#include <gtk/gtk.h>

 /*Global variable used to indicate active state of the

spinner. TRUE = active, FALSE = not-active. This is because 

there isn't a current function for C that does this for us*/

gboolean active;  

/*This is the callback function. It is a handler function 

which reacts to the signal. In this case, it will cause the 

spinner to start and stop according to how many times the user 

presses the spacebar.*/ 

static gboolean

key_pressed_event (GtkWidget *widget,

                   GdkEvent  *event,

                   gpointer   user_data)

{

  GtkWidget *spinner = user_data;

  guint keyval;

  /*Extracts the keyval from an event. And stores it in the  variable 

  "keyval" (we give the function the address). In this case, the 

  event is GdkEventKey, a key press event*/

  gdk_event_get_keyval (event, &keyval);  

  /*Grabbing the boolean value from the spinner*/

  g_object_get (GTK_SPINNER (spinner), "active", &active, NULL);

  if (keyval == GDK_KEY_space) {

     if (active) {

         gtk_spinner_stop (GTK_SPINNER (spinner));

     }

     else {

         gtk_spinner_start (GTK_SPINNER (spinner));

     } 

  }

return TRUE;

}

static void

activate (GtkApplication *app,

          gpointer        user_data)

{

  GtkWidget *window;

  GtkWidget *spinner;

  /*Create a window with a title, border width and a default size*/

  window = gtk_application_window_new (app);

  gtk_window_set_title (GTK_WINDOW (window), "Spinner Example");

  gtk_window_set_default_size (GTK_WINDOW (window), 200, 200);

  gtk_container_set_border_width (GTK_CONTAINER(window), 30);

  /*Create a spinner, with extra horizontal and vertical space*/

  spinner = gtk_spinner_new ();

  gtk_spinner_start (GTK_SPINNER (spinner));

  gtk_container_add (GTK_CONTAINER (window), spinner);

  /*Connecting the key-press-event signal to the callback*/

  g_signal_connect (GTK_WINDOW (window), "key-press-event", 

                    G_CALLBACK (key_pressed_event), spinner);

  gtk_widget_show_all (window);

}

int

main (int argc, char **argv)

{

  GtkApplication *app;

  int status;

  app = gtk_application_new ("org.gtk.example", G_APPLICATION_FLAGS_NONE);

  g_signal_connect (app, "activate", G_CALLBACK (activate), NULL);

  status = g_application_run (G_APPLICATION (app), argc, argv);

  g_object_unref (app);

  return status;

}