Re: Problems with expose_event->region patch

[Owen Taylor <otaylor redhat com>]

srlytle_list yahoo com writes:

> > Hmm looking at that reminds me, we were going to remove
> > gdk_window_get_update_area() once the expose event included the
> > region, I think.
> 
> this is kind of tangential, gdk_window_get_update_area sounded like
> what i wanted. i checked the source and its not, so i'll ask.
> 
> i would like to be able to figure out what hunk of the a GdkWindow
> is actually visible to the user ie not obscured by another 
> window or hidden by the pager, ie to figure out which pixels of
> a window actually correspond to physical screen pixels.
> 
> is there such a function? it would be useful for animations so as 
> to avoid using cpu updating a window that the user cannot 
> appreciate.

There is an inherent race condition there - what if a window
on top is moved between the time you make the call and the
time you draw?

gdk_drawable_get_visible_region() returns a conservative estimate
that takes into account some of the clipping that GTK+ knows
about:

/**
 * gdk_drawable_get_visible_region:
 * @drawable: 
 * 
 * Computes the region of a drawable that is potentially visible.
 * This does not necessarily take into account if the window is
 * obscured by other windows, but no area outside of this region
 * is visible.
 * 
 * Return value: a #GdkRegion. This must be freed with gdk_region_destroy()
 *               when you are done.
 **/

This is mostly interesting for something like a viewport where only a
portion of a large window is visible.

Regards,
                                        Owen