drawing area in a scrolled window

["Christopher Garrett" <ctg24 admin cam ac uk>]

Hi,
 
I have coded a drawing area (which has a gdkpixbuf rendered to it), which sits
inside an alignment (0.5, 0.5, 0, 0) which itself is inside a viewport
associated with a GtkScrolledWindow.  Scrolling works as expected, and if the
window is resized to be bigger than the drawing area you see a grey border
filling the area between the drawing area and the scrollbars / edge of the
viewport.
 
However, I have only been able to get mouse coordinates from the drawing area.
I would like to get coordinates from the origin in the top left of the scrolled
window.  What do I need to do?  I tried getting coords from the alignment, but
that seems to cover exactly the same area as the drawing area itself...
 
I provide a code snippet below.  If anyone wants the full listing (its not long
- its purely to test this implementation problem) I can send it to them.
 
Best regards,
 
Chris.
 
 vbox = gtk_vbox_new(FALSE, 0);
 gtk_container_add(GTK_CONTAINER(window), vbox);
 
 canvas->darea=gtk_drawing_area_new();
 canvas->scrollarea = gtk_scrolled_window_new(NULL, NULL);
 alignment = gtk_alignment_new(0.5, 0.5, 0, 0);

 gtk_widget_set_size_request(canvas->darea, canvas->width, canvas->height);
 gtk_box_pack_start(GTK_BOX(vbox), canvas->scrollarea, TRUE, TRUE, 0);
 horizontal =
gtk_scrolled_window_get_hadjustment(GTK_SCROLLED_WINDOW(canvas->scrollarea));
 vertical =
gtk_scrolled_window_get_vadjustment(GTK_SCROLLED_WINDOW(canvas->scrollarea));
 viewport = gtk_viewport_new(horizontal, vertical);
 gtk_scrolled_window_add_with_viewport(GTK_SCROLLED_WINDOW(canvas->scrollarea),
alignment);
 gtk_container_add(GTK_CONTAINER(alignment), canvas->darea);

 g_signal_connect(GTK_OBJECT(canvas->darea), "expose-event", 
  GTK_SIGNAL_FUNC(imcanvas_on_expose), (gpointer) canvas);
 g_signal_connect(GTK_OBJECT(canvas->darea), "motion_notify_event", 
  GTK_SIGNAL_FUNC(imcanvas_motion_notify_event), (gpointer) canvas);
 g_signal_connect(GTK_OBJECT(canvas->darea), "button_press_event", 
  GTK_SIGNAL_FUNC(imcanvas_button_press_event), (gpointer) canvas);
 g_signal_connect(GTK_OBJECT(canvas->darea), "button_release_event", 
  GTK_SIGNAL_FUNC(imcanvas_button_release_event), (gpointer) canvas);

 gtk_widget_set_events(canvas->darea, GDK_EXPOSURE_MASK
  | GDK_LEAVE_NOTIFY_MASK
  | GDK_BUTTON_PRESS_MASK
  | GDK_POINTER_MOTION_MASK
  | GDK_POINTER_MOTION_HINT_MASK
  | GDK_BUTTON_RELEASE_MASK
 );

 GTK_WIDGET_SET_FLAGS(canvas->darea, GTK_CAN_FOCUS);
 gtk_window_set_focus (GTK_WINDOW(window), canvas->darea);