#include <gtk/gtk.h>

/* This is a callback function. The data arguments are ignored

 * in this example. More on callbacks below. */

static void hello( GtkWidget *widget,

                   gpointer   data )

{

    g_print ("Hello World\n");

}

static gboolean delete_event( GtkWidget *widget,

                              GdkEvent  *event,

                              gpointer   data )

{

    /* If you return FALSE in the "delete_event" signal handler,

     * GTK will emit the "destroy" signal. Returning TRUE means

     * you don't want the window to be destroyed.

     * This is useful for popping up 'are you sure you want to quit?'

     * type dialogs. */

    g_print ("delete event occurred\n");

    /* Change TRUE to FALSE and the main window will be destroyed with

     * a "delete_event". */

    return TRUE;

}

/* Another callback */

static void destroy( GtkWidget *widget,

                     gpointer   data )

{

    gtk_main_quit ();

}

int main( int   argc,

          char *argv[] )

{

    /* GtkWidget is the storage type for widgets */

    GtkWidget *window;

    GtkWidget *button;

    /* This is called in all GTK applications. Arguments are parsed

     * from the command line and are returned to the application. */

    gtk_init (&argc, &argv);

    /* create a new window */

    window = gtk_window_new (GTK_WINDOW_TOPLEVEL);

    /* When the window is given the "delete_event" signal (this is given

     * by the window manager, usually by the "close" option, or on the

     * titlebar), we ask it to call the delete_event () function

     * as defined above. The data passed to the callback

     * function is NULL and is ignored in the callback function. */

    g_signal_connect (G_OBJECT (window), "delete_event",

		      G_CALLBACK (delete_event), NULL);

    /* Here we connect the "destroy" event to a signal handler.  

     * This event occurs when we call gtk_widget_destroy() on the window,

     * or if we return FALSE in the "delete_event" callback. */

    g_signal_connect (G_OBJECT (window), "destroy",

		      G_CALLBACK (destroy), NULL);

    /* Sets the border width of the window. */

    gtk_container_set_border_width (GTK_CONTAINER (window), 10);

    /* Creates a new button with the label "Hello World". */

    button = gtk_button_new_with_label ("Hello World");

    /* When the button receives the "clicked" signal, it will call the

     * function hello() passing it NULL as its argument.  The hello()

     * function is defined above. */

    g_signal_connect (G_OBJECT (button), "clicked",

		      G_CALLBACK (hello), NULL);

    /* This will cause the window to be destroyed by calling

     * gtk_widget_destroy(window) when "clicked".  Again, the destroy

     * signal could come from here, or the window manager. */

    g_signal_connect_swapped (G_OBJECT (button), "clicked",

			      G_CALLBACK (gtk_widget_destroy),

                              G_OBJECT (window));

    /* This packs the button into the window (a gtk container). */

    gtk_container_add (GTK_CONTAINER (window), button);

    /* The final step is to display this newly created widget. */

    gtk_widget_show (button);

    /* and the window */

    gtk_widget_show (window);

    /* All GTK applications must have a gtk_main(). Control ends here

     * and waits for an event to occur (like a key press or

     * mouse event). */

    gtk_main ();

    return 0;

}