Documentation/Labs/ViewInfrastructureImprovements

Goals

• Update Slicer code base to listen to interactor instead of interactor style
• Add support for interactor style switch per view
• Allow access to vtkRenderWindow from vtkMRMLViewNode

Motivation

• We would like to conveniently be able to change the interactor style without having to reset all observer for the displayable managers.
• Accessing the vtkRenderWindow would allow us to do (for example) screenshots given a specific viewNode.

InteractorStyle management

Workaround

Access 3D View

• Created a new Action menu in qSlicerMouseModeToolBar following this method.
• Accessed all qMRMLThreeDView through the layoutManager :

void qSlicerMouseModeToolBar::switchToTrackBallInteractorStyle()
{
  qMRMLLayoutManager *layoutManager = qSlicerApplication::application()->layoutManager();

  // loop through all existing threeDViews
  vtkNew<vtkThreeDViewInteractorStyle> interactorStyle;
  for (int i=0; i < layoutManager->threeDViewCount(); ++i)
    {
    qMRMLThreeDView* view = layoutManager->threeDWidget(i)->threeDView();
    // Update Interactor style
    this->SetInteractorStyle(view, interactorStyle.GetPointer());
    // Reset focal point
    view->resetFocalPoint();
    }

  // Update icon
  Q_D(qSlicerMouseModeToolBar);
  d->InteractorStyleToolButton->setIcon(QIcon(":/Icons/TrackBall.png"));
}

• Issue : not setting the interactor per view but for all views
• Possible solution : adding the switch in each 3D View Qt controller

Update InteractorStyle

• Set the interactorStyle to the qMRMLThreeDView interactor :

void qSlicerMouseModeToolBar::SetInteractorStyle(qMRMLThreeDView* view,
                                                 vtkInteractorStyle* interactorStyle)
{
  // Set InteractorStyle on renderview
  view->interactor()->SetInteractorStyle(interactorStyle);

  // Get DMs
  vtkNew<vtkCollection> collection;
  view->getDisplayableManagers(collection.GetPointer());
  int numManagers = collection->GetNumberOfItems();

  // Set and Observe InteractorStyle for cameraDM
  for (int i = 0; i < numManagers; ++i)
    {
    vtkMRMLCameraDisplayableManager *cameraDM =
        vtkMRMLCameraDisplayableManager::SafeDownCast(collection->GetItemAsObject(i));
    if (cameraDM)
      {
      cameraDM->SetCameraToInteractor();
      }
    }

  collection->RemoveAllItems();
}

• Issues :
  • Should need to update the observations for all the DM using SetAndObserveInteractorStyle(), but this crashes Slicer.
  • The camera was not set anymore after a change of interactor styles in the vtkMRMLCameraDisplayableManager, so we had to use SetCameraToInteractor() and define it as a public method.

• Possible solution : updating Slicer core so that it listen only to the interactor instead of the interactorStyle.

Design & implementation

TODO

vtkRenderWindow mapping

Workaround

• Created a method that accessed the renderWindow through the layout manager MRMLViewFactory :

vtkRenderWindow* getMRMLViewRenderWindow(vtkMRMLViewNode* viewNode)
{
  qSlicerLayoutManager *layoutManager = qSlicerApplication::application()->layoutManager();
  qMRMLThreeDWidget* threeDWidget = qobject_cast<qMRMLThreeDWidget*>(layoutManager->mrmlViewFactory("vtkMRMLViewNode")->viewWidget(viewNode));
  vtkRenderWindow *renderWindow = threeDWidget->threeDView()->renderWindow();

  return renderWindow;
}

• Issue : calls to qMRML while we would prefer to stay with vtkMRML only
• Possible solution : map the vtkRenderWindow to the vtkMRMLViewNode in the view factory when creating the widget

Design & implementation

TODO