Re: OCaml's long range graphical direction?

[Jerome Vouillon <Jerome.Vouillon@inria.fr>]

On Fri, Feb 09, 2001 at 06:49:01PM +0900, Jacques Garrigue wrote:
> In fact, the gnome project has a GUI builder called glade, which
> allows one to produce either C code or an XML representation of the
> interface. There is even a library libglade which allows one to
> dynamically load such an XML representation and use it in a program.
> 
> It would be pretty easy to either interface to this library,

I don't think it would be a good idea to interface to this library, as
it is designed for C, which does not have higher-order function (so,
the library assumes that there is one function by call-back).

> or, more
> interestingly, build a parser and interpreter for it, so as to be able
> to use glade's output in lablgtk or mlgtk programs.

For the parser, one can just use PXP.  The interpreter is a lot of
work though...  Some time ago, I started to write one, but it only
supports a few widgets yet.

> Still, I'm not sure I would use it personally. Basically, when I write
> a lablgtk application, the code is not in the GUI layout: this is just
> one line per widget. It is in all the callbacks and dynamic
> processing.  I'm not so sure a GUI builder will help you a lot with
> that, because it can also get in your way.

I disagree.  When designing an interface, there are a lot of tweakings
(frame widths, alignements, ...) which are easily done using an
interface builder but much more tedious to program (and you often need
to recompile a lot of time to get them right).

> The last problem is how to stay type safe when you load a text file.
> Basically this means that you will be more verbose, and that will
> compare badly with guile-gtk or python-gtk based applications.

I get some code that look like this.  This does not look that verbose to me.

  let select_date w0 date cont =
    let gl = interface () in
    let (w, ctx) =
      create_dialog gl "choix de la date"
        ["valider",
         any (fun ctx _ _ ->
                (toplevel ctx)#destroy (); w0#misc#set_sensitive true;
                let (year, month, day) = (calendar ctx "calendrier")#date in
                cont {day = day; month = month + 1; year = year});
         "annuler",
         any (fun ctx _ _ ->
                (toplevel ctx)#destroy (); w0#misc#set_sensitive true)]
    in
    w0#misc#set_sensitive false;
    w#set_transient_for w0;
    begin match date with
      None -> ()
    | Some d ->
        let c = calendar ctx "calendrier" in
        c#select_month (d.month - 1) d.year;
        c#select_day d.day
    end;
    w#show ()

-- Jerome