#include <gtk/gtk.h>

static gint delete_event_cb(GtkWidget* w, GdkEventAny* e, gpointer data);
static void button_click_cb(GtkWidget* w, gpointer data);

int 
main(int argc, char* argv[])
{
  GtkWidget* window;
  GtkWidget* button;
  GtkWidget* label;

  gtk_init(&argc, &argv);  

  window = gtk_window_new(GTK_WINDOW_TOPLEVEL);

  button = gtk_button_new();

  label  = gtk_label_new("Hello, World!");

  gtk_container_add(GTK_CONTAINER(button), label);
  gtk_container_add(GTK_CONTAINER(window), button);

  gtk_window_set_title(GTK_WINDOW(window), "Hello");
  gtk_container_set_border_width(GTK_CONTAINER(button), 10);
  
  gtk_signal_connect(GTK_OBJECT(window),
                     "delete_event",
                     GTK_SIGNAL_FUNC(delete_event_cb),
                     NULL);

  gtk_signal_connect(GTK_OBJECT(button),
                     "clicked",
                     GTK_SIGNAL_FUNC(button_click_cb),
                     label);

  gtk_widget_show_all(window);

  gtk_main();

  return 0;
}

static gint 
delete_event_cb(GtkWidget* window, GdkEventAny* e, gpointer data)
{
  gtk_main_quit();
  return FALSE;
}

static void 
button_click_cb(GtkWidget* w, gpointer data)
{
  GtkWidget* label;
  gchar* text;
  gchar* tmp;

  label = GTK_WIDGET(data);

  gtk_label_get(GTK_LABEL(label), &text);

  tmp = g_strdup(text);

  g_strreverse(tmp);

  gtk_label_set_text(GTK_LABEL(label), tmp);

  g_free(tmp);
}