Re: Scrolled windows and drawing_areas

[Owen Taylor <owt1 cornell edu>]

Ales Hvezda <ahvezda@cybercom.net> writes:

> Hi All,
> 
> 
> 	Quick question.  I have a drawing_area which is inside a scrolled
> window.  I want to attach some key accelerators to do the scrolling (to 
> supplement the scrollbars).  I can set the value of the scrollbars using 
> gtk_viewport_set_[v|h]adjustment (is that the proper way to set the value 
> of the scrollbar(s)?)  But what is the proper way to tell the drawing_area 
> (the child of the scrolled window) to update itself to reflect the new 
> scrollbar settings?  

gtk_viewport_set_[vh]adjustments changes the adjustment that is
controlling the viewport.

You actually want to change the _value_ of the adjustment.

  GtkAdjustment hadjustment;
  hadjustment = gtk_viewport_get_hadjustment (GTK_VIEWPORT(viewport))
  hadjustment->value = new_value;
  gtk_signal_emit (GTK_OBJECT (hadjustment), "value_changed");

You don't have to do anything to tell the drawing area.

The viewport puts the drawing area into a big X window, of which 
only a portion is visible, and moves that window around as controlled
by the scrollbars. X clips the large window to the Viewport's main
window (Which acts as a "view port" on the big window), and the
correct portion will automatically be shown on the screen and receive
expose events.

Regards,
                                        Owen