Introduction to Perl/Tk

Tk is a module that extends Perl. It permits a Perl program to have a graphical interface very similar to what one could achieve with the Visual C++ or Java Swing graphical user interfaces (GUI). Here is '', the simplest of Tk programs:
use Tk; my $mw = MainWindow->new; MainLoop;
In order to make this work the Tk module must first be installed. See the previous section for a general discussion of how to install modules with PPM.
C:> ppm PPM> install Tk Install package 'Tk?' (y/N): y ... ... PPM> quit
Installing a module also installs the documentation for that module. Click here to see the main page for Perl documentation. Scroll down on the left hand side until you see Tk in the Libraries section. If you intend to use Tk a lot it makes sense to get a book on the subject. There is the definitive and excellent one from O'Reilly:
Click on the book above to buy it from O'Reilly.

With Tk installed, we can now invoke the program '' and this is what appears:

Cool, huh?! Now we can start embellishing. Changes are marked in green.
use Tk; my $mw = MainWindow->new( -title => "Simple Tk Program", -background => "red", ); MainLoop;
which makes the background red and puts a better title in the title bar:
Tk provides many 'widgets' - user interface elements like buttons, checkboxes, scrollbars, menus, drawing areas, sliders, text areas, etc. To demonstrate how these are created and configured we will make a Button with the text "Push Me!"; it will have a blue background. One critical step is to 'pack' it into the main window.
use Tk; my $mw = MainWindow->new( -title => "Simple Tk Program", -background => "red", ); my $button = $mw->Button( -text => "Push Me!", -bg => "blue", ); $button->pack; MainLoop;
Look what happens to the window:
We can keep the window from collapsing around the button with this:
use Tk; my $mw = MainWindow->new( -title => "Simple Tk Program", -background => "red", ); $mw->minsize(300, 400); my $button = $mw->Button( -text => "Push Me!", -bg => "blue", ); $button->pack; MainLoop;
And we get this:
The button does not do anything at all but you can push it! To make it do something - like printing 'hello there', we do this:
use Tk; my $mw = MainWindow->new( -title => "Simple Tk Program", -background => "red", ); $mw->minsize(400, 300); sub hello { print "hello there\n"; } my $button = $mw->Button( -text => "Push Me!", -bg => "blue", -command => \&hello, ); $button->pack; MainLoop;
The syntax "\&hello" will cause the subroutine 'hello' to be executed each time the button is pushed. The string "hello there" will appear in the DOS window (which was iconified automatically). Within the subroutine 'hello' you can do whatever you wish - including exiting the program, making other buttons, changing colors, writing files; the full power of Perl is at your disposal. Here are some further enhancements:
use Tk; my $mw = MainWindow->new( -title => "Simple Tk Program", -background => "red", ); $mw->minsize(400, 300); my $button = $mw->Button( -text => "Push Me!", -bg => "blue", -command => sub { print "hello there\n"; }, ); $button->pack; sub change_color { $button->configure( -background => "yellow", ); } $mw->Button( -text => "Color Change", -bg => "green", -activebackground => "orange", -command => \&change_color, )->pack; MainLoop;
This demonstrates three things:
For the last enhancement we show how you can query the button to see what its properties are:
use Tk; my $mw = MainWindow->new( -title => "Simple Tk Program", -background => "red", ); $mw->minsize(400, 300); my $button = $mw->Button( -text => "Push Me! 1", -bg => "blue", -command => sub { print "hello there\n"; }, ); $button->pack; sub change_color { # # what is the text on $button? # my $text = $button->cget("-text"); $text =~ s/(\d+)/$1 + 1/e; # # what is $button's color? # my $color = $button->cget("-bg"); $color = ($color eq "blue")? "yellow": "blue"; $button->configure( -bg => $color, -text => $text, ); } $mw->Button( -text => "Color Change", -bg => "green", -activebackground => "orange", -command => \&change_color, )->pack; MainLoop;
This is what it will look like after pressing the "Color Change" button 3 times:
This ends the introduction to Tk. The next topic shows how you can do drawing in Tk.

Be assured that the Tk graphical toolkit is very rich in function and can very likely do whatever you want.

Click here for some more resources on the web (including mailing list archives) for Perk/Tk.