#!/usr/bin/env perl

use strict;
use warnings;

use Tk;
use Tk::ROText;

my $mw = MainWindow::->new();
$mw->geometry('512x288+100+150');

my $ctrl_F = $mw->Frame(
)->pack(-side => 'left', -fill => 'y');
my $text_F = $mw->Frame(
)->pack(-side => 'left', -fill => 'both', -expand => 1);

my $fill_x = $ctrl_F->Button(-text => 'Fill X')->pack();
my $fill_y = $ctrl_F->Button(-text => 'Fill Y')->pack();
my $text = $text_F->Scrolled('ROText',
    -scrollbars => 'osoe', -wrap => 'none',
)->pack(-fill => 'both', -expand => 1);

$fill_x->configure(-command => sub {
    $_->configure(-state => 'disabled') for $fill_x, $fill_y;
    my $ms = 50 * (1 + int rand 10);
    my $iters = 1 + int rand 100;
    my $iter = 0;
    my $id;
    $id = $mw->repeat($ms, sub {
        if (++$iter < $iters) {
            text_show($text, 'X');
        }
        else {
            text_show($text, "\n");
            $id->cancel;
            $_->configure(-state => 'normal') for $fill_x, $fill_y;
        }
    });
});

$fill_y->configure(-command => sub {
    $_->configure(-state => 'disabled') for $fill_x, $fill_y;
    my $ms = 50 * (1 + int rand 10);
    my $iters = 1 + int rand 100;
    my $iter = 0;
    my $id;
    $id = $mw->repeat($ms, sub {
        if (++$iter < $iters) {
            my $str = 'Y' x (1 + int rand 100) . "\n";
            text_show($text, $str);
        }
        else {
            $id->cancel;
            $_->configure(-state => 'normal') for $fill_x, $fill_y;
        }
    });
});

MainLoop;

{
    my ($line, $char); BEGIN { ($line, $char) = (1, 0) }

    sub text_show {
        my ($text, $str) = @_;

        $text->insert("$line.$char" => $str);
        $text->see("$line.$char");

        if (-1 < index $str, "\n") {
            $line += $str =~ y/\n//;
            $char = length(substr $str, rindex $str, "\n") - 1;
        }
        else {
            $char += length $str;
        }
    }
}