IA__gtk_main_quit: assertion `main_loops != NULL' failed

Felix · **Joined:** Mon Oct 17, 2011 10:18 am **Posts:** 26

Hello All,

I will be more than grateful if you could find time for answering me.

General:
I am writing a GUI, in which I receive real time video from several cameras of a robot (using ROS).

The problem:
Everything works perfectly, until the stage I want to close the top level window (by clicking the X button).
The window is destroyed, but I receive this critical warning:

Quote:

Gtk-CRITICAL **: IA__gtk_main_quit: assertion `main_loops != NULL' failed

My analysis:
I connect the "destroy" signal to the function "gtk_main_quit" in the next way:

Code:

g_signal_connect( G_OBJECT(globalTopLevelWindow), "destroy", G_CALLBACK(gtk_main_quit), NULL ); 

After analysing the code I have inferred that this warning is thrown by this line of code:

Code:

g_return_if_fail (main_loops != NULL)

which is the first line of "gtk_main_quit" function.
And it means that there are no main loops executing when the process is in this line of code.

The questions:
1. Actually I don´t understand why the warning exists? It is OK, the assertion should fail. Am I right? Should I ignore this? Hmm...:-\
2. How can I fix this?

Thanks in advance,
Felix.

P.S. The code of my main (for your convenience):

Code:

int main(int argc, char **argv)
{
   ros::init(argc, argv, "image_listener");
    ros::NodeHandle nh;
   ros::Rate loop_rate(100);                                                                   // Rate class instance.   
   ImageManagmentStruct LeftCameraImageStruct, RightCameraImageStruct, KinectImageStruct;      // Structs for image menagment.      
    
    // Getting the resizing parameter from the launch file.
    if ( !nh.getParam("resizing_factor", globalResizingFactor) )
    {
        ROS_ERROR ("The resizing factor was not loaded succesfully. Aborting...\n");
        ros::shutdown();
    }

    // Initializing the image/camera data structures.   
   dataStructuresInitialization ( &LeftCameraImageStruct, &RightCameraImageStruct, &KinectImageStruct );
       
    // GTK library initialization
   gtk_init ( &argc, &argv );

    // Creating a top level window and connecting it to a sygnal.    
    createMainInterfaceWindow (); 
    
    // Creating a fixed container, which will hold all the widgets of the GUI.
    createFixedContainer ();
    
    // Creating a GtkGrid widget, which will contain all the images.
    createGtkTable ();
    
    // Attaching the created table to the Container.
    gtk_fixed_put (GTK_FIXED (pGlobalFixedContainer), pGlobalGtkTable, IMAGES_HORIZONTAL_PLACEMENT, IMAGES_VERTIACL_PLACEMENT);
     
    // Subscribing in order to receive images.
   ros::Subscriber subLeft = nh.subscribe<sensor_msgs::Image> ("leftCameraTopic", 10, boost::bind(imageCallback, _1, globalArrayOfImages[0]));    
    ros::Subscriber subRight = nh.subscribe<sensor_msgs::Image> ("rightCameraTopic", 10, boost::bind(imageCallback, _1, globalArrayOfImages[1])); 
    ros::Subscriber subKinect = nh.subscribe<sensor_msgs::Image> ("kinectCameraTopic", 10, boost::bind(imageCallback, _1, globalArrayOfImages[2]));
       
    while ( ros::ok() )
    {
      // Showing the main window, with the attached image.
      if ( GTK_IS_WIDGET (globalTopLevelWindow) )
      {
         gtk_widget_show_all ( globalTopLevelWindow );       
      }
      else
      {
           ROS_INFO ("The top level window of the application was closed...Exiting the program.\n");
           return 0;
      } 
       
      // Allowing "imageCallback" to be called. 
      ros::spinOnce();
       
              // Running the main GTK iteration loop.
      gtk_main_iteration_do(0);   
          
      // Sleep
       loop_rate.sleep ();    
    }  
    return 0;
}

Paul Childs · **Posted:** Tue Jan 03, 2012 8:40 pm

return_if_fail (main_loops!=NULL) returning means you have no main loops running.
This is the case as you have called gtk_main_iteration_do which only runs once and then quits (leaving no main loops). By the time you click the x your program will be running the sleep command rather than the gtk_main loop. You should use gtk_main rather than gtk_main_iteration_do

errol · **Posted:** Wed Jan 04, 2012 8:01 am

Hi,

This is how I would get around your problem. First it avoids the use of a macro that is really for the implementation of GtkWidget. By using a combination of 'gtk_main()' and 'g_timeout_add()' I have been able to avoid having to busy loop, but still have ROS called at a rate of 100Hz. Also I am not forcing the system to sleep and do no work so you should get a more snappier GUI response.

Code:

gboolean do_ros(gpointer data)
{
    if (ros::ok())
        ros::spinOnce();
    else
        gtk_main_quit();

    return TRUE;
}

int main(int argc, char **argv)
{
   ros::init(argc, argv, "image_listener");
    ros::NodeHandle nh;
   ImageManagmentStruct LeftCameraImageStruct, RightCameraImageStruct, KinectImageStruct;      // Structs for image menagment.      
   
    // Getting the resizing parameter from the launch file.
    if ( !nh.getParam("resizing_factor", globalResizingFactor) )
    {
        ROS_ERROR ("The resizing factor was not loaded succesfully. Aborting...\n");
        ros::shutdown();
    }

    // Initializing the image/camera data structures.   
   dataStructuresInitialization ( &LeftCameraImageStruct, &RightCameraImageStruct, &KinectImageStruct );
       
    // GTK library initialization
   gtk_init ( &argc, &argv );

    // Creating a top level window and connecting it to a sygnal.   
    createMainInterfaceWindow ();
   
    // Creating a fixed container, which will hold all the widgets of the GUI.
    createFixedContainer ();
   
    // Creating a GtkGrid widget, which will contain all the images.
    createGtkTable ();
   
    // Attaching the created table to the Container.
    gtk_fixed_put (GTK_FIXED (pGlobalFixedContainer), pGlobalGtkTable, IMAGES_HORIZONTAL_PLACEMENT, IMAGES_VERTIACL_PLACEMENT);
     
   // Subscribing in order to receive images.
   ros::Subscriber subLeft = nh.subscribe<sensor_msgs::Image> ("leftCameraTopic", 10, boost::bind(imageCallback, _1, globalArrayOfImages[0]));    
    ros::Subscriber subRight = nh.subscribe<sensor_msgs::Image> ("rightCameraTopic", 10, boost::bind(imageCallback, _1, globalArrayOfImages[1]));
    ros::Subscriber subKinect = nh.subscribe<sensor_msgs::Image> ("kinectCameraTopic", 10, boost::bind(imageCallback, _1, globalArrayOfImages[2]));
 

    g_timeout_add(1000 / 100, do_ros, NULL);

    gtk_widget_show_all(globalTopLevelWindow);

    gtk_main();

    ROS_INFO ("The top level window of the application was closed...Exiting the program.\n");

    return 0;
}

Felix · **Joined:** Mon Oct 17, 2011 10:18 am **Posts:** 26

Paul Childs wrote:

return_if_fail (main_loops!=NULL) returning means you have no main loops running.
This is the case as you have called gtk_main_iteration_do which only runs once and then quits (leaving no main loops). By the time you click the x your program will be running the sleep command rather than the gtk_main loop. You should use gtk_main rather than gtk_main_iteration_do

Paul, thank you for your answer.

Felix · **Joined:** Mon Oct 17, 2011 10:18 am **Posts:** 26

errol wrote:

Hi,

This is how I would get around your problem. First it avoids the use of a macro that is really for the implementation of GtkWidget. By using a combination of 'gtk_main()' and 'g_timeout_add()' I have been able to avoid having to busy loop, but still have ROS called at a rate of 100Hz. Also I am not forcing the system to sleep and do no work so you should get a more snappier GUI response.

Code:

gboolean do_ros(gpointer data)
{
    if (ros::ok())
        ros::spinOnce();
    else
        gtk_main_quit();

    return TRUE;
}

int main(int argc, char **argv)
{
   ros::init(argc, argv, "image_listener");
    ros::NodeHandle nh;
   ImageManagmentStruct LeftCameraImageStruct, RightCameraImageStruct, KinectImageStruct;      // Structs for image menagment.      
   
    // Getting the resizing parameter from the launch file.
    if ( !nh.getParam("resizing_factor", globalResizingFactor) )
    {
        ROS_ERROR ("The resizing factor was not loaded succesfully. Aborting...\n");
        ros::shutdown();
    }

    // Initializing the image/camera data structures.   
   dataStructuresInitialization ( &LeftCameraImageStruct, &RightCameraImageStruct, &KinectImageStruct );
       
    // GTK library initialization
   gtk_init ( &argc, &argv );

    // Creating a top level window and connecting it to a sygnal.   
    createMainInterfaceWindow ();
   
    // Creating a fixed container, which will hold all the widgets of the GUI.
    createFixedContainer ();
   
    // Creating a GtkGrid widget, which will contain all the images.
    createGtkTable ();
   
    // Attaching the created table to the Container.
    gtk_fixed_put (GTK_FIXED (pGlobalFixedContainer), pGlobalGtkTable, IMAGES_HORIZONTAL_PLACEMENT, IMAGES_VERTIACL_PLACEMENT);
     
   // Subscribing in order to receive images.
   ros::Subscriber subLeft = nh.subscribe<sensor_msgs::Image> ("leftCameraTopic", 10, boost::bind(imageCallback, _1, globalArrayOfImages[0]));    
    ros::Subscriber subRight = nh.subscribe<sensor_msgs::Image> ("rightCameraTopic", 10, boost::bind(imageCallback, _1, globalArrayOfImages[1]));
    ros::Subscriber subKinect = nh.subscribe<sensor_msgs::Image> ("kinectCameraTopic", 10, boost::bind(imageCallback, _1, globalArrayOfImages[2]));
 

    g_timeout_add(1000 / 100, do_ros, NULL);

    gtk_widget_show_all(globalTopLevelWindow);

    gtk_main();

    ROS_INFO ("The top level window of the application was closed...Exiting the program.\n");

    return 0;
}

Dear Errol,

Again, as before, I am grateful for your professional answer and the time you have spent to write it. I really appreciate your help, and I will try to use your advice.

Best,
Felix.

Felix · **Joined:** Mon Oct 17, 2011 10:18 am **Posts:** 26

errol wrote:

Hi,

This is how I would get around your problem. First it avoids the use of a macro that is really for the implementation of GtkWidget. By using a combination of 'gtk_main()' and 'g_timeout_add()' I have been able to avoid having to busy loop, but still have ROS called at a rate of 100Hz. Also I am not forcing the system to sleep and do no work so you should get a more snappier GUI response.

Code:

gboolean do_ros(gpointer data)
{
    if (ros::ok())
        ros::spinOnce();
    else
        gtk_main_quit();

    return TRUE;
}

int main(int argc, char **argv)
{
   ros::init(argc, argv, "image_listener");
    ros::NodeHandle nh;
   ImageManagmentStruct LeftCameraImageStruct, RightCameraImageStruct, KinectImageStruct;      // Structs for image menagment.      
   
    // Getting the resizing parameter from the launch file.
    if ( !nh.getParam("resizing_factor", globalResizingFactor) )
    {
        ROS_ERROR ("The resizing factor was not loaded succesfully. Aborting...\n");
        ros::shutdown();
    }

    // Initializing the image/camera data structures.   
   dataStructuresInitialization ( &LeftCameraImageStruct, &RightCameraImageStruct, &KinectImageStruct );
       
    // GTK library initialization
   gtk_init ( &argc, &argv );

    // Creating a top level window and connecting it to a sygnal.   
    createMainInterfaceWindow ();
   
    // Creating a fixed container, which will hold all the widgets of the GUI.
    createFixedContainer ();
   
    // Creating a GtkGrid widget, which will contain all the images.
    createGtkTable ();
   
    // Attaching the created table to the Container.
    gtk_fixed_put (GTK_FIXED (pGlobalFixedContainer), pGlobalGtkTable, IMAGES_HORIZONTAL_PLACEMENT, IMAGES_VERTIACL_PLACEMENT);
     
   // Subscribing in order to receive images.
   ros::Subscriber subLeft = nh.subscribe<sensor_msgs::Image> ("leftCameraTopic", 10, boost::bind(imageCallback, _1, globalArrayOfImages[0]));    
    ros::Subscriber subRight = nh.subscribe<sensor_msgs::Image> ("rightCameraTopic", 10, boost::bind(imageCallback, _1, globalArrayOfImages[1]));
    ros::Subscriber subKinect = nh.subscribe<sensor_msgs::Image> ("kinectCameraTopic", 10, boost::bind(imageCallback, _1, globalArrayOfImages[2]));
 

    g_timeout_add(1000 / 100, do_ros, NULL);

    gtk_widget_show_all(globalTopLevelWindow);

    gtk_main();

    ROS_INFO ("The top level window of the application was closed...Exiting the program.\n");

    return 0;
}

Dear Errol,

I have changed my implementation, and everything works perfectly!!!
Thank you for your professionalism and your help :)

Felix.

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