ObserverMemberFunction

#include <vtkPolyDataMapper.h>
#include <vtkObjectFactory.h>
#include <vtkCommand.h>
#include <vtkActor.h>
#include <vtkSmartPointer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkInteractorStyle.h>
#include <vtkPolyData.h>
#include <vtkSphereSource.h>
#include <vtkInteractorStyleTrackballCamera.h>

// A class not derived from vtkObjectBase
class MyClass
{
  public:
    void KeypressCallbackFunction(vtkObject*,
                                  long unsigned int vtkNotUsed(eventId),
                                  void* vtkNotUsed(callData))
    {
    std::cout << "Caught event in MyClass" << std::endl;
    }

};

// A class that is derived from vtkObjectBase
class MyInteractorStyle : public vtkInteractorStyleTrackballCamera
{
public:
  static MyInteractorStyle* New();
  vtkTypeMacro(MyInteractorStyle, vtkInteractorStyleTrackballCamera);

  void KeypressCallbackFunction(vtkObject*,
                                long unsigned int vtkNotUsed(eventId),
                                void* vtkNotUsed(callData) )
  {
    std::cout << "Caught event in MyInteractorStyle" << std::endl;
  }

};
vtkStandardNewMacro(MyInteractorStyle);

int main(int, char *[])
{
  // Create a sphere
  vtkSmartPointer<vtkSphereSource> sphereSource =
    vtkSmartPointer<vtkSphereSource>::New();
  sphereSource->SetCenter(0.0, 0.0, 0.0);
  sphereSource->SetRadius(5.0);
  sphereSource->Update();

  vtkSmartPointer<vtkPolyDataMapper> mapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  mapper->SetInputConnection(sphereSource->GetOutputPort());

  // Create an actor
  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);

  // An interactor
  vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  renderWindowInteractor->SetRenderWindow(renderWindow);

  MyClass myClass;
  renderWindowInteractor->AddObserver(vtkCommand::KeyPressEvent, &myClass, &MyClass::KeypressCallbackFunction);

  vtkSmartPointer<MyInteractorStyle> style =
    vtkSmartPointer<MyInteractorStyle>::New();
  renderWindowInteractor->AddObserver(vtkCommand::KeyPressEvent, style, &MyInteractorStyle::KeypressCallbackFunction);

  vtkSmartPointer<MyInteractorStyle> style2 =
    vtkSmartPointer<MyInteractorStyle>::New();
  renderWindowInteractor->AddObserver(vtkCommand::KeyPressEvent, style2, &MyInteractorStyle::KeypressCallbackFunction);

  renderer->AddActor(actor);
  renderer->SetBackground(1,1,1); // Background color white
  renderWindow->Render();
  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(ObserverMemberFunction)

find_package(VTK COMPONENTS 
  vtkvtkCommonCore
  vtkvtkCommonDataModel
  vtkvtkFiltersSources
  vtkvtkInteractionStyle
  vtkvtkRenderingContextOpenGL2
  vtkvtkRenderingCore
  vtkvtkRenderingFreeType
  vtkvtkRenderingGL2PSOpenGL2
  vtkvtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
  message("Skipping ObserverMemberFunction: ${VTK_NOT_FOUND_MESSAGE}")
  return ()
endif()
message (STATUS "VTK_VERSION: ${VTK_VERSION}")
if (VTK_VERSION VERSION_LESS "8.90.0")
  # old system
  include(${VTK_USE_FILE})
  add_executable(ObserverMemberFunction MACOSX_BUNDLE ObserverMemberFunction.cxx )
  target_link_libraries(ObserverMemberFunction PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(ObserverMemberFunction MACOSX_BUNDLE ObserverMemberFunction.cxx )
  target_link_libraries(ObserverMemberFunction PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS ObserverMemberFunction
    MODULES ${VTK_LIBRARIES}
    )
endif ()

cd ObserverMemberFunction/build

cmake ..

cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

make

./ObserverMemberFunction