# KeypressObserver

VTKExamples/Cxx/Interaction/KeypressObserver

### Code

KeypressObserver.cxx

    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkSmartPointer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkPolyData.h>
    #include <vtkSphereSource.h>
    #include <vtkCallbackCommand.h>
    #include <vtkCommand.h>

    void KeypressCallbackFunction (
      vtkObject* caller,
      long unsigned int eventId,
      void* clientData,
      void* callData );

    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);

      vtkSmartPointer<vtkCallbackCommand> keypressCallback =
        vtkSmartPointer<vtkCallbackCommand>::New();
      keypressCallback->SetCallback ( KeypressCallbackFunction );
      renderWindowInteractor->AddObserver ( vtkCommand::KeyPressEvent, keypressCallback );

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

      return EXIT_SUCCESS;
    }

    void KeypressCallbackFunction ( vtkObject* caller, long unsigned int vtkNotUsed(eventId), void* vtkNotUsed(clientData), void* vtkNotUsed(callData) )
    {
      std::cout << "Keypress callback" << std::endl;

      vtkRenderWindowInteractor *iren =
        static_cast<vtkRenderWindowInteractor*>(caller);

      std::cout << "Pressed: " << iren->GetKeySym() << std::endl;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(KeypressObserver)

    find_package(VTK REQUIRED)
    include(${VTK_USE_FILE})

    add_executable(KeypressObserver MACOSX_BUNDLE KeypressObserver.cxx )

    target_link_libraries(KeypressObserver ${VTK_LIBRARIES})

### Download and Build KeypressObserver

Click here to download KeypressObserver and its CMakeLists.txt file. Once the tarball KeypressObserver.tar has been downloaded and extracted,

    cd KeypressObserver/build

If VTK is installed:

    cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

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

Build the project:

    make

and run it:

    ./KeypressObserver

WINDOWS USERS PLEASE NOTE: Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.