Learning Perl/Tk

8.3. A Short Break for a Simple Example

Before we get into some of the more complex (and more fun) things you can do with a text widget, let's look at complete use of the text widget.

This is a short program that will display a file, let you make changes to it, and then save it:

use Tk; $mw = MainWindow->new; # Create necessary widgets $f = $mw->Frame->pack(-side => 'top', -fill => 'x'); $f->Label(-text => "Filename:")->pack(-side => 'left', -anchor => 'w'); $f->Entry(-textvariable => \$filename)->pack(-side => 'left', -anchor => 'w', -fill => 'x', -expand => 1); $f->Button(-text => "Exit", -command => sub { exit; } )-> pack(-side => 'right'); $f->Button(-text => "Save", -command => \&save_file)-> pack(-side => 'right', -anchor => 'e'); $f->Button(-text => "Load", -command => \&load_file)-> pack(-side => 'right', -anchor => 'e'); $mw->Label(-textvariable => \$info, -relief => 'ridge')-> pack(-side => 'bottom', -fill => 'x'); $t = $mw->Scrolled("Text")->pack(-side => 'bottom', -fill => 'both', -expand => 1); MainLoop; # load_file checks to see what the filename is and loads it if possible sub load_file { $info = "Loading file '$filename'..."; $t->delete("1.0", "end"); if (!open(FH, "$filename")) { $t->insert("end", "ERROR: Could not open $filename\n"); return; } while (<FH>) { $t->insert("end", $_); } close (FH); $info = "File '$filename' loaded"; } # save_file saves the file using the filename in the entry box. sub save_file { $info = "Saving '$filename'"; open (FH, ">$filename"); ...