VTK/Examples/Cxx/Widgets/HoverWidget

#include <vtkActor.h>
#include <vtkCommand.h>
#include <vtkHoverWidget.h>
#include <vtkPolyDataMapper.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkSmartPointer.h>
#include <vtkSphereSource.h>
 
class vtkHoverCallback : public vtkCommand
{
  public:
    static vtkHoverCallback *New()
    {
      return new vtkHoverCallback;
    }
 
    vtkHoverCallback() {}
 
    virtual void Execute(vtkObject*, unsigned long event, void *vtkNotUsed(calldata))
    {
      switch (event) 
        {
        case vtkCommand::TimerEvent:
          std::cout << "TimerEvent -> the mouse stopped moving and the widget hovered" << std::endl; 
          break;
        case vtkCommand::EndInteractionEvent:
          std::cout << "EndInteractionEvent -> the mouse started to move" << std::endl; 
          break;
        }
    }
};
 
int main(int, char *[])
{
  vtkSmartPointer<vtkSphereSource> sphereSource = 
      vtkSmartPointer<vtkSphereSource>::New();
  sphereSource->Update();
 
  // Create a mapper and actor
  vtkSmartPointer<vtkPolyDataMapper> mapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  mapper->SetInputConnection(sphereSource->GetOutputPort());
  vtkSmartPointer<vtkActor> actor =
    vtkSmartPointer<vtkActor>::New();
  actor->SetMapper(mapper);
 
  // A renderer and render window
  vtkSmartPointer<vtkRenderer> renderer =
    vtkSmartPointer<vtkRenderer>::New();
  vtkSmartPointer<vtkRenderWindow> renderWindow = 
    vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->AddRenderer(renderer);
  renderer->AddActor(actor);
 
  // An interactor
  vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor = 
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  renderWindowInteractor->SetRenderWindow(renderWindow);
 
  // Create the widget
  vtkSmartPointer<vtkHoverWidget> hoverWidget =
    vtkSmartPointer<vtkHoverWidget>::New();
  hoverWidget->SetInteractor(renderWindowInteractor);
  hoverWidget->SetTimerDuration(1000);
 
  // Create a callback to listen to the widget's two VTK events
  vtkSmartPointer<vtkHoverCallback> hoverCallback =
    vtkSmartPointer<vtkHoverCallback>::New();
  hoverWidget->AddObserver(vtkCommand::TimerEvent,hoverCallback);
  hoverWidget->AddObserver(vtkCommand::EndInteractionEvent,hoverCallback);
 
  renderWindow->Render();
 
  renderWindowInteractor->Initialize();
  renderWindow->Render();
  hoverWidget->On();
 
  renderWindowInteractor->Start();
 
  return EXIT_SUCCESS;
}