The code below illustrates a problem I'm having with
Gtk2::TreeViewhttp://gtk2-perl.sourceforge.net/doc/pod/Gtk2/TreeView.html (or
herehttp://developer.gnome.org/gtk/2.24/GtkTreeView.html). It just displays a
list of random words, and adds a new one at the bottom once every second. I'd
like to automatically scroll the new word into view, but only if the one just
before it was visible. That way, this automatic scrolling won't annoy someone
looking elsewhere in the tree view.
Everything words fine until something causes the tree view to shrink. Making
the window smaller is an example. The actual application I'm working on has
other examples, e.g., a
Gtk2::Expanderhttp://gtk2-perl.sourceforge.net/doc/pod/Gtk2/Expander.html (or
herehttp://developer.gnome.org/gtk/2.24/GtkExpander.html). If you resize the
window to be smaller, you should see the problem. The gravity of the scroll
bar, or whatever, moves it slightly off the bottom of the view after the
shrink, turning off the automatic scrolling.
How can I keep my automatic scrolling, even after these kinds of events? I've
tried reacting to various signals, but the tree view seems too stale for
$tree-get_visible_range() or $tree-scroll_to_cell() to work.
Thanks,
Jim
#!/usr/bin/perl
use strict;
use warnings;
use Glib qw(TRUE FALSE);
use Gtk2 -init;
my($win,$tree)=createWin();
Glib::Timeout-add(1000,sub {tickCB($tree)});
$win-show_all();
Gtk2-main();
#
# Creates the widgets in the application. Returns the main
# window and tree view.
#
sub createWin
{
my($win,$scroll,$tree,$model);
$win=new Gtk2::Window();
$win-set_default_size(250,300);
$win-signal_connect(destroy = \Gtk2::main_quit);
$win-add($scroll=new Gtk2::ScrolledWindow());
$scroll-add($tree=new Gtk2::TreeView());
$tree-set_rules_hint(TRUE);
$tree-insert_column_with_attributes(-1,'Goo',
new Gtk2::CellRendererText(),text = 0);
$tree-set_model($model=
new Gtk2::ListStore('Glib::String'));
addWord($model) for 0 .. 100;
showLast($tree);
return ($win,$tree);
}
#
# Called at regular intervals to add another random word
# to the bottom of the tree view. If the previous word was
# visible beforehand, scrolls the tree view so the new word
# is visible.
#
sub tickCB
{
my($tree)=@_;
my($model)=$tree-get_model();
my($numRows)=$model-iter_n_children(undef);
my($lastVis)=($tree-get_visible_range())[1];
my($mustScroll)=$lastVis
$lastVis-get_indices() == $numRows-1;
addWord($model);
showLast($tree) if $mustScroll;
return TRUE;
}
#
# Adds a random word to the bottom of the tree view.
#
sub addWord
{
my($model)=@_;
my(@cons)=grep !/[aeiou]/,'a' .. 'z';
$model-set($model-append(),0,
$cons[rand @cons] . 'oo');
}
#
# Scrolls the tree view so the last row is visible.
#
sub showLast
{
my($tree)=@_;
my($numRows)=$tree-get_model()-iter_n_children(undef);
$tree-scroll_to_cell(
new Gtk2::TreePath($numRows-1),undef,TRUE,0.0,1.0);
}
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