This is a bit confusing, because your code example does not seem to have much in common with your initial request, which was:

I'm trying to write a Tk UI where text widgets autoexpand to have the necessary height to show all text.

This would involve using the length of the string being displayed in order to do one of two things: assign initial "-width" and "-height" attributes when the text widget is created, or else use the widget's "configure()" method after it has been created. The former works if the string length is known before creating the widget; the latter if the string is created or changed after the widget is in place.

But you don't seem to be using the length of the string to set the widget dimensions yet.

I haven't been able to find any way of determining how many lines high the text widget needs to be to accomodate the contained text in full view.

The easiest way (which can tend to make the text hard to read at runtime) is to set the text widget for character wrapping (as opposed to no-wrap or word-wrap), keep a fixed width for the widget (say, 40), and divide the string length by that width to decide how many lines are needed.

I've added a little to your example to demonstrate using string length to configure widget dimensions. But I have to admit there are things I don't get, like why you have a set of smaller unscrolled text widgets in a bigger scrolled one, or how the "print_info" is expected to help things.

use strict;
use Tk;

my $mw= MainWindow->new;
$mw->title('vartext');
my $f = $mw->Frame->pack(-side=>'bottom');
$f->Button(-text=>'Print',-command=>\&print_info)->pack(-side=>'left')
+;
my $t=$mw->Scrolled("Text", -width=>40, -wrap=>'none')->pack(-expand=>
+1, -fill=>'both');
my @widget_list = ();
my @strings = (" a..5 a.10 a.15 a.20 a.25 a.30 a.35 a.40 a.45 a.50",
               " b..5 b.10 b.15 b.20 b.25 b.30 b.35 b.40",
               " c..5 c.10 c.15 c.20 c.25 c.30",
               " d..5 d.10 d.15 d.20",
               );
my $wdth = 20;
foreach ( @strings ) {
    my $hght = int( length() / $wdth );
    $hght++ if ( length() % $wdth );
    my $w= $t->Text( -width=>20, -height=>$hght, -wrap=>'char');
    $w->insert('end',$_);
    $t->windowCreate('end',-window=>$w);
    $t->insert('end', "\n");
    push @widget_list, $w;
}

sub print_info {
    foreach my $text (@widget_list) {
        print join "  ", $text->yview;
        print "\n";
        my $index = $text->index('end');
        print qq§ index : $index \n§;
    }
    print "----------\n";
}
MainLoop;
[download]

It would be a little trickier (but easier for a user to read) if you used word wrapping instead of character wrapping: you may have to replicate the widget's wrapping behavior to figure out how many display lines will be needed -- or just "pre-wrap" the lines yourself (and you can find a lot of useful ideas for word-boundary-based line wrapping by searching this site).

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