
     if (EndOnEdge) {	  
       Standard_Boolean Start = 0;
       Trim.AddOrConfuse(Start, E[0], E[1], Params);
-      if (Params.Length() == Vertices.Length()) 
+      if (Params.Length() == Vertices.Length() && Params.Length() != 0)
         Vertices.SetValue(Params.Length(),VE);
       
       else
@@ -962,7 +962,7 @@ void BRepFill_OffsetWire::PerformWithBiLo
     // Storage of vertices on parallel edges.
     // fill MapBis and MapVerPar.
     //----------------------------------------------
-    if (!Vertices.IsEmpty()) {
+    if (!Vertices.IsEmpty() && Params.Length() == Vertices.Length()) {
       for (k = 0; k <= 1; k++) {
         if (!MapBis.IsBound(E[k])) {
           MapBis   .Bind(E[k],EmptySeq);
@@ -1298,7 +1298,7 @@ void BRepFill_OffsetWire::UpdateDetromp (BRepFill_DataMapOfOrientedShapeListOfSh
       ii++; 
     }
     
-    while (ii <= Vertices.Length()) {
+    while (ii <= Vertices.Length() && ii <= Params.Length()) {
       U2 = Params.Value(ii).X();
       V2 = TopoDS::Vertex(Vertices.Value(ii));
       
diff --git a/tests/bugs/modalg_8/bug33146 b/tests/bugs/modalg_8/bug33146
new file mode 100644
index 0000000000..2c5bca48ee
--- /dev/null
+++ b/tests/bugs/modalg_8/bug33146
@@ -0,0 +1,10 @@
+puts "==============================================================="
+puts "0033146: Modeling Algorithms - 2D Offset with arc-lin approximation fails on open B-spline edge"
+puts "==============================================================="
+puts ""
+
+pload MODELING
+restore [locate_data_file bug33146.brep] a
+wire a a
+openoffset result a 1 1. -approx
+checkview -display result_1 -2d -path ${imagedir}/${test_image}.png