# LineWidget2

VTKExamples/Cxx/Widgets/LineWidget2

### Code

LineWidget2.cxx

    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkPolyData.h>
    #include <vtkSmartPointer.h>
    #include <vtkSphereSource.h>
    #include <vtkLineWidget2.h>
    #include <vtkLineRepresentation.h>
    #include <vtkCommand.h>

    // This does the actual work.
    // Callback for the interaction
    class vtkLineCallback : public vtkCommand
    {
      public:
        static vtkLineCallback *New()
        {
          return new vtkLineCallback;
        }

        virtual void Execute(vtkObject *caller, unsigned long, void*)
        {

          vtkLineWidget2 *lineWidget =
              reinterpret_cast<vtkLineWidget2*>(caller);

          // Get the actual box coordinates of the line
          vtkSmartPointer<vtkPolyData> polydata =
              vtkSmartPointer<vtkPolyData>::New();
          static_cast<vtkLineRepresentation*>(lineWidget->GetRepresentation())->GetPolyData (polydata);

          // Display one of the points, just so we know it's working
          double p[3];
          polydata->GetPoint(0,p);
          std::cout << "P: " << p[0] << " " << p[1] << " " << p[2] << std::endl;
        }
        vtkLineCallback(){}

    };

    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);

      vtkSmartPointer<vtkLineWidget2> lineWidget =
        vtkSmartPointer<vtkLineWidget2>::New();
      lineWidget->SetInteractor(renderWindowInteractor);
      lineWidget->CreateDefaultRepresentation();

      // You could do this if you want to set properties at this point:
      //vtkSmartPointer<vtkLineRepresentation> lineRepresentation =
        //vtkSmartPointer<vtkLineRepresentation>::New();
      //lineWidget->SetRepresentation(lineRepresentation);

      vtkSmartPointer<vtkLineCallback> lineCallback =
        vtkSmartPointer<vtkLineCallback>::New();

      lineWidget->AddObserver(vtkCommand::InteractionEvent,lineCallback);

      // Render
      renderWindow->Render();

      renderWindowInteractor->Initialize();
      renderWindow->Render();
      lineWidget->On();

      // Begin mouse interaction
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(LineWidget2)

    find_package(VTK COMPONENTS
      vtkCommonCore
      vtkCommonDataModel
      vtkFiltersSources
      vtkInteractionStyle
      vtkInteractionWidgets
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping LineWidget2: ${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(LineWidget2 MACOSX_BUNDLE LineWidget2.cxx )
      target_link_libraries(LineWidget2 PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(LineWidget2 MACOSX_BUNDLE LineWidget2.cxx )
      target_link_libraries(LineWidget2 PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS LineWidget2
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build LineWidget2

Click here to download LineWidget2 and its CMakeLists.txt file. Once the tarball LineWidget2.tar has been downloaded and extracted,

    cd LineWidget2/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:

    ./LineWidget2

WINDOWS USERS

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