Re^2: Perl/Tk Oddities

[zentara]

Funny, I was just working on ways to do these dialog tricks with Tk and Gtk2. For Tk, I came up with Tk RGBColorDialog as an example of using a toplevel as a dialog. To avoid the problem of the predefined Ok button, yet still wait for a response in a Show() method, I used a waitVariable hack in Show(). It works by having the $self->{RESULT} being set to '', and when the Ok button is pressed, it is set to $self->{value} (the return data). You probably can work out a way in Show to test the value before returning it. Like this simple way with a LABEL (there is probably a better way)

WAIT:
$self->waitVariable(\$self->{RESULT});

#test result
my $string = $self->{RESULT};

if( $string  lt '#333333' ){ goto WAIT  }
   else{
   $self->grabRelease;
   $self->withdraw;
   &$old_focus;
   &$old_grab;
      
   return $self->{RESULT};
  }
} # end  Show method

In Gtk2, the preferred method is to wrap the dialog like this. It can be done because the destroy is handled by you outside of the Dialog object. Thanks to muppet and Mathew Braid, for showing me this.

sub get_string {
 my ($title, $parent, $prompt, $initial_value, $default_cancel) = @_;

 my $dialog = Gtk2::Dialog->new ($title, $parent, [],
 'gtk-cancel' => 'cancel',
 'gtk-ok' => 'accept');

 my $label = Gtk2::Label->new ($prompt || '');
 $dialog->vbox->add ($label);
 $label->show ();

 my $entry = Gtk2::Entry->new ();
 $entry->set_text ($initial_value) if defined $initial_value;
 $dialog->vbox->add ($entry);
 $entry->show ();

 $dialog->set_default_response ($default_ok ? 'accept' :  'cancel');

 my $ret;
 if ('accept' eq $dialog->run ()) {
 $ret = $entry->get_text ();
 }
 $dialog->destroy ();

 return $ret;
}

It may be possible to subclass the Tk::Dialogbox, and override the default button presses. It has the wait Show and exit methods available, so you should be able to redefine them in a subclass, use

use base   qw/Tk::Derived Tk::DialogBox/;

You can google for Tk::Derived and find examples how to do it. Basically you just make a package called MyDialog, copy the Show() sub from the Dialogbox.pm into it, and modify it to your liking. You will see where I got the idea for my code in the Dialogbox.pm. :-)

Probably the best solution, is to emulate Gtk2's wrapping of the dialog, by redefining exit() in your subclassed DialogBox, so it is controlled from outside the object.

[TomKane]

Thanks for the feedback, Zentara. You led me indirectly to the answer that I was looking for.

As I was formerly a C++ programmer, I am familiar with the concept of overriding functionality. I just hadn't done it in Perl and had been hesitant to start digging down to that level when it came to base functionality of the language. But I started looking into some of the DialogBox.pm code and then discovered XDialogBox.pm. As I was looking at that bunch I discovered that whenever I used an XDialogBox widget, it always resulted in having an extra icon at the bottom of the screen, which is exactly what I've been trying to avoid. Then I saw that there were a couple of commented out lines of code and tried uncommenting them. It turns out that the Toplevel->transient() function was one of them and when I turned it back on, voila, no icon.

So, the quick and simple answer to my long search was there all along. Even in "Mastering Perl/Tk", Lidie doesn't mention that particular functionality (the index has the wrong page number, it's really p. 246) for making a new Toplevel appear as a part of the main. That is, the new Toplevel is a "transient" but detached widget within the "master" module that opened the new Toplevel.

Now the fun begins, however, because if I use a Toplevel as a dialog box, then I have to have a button or something that will "close" the dialog -- which is done really with the withdraw() function. But this doesn't tell the "master" module that it's closed. As long as the "master" is itself a module and can have a function accessible to the transient Toplevel, the latter can call the former with the message that it (the transient Toplevel) has "closed".

I better look into the grab() methods now.

Thanks again.

Tom