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KeypressEvents

vtk-examples/Cxx/Interaction/KeypressEvents


Description

This example shows how to catch keypress events. For example, do something if the user presses the 's' key.

Question

If you have a question about this example, please use the VTK Discourse Forum

Code

KeypressEvents.cxx

#include <vtkActor.h>
#include <vtkInteractorStyleTrackballCamera.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkObjectFactory.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSphereSource.h>

namespace {

// Define interaction style
class KeyPressInteractorStyle : public vtkInteractorStyleTrackballCamera
{
public:
  static KeyPressInteractorStyle* New();
  vtkTypeMacro(KeyPressInteractorStyle, vtkInteractorStyleTrackballCamera);

  virtual void OnKeyPress() override
  {
    // Get the keypress
    vtkRenderWindowInteractor* rwi = this->Interactor;
    std::string key = rwi->GetKeySym();

    // Output the key that was pressed
    std::cout << "Pressed " << key << std::endl;

    // Handle an arrow key
    if (key == "Up")
    {
      std::cout << "The up arrow was pressed." << std::endl;
    }

    // Handle a "normal" key
    if (key == "a")
    {
      std::cout << "The a key was pressed." << std::endl;
    }

    // Forward events
    vtkInteractorStyleTrackballCamera::OnKeyPress();
  }
};
vtkStandardNewMacro(KeyPressInteractorStyle);

} // namespace

int main(int, char*[])
{
  vtkNew<vtkNamedColors> colors;

  vtkNew<vtkSphereSource> sphereSource;
  sphereSource->SetCenter(0.0, 0.0, 0.0);
  sphereSource->SetRadius(5.0);
  sphereSource->Update();

  vtkNew<vtkPolyDataMapper> mapper;
  mapper->SetInputConnection(sphereSource->GetOutputPort());

  // Create an actor
  vtkNew<vtkActor> actor;
  actor->SetMapper(mapper);
  actor->GetProperty()->SetColor(colors->GetColor3d("MistyRose").GetData());

  // A renderer and render window
  vtkNew<vtkRenderer> renderer;
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->AddRenderer(renderer);
  renderWindow->SetWindowName("KeypressEvents");

  // An interactor
  vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
  renderWindowInteractor->SetRenderWindow(renderWindow);

  vtkNew<KeyPressInteractorStyle> style;
  renderWindowInteractor->SetInteractorStyle(style);
  style->SetCurrentRenderer(renderer);

  renderer->AddActor(actor);
  renderer->SetBackground(colors->GetColor3d("SlateGray").GetData());

  renderWindow->Render();

  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(KeypressEvents)

find_package(VTK COMPONENTS 
  vtkCommonColor
  vtkCommonCore
  vtkCommonDataModel
  vtkFiltersSources
  vtkInteractionStyle
  vtkRenderingContextOpenGL2
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingGL2PSOpenGL2
  vtkRenderingOpenGL2
  QUIET
)

if (NOT VTK_FOUND)
  message("Skipping KeypressEvents: ${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(KeypressEvents MACOSX_BUNDLE KeypressEvents.cxx )
  target_link_libraries(KeypressEvents PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(KeypressEvents MACOSX_BUNDLE KeypressEvents.cxx )
  target_link_libraries(KeypressEvents PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS KeypressEvents
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build KeypressEvents

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

cd KeypressEvents/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:

./KeypressEvents

WINDOWS USERS

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