[vtk-developers] VTK containers are gone; long live VTK containers

[Andy Cedilnik]

Hello All,

After long time of worrying and wondering about the possible solutions
to container problems in VTK, we finally made a decision. VTK will start
internally using STL containers. That means so called Andy's containers
(vtkVector, vtkHashMap, vtkLinkedList...) are out. Brad modified all the
VTK classes that used VTK containers to use STL containers and he did
some magic so that they will compile on all platforms.

Some gains:

1. Standard interface STL
2. Use of STL algorithms 
3. Optimized and verified implementations

Some potential loses:

1. Reference counting

The VTK containers did some magic with overloaded functions which
resulted in automatic reference counting for VTK objects. Unfortunately,
that meant that VTK objects were always reference counted. The STL
containers on the other hand do not do any reference counting. The
workaround is to use smart pointer. The gain here is that you can chose
between doing reference counting and not. 

Example of container that uses reference counting:

vtkstd::vector< vtkSmartPointer< vtkActor > > v;

4. Need to use namespace hack

The use of STL containers unfortunately involves the use of namespace on
some platforms. Current VTK implementation of IO streams does this all
useful IO streams things into global namespace. For containers, we
decide to actually have a macro which points to the right namespace. So
instead of:

map<string, vector<int> > m;

or 

std::map<std::string, std::vector<int> > m;

you will always have to do:

vtkstd::map<vtkstd::string, vtkstd::vector<int> > m;

If you use map, you have to do:

#include <map>

and so on for other containers. 

That is all.

Please send comments to the list.

Thank you.

                     Andy Cedilnik
                     Kitware Inc.