[vtkusers] possible BUG: segmentation fault by deleting a vtkRenderer

[Thomas Faust]

Hi vtkusers.

I found a problem in the application I am working with.
I changed the sequence of creating and destroying objects and found a
segmentation fault that could be a possible bug and should be removed.

My program was creating a renderer and a renderwindow and all used vtk
objects (interactor, mapper, data, filter...) after this. Now it changed:
I create a renderer and all vtk objects and assemble the graphic pipeline
without my GUI. After this I create a (offscreen) renderwindow add the
renderer, render a image, remove the renderer and delete the renderwindow
again.

The problem results from a invalid pointer to a renderwindow after
deleting it from the renderer.
The function vtkRenderWindow::RemoveRenderer() should be extended to set
Renderer::RenderWindow to NULL. This will avoid the segmentation fault
when deleting the renderer (when the renderwindow is already gone)

// Remove a renderer from the list of renderers.
void vtkRenderWindow::RemoveRenderer(vtkRenderer *ren)
{
    ren->SetRenderWindow(NULL); // !!!! don't forget the remove the
renderwindow from the renderer
    this->Renderers->RemoveItem(ren);
}


try the following code to reproduce the problem:


#include "vtkSphereSource.h"
#include "vtkPolyDataMapper.h"
#include "vtkActor.h"
#include "vtkRenderWindow.h"
#include "vtkRenderer.h"
#include "vtkRenderWindowInteractor.h"
#include "vtkProperty.h"

int main ()
{

    // create sphere geometry
    vtkSphereSource *sphere = vtkSphereSource::New();
    sphere->SetRadius(1.0);
    sphere->SetThetaResolution(18);
    sphere->SetPhiResolution(18);

    // map to graphics library
    vtkPolyDataMapper *map = vtkPolyDataMapper::New();
    map->SetInput(sphere->GetOutput());
    sphere->Delete();  // sphere as referernce in mapper -> not needed here
anymore

    // actor coordinates geometry, properties, transformation
    vtkActor *aSphere = vtkActor::New();
    aSphere->SetMapper(map);
    aSphere->GetProperty()->SetColor(0,0,1); // sphere color blue
    map->Delete(); // mapper has reference in actor

    // a renderer and render window
    vtkRenderer *ren1 = vtkRenderer::New();
    // add the actor to the scene
    ren1->AddActor(aSphere);
    ren1->SetBackground(1,1,1); // Background color white
    aSphere->Delete();  // actor has reference in renderer -> not needed
here anymore


    // create a offscreen render window to write a picture
    vtkRenderWindow *renWin = vtkRenderWindow::New();
    renWin->OffScreenRenderingOn();
    renWin->AddRenderer(ren1);
    // render an image (lights and cameras are created automatically)
    renWin->Render();
    // write the picture with windowtoimage filter
    renWin->RemoveRenderer(ren1);  // !!!!!!!!!! BUG !!!!!!!!!!!
    renWin->Delete();


    // Segantation Fault because the ren1->RenderWindow is invalif pointer
    ren1->Delete();

    return 0;
}