[vtkusers] multiple instances of subclass allocated by factory when unrelated class New() is called

[David E DeMarle]

	this->RegisterOverride("vtkPolyData",
		                   "BuildingPolyData",
						   "Building Poly Data",
						   1,
						   vtkObjectFactoryCreateBuildingPolyData);

Means that that every time the application calls vtkPolyData:New(),
BuildingPolyData() is called instead. vtkPolyData's are made inside
VTK in many places (grep for vtkPolyData::New()).

The intended use for object overriding is to make a specialization of
a generic class. For instance vtkRenderWindow::New makes
vtkX11OpenGLRenderWindows on Linux or vtkCarbonRenderWindows on Macs
etc. Once created the objects persist until the reference count goes
to zero.

David E DeMarle
Kitware, Inc.
R&D Engineer
28 Corporate Drive
Clifton Park, NY 12065-8662
Phone: 518-371-3971 x109



On Wed, Nov 4, 2009 at 7:43 PM, Alex Malyushytskyy <alexmalvtk at gmail.com> wrote:
> Hi,
>
> I am using VTK 5.4.2 compiled as dlls with QT 4 support. Language used is C++.
>
> I derived my class BuidingPolyData from vtkPolyData according to the
> VTK User's Guide.
> Factory is installed with RegisterFactory. according to the same guide
> (case when  factory is compiled in application).
>
> On the first glance code works, but if you start looking deeper you
> find very strange and scary things happening.
>
> In model3dView (model3dView.cpp) constructor my code instantiate
> pipeline , mapper , actors and a few widgets.
> There is no BuidingPolyData instances supposed to be created by me
> yet. It will be created later when user read data from stl file.
>
> But ::New() calls for other classes lead to the
> VTK_CREATE_CREATE_FUNCTION( BuildingPolyData ); macro execution.
>
> These objects are not only created, most of them persist until program exit.
>
> I put counters in the BuildingPolyData constructor. One shows how many
> instances are currently allocated, another shows how many instances
> still remain.
>
> For example call to:
>
> vtkAxesActor* testActor = vtkAxesActor::New();
> will create 16 additional instances of BuildingPolyData ( see debug.out)
>
> By the time all objects are initialized  there are like 38 instances
> of BuidingPolyData  created.
> NONE of them are created by me yet. All are results of the function
> New calls for unrelated classes.
>
> Could anybody  give me an idea why this may  happen,  what can be
> wrong, how it could be fixed?
> There are files in attachment. I tried to remove unrelated code to
> make it simple.
>
> Thanks in advance and best regards,
>          Alex
>
> _______________________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html
>
> Please keep messages on-topic and check the VTK FAQ at: http://www.vtk.org/Wiki/VTK_FAQ
>
> Follow this link to subscribe/unsubscribe:
> http://www.vtk.org/mailman/listinfo/vtkusers
>
>