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

static gboolean
on_window2_configure	(GtkWidget	      *window,
			 GdkEventConfigure    *event,
			 gpointer	       useless_data)
{
      GtkWidget *window1;
      gint  x,  y;
      gint dx, dy;
      gint x2, y2;

      x = GPOINTER_TO_INT (g_object_get_data (G_OBJECT(window), "pos_x"));
      y = GPOINTER_TO_INT (g_object_get_data (G_OBJECT(window), "pos_y"));
  
      dx = event->x - x;
      dy = event->y - y;

      window1 = GTK_WIDGET(useless_data); 

      g_message ("dx:%d, dy:%d", dx, dy);

      g_object_set_data (G_OBJECT(window), "pos_x", GINT_TO_POINTER(event->x));
      g_object_set_data (G_OBJECT(window), "pos_y", GINT_TO_POINTER(event->y));

      gtk_window_get_position (GTK_WINDOW(window1), &x2, &y2);

      x2 += dx;
      y2 += dy;

      gtk_window_move (GTK_WINDOW(window1), x2, y2);

      return FALSE;
}

static void
on_window1_button_press	    (GtkWidget	    *widget,
			     GdkEventButton *event,
			     gpointer	     null)
{
    if (event->button == 1)
      {
	gtk_window_begin_move_drag (GTK_WINDOW(widget), event->button, event->x_root, event->y_root, event->time);
      }
}

static void
on_window2_button_press	    (GtkWidget	    *widget,
			     GdkEventButton *event,
			     gpointer	     null)
{
    if (event->button == 1)
      {
	gtk_window_begin_move_drag (GTK_WINDOW(widget), event->button, event->x_root, event->y_root, event->time);
      }
}

gint
main (gint argc, gchar **argv)
{
      GtkWidget	    *window1,
		    *window2;

      gtk_init (&argc, &argv);

      window1 = gtk_window_new (GTK_WINDOW_TOPLEVEL);
      gtk_widget_add_events (window1, GDK_BUTTON_PRESS_MASK);
      gtk_widget_realize (window1);
      gtk_widget_set_size_request (window1, 100, 100);
    
      gtk_window_set_decorated (GTK_WINDOW(window1), FALSE);
      gtk_widget_show_all (window1);
      gtk_window_move (GTK_WINDOW(window1), 100, 100);

      window2 = gtk_window_new (GTK_WINDOW_TOPLEVEL);
      gtk_widget_add_events (window2, GDK_BUTTON_PRESS_MASK);
      gtk_widget_realize (window2);
      gtk_widget_set_size_request (window2, 100, 100);

      gtk_window_set_decorated (GTK_WINDOW(window2), FALSE);
      gtk_widget_show_all (window2);
      gtk_window_move (GTK_WINDOW(window2), 200, 300);

      g_object_set_data (G_OBJECT(window2), "pos_x", GINT_TO_POINTER(200));
      g_object_set_data (G_OBJECT(window2), "pos_y", GINT_TO_POINTER(300));

      g_signal_connect (G_OBJECT(window2),
			"configure-event",
			G_CALLBACK(on_window2_configure),
			window1);

      g_signal_connect (G_OBJECT(window1),
			"button-press-event",
			G_CALLBACK(on_window1_button_press),
			NULL);

      g_signal_connect (G_OBJECT(window2),
			"button-press-event",
			G_CALLBACK(on_window2_button_press),
			NULL);

      gtk_main ();

      return EXIT_SUCCESS;
}