# ClientData

VTKExamples/Cxx/Interaction/ClientData

### Code

ClientData.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>

    static 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();

      // Allow the observer to access the sphereSource
      keypressCallback->SetClientData(sphereSource);
      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*, long unsigned int vtkNotUsed(eventId), void* clientData, void* vtkNotUsed(callData) )
    {
      // Prove that we can access the sphere source
      vtkSphereSource* sphereSource =
        static_cast<vtkSphereSource*>(clientData);
      std::cout << "Radius is " << sphereSource->GetRadius() << std::endl;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(ClientData)

    find_package(VTK COMPONENTS
      vtkCommonCore
      vtkCommonDataModel
      vtkFiltersSources
      vtkInteractionStyle
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping ClientData: ${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(ClientData MACOSX_BUNDLE ClientData.cxx )
      target_link_libraries(ClientData PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(ClientData MACOSX_BUNDLE ClientData.cxx )
      target_link_libraries(ClientData PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS ClientData
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build ClientData

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

    cd ClientData/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:

    ./ClientData

WINDOWS USERS

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