vtkInteractorStyles that draw selected area fail with QQuickVtkItem

Support
1

I use vtkInteractorStyleRubberBandPick with QQuickVtkItem with VTK 9.3 in my C++ application that uses Qt and VTK. However when I drag the left mouse button, a selection area is not drawn but many warning/error messages are written to stderr. The same occurs when I use any vtkInteractorStyle that attempts to draw a selected area, such as vtkInteractorStyleDrawPolygon. These warning/error messages are generated when I begin left mouse button drag:

ESC[0mESC[33m2025-07-08 15:00:17.362 ( 28.565s) [ 7F8182151640] vtkOpenGLState.cxx:57 WARN| Error in cache state for GL_DEPTH_WRITEMASKESC[0m

ESC[0mESC[33m2025-07-08 15:00:17.362 ( 28.565s) [ 7F8182151640] vtkOpenGLState.cxx:133 WARN| Error in cache state for GL_VIEWPORTESC[0m

ESC[0mESC[33m2025-07-08 15:00:17.368 ( 28.570s) [ 7F8182151640] vtkOpenGLState.cxx:263 WARN| at stack loc

0x7f86cda15ba1 : ??? [(???) ???:-1]

0x7f86cda101db : vtksys::SystemInformation::GetProgramStack[abi:cxx11](int, int) [(libvtksys-9.3.so.1) ???:-1]

0x7f86c690333f : vtkOpenGLState::CheckState() [(libvtkRenderingOpenGL2-9.3.so.1) ???:-1]

0x7f86c6905061 : vtkOpenGLState::vtkglBindFramebuffer(unsigned int, unsigned int) [(libvtkRenderingOpenGL2-9.3.so.1) ???:-1]

0x7f86c690501d : vtkOpenGLState::vtkBindFramebuffer(unsigned int, vtkOpenGLFramebufferObject*) [(libvtkRenderingOpenGL2-9.3.so.1) ???:-1]

0x7f86c68026b0 : vtkOpenGLFramebufferObject::Bind(unsigned int) [(libvtkRenderingOpenGL2-9.3.so.1) ???:-1]

0x7f86c68d084a : vtkOpenGLRenderWindow::SetRGBACharPixelData(int, int, int, int, unsigned char*, int, int, int) [(libvtkRenderingOpenGL2-9.3.so.1) ???:-1]

0x7f86c67b5318 : vtkGenericOpenGLRenderWindow::SetRGBACharPixelData(int, int, int, int, unsigned char*, int, int, int) [(libvtkRenderingOpenGL2-9.3.so.1) ???:-1]

0x7f86ca42d075 : vtkInteractorStyleRubberBandPick::RedrawRubberBand() [(libvtkInteractionStyle-9.3.so.1) ???:-1]

0x7f86ca42c9c6 : vtkInteractorStyleRubberBandPick::OnMouseMove() [(libvtkInteractionStyle-9.3.so.1) ???:-1]

0x7f86c94b54b7 : vtkInteractorStyle::ProcessEvents(vtkObject*, unsigned long, void*, void*) [(libvtkRenderingCore-9.3.so.1) ???:-1]

0x7f86cf20f0cb : vtkCallbackCommand::Execute(vtkObject*, unsigned long, void*) [(libvtkCommonCore-9.3.so.1) ???:-1]

0x7f86cf3ef5f2 : ??? [(???) ???:-1]

0x7f86cf3efbe9 : vtkObject::InvokeEvent(unsigned long, void*) [(libvtkCommonCore-9.3.so.1) ???:-1]

0x7f86cb519b86 : QVTKInteractorAdapter::ProcessEvent(QEvent*, vtkRenderWindowInteractor*) [(libvtkGUISupportQt-9.3.so.1) ???:-1]

0x7f86d0211263 : ??? [(???) ???:-1]

0x7f86d02119c9 : ??? [(???) ???:-1]

0x7f86d021185a : ??? [(???) ???:-1]

0x7f86d0211707 : ??? [(???) ???:-1]

0x7f86d0213961 : ??? [(???) ???:-1]

0x7f86d0210d07 : QQuickVTKItem::updatePaintNode(QSGNode*, QQuickItem::UpdatePaintNodeData*) [(libvtkGUISupportQtQuick-9.3.so.1) ???:-1]

0x7f86cc3748b8 : QQuickWindowPrivate::updateDirtyNode(QQuickItem*) [(libQt6Quick.so.6) ???:-1]

0x7f86cc375234 : QQuickWindowPrivate::updateDirtyNodes() [(libQt6Quick.so.6) ???:-1]

0x7f86cc37925e : QQuickWindowPrivate::syncSceneGraph() [(libQt6Quick.so.6) ???:-1]

0x7f86cc589bdc : ??? [(???) ???:-1]

0x7f86cc58b114 : ??? [(???) ???:-1]

0x7f86cc58c3a7 : ??? [(???) ???:-1]

0x7f86ccb76ef8 : ??? [(???) ???:-1]

0x7f86cb680ac3 : ??? [(???) ???:-1]

0x7f86cb712850 : ??? [(???) ???:-1]

My code works properly when I use a vtkInteractorStyle that does not attempt to select an area, such as vtkInteractorStyleTrackballCamera, vtkInteractorStyleFlight, vtkInteractorStyleTerrain.

Seemingly most relevant part of my code:

  pipeline->interactorStyle_->SetDefaultRenderer(pipeline->renderer_);

  pipeline->qVtkInteractor_->SetPicker(pipeline->areaPicker_);
  pipeline->qVtkInteractor_->SetInteractorStyle(pipeline->interactorStyle_);
  pipeline->qVtkInteractor_->SetRenderWindow(renderWindow_);

where interactorStyle_ points to vtkInteractorStyle. E.g. it can point to vtkInteractorStyleTrackballCamera - which works - or vtkInteractorStyleDrawPolygon - which fails as described above.

What might be causing this behavior and how to fix it? Is this an issue with QVtkInteractor, QQuickVtkItem, or both?
Thanks!

2

Has no one encountered this issue before?
Also I note that QQuickVtkItem exits with an error message if handed a vtkRenderWindowInteractor that is not a QVtkInteractor.

3

Hi @Tomasso, my guess is youā€™re running into threading issues. QtQuick uses a threaded scenegraph with a main thread and a separate render thread. VTK draw calls should just be made on the render thread. This is why QQuickVTKItem exposes a dispatch_async method to ā€œscheduleā€ tasks on the render thread. The interactor styles you mentioned arenā€™t aware of this and likely try to make render calls on the main thread. Youā€™d have to subclass the style and use dispatch_async wherever it makes direct Render calls.

1 Like
4

Thanks @sankhesh, Iā€™ve done as you suggest - made a local copy of vtkInteractorStyleRubberBandPick, renamed it MyRubberBandStyle; Iā€™ve added a class member qquickVTKItem_ that points to my QQuickVTKItem object. The errors I describe happen in MyRubberBandStyle::RedrawRubberBand(), called by MyRubberBandStyle::OnMouseMove(), i.e. both these are running in the same thread. I modified OnMouseMove() so that it queues RedrawRubberBand() to execute in the Qt-Render thread (instead of calling RedrawRubberBand() directly), by calling QQuickVTKItem::dispatch_async():

  // Dispatch lambda function to redraw rubber band in Qt render thread
  qquickVTKItem_->dispatch_async([this](vtkRenderWindow *renderWindow,
		  vtkSmartPointer<vtkObject> userData) {
    this->RedrawRubberBand();
  });

However this does not fix the errors, which are still emitted by RedrawRubberBand(). Debugging this, I see that RedrawRubberBand() is still running in the same thread as OnMouseMove(), despite being queued to run in the Qt-Render thread. Why is this? How can I make RedrawRubberBand() run in the Qt-render thread?

5

More detail - I copied vtkInteractorStyleRubberBandPick to MyRubberBandStyle, and see that the scene-graph related errors occur in MyRubberBandStyle::RedrawRubberBand(); this function attempts to draw a rectangle around the selected area as the mouse is dragged. Within RedrawRubberBand() Iā€™ve established that the errors occur here:

  this->Interactor->
    GetRenderWindow()->SetRGBACharPixelData(
					    0, 0, size[0] - 1, size[1] - 1,
					    pixels, 0);

Document for SetRGBACharPixelData() is here.
I added debug statements to my code, printing out thread ID at various locations. I implemented a slot that I connect to QQuickWindow::beforeSynchronizing, which is emitted by the Qt-Render thread, so I get a definitive ID for the QT-Render thread. Here are the thread IDs:

main() thread:                                139815893882176
reassemblePipeline() thread:                  139815893882176   calls vtkRendering() with QQuickVTKItem::dispatch_async()
vtkRendering() thread:                        139815085459008   invokes VTK rendering
MyRubberBandStyle::OnMouseMove() thread:      139815085459008
MyRubberBandStyle::RedrawRubberBand() thread: 139815085459008   invokes VTK rendering
qt render thread:                             139815085459008   in my slot that's connected to  QQuickWindow::beforeSynchronizing

So calls to vtkRendering() and RedrawRubberBand(), which both invoke VTK Render calls, are running in the QT-render thread, and yet the SceneGraph-related errors still occur:

0x7f98511cfd07 : QQuickVTKItem::updatePaintNode(QSGNode*, QQuickItem::UpdatePaintNodeData*) [(libvtkGUISupportQtQuick-9.3.so.1) ???:-1]
0x7f984d3338b8 : QQuickWindowPrivate::updateDirtyNode(QQuickItem*) [(libQt6Quick.so.6) ???:-1]
0x7f984d334234 : QQuickWindowPrivate::updateDirtyNodes() [(libQt6Quick.so.6) ???:-1]
0x7f984d33825e : QQuickWindowPrivate::syncSceneGraph() [(libQt6Quick.so.6) ???:-1]

@sankhesh or anyone, can you recommend next things to try?
Thanks!

6

Hi @Tomasso, That looks correct. The error log that you posted seems more like a stack trace. What error do you get now?

7

@sankhesh these are the errors that appear on stderr as Iā€™m dragging the mouse, i.e. not a stack trace:

0x7f98511cfd07 : QQuickVTKItem::updatePaintNode(QSGNode*, QQuickItem::UpdatePaintNodeData*) [(libvtkGUISupportQtQuick-9.3.so.1) ???:-1]
0x7f984d3338b8 : QQuickWindowPrivate::updateDirtyNode(QQuickItem*) [(libQt6Quick.so.6) ???:-1]
0x7f984d334234 : QQuickWindowPrivate::updateDirtyNodes() [(libQt6Quick.so.6) ???:-1]
0x7f984d33825e : QQuickWindowPrivate::syncSceneGraph() [(libQt6Quick.so.6) ???:-1]

But here is an interesting development. I provided claude.ai with the information provided in this post, and it responded with several possible solutions, one of which ā€˜fixedā€™ those errors, i.e. they no longer appear on stderr while dragging the mouse. The solution was this:

  /* **** Recommended by Claude.ai *** */
  vtkOpenGLRenderWindow* renWin = 
    vtkOpenGLRenderWindow::SafeDownCast(this->Interactor->GetRenderWindow());

  vtkOpenGLState* ostate;
  if (renWin) {
    std::cerr << "got renWin\n";
    ostate = renWin->GetState();
        
    // Push current state
    ostate->Push();
  }
  /* ******************************* */
  std::cerr << "RedrawRubberBand(): set rgb pixel data\n";

  this->Interactor->
    GetRenderWindow()->SetRGBACharPixelData(
					    0, 0, size[0] - 1, size[1] - 1,
					    pixels, 0);

  
  std::cerr << "RedrawRubberBand(): get render window frame\n";
  this->Interactor->GetRenderWindow()->Frame();

  std::cerr << "RedrawRubberBand(): delete tmpPixelArray\n";
  tmpPixelArray->Delete();
  std::cerr << "RedrawRubberBand(): tmpPixelArray DELETED\n";  

  /* **** Recommended by Claude.ai *** */
  if (renWin) {
    // Pop back to previous state
    ostate->Pop();
  }
  /* ******************************* */

So I donā€™t see error messages on mouse drag - but also do not see a red box tracking the area selected by the mouse. I.e. the call to SetRGBACharPixelData() doesnā€™t result in a red box. I do see a red box when using MyRubberBandStyle with a VTK-only application (i.e. no integration with Qt). Why might this be so? Here is the complete source for MyRubberBandStyle::RedrawRubberBand():

//------------------------------------------------------------------------------
void MyRubberBandStyle::RedrawRubberBand()
{
  std::cerr << "MyRubberBandStyle::RedrawRubberBand() thread: " <<
    std::this_thread::get_id() << "\n";
  
  // update the rubber band on the screen
  const int* size = this->Interactor->GetRenderWindow()->GetSize();

  vtkUnsignedCharArray* tmpPixelArray = vtkUnsignedCharArray::New();
  tmpPixelArray->DeepCopy(this->PixelArray);
  unsigned char* pixels = tmpPixelArray->GetPointer(0);

  int min[2], max[2];

  min[0] =
    this->StartPosition[0] <= this->EndPosition[0] ? this->StartPosition[0] : this->EndPosition[0];
  if (min[0] < 0)
  {
    min[0] = 0;
  }
  if (min[0] >= size[0])
  {
    min[0] = size[0] - 1;
  }

  min[1] =
    this->StartPosition[1] <= this->EndPosition[1] ? this->StartPosition[1] : this->EndPosition[1];
  if (min[1] < 0)
  {
    min[1] = 0;
  }
  if (min[1] >= size[1])
  {
    min[1] = size[1] - 1;
  }

  max[0] =
    this->EndPosition[0] > this->StartPosition[0] ? this->EndPosition[0] : this->StartPosition[0];
  if (max[0] < 0)
  {
    max[0] = 0;
  }
  if (max[0] >= size[0])
  {
    max[0] = size[0] - 1;
  }

  max[1] =
    this->EndPosition[1] > this->StartPosition[1] ? this->EndPosition[1] : this->StartPosition[1];
  if (max[1] < 0)
  {
    max[1] = 0;
  }
  if (max[1] >= size[1])
  {
    max[1] = size[1] - 1;
  }

  int i;
  for (i = min[0]; i <= max[0]; i++)
  {
    pixels[4 * (min[1] * size[0] + i)] = 255 ^ pixels[4 * (min[1] * size[0] + i)];
    pixels[4 * (min[1] * size[0] + i) + 1] = 255 ^ pixels[4 * (min[1] * size[0] + i) + 1];
    pixels[4 * (min[1] * size[0] + i) + 2] = 255 ^ pixels[4 * (min[1] * size[0] + i) + 2];
    pixels[4 * (max[1] * size[0] + i)] = 255 ^ pixels[4 * (max[1] * size[0] + i)];
    pixels[4 * (max[1] * size[0] + i) + 1] = 255 ^ pixels[4 * (max[1] * size[0] + i) + 1];
    pixels[4 * (max[1] * size[0] + i) + 2] = 255 ^ pixels[4 * (max[1] * size[0] + i) + 2];
  }
  for (i = min[1] + 1; i < max[1]; i++)
  {
    pixels[4 * (i * size[0] + min[0])] = 255 ^ pixels[4 * (i * size[0] + min[0])];
    pixels[4 * (i * size[0] + min[0]) + 1] = 255 ^ pixels[4 * (i * size[0] + min[0]) + 1];
    pixels[4 * (i * size[0] + min[0]) + 2] = 255 ^ pixels[4 * (i * size[0] + min[0]) + 2];
    pixels[4 * (i * size[0] + max[0])] = 255 ^ pixels[4 * (i * size[0] + max[0])];
    pixels[4 * (i * size[0] + max[0]) + 1] = 255 ^ pixels[4 * (i * size[0] + max[0]) + 1];
    pixels[4 * (i * size[0] + max[0]) + 2] = 255 ^ pixels[4 * (i * size[0] + max[0]) + 2];
  }

  /* **** Recommended by Claude.ai *** */
  vtkOpenGLRenderWindow* renWin = 
    vtkOpenGLRenderWindow::SafeDownCast(this->Interactor->GetRenderWindow());

  vtkOpenGLState* ostate;
  if (renWin) {
    std::cerr << "got renWin\n";
    ostate = renWin->GetState();
        
    // Push current state
    ostate->Push();
  }
  /* ******************************* */
  std::cerr << "RedrawRubberBand(): set rgb pixel data\n";

  this->Interactor->
    GetRenderWindow()->SetRGBACharPixelData(
					    0, 0, size[0] - 1, size[1] - 1,
					    pixels, 0);

  
  std::cerr << "RedrawRubberBand(): get render window frame\n";
  this->Interactor->GetRenderWindow()->Frame();

  std::cerr << "RedrawRubberBand(): delete tmpPixelArray\n";
  tmpPixelArray->Delete();
  std::cerr << "RedrawRubberBand(): tmpPixelArray DELETED\n";  

  /* **** Recommended by Claude.ai *** */
  if (renWin) {
    // Pop back to previous state
    ostate->Pop();
  }
  /* ******************************* */  


  std::cerr << "Leave MyRubberBandStyle::RedrawRubberBand()\n";  
}