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# HoverWidget

VTKEx/Cxx/Widgets/HoverWidget

Question

If you have a simple question about this example contact us at VTKExProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

### Code

HoverWidget.cxx

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

    class vtkHoverCallback : public vtkCommand
    {
      public:
        static vtkHoverCallback *New()
        {
          return new vtkHoverCallback;
        }

        vtkHoverCallback() {}

        virtual void Execute(vtkObject*, unsigned long event, void *vtkNotUsed(calldata))
        {
          switch (event)
          {
            case vtkCommand::TimerEvent:
              std::cout << "TimerEvent -> the mouse stopped moving and the widget hovered" << std::endl;
              break;
            case vtkCommand::EndInteractionEvent:
              std::cout << "EndInteractionEvent -> the mouse started to move" << std::endl;
              break;
          }
        }
    };

    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);

      // Create the widget
      vtkSmartPointer<vtkHoverWidget> hoverWidget =
        vtkSmartPointer<vtkHoverWidget>::New();
      hoverWidget->SetInteractor(renderWindowInteractor);
      hoverWidget->SetTimerDuration(1000);

      // Create a callback to listen to the widget's two VTK events
      vtkSmartPointer<vtkHoverCallback> hoverCallback =
        vtkSmartPointer<vtkHoverCallback>::New();
      hoverWidget->AddObserver(vtkCommand::TimerEvent,hoverCallback);
      hoverWidget->AddObserver(vtkCommand::EndInteractionEvent,hoverCallback);

      renderWindow->Render();

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

      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(HoverWidget)

    find_package(VTK COMPONENTS
      vtkvtkCommonCore
      vtkvtkFiltersSources
      vtkvtkInteractionStyle
      vtkvtkInteractionWidgets
      vtkvtkRenderingContextOpenGL2
      vtkvtkRenderingCore
      vtkvtkRenderingFreeType
      vtkvtkRenderingGL2PSOpenGL2
      vtkvtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping HoverWidget: ${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(HoverWidget MACOSX_BUNDLE HoverWidget.cxx )
      target_link_libraries(HoverWidget PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(HoverWidget MACOSX_BUNDLE HoverWidget.cxx )
      target_link_libraries(HoverWidget PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS HoverWidget
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build HoverWidget

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

    cd HoverWidget/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:

    ./HoverWidget

WINDOWS USERS

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