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Re: [perl-win32-gui-users] strange gui behaviour
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From: Charles A. <cha...@al...> - 2007-03-20 21:07:23
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Hi,
You're correct that your problem is in the nested subroutines. The =20
behavior of the handlers you set up inside of verify() is not what =20
you're expecting. There's a lot of stuff going on here that can trap =20
you.
First of all, when you try running this script with warnings enabled =20
(perl -w myscript.pl), you'll get messages like this:
Variable "$result" will not stay shared at verify.pl line 68.
Variable "$outputfield" will not stay shared at verify.pl line 69.
Variable "$result" will not stay shared at verify.pl line 74.
Variable "$outputfield" will not stay shared at verify.pl line 75.
It's always a good idea to use strict and use warnings when you're =20
writing Perl.
Basically, the two variables you're referring to in the handlers =20
($result and $outputfield) are recreated each time you call verify(), =20
but the handlers will only see the first instance of $result and =20
$outputfield. Successive calls to the handlers are meaningless =20
because $result and $outputfield were local to the first call to =20
verify().
Here's some comments:
sub Pass_Click {
# Here you are assigning to the $result variable that was privately
# scoped within the first call to verify()
$result =3D 1;
# Same thing here. You are modifying the text field in the first text
# field created on the first call to verify()
$outputfield->Text("result : $result");
# Try returning 0 in this handler and in the Fail_Click handler.
# You'll see that the output field is changing to what you would think =
at
# first, but when you close (X out) the first window, the successive
# windows' text fields won't get updated
-1; # say 'return 0' instead;
}
For a better explanation on nested subroutines and private variables, =20
check out these articles:
* http://www.webreference.com/programming/perl/subroutines/2.html
* http://perl.com/pub/a/2002/05/07/mod_perl.html
My take on nested subroutines: If you never plan on using mod_perl, =20
you could probably just completely avoid nested subroutines and be =20
just fine.
So anyway, back to your problem. I'm not really sure what you're =20
trying to accomplish with this script, but an alternative approach you =20
could take could be to only create your window once (at the startup of =20
your script). When you later call verify, (1) show the window, (2) =20
enter the Dialog, (3) handle user input, (4) exit the dialog, (5) then =20
hide the window.
Good Luck,
Charles Alderman
Quoting luksedj the first <lu...@ya...>:
> Hello,
>
> I'm just starting to use Win32::GUI and I can't seem to explain the =20
> behavior of my application.
>
> I have a main perl program that occasionally needs user input. On =20
> those occasions I call a function (sub) that builds the window and =20
> starts the dialog, and returns a result gathered from the user input.
>
> The first time this function is called, it works as expected. The =20
> user clicks a button, the button callback sets a value, and =20
> terminates the Dialog(). The value that was set is the return value =20
> of the function.
>
> However, on the second and following times that the function is =20
> called, the window is shown, via printouts I can see the return =20
> value being set, but when the dialog exits and the function is about =20
> to return its return value, the return value is the default one, in =20
> stead of the set one. I assume that it has to do something with me, =20
> coding the event handlers inside the function that does all the gui =20
> stuff. If that is so, can someone explain this behavior? I don;t =20
> mind changing my code, but then I want to understand why it behaves =20
> like this.
>
> The code is pasted below. The behavior I want is that the user =20
> clicks on the pass button which returns 1 to the calling function. =20
> If you press 'passed' in every test, then you'll see the return =20
> value is 0 starting from the second call to the 'verify' function.
>
>
> use Win32::GUI();
>
>
>
> my $canvas_height =3D 328;
> my $title_height =3D 32;
> my $margin =3D 15;
>
>
> for ($i=3D0; $i<5;$i++){
> my $output =3D "test $i";
> print "$output ";
> my $result_1 =3D verify($output);
> print $result_1;
> print " $output\r\n";
> }
>
>
> sub verify {
> my $output =3D shift;
>
> my $result =3D 0;
> my $main =3D
> Win32::GUI::DialogBox->new(
> -name =3D> 'Main',
> -width =3D> 280,
> -height =3D> $canvas_height+$title_height,
> -text =3D> 'Test Step Output Verification',
> -helpbox =3D> 0,
> );
>
>
> my $outputfield =3D $main->AddTextfield(
> -name =3D> 'Outputfield',
> -multiline =3D> 1,
> -hscroll =3D> 1,
> -vscroll =3D> 1,
> -width =3D> 215,
> -height =3D> 200,
> -pos =3D> [ $margin, 60],
> -disabled =3D> 0,
> -readonly =3D> 1,
> );
>
> my $pass =3D $main->AddButton(
> -text =3D> 'Passed',
> -width =3D> 100,
> -height =3D> 25,
> -pos =3D> [$outputfield->Left(),
> $outputfield->Height() + $outputfield->Top() + $margi=
n],
> -name =3D> 'Pass',
> -tabstop =3D> 1
> );
>
> my $fail =3D $main->AddButton(
> -text =3D> 'Failed',
> -width =3D> 100,
> -height =3D> 25,
> -pos =3D> [$outputfield->Left() + =20
> $outputfield->Width() - 100,
> $pass->Top()],
> -name =3D> 'Fail',
> -tabstop =3D> 1
> );
>
>
> sub Pass_Click {
> $result =3D 1;
> $outputfield->Text("result : $result");
> -1;
> }
>
> sub Fail_Click {
> $result =3D 0;
> $outputfield->Text("result : $result");
> -1;
> }
>
> sub Main_Terminate {
> -1;
> }
>
>
> $outputfield->Text($output);
> $main->Show();
> Win32::GUI::Dialog();
> return $result;
> }
>
>
> Thanks for any hints,
>
> luksedj
>
>
>
>
>
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