# Black screen and vtkOutputWindow errors when replacing interactor in QVTKOpenGLNativeWidget (VTK 9.5.2 + Qt 5.15.0)

**URL:** https://discourse.vtk.org/t/black-screen-and-vtkoutputwindow-errors-when-replacing-interactor-in-qvtkopenglnativewidget-vtk-9-5-2-qt-5-15-0/16167
**Category:** Support
**Tags:** code
**Created:** [December 1, 2025, 10:25am UTC](https://discourse.vtk.org/t/black-screen-and-vtkoutputwindow-errors-when-replacing-interactor-in-qvtkopenglnativewidget-vtk-9-5-2-qt-5-15-0/16167 "2025-12-01T10:25:22Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![Artsiom\_Nedzvedz](https://discourse.vtk.org/user_avatar/discourse.vtk.org/artsiom_nedzvedz/32/10376_2.png) [@Artsiom\_Nedzvedz](https://discourse.vtk.org/u/Artsiom_Nedzvedz)
#### Post date: [December 1, 2025, 10:25am UTC](https://discourse.vtk.org/t/black-screen-and-vtkoutputwindow-errors-when-replacing-interactor-in-qvtkopenglnativewidget-vtk-9-5-2-qt-5-15-0/16167/1 "2025-12-01T10:25:22Z")

</div>

We’re upgrading a Qt/VTK application from **VTK 9.0.5 → 9.5.2** (Qt 5.15.0, MSVC 2019 x86, static linking, no CMake).  
Our custom interactor — a subclass of `vtkGenericRenderWindowInteractor` — worked flawlessly in **VTK 9.0** , but now in **9.5.2** it leads to:

- black screen,

- `vtkOutputWindow` with errors like:

- crash or infinite loop if `Initialize()` is called manually before `setRenderWindow()`.

✅ With the _default_ interactor (i.e. letting `QVTKOpenGLNativeWidget` create it), rendering (including NIFTI) works fine.

But we need a **custom interactor** (e.g. to override `CharEvent`, add timers, sync external devices), so simply changing the style isn’t enough.

Our current approach (which worked in 9.0):

auto myInteractor = vtkSmartPointer::New(); // vtkGenericRenderWindowInteractor subclass  
myInteractor-\>SetRenderWindow(renderWindow);  
myInteractor-\>SetInteractorStyle(vtkSmartPointer::New());

// In 9.0: widget-\>setRenderWindow(renderWindow) handled the rest.  
// In 9.5.2: OpenGL context never becomes valid → black screen.

widget-\>setRenderWindow(renderWindow); // ← expected to bind Qt adapter and initialize safely  
widget-\>show();  
renderWindow-\>Render();

We verified:

- `VTK_MODULE_INIT(vtkRenderingOpenGL2)` and `VTK_MODULE_INIT(vtkRenderingQt)` are present in `main()`,

- `renderWindow` is `vtkGenericOpenGLRenderWindow`,

- pipeline data (e.g. `vtkNIFTIImageReader`) is valid and renders with default interactor.

🔍 **Hypothesis** : VTK 9.5+ became stricter about OpenGL context lifecycle and Qt interactor binding — especially around _when_ and _how_ `Initialize()` is called on a user-provided interactor.

**Main question** :  
What is the _correct, minimal, and safe_ way in **VTK 9.5.2** to inject a **custom `vtkGenericRenderWindowInteractor` subclass** _before_ `QVTKOpenGLNativeWidget::setRenderWindow()` — such that:

1. Qt event binding (`QVTKInteractorAdapter`) is preserved,

2. OpenGL context is correctly created and activated,

3. No manual `Initialize()` is needed (or it’s done safely).

Is there a new required override (e.g. `SetInteractor()`, `Enable()`), or a timing-sensitive step we’re missing?

Thanks in advance — this seems like a subtle but critical change in interactor ownership between 9.0 and 9.5.