Re: Restoring a List View's position

[Matthew Braid <ptkperl mdb id au>]

Hi again,

Look at me, I'm replying to myself!

2009/3/17 Matthew Braid <ptkperl mdb id au>:
> In case someone is searching for some code to help in future, the
> following works (although doesn't handle the horizontal scrollbars
> obviously):
>
> Glib::Idle->add(sub {
>  my $args = shift;
>  my ($pos, $list) = @$args;
>  my $adj = $list->get_vadjustment;
>  return 0 if not defined $adj; ## JIC
>  $pos = $adj->upper if $pos > $adj->upper; # In case the list has shrunk since
>  $adj->set_value($pos);
>  0;
> }, [$listposition, $listview]);

As it turns out, this is not quite correct. If a list's contents have
shrunk significantly between loads, resetting the position to the
adjustment's upper value may be too far. The position is where the
_top_ of the scroll bar page should be, not the bottom, so if you tell
it to go too low you get a weird empty list with a scroll bar with no
page position and an active 'up' button. Scrolling up fixes
everything, but is obviously not what the user (or the programmer for
that matter) is expecting.

To fix that little issue, the above becomes:

Glib::Idle->add(sub {
 my $args = shift;
 my ($pos, $list) = @$args;
 my $adj = $list->get_vadjustment;
 return 0 if not defined $adj; ## JIC
 $pos = $adj->upper - $adj->page_size       ## Set the top position correctly
    if $pos > $adj->upper - $adj->page_size; # In case the list has shrunk since
 $adj->set_value($pos);
 0;
}, [$listposition, $listview]);

Ta,
MB