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Re: Using Guile in a wxWidgets app

From: Neil Jerram
Subject: Re: Using Guile in a wxWidgets app
Date: Sun, 05 Feb 2006 09:42:22 +0000
User-agent: Gnus/5.1007 (Gnus v5.10.7) Emacs/21.4 (gnu/linux)

John Steele Scott <address@hidden> writes:

> I have written a small piece about embedding Guile in wxWidgets GUI program.
> You can read it at:
> <>
> Does anyone have any comments about it?

Overall it looks like a great tutorial to me.  (Although I'm not
familiar with wxWidgets code.)

Some detailed comments...

"if (modifiers == NULL)"

The constant indicating an empty list is SCM_EOL, not NULL, so this
should at least be (modifiers == SCM_EOL).  Even better, though, would
be "if (SCM_NULLP (modifiers))".

> In particular, I would appreciate feedback on the way I have wrapped the
> wxWidgets MessageBox() function. I used symbols instead of ORing bits for
> the modifier parameter, so that 
> (message-box "Really quit?" "Quit?" 'yes/no 'question)
> is equivalent to
> wxMessageBox("Really quit?", "Quit?", wxYES_NO|wxICON_QUESTION).

IMO this is a nice schemely touch.  You could of course compute the
symbols ahead of time, and store them, rather than constructing them
every time message_box is called, but it doesn't matter that much.

> Also, in my MyFrame::OnQuit method, I create a variable in the Guile world,
> and then look it up again after calling the hook. Is this really necessary,
> or can I somehow bind *quit-do-close* directly to a SCM in
> MyFrame::OnQuit's stack frame, which Guile will modify directly, removing
> the need for the call to scm_variable_ref(scm_c_lookup("*quit-do-close*"))?

Well you could do this, which feels a bit more natural (and closer to
what you have requested):

  SCM qdcvar = scm_c_lookup("*quit-do-close*");

  scm_variable_set_x(qdcvar, SCM_BOOL_T);

  scm_c_run_hook(quit_hook, SCM_EOL);

  if (SCM_NFALSEP(scm_variable_ref(qdcvar)))

(Alternatively, you could question whether quit-hook really needs to be
a hook, rather than a single function.  If it was a single function,
you could call it from C directly and use its return value instead of
the global *quit-do-close*.)


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