#include <gtk/gtk.h>
#include <stdlib.h>
#include <stdio.h>

static GtkWidget *entry1, *entry2, *entry3;

static void
button_clicked (void)
{
  const char *str1 = gtk_entry_get_text (GTK_ENTRY (entry1));
  const char *str2 = gtk_entry_get_text (GTK_ENTRY (entry2));

  int i1 = atoi (str1);
  int i2 = atoi (str2);
  
  char buf[10];
  snprintf (buf, 10, "%i", i1+i2);

  gtk_entry_set_text (GTK_ENTRY (entry3), buf);
}


int
main (int argc, char *argv[])
{
  GtkWidget *win;
  GtkWidget *vbox;
  GtkWidget *button;

  gtk_init (&argc, &argv);

  win = gtk_window_new (GTK_WINDOW_TOPLEVEL);

  vbox = gtk_vbox_new (TRUE, 0);
  gtk_container_add (GTK_CONTAINER (win), vbox);

  entry1 = gtk_entry_new ();
  gtk_box_pack_start (GTK_BOX (vbox), entry1, FALSE, FALSE, 0);
  entry2 = gtk_entry_new ();
  gtk_box_pack_start (GTK_BOX (vbox), entry2, FALSE, FALSE, 0);

  button = gtk_button_new_with_label ("Add");
  gtk_signal_connect (GTK_OBJECT (button), "clicked",
		      GTK_SIGNAL_FUNC (button_clicked),
		      NULL);
  gtk_box_pack_start (GTK_BOX (vbox), button, FALSE, FALSE, 0);

  entry3 = gtk_entry_new ();
  gtk_box_pack_start (GTK_BOX (vbox), entry3, FALSE, FALSE, 0);

  gtk_widget_show_all (win);

  gtk_main ();

  return 0;
}