# MouseEventsObserver

VTKExamples/Cxx/Interaction/MouseEventsObserver

### Description

This example shows how to add an event observer to an existing style class.

See MouseEvents for a different approach that subclasses an existin interactor style to implement custom behaviors.

### Code

MouseEventsObserver.cxx

    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>
    #include <vtkSphereSource.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkCommand.h>
    #include <vtkActor.h>
    #include <vtkCallbackCommand.h>
    #include <vtkSmartPointer.h>
    #include <vtkPointPicker.h>
    #include <vtkCamera.h>
    #include <vtkNamedColors.h>

    namespace
    {
    void ClickCallbackFunction ( vtkObject* caller, long unsigned int eventId, void* clientData, void* callData );
    }

    int main(int, char *[])
    {

      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());

      vtkSmartPointer<vtkActor> actor =
        vtkSmartPointer<vtkActor>::New();
      actor->SetMapper(mapper);

      vtkSmartPointer<vtkNamedColors> colors =
        vtkSmartPointer<vtkNamedColors>::New();

      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      renderer->SetBackground(colors->GetColor3d("Slate_grey").GetData());
      renderer->AddActor(actor);

      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);

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

      vtkSmartPointer<vtkCallbackCommand> clickCallback =
        vtkSmartPointer<vtkCallbackCommand>::New();
      clickCallback->SetCallback ( ClickCallbackFunction );

      renderWindowInteractor->AddObserver ( vtkCommand::LeftButtonPressEvent, clickCallback );
      renderWindowInteractor->AddObserver ( vtkCommand::RightButtonPressEvent, clickCallback );
      renderWindowInteractor->AddObserver ( vtkCommand::KeyPressEvent, clickCallback );

      renderWindowInteractor->Initialize();
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

    namespace
    {
    void ClickCallbackFunction (
      vtkObject* vtkNotUsed(caller),
      long unsigned int eventId,
      void* vtkNotUsed(clientData),
      void* vtkNotUsed(callData) )
    {
      std::cout << "Click callback" << std::endl;
      std::cout << "Event: " << vtkCommand::GetStringFromEventId(eventId) << std::endl;

      // Get the interactor like this:
      // vtkRenderWindowInteractor *iren =
      //  static_cast<vtkRenderWindowInteractor*>(caller);

    }
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(MouseEventsObserver)

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

    add_executable(MouseEventsObserver MACOSX_BUNDLE MouseEventsObserver.cxx )

    target_link_libraries(MouseEventsObserver ${VTK_LIBRARIES})

### Download and Build MouseEventsObserver

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

    cd MouseEventsObserver/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:

    ./MouseEventsObserver

WINDOWS USERS

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