From b55bd02353519ebba14575f8056bb2b14585089e Mon Sep 17 00:00:00 2001
From: nbv <nbv@opencascade.com>
Date: Mon, 11 Apr 2016 10:38:50 +0300
Subject: [PATCH] 0027269: Intersection algorithm produces null-length curve

Restriction line can correspond to a degenerated edge. In this case we shall return null-curve (instead of Null-length curve).
---
 src/GeomInt/GeomInt_IntSS_1.cxx | 37 +++++++++++++++++++++++++++++++++
 tests/bugs/modalg_6/bug27269    | 36 ++++++++++++++++++++++++++++++++
 tests/bugs/modalg_6/bug27325    |  2 +-
 3 files changed, 74 insertions(+), 1 deletion(-)
 create mode 100644 tests/bugs/modalg_6/bug27269

diff --git a/src/GeomInt/GeomInt_IntSS_1.cxx b/src/GeomInt/GeomInt_IntSS_1.cxx
index 1a3f583084..f95970b1c9 100644
--- a/src/GeomInt/GeomInt_IntSS_1.cxx
+++ b/src/GeomInt/GeomInt_IntSS_1.cxx
@@ -224,6 +224,37 @@ static void IntersectCurveAndBoundary(const Handle(Geom2d_Curve)& theC2d,
   }
 }
 
+//=======================================================================
+//function : isDegenerated
+//purpose  : Check if theAHC2d corresponds to a degenerated edge.
+//=======================================================================
+static Standard_Boolean isDegenerated(const Handle(GeomAdaptor_HSurface)& theGAHS,
+                                      const Handle(Adaptor2d_HCurve2d)& theAHC2d,
+                                      const Standard_Real theFirstPar,
+                                      const Standard_Real theLastPar)
+{
+  const Standard_Real aSqTol = Precision::Confusion()*Precision::Confusion();
+  gp_Pnt2d aP2d;
+  gp_Pnt aP1, aP2;
+
+  theAHC2d->D0(theFirstPar, aP2d);
+  theGAHS->D0(aP2d.X(), aP2d.Y(), aP1);
+
+  theAHC2d->D0(theLastPar, aP2d);
+  theGAHS->D0(aP2d.X(), aP2d.Y(), aP2);
+
+  if(aP1.SquareDistance(aP2) > aSqTol)
+    return Standard_False;
+
+  theAHC2d->D0(0.5*(theFirstPar+theLastPar), aP2d);
+  theGAHS->D0(aP2d.X(), aP2d.Y(), aP2);
+
+  if(aP1.SquareDistance(aP2) > aSqTol)
+    return Standard_False;
+
+  return Standard_True;
+}
+
 //=======================================================================
 //function : MakeCurve
 //purpose  : 
@@ -1117,6 +1148,12 @@ void GeomInt_IntSS::TreatRLine(const Handle(IntPatch_RLine)& theRL,
   {
     return;
   }
+
+  //Restriction line can correspond to a degenerated edge.
+  //In this case we return null-curve.
+  if(isDegenerated(aGAHS, anAHC2d, tf, tl))
+    return;
+
   //
   //To provide sameparameter it is necessary to get 3d curve as
   //approximation of curve on surface.
diff --git a/tests/bugs/modalg_6/bug27269 b/tests/bugs/modalg_6/bug27269
new file mode 100644
index 0000000000..b8a5e200c9
--- /dev/null
+++ b/tests/bugs/modalg_6/bug27269
@@ -0,0 +1,36 @@
+puts "============"
+puts "OCC27269"
+puts "============"
+puts ""
+###############################
+## Intersection algorithm produces null-length curve
+###############################
+
+
+restore [locate_data_file bug27267_cmpd.brep] a
+explode a f
+
+#############################
+set log [bopcurves a_1 a_7 -2d]
+#############################
+
+regexp {Tolerance Reached=+([-0-9.+eE]+)\n+([-0-9.+eE]+)} ${log} full Toler NbCurv
+
+for {set i 1} {$i <= ${NbCurv}} {incr i} {
+  bounds c_$i U1 U2
+  
+  dump U1 U2
+  
+  if {[dval U2-U1] < 1.0e-20} {
+    puts "Error: Wrong curve's range!"
+  }
+  
+  set le [length c_$i]
+  regexp "The length c_$i is +(\[-0-9.+eE\]+)" ${le} full ll
+  
+  if { $ll < 1.0e-7 } {
+    puts "Error: Curve c_$i is too small!"
+  }
+}
+
+
diff --git a/tests/bugs/modalg_6/bug27325 b/tests/bugs/modalg_6/bug27325
index 2c3f19e399..e0ec80c88e 100644
--- a/tests/bugs/modalg_6/bug27325
+++ b/tests/bugs/modalg_6/bug27325
@@ -1,4 +1,4 @@
-   puts "============"
+puts "============"
 puts "OCC27325"
 puts "============"
 puts ""
-- 
2.20.1