Part: ArcOfParabola extension to set the symmetry axis

src/Mod/Part/App/Geometry.cpp

@@ -2322,6 +2322,49 @@ void GeomArcOfParabola::setFocal(double length)
     }
 }
 
+/*!
+ * \brief GeomArcOfParabola::getXAxisDir
+ * \return the direction vector (unit-length) of symmetry axis of the parabola. The
+ * direction also points to the focus.
+ */
+Base::Vector3d GeomArcOfParabola::getXAxisDir() const
+{
+    Handle_Geom_Parabola c = Handle_Geom_Parabola::DownCast( myCurve->BasisCurve() );
+    assert(!c.IsNull());
+    gp_Dir xdir = c->XAxis().Direction();
+    return Base::Vector3d(xdir.X(), xdir.Y(), xdir.Z());
+}
+
+/*!
+ * \brief GeomArcOfParabola::setXAxisDir Rotates the parabola in its plane, so
+ * that its symmetry axis is as close as possible to the provided direction.
+ * \param newdir [in] is the new direction. If the vector is small, the
+ * orientation of the parabola will be preserved. If the vector is not small,
+ * but its projection onto plane of the parabola is small, an exception will be
+ * thrown.
+ */
+void GeomArcOfParabola::setXAxisDir(Base::Vector3d newdir)
+{
+    Handle_Geom_Parabola c = Handle_Geom_Parabola::DownCast( myCurve->BasisCurve() );
+    assert(!c.IsNull());
+    #if OCC_VERSION_HEX >= 0x060504
+    if (newdir.Sqr() < Precision::SquareConfusion())
+    #else
+    if (newdir.Length() < Precision::Confusion())
+    #endif
+        return;//zero vector was passed. Keep the old orientation.
+    
+    try {
+        gp_Ax2 pos = c->Position();
+        pos.SetXDirection(gp_Dir(newdir.x, newdir.y, newdir.z));//OCC should keep the old main Direction (Z), and change YDirection to accomodate the new XDirection.
+        c->SetPosition(pos);
+    }
+    catch (Standard_Failure) {
+        Handle_Standard_Failure e = Standard_Failure::Caught();
+        throw Base::Exception(e->GetMessageString());
+    }
+}
+
 Base::Vector3d GeomArcOfParabola::getFocus(void) const
 {
     Handle_Geom_Parabola p = Handle_Geom_Parabola::DownCast(myCurve->BasisCurve());

src/Mod/Part/App/Geometry.h

@@ -497,6 +497,9 @@ public:
     double getFocal(void) const;
     void setFocal(double length);
     
+    Base::Vector3d getXAxisDir() const;
+    void setXAxisDir(Base::Vector3d newdir);
+    
     Base::Vector3d getFocus(void) const;
     
     virtual void getRange(double& u, double& v, bool emulateCCWXY) const;