# RGB format a text document using a highlight colour. 
# RGB 0-255 like HTML 0x00-0xFF
# Output should be valid RTF but YMMV

sub RTFhighlight {
    my ($text, $highlight, $r, $g, $b, $font) = @_;
    $font ||= "Arial";
    $text =~ s/([\\{}])/\\$1/g;  # escape \ and { }
    $text =~ s/\n/\\par\n/g;     # convert \n to \par
    $text =~ s/\b\Q$highlight\E\b/\\cf1 $highlight\\cf0 /g;
    my $header = "{\\rtf1\\ansi\\ansicpg1252\\deff0\\deflang1033{\\fonttbl{\\f0\\fswiss\\fcharset0 $font;}}\n";
    $header   .= "{\\colortbl ;\\red$r\\green$g\\blue$b;}\n";
  return $header.$text;
}

print RTFhighlight("hello be seabe be because", "be", 0, 0, 0xFF);

##</code><code>##

use Win32::GUI;
use warnings;
use strict;

my $Win = new Win32::GUI::Window(
      -left   => 3,
      -top    => 5,
      -width  => 640,
      -height => 480,
      -name   => "Win",
);

my $font = Win32::GUI::Font->new(
           -name => "Courier New",
           -size => 12,
);

$Win->AddButton(
       -text    => "Run",
       -name    => "Button1",
       -left    => 23,
       -top     => 10,
       -width   => 56,
       -height  => 36,
       -foreground    => 0,
);

my $RichText = $Win->AddRichEdit(
       -text    => "Click Run.....\n",
       -name    => "RichText_Output",  # OutPut Rich Text
       -left    => 41,
       -top     => 91,
       -width   => 580,
       -height  => 313,
       -multiline    => 1,
       -vscroll    => 1,
);

$RichText->SetLimitText(4194304);
$Win->Show();
Win32::GUI::Dialog();

sub Win_Terminate {
   return -1;
}

sub Button1_Click {
    my $file = "bigfile.txt";
    my $PATTERN = "be";
    $RichText->Select(0,-1);
    $RichText->ReplaceSel("Loading and highlighting.....\n");
    $Win->Update;
    open FILE, $file or die "Can't open $file because $!\n";
    local $/;
    my $text = <FILE>;
    close FILE;
    $text = RTFhighlight($text, $PATTERN, 0xFF, 0, 0, "Courier New" );
    $RichText->Select(0,-1);
    $RichText->ReplaceSel($text);
}

# rft format a document using a highlight colour. RGB 0-255 like HTML.
sub RTFhighlight {
    my ($text, $highlight, $r, $g, $b, $font) = @_;
    $font ||= "Arial";
    $text =~ s/([\\{}])/\\$1/g;  # escape \ and { }
    $text =~ s/\n/\\par\n/g;     # convert \n to \par
    $text =~ s/\b\Q$highlight\E\b/\\cf1 $highlight\\cf0 /g;
    my $header = "{\\rtf1\\ansi\\ansicpg1252\\deff0\\deflang1033{\\fonttbl{\\f0\\fswiss\\fcharset0 $font;}}\n";
    $header   .= "{\\colortbl ;\\red$r\\green$g\\blue$b;}\n";
  return $header.$text;
}