vtkRenderWindow segfault when accessing Interactor variable

Support
1

Hi everyone,

Not sure if this is the correct venue, so please forgive my inexperience.

I have an application that uses VTK with QT, on Ubuntu 20.04 LTS. It compiles just fine and most of the application works. However, when I try to create a vtkRenderWindow, it crashes with a segfault. Specifically, whenever my application tries to access or interact with the vtkRenderWindow object’s Interactor variable (declared in vtkRenderWindow.h:754).

  vtkRenderWindowInteractor* Interactor;

Thus far, I’ve had it crashing with (1) vtkRenderWindow::GetInteractor(), (2) vtkRenderWindow::SetInteractor(), and (3) vtkRenderWindow::MakeRenderWindowInteractor().

(1) To be more precise, the program crashes the moment it attempts to call vtkRenderWindow::GetInteractor(). The code in question:

    vtkRenderer* m_Ren1;
    vtkRenderWindow* renwin;
    QVTKOpenGLStereoWidget* qVTK1;

    m_Ren1 = vtkRenderer::New();
    renwin = vtkRenderWindow::New();
    renwin->AddRenderer(m_Ren1);
    ui->qVTK1->setRenderWindow(renwin);

    ui->qVTK1->renderWindow()->GetInteractor();

(2) When calling vtkRenderWindow::SetInteractor(), it crashes at vtkRenderWindow.cxx:155, at the line
if (this->Interactor != rwi). I show the code I use below:

    vtkRenderer* m_Ren1;
    vtkRenderWindow* renwin;
    QVTKOpenGLStereoWidget* qVTK1;

    m_Ren1 = vtkRenderer::New();
    renwin = vtkRenderWindow::New();
    renwin->AddRenderer(m_Ren1);
    ui->qVTK1->setRenderWindow(renwin);

    vtkRenderWindowInteractor* t1 = vtkRenderWindowInteractor::New();
    ui->qVTK1->renderWindow()->SetInteractor(t1);

(3) When calling vtkRenderWindow::MakeRenderWindowInteractor(), it crashes at vtkObjectFactory.cxx:438, specifically when it calls the strcmp function.

if (this->OverrideArray[i].EnabledFlag &&
      strcmp(this->OverrideClassNames[i], vtkclassname) == 0)

Again, I show the code I use to test this below:

    vtkRenderer* m_Ren1;
    vtkRenderWindow* renwin;
    QVTKOpenGLStereoWidget* qVTK1;

    m_Ren1 = vtkRenderer::New();
    renwin = vtkRenderWindow::New();
    renwin->AddRenderer(m_Ren1);
    ui->qVTK1->setRenderWindow(renwin);
    ui->qVTK1->renderWindow()->MakeRenderWindowInteractor();

Curiously, the program does not crash if I create a new RenderWindow as below, despite both test and qVTK1->renderWindow() being of type vtkXOpenGLRenderWindow. It does crash regardless of if I set qVTK1->renderWindow()'s interactor to t1 or t2:

    vtkRenderWindow* test = vtkRenderWindow::New();
    vtkRenderWindowInteractor* t2 = test->GetInteractor();
    vtkRenderWindowInteractor* t1 = vtkRenderWindowInteractor::New();
    test->SetInteractor(t1);
    ui->qVTK1->renderWindow()->SetInteractor(t1);
    ui->qVTK1->renderWindow()->SetInteractor(t2);

Again, please forgive my inexperience. If anyone has any idea why this occurs or how to deal with it, I would very much appreciate it.

Thanks!

2

Solved! The problem actually came about from the QT side. QVTKOpenGLRenderWindow cannot deal with vtkXOpenGLRenderWindow, it requires vtkGenericOpenGLRenderWindow. But vtkGenericOpenGLRenderWindow cannot be created with vtkRenderWindow::New(). The solution is to declare the renderwindow in a different way:

    vtkRenderer* m_Ren1;
    vtkRenderWindow* renwin;
    QVTKOpenGLStereoWidget* qVTK1;

    m_Ren1 = vtkRenderer::New();```
    vtkNew<vtkGenericOpenGLRenderWindow> rw;
    renwin = rw;```
    renwin->AddRenderer(m_Ren1);
    ui->qVTK1->setRenderWindow(renwin);

This solves the problem with the interactor.