0024303: Precision degradation for Geom2dGcc_Circ2d2TanRad in OCCT6.6.0.

1. DRAW-command.
2. Initial point (the center of found circle), which is found by standard algorithm, is precised in function PrecRoot(...). Correction is called, if and only if initial point is in tangent zone.
3. Handling of possible divergences and of possible exceptions in PrecRoot() function is added.

Test cases for issue CR24303

src/QABugs/QABugs_9.cxx

@@ -148,12 +148,85 @@ static Standard_Integer OCC137_z (Draw_Interpretor& di, Standard_Integer argc, c
   return 0;
 }
 
+#include <GccEnt_Position.hxx>
+#include <Geom2dGcc_QualifiedCurve.hxx>
+#include <Geom2dGcc_Circ2d2TanRad.hxx>
+#include <gp_Elips2d.hxx>
+#include <Geom2d_Ellipse.hxx>
+#include <Geom2d_Circle.hxx>
+
+static Standard_Integer OCC24303(Draw_Interpretor& di, Standard_Integer n, const char** a)
+{
+  if(n < 2)
+    return 1;
+
+  const Standard_Integer SolID = Draw::Atoi(a[1]);
+
+  //Ellipses
+  Standard_Real majorRadius = 2.0;
+  Standard_Real minorRadius = 1.0;
+  gp_Pnt2d p0(gp::Origin2d());
+  gp_Pnt2d p1(4.0,0.0);
+
+  gp_Elips2d ellipse1 = gp_Elips2d( gp_Ax2d(p0,gp::DX2d()),majorRadius, minorRadius,true);
+  gp_Elips2d ellipse2 = gp_Elips2d( gp_Ax2d(p1,gp::DX2d()),majorRadius, minorRadius,true);
+
+  Handle_Geom2d_Curve curve1 = new Geom2d_Ellipse(ellipse1);
+  Handle_Geom2d_Curve curve2 = new Geom2d_Ellipse(ellipse2);
+  DrawTrSurf::Set("c1", curve1);
+  DrawTrSurf::Set("c2", curve2);
+  //Expected tangent
+  gp_Pnt2d centre(5.0,0.0);
+  Standard_Real radius = 3.0;
+  gp_Circ2d theorical_tangent = gp_Circ2d(gp_Ax2d(centre,gp::DX2d()),radius);
+
+  //Calculate the tangent with Geom2dGcc_Circ2dTanRan
+
+  const Geom2dAdaptor_Curve  AdaptedCurve1 ( curve1 );
+  const Geom2dAdaptor_Curve  AdaptedCurve2 ( curve2 );
+
+  GccEnt_Position  curveQualif1 = GccEnt_unqualified;
+  GccEnt_Position  curveQualif2 = GccEnt_unqualified;
+
+  const Geom2dGcc_QualifiedCurve qualifiedCurve1 ( AdaptedCurve1, curveQualif1 );
+  const Geom2dGcc_QualifiedCurve qualifiedCurve2 ( AdaptedCurve2, curveQualif2 );
+
+  const Geom2dGcc_Circ2d2TanRad circCalc(qualifiedCurve1,qualifiedCurve2,radius,/*Precision::Approximation()*/ 1.0e-9);
+
+  const Standard_Integer aNbSol = circCalc.NbSolutions();
+  di << "Solutions " << aNbSol << "\n";
+
+  if((SolID < 1) || (SolID > aNbSol))
+  {
+    di << "Wrong SolID value\n";
+    return 1;
+  }
+
+  gp_Circ2d calculated_tangent = circCalc.ThisSolution(SolID);
+
+  char Buf[10];
+  for (Standard_Integer i = 1; i <= aNbSol; i++)
+  {
+    gp_Circ2d ct = circCalc.ThisSolution(i);
+    Handle (Geom2d_Circle) GSol = new Geom2d_Circle(ct);
+    Sprintf(Buf, "Sol%d",i);
+    DrawTrSurf::Set(Buf, GSol);
+  }
+
+  //This distance is different in OC 6.5.4 and OC 6.6.0
+  Standard_Real dist = theorical_tangent.Location().Distance(calculated_tangent.Location());
+  di << "Distance = " << dist << "\n";
+
+  return 0;
+}
+
 void QABugs::Commands_9(Draw_Interpretor& theCommands) {
   const char *group = "QABugs";
 
   theCommands.Add ("BUC60857", "BUC60857", __FILE__, BUC60857, group);
   theCommands.Add("OCC137","OCC137 mode [shape]",__FILE__,OCC137,group);
   theCommands.Add("OCC137_z","OCC137_z [ZDetection_mode]",__FILE__,OCC137_z,group);
+  theCommands.Add("OCC24303", "OCC24303 SolID ",	__FILE__,	OCC24303,group);
 
   return;
 }

tests/bugs/modalg_5/bug24303

@@ -0,0 +1,67 @@
+puts "============"
+puts "OCC24303"
+puts "============"
+puts ""
+###############################
+## Precision degradation for Geom2dGcc_Circ2d2TanRad in OCCT6.6.0.
+###############################
+
+pload QAcommands
+
+set status 0
+
+set info1 [OCC24303 4]
+regexp {Solutions +([-0-9.+eE]+)} ${info1} full Solution
+regexp {Distance += +([-0-9.+eE]+)} ${info1} full Distance
+
+if { [info exists Sol4] } {
+   set info2 [dump Sol4]
+   regexp {Center +:([-0-9.+eE]+), +([-0-9.+eE]+)} ${info2} full CenterX CenterY
+   regexp {XAxis +:([-0-9.+eE]+), +([-0-9.+eE]+)} ${info2} full XAxisX XAxisY
+   regexp {YAxis +:([-0-9.+eE]+), +([-0-9.+eE]+)} ${info2} full YAxisX YAxisY
+   regexp {Radius +:([-0-9.+eE]+)} ${info2} full Radius
+   set good_CenterX 5
+   set good_CenterY 0
+   set good_XAxisX 1
+   set good_XAxisY 0
+   set good_YAxisX 0
+   set good_YAxisY 1
+   set good_Radius 3
+   if { ${CenterX} != ${good_CenterX} } {
+      puts "Faulty : Bad CenterX"
+      set status 1
+   }
+   if { ${CenterY} != ${good_CenterY} } {
+      puts "Faulty : Bad CenterY"
+      set status 1
+   }
+   if { ${XAxisX} != ${good_XAxisX} } {
+      puts "Faulty : Bad XAxisX"
+      set status 1
+   }
+   if { ${XAxisY} != ${good_XAxisY} } {
+      puts "Faulty : Bad XAxisY"
+      set status 1
+   }
+   if { ${YAxisX} != ${good_YAxisX} } {
+      puts "Faulty : Bad YAxisX"
+      set status 1
+   }
+   if { ${YAxisY} != ${good_YAxisY} } {
+      puts "Faulty : Bad YAxisY"
+       set status 1
+  }
+   if { ${Radius} != ${good_Radius} } {
+      puts "Faulty : Bad Radius"
+      set status 1
+   }
+   } else {
+   puts "Faulty : Bad solution"
+   set status 1
+}
+
+if { ${status} != 0 } {
+    puts "Faulty : solution is wrong"
+} else {
+    puts "OK : solution is correct"
+}