If the function returns (LtMeshingCallBacks)NULL, a memory allocation error has occurred, or invalid input has been encountered.

Once a meshing callbacks data structure has been created, the API user can manipulate the callbacks which it represents, and attach the whole thing to a meshing refinement, so that the callbacks can be utilised inside the triangulation code.

/*
 * Copy an existing meshing callbacks
 */
mesh_calls2 = LiMeshingCallBacksCopy(mesh_calls);
data = LiDataCreate();
if ( mesh_calls2 && data )
{
   LiDataSetGenericPtr(data, (LtGenericPtr)mesh_calls2);
   status = 
      LiMeshingRefinementSetCriterion(meshref,
                                      LI_MESH_CRIT_CALLBACKS,
                                      data);
   ...
}