[Kde-bindings] question of c++ template class

[Dongxu Ma]

>
> Message: 2
> Date: Sat, 28 Apr 2007 09:33:24 +0100
> From: Richard Dale <rdale at foton.es>
> Subject: Re: [Kde-bindings] question of c++ template class
> To: KDE bindings for other programming languages
>         <kde-bindings at kde.org>
> Message-ID: <200704280933.25574.rdale at foton.es>
> Content-Type: text/plain;  charset="utf-8"
>
> On Friday 27 April 2007, Dongxu Ma wrote:
> > > > Hi Richard, CC: all,
> > > >
> > > > I am recently thinking about how to deal with c++ template class in
> > >
> > > QT/KDE
> > >
> > > > bindings.
> > > > Inside QT4 I found three places where templates get involved:
> > > > 1) typedef
> > >
> > > You need to be able to marshaller each typedef'd variant of the
> template
> >
> > yes, the disadvantage is to collect all involved ones priorly. ?I am
> > working on a
> > script to build the list.
> OK, I think you could generate some marshallers along with the bindings,
> but
> not all of them. The bindings that use the smoke lib have a hash of
> strings
> for the various types as keys, with a values as function pointer of the
> corresponding marshaller


Definitely. QHash  is the hardest one. Such  pre-built  type dictionary
could not
easily cover all available ones. The way of smoke makes sense.

> > 2) function parameter, return type
> > > A lot of the template types are lists or hashes, and the solution that
> > > qtruby/qyoto uses is to have marshallers <--> bindings language as
> > > templated
> > > code. This means you only write the marshalling code once, and then
> have
> > > a different template type for each the the C++ template types with a
> > > macro to
> > > invoke it. See the code in handlers.cpp of either the QtRuby or Qyoto
> > > projects for a example. For instance, this line:
> > >
> > > DEF_VALUELIST_MARSHALLER( QUrlList, QList<QUrl>, QUrl )
> > >
> > > The DEF_VALUELIST_MARSHALLER() will define a new template based
> > > marshaller for
> > > QLists of QUrls.
> > >
> > > > 3) QT signal, slot
> > >
> > > You can't have have commas in signal and slot types, but you can have
> > > simple
> > > template types. The template types are mostly lists which have to be
> > > marshalled as Arrays or Lists in the bindings language.
> >
> > yes, noticed that. Just 4 or 5 found in my current QT4 headers.
> I think there are more than that.


;-)

> > It is a little bit hard to support template class inside scripting
> > >
> > > > language, how do you
> > > > make it available for qtruby (or not) ? This was not mentioned on
> > > > kdebindings ruby
> > > > page. Sorry I am totally new to ruby.
> > > >
> > > > Idea in my mind is:
> > > > 1) get all template declarations from source;
> > > > 2) introduce a base template in perl for those types which share the
> > >
> > > same
> > >
> > > > base template
> > > > ? ? like QList<Q3DockWindow *>, QList<Q3ToolBar *> we create QList.
> > > > ? ? such base template can create a specific namespace for demanded
> > > > type runtimely, say
> > > > ? ? QList_Q3DockWindow_Ptr (cached in future), and push all
> available
> > > > methods into it.
> > > > ? ? Inside QList c++ code holds a function dictionary to cast
> generic
> > > > pointer from vm to
> > > > ? ? template type instance (possibly by interpret_cast or
> static_cast);
> > >
> > > Yes, that sounds similar to the code in handlers.cpp that I describe
> > > above.
> > >
> > > > Could you pls explain something you've done in qtbudy or your ideas?
> > > > From my personal point of view, that'll be nice if we can setup a
> > >
> > > generic
> > >
> > > > solution, across
> > > > different scripting languages.
> > >
> > > Well, yes that is the idea of the Smoke library. And it allows the
> code
> > > for
> > > the QtRuby bindings (derived from PerlQt), and the Qyoto C# bindings
> to
> > > be very similar.
> >
> > The way to keep instance pointer differ in various languages. That'll be
> > nice
> > to define marshall layer plugin for each one and plug to use.
> >
> > Note that I think someone is working on a Qt4 version of the Smoke based
> >
> > > PerlQt, and you need to be a bit careful about naming your project
> > > something
> > > different from just 'PerlQt' to avoid confusion.
> >
> > namespace is ok. ?I'd like to know him/her. Is him/her on the maillist?
> Yes, there is a mailing list kde-perl at kde.org


thanks for the information. I'll make a subscription later.

-- Richard
>
>


-- 
cheers,
-dongxu
__END__
http://search.cpan.org/~dongxu
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