# shows progress of classification

sub progress_ui {
   my($top_root) = @_;
   $progress_main->destroy
      if Exists($progress_main);
   $progress_main = $top_root->Toplevel;
   my($root) = $progress_main->Frame()->pack(
                                    -fill=>'both',
                                    -expand=>1
                                   );
   $progress_main->title('SpikeSort Progress');
   $progress_main->iconname('SpikeSortProgress');

        # widget creation

        my($label_2) = $root->Label (
                -text => 'Percentage of trace classified:',
        );
   # this is global
        $progress_canvas = $root->Canvas (
                -height => '0',
                -highlightthickness => '0',
                -width => '0',
        );
        my($label_1) = $root->Label (
                -textvariable => \$spikes_found,
        );

        # Geometry management

        $label_2->grid(
                -in => $root,
                -column => '1',
                -row => '1'
        );
        $progress_canvas->grid(
                -in => $root,
                -column => '1',
                -row => '2',
                -sticky => 'nesw'
        );
        $label_1->grid(
                -in => $root,
                -column => '1',
                -row => '3'
        );

        # Resize behavior management

        # container $root (rows)
        $root->gridRowconfigure(1, -weight  => 0, -minsize  => 30);
        $root->gridRowconfigure(2, -weight  => 0, -minsize  => 80);
        $root->gridRowconfigure(3, -weight  => 0, -minsize  => 30);

        # container $root (columns)
        $root->gridColumnconfigure(1, -weight => 0, -minsize => 420);

        # additional interface code

   # draw the thermometer of progress..
   $progress_canvas->create(
                            'line', '25', '40', '395', '40',
                            -width => '40',
                            -fill => 'black',
                            -cap => 'butt',
                           );
}

##</code><code>##

...
      elsif ( $added_text =~ /^sample index: (\d+)/ ) {
         $progress_width = 25 + 370 * $1 / $total_samples;
         $progress_canvas->create(
                               'line', '25', '40', $progress_width, '40',
                               -width => '40',
                               -fill => 'blue',
                               -cap => 'butt',
                              )
            if $progress_canvas;
      }
...