[Gambas-user] WAIT waits forever - help needed

[Stefano Palmeri]

Alle 12:43, sabato 10 novembre 2007, Benoit Minisini ha scritto:
> On mercredi 7 novembre 2007, Stefano Palmeri wrote:
> > Hi, all. Hi, Benoit.
> >
> > I made a little utility to convert some audio files
> > from a format to another (nothing new) for personal use.
> >
> > In the FMain class there's a function called
> > StartAudioConversion(). That function calls
> > UpdateMain() that should refresh the Form before
> > starting the conversion progress. Here is the problem:
> >
> > If I put a "WAIT 0.1" after UpdateMain() the Form is refreshed,
> > but the application *waits* forever, I mean it freezes.
> >
> > If I don't put the "WAIT 0.1" the Form is refreshed after
> > the audio conversion process is done.
> >
> > Any help or explanation will be appreciated.
> >
> > To test the app you need at least mplayer and
> > you have to choose a 4Mb file to see the delay
> > in refreshing.
> >
> > Gambas 1.9.90
> >
> > Regards,
> >
> > Stefano Palmeri
>
> The application does not wait forever. It acts actually exactly as you
> wrote it, and you wrote it badly.
>
> Just trace your application step by step, and you will see:
>
> * You open the file dialog to select a file to convert.
> * You run a modal dialog to select the destination format.
> * You store what to do in some public variable of the modal dialog.
> * You close the dialog. As it is not persistent, it will be destroyed.
> * You wait (or not) a little.
> * You use the public variables of the closed dialog to select the encoder.
>
> Now the trick is that a GUI object is never destroyed immediately, but when
> the event loop returns at the same nested level the object was created.
>
> I did that because of the way QT and other GUI toolkit handle events. A C++
> object can be destroyed whereas it is used in the stack by some event
> handler. And that usually leads to segmentation faults.
>
> So, if you do not wait, the QT object is not destroyed, and so the
> associated Gambas form too. So the public variables keep their values, and
> everything works as expected.
>
> But if you wait, then the QT object is destroyed during the wait, and when
> you access the public variables, another form is created (because the Form
> class is in "auto-create" mode, like in Visual Basic), with public
> variables all initialized to their default values.
>
> You select your encoder by a SELECT ... END SELECT that does not use the
> DEFAULT or CASE ELSE keyword. So when the encoder variable is null, the
> program does not freeze, it just does nothing.
>
> I hope I was clear :-)
>
> Regards,

First of all, thank for detailed info. I will store the mail in my gambas doc.
Second, in last days I came to the solution and the app is working. Thanks
for attention.

Stefano 


-------------- next part --------------
A non-text attachment was scrubbed...
Name: gac-0.0.1.tar.gz
Type: application/x-tgz
Size: 10224 bytes
Desc: not available
URL: <http://lists.gambas-basic.org/pipermail/user/attachments/20071110/5b3b51f5/attachment.bin>