perl-win32-gui-users

[perl-win32-gui-users] strange gui behaviour

[luksedj t. f. <lu...@ya...>]

Hello,=0A=0AI'm just starting to use Win32::GUI and I can't seem to explain=
 the behavior of my application.=0A=0AI have a main perl program that occas=
ionally needs user input. On those occasions I call a function (sub) that b=
uilds the window and starts the dialog, and returns a result gathered from =
the user input.=0A=0AThe first time this function is called, it works as ex=
pected. The user clicks a button, the button callback sets a value, and ter=
minates the Dialog(). The value that was set is the return value of the fun=
ction.=0A=0AHowever, on the second and following times that the function is=
 called, the window is shown, via printouts I can see the return value bein=
g set, but when the dialog exits and the function is about to return its re=
turn value, the return value is the default one, in stead of the set one. I=
 assume that it has to do something with me, coding the event handlers insi=
de the function that does all the gui stuff. If that is so, can someone exp=
lain this behavior? I don;t mind changing my code, but then I want to under=
stand why it behaves like this.=0A=0AThe code is pasted below. The behavior=
 I want is that the user clicks on the pass button which returns 1 to the c=
alling function. If you press 'passed' in every test, then you'll see the r=
eturn value is 0 starting from the second call to the 'verify' function.=0A=
=0A=0Ause Win32::GUI();=0A=0A=0A=0Amy $canvas_height =3D 328;=0Amy $title_h=
eight =3D 32;=0Amy $margin =3D 15;=0A=0A=0Afor ($i=3D0; $i<5;$i++){=0A    m=
y $output =3D "test $i";=0A    print "$output ";=0A    my $result_1 =3D ver=
ify($output);=0A    print $result_1;=0A    print " $output\r\n";=0A}=0A  =
=0A=0Asub verify {=0A    my $output =3D shift;=0A    =0A    my $result =3D =
0;=0A    my $main =3D=0A    Win32::GUI::DialogBox->new(=0A                 =
  -name    =3D> 'Main',=0A                   -width   =3D> 280,=0A         =
          -height  =3D> $canvas_height+$title_height,=0A                   =
-text    =3D> 'Test Step Output Verification',=0A                   -helpbo=
x =3D> 0,=0A                   );=0A    =0A    =0A    my $outputfield =3D $=
main->AddTextfield(=0A                      -name =3D> 'Outputfield',=0A   =
                   -multiline =3D> 1,=0A                      -hscroll =3D>=
 1,=0A                      -vscroll =3D> 1,=0A                      -width=
 =3D> 215,=0A                      -height =3D> 200,=0A                    =
  -pos =3D> [ $margin, 60],=0A                      -disabled =3D> 0,=0A   =
                   -readonly =3D> 1,=0A                      );=0A    =0A  =
  my $pass =3D $main->AddButton(=0A                -text =3D> 'Passed',=0A =
               -width =3D> 100,=0A                -height =3D> 25,=0A      =
          -pos =3D> [$outputfield->Left(),=0A                     $outputfi=
eld->Height() + $outputfield->Top() + $margin],=0A                -name =3D=
> 'Pass',=0A                -tabstop =3D> 1=0A                );=0A    =0A =
   my $fail =3D $main->AddButton(=0A                -text    =3D> 'Failed',=
=0A                -width   =3D> 100,=0A                -height  =3D> 25,=
=0A                -pos     =3D> [$outputfield->Left() + $outputfield->Widt=
h() - 100,=0A                         $pass->Top()],=0A                -nam=
e    =3D> 'Fail',=0A                -tabstop =3D> 1=0A                );=0A=
      =0A    =0A    sub Pass_Click {=0A      $result =3D 1;=0A      $output=
field->Text("result : $result");=0A      -1;=0A    }=0A    =0A    sub Fail_=
Click {=0A      $result =3D 0;=0A      $outputfield->Text("result : $result=
");=0A      -1;=0A    }=0A    =0A    sub Main_Terminate {=0A    -1;=0A    }=
=0A    =0A    =0A    $outputfield->Text($output);=0A    $main->Show();=0A  =
  Win32::GUI::Dialog();=0A    return $result;=0A}=0A=0A=0AThanks for any hi=
nts,=0A=0Aluksedj=0A=0A=0A=0A=0A =0A_______________________________________=
_____________________________________________=0AExpecting? Get great news r=
ight away with email Auto-Check. =0ATry the Yahoo! Mail Beta.=0Ahttp://advi=
sion.webevents.yahoo.com/mailbeta/newmail_tools.html 

Re: [perl-win32-gui-users] strange gui behaviour

[Charles A. <cha...@al...>]

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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