Mastering Perl/Tk

The Adjuster Widget

There are times you would like the user to have control over how large a frame is in part of the application. Let’s say you’re listing a large number of font styles along the left side of the application, and the right side of the application contains a Text widget. It would be nice if users could make the font styles list wider or smaller depending on their preferences. We can do this using the Adjuster widget.

Here’s a simple example using two frames that contain a Listbox and a Text widget, respectively:

use Tk;
use Tk::Adjuster;

$mw = MainWindow->new(-title => "Adjuster example");

$leftf = $mw->Frame->pack(-side => 'left', -fill => 'y');
$adj = $mw->Adjuster(-widget => $leftf, -side => 'left')
  ->pack(-side => 'left', -fill => 'y');
$rightf = $mw->Frame->pack(-side => 'right', -fill => 'both', -expand => 1);

# Now put something into our frames.
$lb = $leftf->Scrolled('Listbox', -scrollbars => 'osoe')
  ->pack(-expand => 1, -fill => 'both');
$lb->insert('end', qw/normal bold italics code command email emphasis   
                      emphasisBold Filename FirstTerm KeyCode KeySymbol/);
$rightf->Scrolled('Text', -scrollbars => 'osoe')
  ->pack(-expand => 1, -fill => 'both');

MainLoop;

You can see in Figure 23-11 that the thin line with the small box at the bottom is our adjuster. If you hover your mouse over the line, the cursor will change to a horizontal double-ended arrow, indicating you can click and drag. As you drag to the right, the Listbox becomes larger. As you drag to the left, ...