From 416022a12ff2315850442a0244f59d61888e17e0 Mon Sep 17 00:00:00 2001
From: emv <emv@opencascade.com>
Date: Wed, 27 Apr 2016 16:28:52 +0300
Subject: [PATCH] 0027441: The method IntTools_Context::IsVertexOnLine
 incorrectly computes parameter of the point on the curve

Choosing the closest bound to the checking point.
---
 src/IntTools/IntTools_Context.cxx | 23 ++++++++++++++++-------
 tests/bugs/modalg_6/bug27441      | 16 ++++++++++++++++
 2 files changed, 32 insertions(+), 7 deletions(-)
 create mode 100644 tests/bugs/modalg_6/bug27441

diff --git a/src/IntTools/IntTools_Context.cxx b/src/IntTools/IntTools_Context.cxx
index 66e66cb1b1..03250f8336 100644
--- a/src/IntTools/IntTools_Context.cxx
+++ b/src/IntTools/IntTools_Context.cxx
@@ -840,14 +840,19 @@ Standard_Boolean IntTools_Context::IsVertexOnLine
   aFirst=aC3D->FirstParameter();
   aLast =aC3D->LastParameter();
   //
-  //Checking extermities first
+  // Checking extermities first
+  // It is necessary to chose the closest bound to the point
+  Standard_Boolean bFirstValid = Standard_False;
+  Standard_Real aFirstDist = Precision::Infinite();
+  //
   if (!Precision::IsInfinite(aFirst)) {
     gp_Pnt aPCFirst=aC3D->Value(aFirst);
-    aDist=aPv.Distance(aPCFirst);
-    if (aDist < aTolSum) {
+    aFirstDist = aPv.Distance(aPCFirst);
+    if (aFirstDist < aTolSum) {
+      bFirstValid = Standard_True;
       aT=aFirst;
       //
-      if(aDist > aTolV) {
+      if (aFirstDist > aTolV) {
         Extrema_LocateExtPC anExt(aPv, aGAC, aFirst, 1.e-10);
         
         if(anExt.IsDone()) {
@@ -889,15 +894,16 @@ Standard_Boolean IntTools_Context::IsVertexOnLine
         }
 
       }
-      //
-      return Standard_True;
     }
   }
   //
-  //if (!Precision::IsInfinite(aFirst)) {
   if (!Precision::IsInfinite(aLast)) {
     gp_Pnt aPCLast=aC3D->Value(aLast);
     aDist=aPv.Distance(aPCLast);
+    if (bFirstValid && (aFirstDist < aDist)) {
+      return Standard_True;
+    }
+    //
     if (aDist < aTolSum) {
       aT=aLast;
       //
@@ -946,6 +952,9 @@ Standard_Boolean IntTools_Context::IsVertexOnLine
       return Standard_True;
     }
   }
+  else if (bFirstValid) {
+    return Standard_True;
+  }
   //
   GeomAPI_ProjectPointOnCurve& aProjector=ProjPT(aC3D);
   aProjector.Perform(aPv);
diff --git a/tests/bugs/modalg_6/bug27441 b/tests/bugs/modalg_6/bug27441
new file mode 100644
index 0000000000..1489df5d68
--- /dev/null
+++ b/tests/bugs/modalg_6/bug27441
@@ -0,0 +1,16 @@
+puts "============"
+puts "OCC27441"
+puts "============"
+puts ""
+###############################
+## The method IntTools_ContextIsVertexOnLine incorrectly computes parameter of the point on the curve
+###############################
+
+restore [locate_data_file bug27428_shapes.brep] b
+explode b
+bsection result b_1 b_2
+set bcheck [bopcheck result]
+puts $bcheck
+if {![regexp {This shape seems to be OK.} $bcheck]} {
+    puts "Error: bopcheck failed"
+}
-- 
2.20.1