Re: what is the status of a scrolled-out widget ?

[Owen Taylor <otaylor redhat com>]

Paul Barton-Davis <pbd@Op.Net> writes:

> if you pack a widget into a box, and put the box into a scrolled
> window: when you scroll so that widget vanishes, what has happened to
> it ? it appears not to be unmapped, and it also still claims to be
> visible. what's the trick ? 

A GtkViewport is two nested windows, one as big as the scrolled
area, and a smaller one that acts as a viewport onto the 
larger areas. The invisible widgets are still mapped, they
are just clipped by the smaller window and not visible on
the screen. 
 
> i want to label the end points (and only the endpoints) of the set of
> widgets currently viewable in a scrolled window, but i can't figure
> out how to differentiate those widgets that are truly visible and
> those that just think they are.

You'll want to look at the adjustments of the scrollbars
for the scrolled window and compare the value and page
size to the allocations of the widgets within the scrolled
window to figure out which ones are visible.

Regards,
                                        Owen