#!/usr/bin/perl
use warnings;
use strict;
use Tk;
use Tk::ROText;
use IPC::Open3;

$|++;

my $mw = MainWindow->new;
my $canvas = $mw->Canvas(
                  -bg => 'white',
		  -height =>500,
		  -width =>500,
		  )->pack();

my $text = $mw->ROText(-bg=>'white')
     ->pack( -fill => 'both', -expand => 1 );

$text->tagConfigure( 'red', -foreground => 'red' );

my $pid = open3( \*IN, \*OUT, \*ERR, "/usr/bin/gnuplot" ) || die;
$mw->fileevent( \*OUT, readable => \&read_out );
$mw->fileevent( \*ERR, readable => \&read_err );

print IN "set term tkcanvas perltk interactive\n";
print IN "a=1\n";
print IN "set output \'plot.z\'\n";
print IN "plot a\n";

my $gnuplot = do "plot.z";
$gnuplot->($canvas);

MainLoop;

sub read_out {
}

sub read_err {
    print "read_err()\n";
    my $num = sysread(ERR, my $buffer, 1024 );
    $text->insert( 'end', $buffer, 'red' );
}