pclvisualizer's interactor_ is nullptr

[renc]

Hello,

pclvisualizer's interactor_ is nullptr at this usage:

        //m_pViewWidget is a qvtkWidget instance
	m_pViewer.reset(new pcl::visualization::PCLVisualizer("viewer", false));
	m_pViewWidget->SetRenderWindow(m_pViewer->getRenderWindow()); 
	// to use interactor from qvtkWidget
	m_pViewer->setupInteractor(m_pViewWidget->GetInteractor(), m_pViewWidget->GetRenderWindow());
	m_pViewWidget->update();

after this code, the interactor_ is still nullptr, so crash for example m_pViewer->spinOnce().

To fix that, i think maybe at

PCLVisualizer::setupInteractor(....) {
    ... // same as the current version. 
    interactor_ = iren; // add this new line. 
} 

any idea?

[renc]

btw, if this fix make sense, i could help to add a patch. thx.

[taketwo]

I'm not entirely sure, but I think you should not call functions like spin() or spinOnce() when you are using external interactor. Your m_pViewWidget will take care of refreshing and redrawing the visualization window.

[renc]

thx taketwo, right that the m_pViewWidget->update() will refresh the window. Leaving interactor_ null seems a bit dangerous.

[taketwo]

It's dangerous, true. All accesses to interactor_ need to be guarded with null checks, which is not the case currently. However, setting interactor_ to the external interactor may be not a good idea either, because then we will start calling functions like DestroyTimer, Start, Render, etc on this external instance, which we are not supposed to.

[denix56]

Some related information with it - when we use QVTKOpenGLWidget it often does not update the displayed object with update() function, you should call Render() method of the current render window. But it seems to be not PCL bug, but VTK.
Maybe it will be useful for somebody.