After some digging, I figured it out. I was deleting a button from the Text widget, as you'd delete text, but that destroys the button completely, so I got an error the next time I tried to re-insert it. It was still in my hash of buttons, though, which made me thing the button still exists. Took me a while to debug my sample code until I made it do what I want :)

If anyone's interested, I'm attaching my sample code. Now on to changing the original to behave the same way...

use strict; 
use Tk;

my $mw = MainWindow->new();
my $input_frame = $mw->Frame()
    ->pack(-expand => 1,
       -fill => 'both');
my $input = $input_frame->Scrolled('Text')
    ->pack(-expand => 1,
       -fill => 'both');
$input->tagConfigure("invisible", -elide => 'true');

my %buttons;
for (my $i = 1; $i < 20; $i++) {
    if ($i % 5 == 0) {
    # Create both buttons
    $buttons{"minus_$i"} = $input->Button(-image => $mw->Getimage('min
+us'),
                          -command => [\&hide,$i]);
    $buttons{"plus_$i"} = $input->Button(-image => $mw->Getimage('plus
+'),
                          -command => [\&reveal,$i]);
    # Insert only the minus button
    $input->windowCreate('end',-window => $buttons{"minus_$i"});
    }
    $input->insert('end',"abcdefghijkl$i\n");
}

MainLoop(); 


sub hide {
    my ($index) = @_;
    my $from = $index + 1;
    my $to = $index + 5;
    $input->tagAdd("invisible","$from.0","$to.0");
    switch_button($index,'plus','minus');
    return;
}

sub reveal {
    my ($index) = @_;
    my $from = $index + 1;
    my $to = $index + 5;
    $input->tagRemove("invisible","$from.0","$to.0");
    switch_button($index, 'minus', 'plus');
    return;
}

sub switch_button {
    my ($j, $new_sign, $old_sign) = @_;
    $input->delete("$j.0");
    if ($old_sign eq 'plus') {
    $buttons{"plus_$j"} = $input->Button(-image => $mw->Getimage('plus
+'),
                         -command => [\&reveal,$j]);
    } else {
    $buttons{"minus_$j"} = $input->Button(-image => $mw->Getimage('min
+us'),
                          -command => [\&hide,$j]);      
    }
    $input->windowCreate("$j.0",-window => $buttons{"${new_sign}_$j"})
+;
    return;
}

[download]

EDIT: I just checked out the code in your other reply, and though I think that for now I'll stay with my version, I definitely learned a couple of new things from it. Thanks!

In reply to Re^4: Editable tree in Tk by anna_black
in thread Editable tree in Tk by anna_black

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.