#!/usr/bin/perl
use strict;
use warnings;
use Tk;

my $mw = MainWindow->new(-title => 'Mac Address Input Example');
my $fr = $mw->Frame()->pack(-expand => 1, -fill => 'both');
my $lb = $fr->Label(-text => 'MAC Address')->pack(-side => 'left');

# widget used to display Entry field errors
my $errW = $fr->Label(-foreground=>'red')->pack(-side=>'bottom');

# hash to hold Entry widgets
my %entries;

# loop thru the number of Entry widgets desired
for(1..6){

  # create the Entry widget
  $entries{$_}{'entry'} = $fr->Entry(
    -textvariable => \$entries{$_}{'addy'},
    -width        => 3,
  );

  # save default widget background
  $entries{$_}{'bg'} = $entries{$_}{'entry'}->cget('-bg');

  # pack/display the widget
  $entries{$_}{'entry'}->pack(-side => 'left');

}

# loop back thru the created widgets
for(1..6){

  # put some bogus values in for testing...
  $entries{$_}{'addy'} = ($_>1) ? $_.$_ : '';
  $entries{$_}{'addy'} .= 'z' if($_ == 3 or $_ == 4);

  # configure the validation for the widget
  $entries{$_}{'entry'}->configure(
#    -validate        => 'focusout',
    -validate        => 'all',
    -validatecommand => [ \&validate,$_ ],
    -invalidcommand  => [ \&show_invalid,$entries{$_}{'entry'},$_ ],
  );
}

# put focus on initial Entry widget
$entries{1}{'entry'}->focus();

# auto-tab thru all Entry widgets to perform validation on pre-populated values
for(1..6){
  $mw->eventGenerate('<Tab>');
#  $mw->idletasks;
  $mw->after(100);
  $mw->update;
}

MainLoop();

sub clear_err {
  my($num) = @_;
  $errW->configure(-text=>'');
  $entries{$num}{'entry'}->configure(-bg=>$entries{$num}{'bg'});
}

# returns `1' if valid, and `0' if invalid
sub validate {
  my($num,$val) = @_;
  unless($val){ print "Field $num has nothing to validate\n";return 1;}

  my $valid = ($val =~ /^[0-9a-f]{1,2}$/i) ? 1 : 0;
  printf "Field %s, validating \`%s'...%s\n",$num,$val,$valid? "ok": "FAILED";

  if($valid){

    # clear error widget
    &clear_err($num);

    # re-enable all other widgets
    for(1..6){
      next if(/^$num$/);
      $entries{$_}{'entry'}->configure(-state=>'normal');
    }

  }else{

    # update the error widget with text indicating a problem with the value
    $errW->configure(-text=>"Field $num value \`$val' is invalid");

  }

  return $valid;
}

sub show_invalid {
  my($widget,$num) = @_;
  $widget->focus();

  # turn the background of the problem field to red
  my $bg = $widget->cget('-bg');
  $widget->configure(-bg => 'red');
  $widget->update();

  # temporarily disable focus on all other widgets
  for(1..6){
    next if(/^$num$/);
    $entries{$_}{'entry'}->configure(-state=>'disabled');
  }

}