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MouseEventsObserver

vtk-examples/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.

Other languages

See (Python)

Question

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

Code

MouseEventsObserver.cxx

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

namespace {

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

}

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());

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

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

  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->AddRenderer(renderer);
  renderWindow->SetWindowName("MouseEventsObserver");

  vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
  renderWindowInteractor->SetRenderWindow(renderWindow);

  vtkNew<vtkCallbackCommand> clickCallback;
  clickCallback->SetCallback(ClickCallbackFunction);

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

  renderWindow->Render();
  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:
  // auto* iren = static_cast<vtkRenderWindowInteractor*>(caller);
}

} // namespace

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(MouseEventsObserver)

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

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

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.