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avoid exception in Mesh_Algorithm.Hypothesis() for mesh w/o shape
[modules/smesh.git] / src / SMESH_SWIG / smeshDC.py
index 6958a9e22581fcc6b37c3fc6421f9dc7f76fed45..d35246229f5a31f9f29772dedf7bffb73d10ebdc 100644 (file)
@@ -794,7 +794,9 @@ class smeshDC(SMESH._objref_SMESH_Gen):
                 return None
             pass
         elif CritType in [FT_FreeBorders, FT_FreeEdges, FT_BadOrientedVolume, FT_FreeNodes,
-                          FT_FreeFaces, FT_LinearOrQuadratic]:
+                          FT_FreeFaces, FT_LinearOrQuadratic,
+                          FT_BareBorderFace, FT_BareBorderVolume,
+                          FT_OverConstrainedFace, FT_OverConstrainedVolume]:
             # At this point the treshold is unnecessary
             if aTreshold ==  FT_LogicalNOT:
                 aCriterion.UnaryOp = self.EnumToLong(FT_LogicalNOT)
@@ -903,6 +905,110 @@ class smeshDC(SMESH._objref_SMESH_Gen):
             pass
         return d
 
+    ## Get minimum distance between two objects
+    #
+    #  If @a src2 is None, and @a id2 = 0, distance from @a src1 / @a id1 to the origin is computed.
+    #  If @a src2 is None, and @a id2 != 0, it is assumed that both @a id1 and @a id2 belong to @a src1.
+    #
+    #  @param src1 first source object 
+    #  @param src2 second source object
+    #  @param id1 node/element id from the first source
+    #  @param id2 node/element id from the second (or first) source
+    #  @param isElem1 @c True if @a id1 is element id, @c False if it is node id
+    #  @param isElem2 @c True if @a id2 is element id, @c False if it is node id
+    #  @return minimum distance value
+    #  @sa GetMinDistance()
+    #  @ingroup l1_measurements
+    def MinDistance(self, src1, src2=None, id1=0, id2=0, isElem1=False, isElem2=False):
+        result = self.GetMinDistance(src1, src2, id1, id2, isElem1, isElem2)
+        if result is None:
+            result = 0.0
+        else:
+            result = result.value
+        return result
+    
+    ## Get measure structure specifying minimum distance data between two objects
+    #
+    #  If @a src2 is None, and @a id2 = 0, distance from @a src1 / @a id1 to the origin is computed.
+    #  If @a src2 is None, and @a id2 != 0, it is assumed that both @a id1 and @a id2 belong to @a src1.
+    #
+    #  @param src1 first source object 
+    #  @param src2 second source object
+    #  @param id1 node/element id from the first source
+    #  @param id2 node/element id from the second (or first) source
+    #  @param isElem1 @c True if @a id1 is element id, @c False if it is node id
+    #  @param isElem2 @c True if @a id2 is element id, @c False if it is node id
+    #  @return Measure structure or None if input data is invalid
+    #  @sa MinDistance()
+    #  @ingroup l1_measurements
+    def GetMinDistance(self, src1, src2=None, id1=0, id2=0, isElem1=False, isElem2=False):
+        if isinstance(src1, Mesh): src1 = src1.mesh
+        if isinstance(src2, Mesh): src2 = src2.mesh
+        if src2 is None and id2 != 0: src2 = src1
+        if not hasattr(src1, "_narrow"): return None
+        src1 = src1._narrow(SMESH.SMESH_IDSource)
+        if not src1: return None
+        if id1 != 0:
+            m = src1.GetMesh()
+            e = m.GetMeshEditor()
+            if isElem1:
+                src1 = e.MakeIDSource([id1], SMESH.FACE)
+            else:
+                src1 = e.MakeIDSource([id1], SMESH.NODE)
+            pass
+        if hasattr(src2, "_narrow"):
+            src2 = src2._narrow(SMESH.SMESH_IDSource)
+            if src2 and id2 != 0:
+                m = src2.GetMesh()
+                e = m.GetMeshEditor()
+                if isElem2:
+                    src2 = e.MakeIDSource([id2], SMESH.FACE)
+                else:
+                    src2 = e.MakeIDSource([id2], SMESH.NODE)
+                pass
+            pass
+        aMeasurements = self.CreateMeasurements()
+        result = aMeasurements.MinDistance(src1, src2)
+        aMeasurements.Destroy()
+        return result
+    
+    ## Get bounding box of the specified object(s)
+    #  @param objects single source object or list of source objects
+    #  @return tuple of six values (minX, minY, minZ, maxX, maxY, maxZ)
+    #  @sa GetBoundingBox()
+    #  @ingroup l1_measurements
+    def BoundingBox(self, objects):
+        result = self.GetBoundingBox(objects)
+        if result is None:
+            result = (0.0,)*6
+        else:
+            result = (result.minX, result.minY, result.minZ, result.maxX, result.maxY, result.maxZ)
+        return result
+
+    ## Get measure structure specifying bounding box data of the specified object(s)
+    #  @param objects single source object or list of source objects
+    #  @return Measure structure
+    #  @sa BoundingBox()
+    #  @ingroup l1_measurements
+    def GetBoundingBox(self, objects):
+        if isinstance(objects, tuple):
+            objects = list(objects)
+        if not isinstance(objects, list):
+            objects = [objects]
+        srclist = []
+        for o in objects:
+            if isinstance(o, Mesh):
+                srclist.append(o.mesh)
+            elif hasattr(o, "_narrow"):
+                src = o._narrow(SMESH.SMESH_IDSource)
+                if src: srclist.append(src)
+                pass
+            pass
+        aMeasurements = self.CreateMeasurements()
+        result = aMeasurements.BoundingBox(srclist)
+        aMeasurements.Destroy()
+        return result
+
 import omniORB
 #Registering the new proxy for SMESH_Gen
 omniORB.registerObjref(SMESH._objref_SMESH_Gen._NP_RepositoryId, smeshDC)
@@ -1068,6 +1174,24 @@ class Mesh:
         else:
             return Mesh_Segment(self, geom)
 
+    ## Creates 1D algorithm importing segments conatined in groups of other mesh.
+    #  If the optional \a geom parameter is not set, this algorithm is global.
+    #  Otherwise, this algorithm defines a submesh based on \a geom subshape.
+    #  @param geom If defined the subshape is to be meshed
+    #  @return an instance of Mesh_UseExistingElements class
+    #  @ingroup l3_algos_basic
+    def UseExisting1DElements(self, geom=0):
+        return Mesh_UseExistingElements(1,self, geom)
+
+    ## Creates 2D algorithm importing faces conatined in groups of other mesh.
+    #  If the optional \a geom parameter is not set, this algorithm is global.
+    #  Otherwise, this algorithm defines a submesh based on \a geom subshape.
+    #  @param geom If defined the subshape is to be meshed
+    #  @return an instance of Mesh_UseExistingElements class
+    #  @ingroup l3_algos_basic
+    def UseExisting2DElements(self, geom=0):
+        return Mesh_UseExistingElements(2,self, geom)
+
     ## Enables creation of nodes and segments usable by 2D algoritms.
     #  The added nodes and segments must be bound to edges and vertices by
     #  SetNodeOnVertex(), SetNodeOnEdge() and SetMeshElementOnShape()
@@ -1199,7 +1323,9 @@ class Mesh:
         return Mesh_RadialPrism3D(self,  geom)
 
     ## Evaluates size of prospective mesh on a shape
-    #  @return True or False
+    #  @return a list where i-th element is a number of elements of i-th SMESH.EntityType
+    #  To know predicted number of e.g. edges, inquire it this way
+    #  Evaluate()[ EnumToLong( Entity_Edge )]
     def Evaluate(self, geom=0):
         if geom == 0 or not isinstance(geom, geompyDC.GEOM._objref_GEOM_Object):
             if self.geom == 0:
@@ -2195,57 +2321,90 @@ class Mesh:
     # Get mesh measurements information:
     # ------------------------------------
 
-    def MinDistance(self, id1, id2, isElem1=False, isElem2=False):
+    ## Get minimum distance between two nodes, elements or distance to the origin
+    #  @param id1 first node/element id
+    #  @param id2 second node/element id (if 0, distance from @a id1 to the origin is computed)
+    #  @param isElem1 @c True if @a id1 is element id, @c False if it is node id
+    #  @param isElem2 @c True if @a id2 is element id, @c False if it is node id
+    #  @return minimum distance value
+    #  @sa GetMinDistance()
+    def MinDistance(self, id1, id2=0, isElem1=False, isElem2=False):
         aMeasure = self.GetMinDistance(id1, id2, isElem1, isElem2)
         return aMeasure.value
     
-    #  @param node1, node2 is nodes to measure distance
+    ## Get measure structure specifying minimum distance data between two objects
+    #  @param id1 first node/element id
+    #  @param id2 second node/element id (if 0, distance from @a id1 to the origin is computed)
+    #  @param isElem1 @c True if @a id1 is element id, @c False if it is node id
+    #  @param isElem2 @c True if @a id2 is element id, @c False if it is node id
     #  @return Measure structure
-    def GetMinDistance(self, id1, id2, isElem1=False, isElem2=False):
-        if isinstance( id1, int):
-            if (isElem1):
-                id1 = self.editor.MakeIDSource([id1], SMESH.FACE)
-            else:
-                id1 = self.editor.MakeIDSource([id1], SMESH.NODE)
-        if isinstance( id2, int):
-            if (isElem2):
+    #  @sa MinDistance()
+    def GetMinDistance(self, id1, id2=0, isElem1=False, isElem2=False):
+        if isElem1:
+            id1 = self.editor.MakeIDSource([id1], SMESH.FACE)
+        else:
+            id1 = self.editor.MakeIDSource([id1], SMESH.NODE)
+        if id2 != 0:
+            if isElem2:
                 id2 = self.editor.MakeIDSource([id2], SMESH.FACE)
             else:
                 id2 = self.editor.MakeIDSource([id2], SMESH.NODE)
+            pass
+        else:
+            id2 = None
         
         aMeasurements = self.smeshpyD.CreateMeasurements()
         aMeasure = aMeasurements.MinDistance(id1, id2)
         aMeasurements.Destroy()
         return aMeasure
     
-    #  @param IDsOfElements is a list of ids of elements or nodes
+    ## Get bounding box of the specified object(s)
+    #  @param objects single source object or list of source objects or list of nodes/elements IDs
+    #  @param isElem if @a objects is a list of IDs, @c True value in this parameters specifies that @a objects are elements,
+    #  @c False specifies that @a objects are nodes
+    #  @return tuple of six values (minX, minY, minZ, maxX, maxY, maxZ)
+    #  @sa GetBoundingBox()
+    def BoundingBox(self, objects=None, isElem=False):
+        result = self.GetBoundingBox(objects, isElem)
+        if result is None:
+            result = (0.0,)*6
+        else:
+            result = (result.minX, result.minY, result.minZ, result.maxX, result.maxY, result.maxZ)
+        return result
+
+    ## Get measure structure specifying bounding box data of the specified object(s)
+    #  @param objects single source object or list of source objects or list of nodes/elements IDs
+    #  @param isElem if @a objects is a list of IDs, @c True value in this parameters specifies that @a objects are elements,
+    #  @c False specifies that @a objects are nodes
     #  @return Measure structure
-    def GetBoundingBox(self, IDs = None, isElem=True):
-        if isinstance( IDs, Mesh ):
-            IDs = [ IDs.mesh ]
-        elif (IDs == None):
-            IDs = [ self.mesh ]
-        elif isinstance( IDs, int):
-            if (isElem):
-                IDs = [ self.editor.MakeIDSource(IDs, SMESH.FACE) ]
-            else:
-                IDs = [ self.editor.MakeIDSource(IDs, SMESH.NODE) ]
-        elif isinstance( IDs, list ) and isinstance( IDs[0], int):
-            if (isElem):
-                IDs = [ self.editor.MakeIDSource(IDs, SMESH.FACE) ]
-            else:
-                IDs = [ self.editor.MakeIDSource(IDs, SMESH.NODE) ]
-        elif hasattr(IDs, "_narrow"):
-            anIDs = IDs._narrow(SMESH.SMESH_IDSource)
-            if (anIDs):
-                IDs = [ anIDs ]
-                
-        aMeasure = None
-        if isinstance(IDs, list):
-            aMeasurements = self.smeshpyD.CreateMeasurements()
-            aMeasure = aMeasurements.BoundingBox(IDs)
-            aMeasurements.Destroy()
-            
+    #  @sa BoundingBox()
+    def GetBoundingBox(self, IDs=None, isElem=False):
+        if IDs is None:
+            IDs = [self.mesh]
+        elif isinstance(IDs, tuple):
+            IDs = list(IDs)
+        if not isinstance(IDs, list):
+            IDs = [IDs]
+        if len(IDs) > 0 and isinstance(IDs[0], int):
+            IDs = [IDs]
+        srclist = []
+        for o in IDs:
+            if isinstance(o, Mesh):
+                srclist.append(o.mesh)
+            elif hasattr(o, "_narrow"):
+                src = o._narrow(SMESH.SMESH_IDSource)
+                if src: srclist.append(src)
+                pass
+            elif isinstance(o, list):
+                if isElem:
+                    srclist.append(self.editor.MakeIDSource(o, SMESH.FACE))
+                else:
+                    srclist.append(self.editor.MakeIDSource(o, SMESH.NODE))
+                pass
+            pass
+        aMeasurements = self.smeshpyD.CreateMeasurements()
+        aMeasure = aMeasurements.BoundingBox(srclist)
+        aMeasurements.Destroy()
         return aMeasure
     
     # Mesh edition (SMESH_MeshEditor functionality):
@@ -3010,7 +3169,7 @@ class Mesh:
 
     ## Generates new elements by extrusion of the elements with given ids
     #  @param IDsOfElements the list of elements ids for extrusion
-    #  @param StepVector vector, defining the direction and value of extrusion
+    #  @param StepVector vector or DirStruct, defining the direction and value of extrusion
     #  @param NbOfSteps the number of steps
     #  @param MakeGroups forces the generation of new groups from existing ones
     #  @return the list of created groups (SMESH_GroupBase) if MakeGroups=True, empty list otherwise
@@ -4125,8 +4284,11 @@ class Mesh_Algorithm:
                 pass
             self.mesh.smeshpyD.SetName(hypo, hyp + a)
             pass
+        geomName=""
+        if self.geom:
+            geomName = GetName(self.geom)
         status = self.mesh.mesh.AddHypothesis(self.geom, hypo)
-        TreatHypoStatus( status, GetName(hypo), GetName(self.geom), 0 )
+        TreatHypoStatus( status, GetName(hypo), geomName, 0 )
         return hypo
 
     ## Returns entry of the shape to mesh in the study
@@ -4664,20 +4826,31 @@ class Mesh_Triangle(Mesh_Algorithm):
         self.Parameters().SetOptionValue(optionName,level)
 
     ## Sets QuadAllowed flag.
-    #  Only for algoType == NETGEN || NETGEN_2D || BLSURF
+    #  Only for algoType == NETGEN(NETGEN_1D2D) || NETGEN_2D || BLSURF
     #  @ingroup l3_hypos_netgen l3_hypos_blsurf
     def SetQuadAllowed(self, toAllow=True):
         if self.algoType == NETGEN_2D:
-            if toAllow: # add QuadranglePreference
-                self.Hypothesis("QuadranglePreference", UseExisting=1, CompareMethod=self.CompareEqualHyp)
-            else:       # remove QuadranglePreference
+            if not self.params:
+                # use simple hyps
+                hasSimpleHyps = False
+                simpleHyps = ["QuadranglePreference","LengthFromEdges","MaxElementArea"]
                 for hyp in self.mesh.GetHypothesisList( self.geom ):
-                    if hyp.GetName() == "QuadranglePreference":
-                        self.mesh.RemoveHypothesis( self.geom, hyp )
+                    if hyp.GetName() in simpleHyps:
+                        hasSimpleHyps = True
+                        if hyp.GetName() == "QuadranglePreference":
+                            if not toAllow: # remove QuadranglePreference
+                                self.mesh.RemoveHypothesis( self.geom, hyp )
+                                pass
+                            return
                         pass
                     pass
+                if hasSimpleHyps:
+                    if toAllow: # add QuadranglePreference
+                        self.Hypothesis("QuadranglePreference", UseExisting=1, CompareMethod=self.CompareEqualHyp)
+                        pass
+                    return
                 pass
-            return
+            pass
         if self.Parameters():
             self.params.SetQuadAllowed(toAllow)
             return
@@ -4686,30 +4859,25 @@ class Mesh_Triangle(Mesh_Algorithm):
     #
     #  @ingroup l3_hypos_netgen
     def Parameters(self, which=SOLE):
-        if self.params:
-            return self.params
-        if self.algoType == NETGEN:
-            if which == SIMPLE:
-                self.params = self.Hypothesis("NETGEN_SimpleParameters_2D", [],
+        if not self.params:
+            if self.algoType == NETGEN:
+                if which == SIMPLE:
+                    self.params = self.Hypothesis("NETGEN_SimpleParameters_2D", [],
+                                                  "libNETGENEngine.so", UseExisting=0)
+                else:
+                    self.params = self.Hypothesis("NETGEN_Parameters_2D", [],
+                                                  "libNETGENEngine.so", UseExisting=0)
+            elif self.algoType == MEFISTO:
+                print "Mefisto algo support no multi-parameter hypothesis"
+            elif self.algoType == NETGEN_2D:
+                self.params = self.Hypothesis("NETGEN_Parameters_2D_ONLY", [],
                                               "libNETGENEngine.so", UseExisting=0)
+            elif self.algoType == BLSURF:
+                self.params = self.Hypothesis("BLSURF_Parameters", [],
+                                              "libBLSURFEngine.so", UseExisting=0)
             else:
-                self.params = self.Hypothesis("NETGEN_Parameters_2D", [],
-                                              "libNETGENEngine.so", UseExisting=0)
-            return self.params
-        elif self.algoType == MEFISTO:
-            print "Mefisto algo support no multi-parameter hypothesis"
-            return None
-        elif self.algoType == NETGEN_2D:
-            print "NETGEN_2D_ONLY algo support no multi-parameter hypothesis"
-            print "NETGEN_2D_ONLY uses 'MaxElementArea' and 'LengthFromEdges' ones"
-            return None
-        elif self.algoType == BLSURF:
-            self.params = self.Hypothesis("BLSURF_Parameters", [],
-                                          "libBLSURFEngine.so", UseExisting=0)
-            return self.params
-        else:
-            print "Mesh_Triangle with algo type %s does not have such a parameter, check algo type"%self.algoType
-        return None
+                print "Mesh_Triangle with algo type %s does not have such a parameter, check algo type"%self.algoType
+        return self.params
 
     ## Sets MaxSize
     #
@@ -4898,33 +5066,34 @@ class Mesh_Tetrahedron(Mesh_Algorithm):
     #
     #  @ingroup l3_hypos_netgen
     def Parameters(self, which=SOLE):
-        if self.params:
-            return self.params
+        if not self.params:
 
-        if self.algoType == FULL_NETGEN:
-            if which == SIMPLE:
-                self.params = self.Hypothesis("NETGEN_SimpleParameters_3D", [],
-                                              "libNETGENEngine.so", UseExisting=0)
-            else:
-                self.params = self.Hypothesis("NETGEN_Parameters", [],
+            if self.algoType == FULL_NETGEN:
+                if which == SIMPLE:
+                    self.params = self.Hypothesis("NETGEN_SimpleParameters_3D", [],
+                                                  "libNETGENEngine.so", UseExisting=0)
+                else:
+                    self.params = self.Hypothesis("NETGEN_Parameters", [],
+                                                  "libNETGENEngine.so", UseExisting=0)
+
+            if self.algoType == NETGEN:
+                self.params = self.Hypothesis("NETGEN_Parameters_3D", [],
                                               "libNETGENEngine.so", UseExisting=0)
-            return self.params
 
-        if self.algoType == GHS3D:
-            self.params = self.Hypothesis("GHS3D_Parameters", [],
-                                          "libGHS3DEngine.so", UseExisting=0)
-            return self.params
+            elif self.algoType == GHS3D:
+                self.params = self.Hypothesis("GHS3D_Parameters", [],
+                                              "libGHS3DEngine.so", UseExisting=0)
 
-        if self.algoType == GHS3DPRL:
-            self.params = self.Hypothesis("GHS3DPRL_Parameters", [],
-                                          "libGHS3DPRLEngine.so", UseExisting=0)
-            return self.params
+            elif self.algoType == GHS3DPRL:
+                self.params = self.Hypothesis("GHS3DPRL_Parameters", [],
+                                              "libGHS3DPRLEngine.so", UseExisting=0)
+            else:
+                print "Algo supports no multi-parameter hypothesis"
 
-        print "Algo supports no multi-parameter hypothesis"
-        return None
+        return self.params
 
     ## Sets MaxSize
-    #  Parameter of FULL_NETGEN
+    #  Parameter of FULL_NETGEN and NETGEN
     #  @ingroup l3_hypos_netgen
     def SetMaxSize(self, theSize):
         self.Parameters().SetMaxSize(theSize)
@@ -4936,7 +5105,7 @@ class Mesh_Tetrahedron(Mesh_Algorithm):
         self.Parameters().SetSecondOrder(theVal)
 
     ## Sets Optimize flag
-    #  Parameter of FULL_NETGEN
+    #  Parameter of FULL_NETGEN and NETGEN
     #  @ingroup l3_hypos_netgen
     def SetOptimize(self, theVal):
         self.Parameters().SetOptimize(theVal)
@@ -5512,6 +5681,73 @@ class Mesh_RadialQuadrangle1D2D(Mesh_Algorithm):
         return hyp
 
 
+# Public class: Mesh_UseExistingElements
+# --------------------------------------
+## Defines a Radial Quadrangle 1D2D algorithm
+#  @ingroup l3_algos_basic
+#
+class Mesh_UseExistingElements(Mesh_Algorithm):
+
+    def __init__(self, dim, mesh, geom=0):
+        if dim == 1:
+            self.Create(mesh, geom, "Import_1D")
+        else:
+            self.Create(mesh, geom, "Import_1D2D")
+        return
+
+    ## Defines "Source edges" hypothesis, specifying groups of edges to import
+    #  @param groups list of groups of edges
+    #  @param toCopyMesh if True, the whole mesh \a groups belong to is imported
+    #  @param toCopyGroups if True, all groups of the mesh \a groups belong to are imported
+    #  @param UseExisting if ==true - searches for the existing hypothesis created with
+    #                     the same parameters, else (default) - creates a new one
+    def SourceEdges(self, groups, toCopyMesh=False, toCopyGroups=False, UseExisting=False):
+        if self.algo.GetName() == "Import_2D":
+            raise ValueError, "algoritm dimension mismatch"
+        hyp = self.Hypothesis("ImportSource1D", [groups, toCopyMesh, toCopyGroups],
+                              UseExisting=UseExisting, CompareMethod=self._compareHyp)
+        hyp.SetSourceEdges(groups)
+        hyp.SetCopySourceMesh(toCopyMesh, toCopyGroups)
+        return hyp
+
+    ## Defines "Source faces" hypothesis, specifying groups of faces to import
+    #  @param groups list of groups of faces
+    #  @param toCopyMesh if True, the whole mesh \a groups belong to is imported
+    #  @param toCopyGroups if True, all groups of the mesh \a groups belong to are imported
+    #  @param UseExisting if ==true - searches for the existing hypothesis created with
+    #                     the same parameters, else (default) - creates a new one
+    def SourceFaces(self, groups, toCopyMesh=False, toCopyGroups=False, UseExisting=False):
+        if self.algo.GetName() == "Import_1D":
+            raise ValueError, "algoritm dimension mismatch"
+        hyp = self.Hypothesis("ImportSource2D", [groups, toCopyMesh, toCopyGroups],
+                              UseExisting=UseExisting, CompareMethod=self._compareHyp)
+        hyp.SetSourceFaces(groups)
+        hyp.SetCopySourceMesh(toCopyMesh, toCopyGroups)
+        return hyp
+
+    def _compareHyp(self,hyp,args):
+        if hasattr( hyp, "GetSourceEdges"):
+            entries = hyp.GetSourceEdges()
+        else:
+            entries = hyp.GetSourceFaces()
+        groups = args[0]
+        toCopyMesh,toCopyGroups = hyp.GetCopySourceMesh()
+        if len(entries)==len(groups) and toCopyMesh==args[1] and toCopyGroups==args[2]:
+            entries2 = []
+            study = self.mesh.smeshpyD.GetCurrentStudy()
+            if study:
+                for g in groups:
+                    ior  = salome.orb.object_to_string(g)
+                    sobj = study.FindObjectIOR(ior)
+                    if sobj: entries2.append( sobj.GetID() )
+                    pass
+                pass
+            entries.sort()
+            entries2.sort()
+            return entries == entries2
+        return False
+
+
 # Private class: Mesh_UseExisting
 # -------------------------------
 class Mesh_UseExisting(Mesh_Algorithm):