Stopping VTK Timer Callback

Question

Referring to This example: https://lorensen.github.io/VTKExamples/site/Cxx/Utilities/Animation/

I made a small change in the callback function, to stop it after certain number of timer count.

#include <vtkSmartPointer.h>
#include <vtkSphereSource.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkCommand.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <iostream>
using namespace std;


class vtkTimerCallback2 : public vtkCommand
{
  public:
    static vtkTimerCallback2 *New()
    {
      vtkTimerCallback2 *cb = new vtkTimerCallback2;
      cb->TimerCount = 0;
      return cb;
    }

    virtual void Execute(vtkObject *caller, unsigned long eventId,
                         void * vtkNotUsed(callData))
    {
      if (vtkCommand::TimerEvent == eventId)
      {
        ++this->TimerCount;
      }
      vtkRenderWindowInteractor *iren = vtkRenderWindowInteractor::SafeDownCast(caller);
      std::cout << this->TimerCount << std::endl;
      if(TimerCount<20)
      {      
          actor->SetPosition(this->TimerCount, this->TimerCount,0);      
          iren->GetRenderWindow()->Render();
      }
      else
     {    
          //iren->DestroyTimer();
          //The following will print 1 if timer is destroyed
          //And 0, if it is not destroyed

          cout << "Timer Destroyed: " <<iren->DestroyTimer() << endl;;
      }

    }

  private:
    int TimerCount;
  public:
    vtkActor* actor;
};

int main(int, char* [])
{
  // Create a sphere
  vtkSmartPointer<vtkSphereSource> sphereSource =
    vtkSmartPointer<vtkSphereSource>::New();
  sphereSource->SetCenter(0.0, 0.0, 0.0);
  sphereSource->SetRadius(5.0);
  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);

  // Create a renderer, render window, and interactor
  vtkSmartPointer<vtkRenderer> renderer =
    vtkSmartPointer<vtkRenderer>::New();
  vtkSmartPointer<vtkRenderWindow> renderWindow =
    vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->AddRenderer(renderer);
  vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  renderWindowInteractor->SetRenderWindow(renderWindow);

  // Add the actor to the scene
  renderer->AddActor(actor);
  renderer->SetBackground(1,1,1); // Background color white

  // Render and interact
  renderWindow->Render();

  // Initialize must be called prior to creating timer events.
  renderWindowInteractor->Initialize();

  // Sign up to receive TimerEvent
  vtkSmartPointer<vtkTimerCallback2> cb =
    vtkSmartPointer<vtkTimerCallback2>::New();
  cb->actor = actor;
  renderWindowInteractor->AddObserver(vtkCommand::TimerEvent, cb);

  int timerId = renderWindowInteractor->CreateRepeatingTimer(100);
  std::cout << "timerId: " << timerId << std::endl;

  // Start the interaction and timer
  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

The issue is that, if I interact with the renderWindowInteractor using mouse during the animation, then later after releasing the mouse, callback function runs forever and it can be confirmed by the console log (Basically cout << "Timer Destroyed: " <<iren->DestroyTimer() << endl; returns 0, meaning timer destruction failed). However, otherwise it works as intended and stops, since nothing is printed "forever" in the console. Am I doing something wrong? Is this behavior expected?

Answer 1

I solved the problem myself. Basically DestroyTimer() without arguments is kept for backward compatibility. DestroyTimer(int timerId) is what needs to be called. Hence, the following works perfectly now:

#include <vtkSmartPointer.h>
#include <vtkSphereSource.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkCommand.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <iostream>
using namespace std;


class vtkTimerCallback2 : public vtkCommand
{
  public:
    int timerId;
    static vtkTimerCallback2 *New()
    {
      vtkTimerCallback2 *cb = new vtkTimerCallback2;
      cb->TimerCount = 0;
      return cb;
    }

    virtual void Execute(vtkObject *caller, unsigned long eventId,
                         void * vtkNotUsed(callData))
    {
      if (vtkCommand::TimerEvent == eventId)
      {
        ++this->TimerCount;
      }
      vtkRenderWindowInteractor *iren = vtkRenderWindowInteractor::SafeDownCast(caller);
      std::cout << this->TimerCount << std::endl;
      if(TimerCount<20)
      {      
          actor->SetPosition(this->TimerCount, this->TimerCount,0);      
          iren->GetRenderWindow()->Render();
      }
      else
     {    
          //iren->DestroyTimer();
          //The following will print 1 if timer is destroyed
          //And 0, if it is not destroyed

          cout << "Timer Destroyed: " <<iren->DestroyTimer(this->timerId) << endl;
      }

    }

  private:
    int TimerCount;
  public:
    vtkActor* actor;
};

int main(int, char* [])
{
  // Create a sphere
  vtkSmartPointer<vtkSphereSource> sphereSource =
    vtkSmartPointer<vtkSphereSource>::New();
  sphereSource->SetCenter(0.0, 0.0, 0.0);
  sphereSource->SetRadius(5.0);
  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);

  // Create a renderer, render window, and interactor
  vtkSmartPointer<vtkRenderer> renderer =
    vtkSmartPointer<vtkRenderer>::New();
  vtkSmartPointer<vtkRenderWindow> renderWindow =
    vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->AddRenderer(renderer);
  vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  renderWindowInteractor->SetRenderWindow(renderWindow);

  // Add the actor to the scene
  renderer->AddActor(actor);
  renderer->SetBackground(1,1,1); // Background color white

  // Render and interact
  renderWindow->Render();

  // Initialize must be called prior to creating timer events.
  renderWindowInteractor->Initialize();

  // Sign up to receive TimerEvent
  vtkSmartPointer<vtkTimerCallback2> cb =
    vtkSmartPointer<vtkTimerCallback2>::New();
  cb->actor = actor;
  renderWindowInteractor->AddObserver(vtkCommand::TimerEvent, cb);

  int timerId = renderWindowInteractor->CreateRepeatingTimer(100);
   cb->timerId = timerId;
  std::cout << "timerId: " << timerId << std::endl;

  // Start the interaction and timer
  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

My mistake, I did not read the documentation carefully. I hope it may be useful.