Re: Return values from gtk2 widget (void) methods

[goran kirra net]

My 2 cents:
1. With void functions we normally don't know if it was
   successful or not.
2. On the other hand it would be nice to have a consistant 
   return value scheme like "0 (zero)"=failed, "not 0"=success 
   so we could do perlish things like:
   $obj->set_label('xx') && $obj->show;

Anyway the interface should be constistant and 
the test suite should check that it is.

/göran

On Tue, Oct 22, 2002 at 02:19:24AM +0100, Dermot Musgrove wrote:
> Guillaume Cottenceau wrote:
> > Dermot Musgrove <dermot glade perl connectfree co uk> writes:
> >
> > > Hi,
> > >
> > > Does Gtk2-Perl return perl or C success values?
> > >
> > > I am not sure how Gtk-Perl handles this but at the moment, AFAIK, 
> [...]
> > Do you have a code example where this problem bites you?
> Hi Guillaume,
>
> It occurred when I was writing Gtk2::Test - with (little) research I found
> that many of the calls I tested return perl undef on success but some 
> return other things:
>
> Call (success)                        Gtk-Perl                Gtk2-Perl
> --------------                        --------                --------
> Gtk2->init                    1                       0
> Gtk2::Window->set_position    undef                   undef
> Gtk2::HBox->add                       ref to widget added     undef
> signal_connect                        connect id              connect id
>
> I have only looked at a few calls but I note that:
>
> 1) Gtk-Perl is inconsistent in what it returned.
>
> 2) Gtk2-Perl is (differently) inconsistent.
>
> 3) Many (most?) calls in both modules return undef.
>
> 4) perldoc perlfunc says:
>   In general, functions in Perl that serve as wrappers for
>   system calls of the same name (like chown(2), fork(2),
>   closedir(2), etc.) all return true when they succeed and
>   `undef' otherwise, as is usually mentioned in the
>   descriptions below.  This is different from the C
>   interfaces, which return `-1' on failure.  Exceptions to
>   this rule are `wait', `waitpid', and `syscall'.  System
>   calls also set the special `$!'  variable on failure.
>   Other functions do not, except accidentally.
>
> So what should happen? As a perler, I like the idea of returning 'true
> when they succeed and 'undef' otherwise.' like system calls. Success is
> easy to spot and failures are not easily confused with anything else.
>
> I like the idea that you could call '$w->method && $w->another_method'
> and this is IMO more perlish. 
>
> I don't understand the gtk2 error handling but is it possible to return
> success/failure centrally? 
>
> However, whatever is decided, I think that it should be consistent.
>
> What do people think?
>
> Regards, Dermot