Re: [Gtk2hs-users] Some early questions about Gtk2Hs

[David P. <fee...@gm...>]

On 8/3/07, Duncan Coutts <dun...@wo...> wrote:
>
> On Fri, 2007-08-03 at 09:49 -0700, David Pollak wrote:
> > Howdy,
> >
> > I've started using Haskell and Gtk2Hs... it's pretty slick.  I'm a
> > Haskell newbie, but have a fair amount of experience with Scala.
> > Anyway, I'm kind of confused about the following construct:
> > window <- xmlGetWidget windowXml castToWindow "window"
> >    onDelete window deleteEvent
> >    onDestroy window destroyEvent
> >
> >
> > The 'onDelete' and 'onDestroy' functions register events on the window
> > that call the particular functions.  I understand what is happening.
> > I don't understand how.  My understanding of Haskell is that there are
> > no side effects for function calls, but it looks from that code like
> > there are side effects galore.
>
> That's right. Almost all the Gtk+ functions are in the IO monad. See:
> http://www.haskell.org/tutorial/io.html
>
> > It looks like some hidden state is being changed.  Can someone help
> > educate me as to what's going on?  Is it that onDelete does in fact
> > have the side effect of calling into Gtk and registered the event
> > callback and thus there is a side effect here?
>
> Yes.
>
> > Also, while my intended deployment target is Windows, I will be doing
> > a fair amount of my development on Mac OS X.  It seems that the
> > MacPorts versions of GTK and Glade and GTK2hs require X windows to
> > run.  Is that correct?  Is there any Aqua version of GTK?
>
> Yes, the current Gtk+  default backend OS X is the X windows one. There
> is a native OS X Gtk+ backend under development:
> http://developer.imendio.com/projects/gtk-macosx
>
> Changed have been going into the main Gtk+ development repo, however it
> has rather slow progress so don't hold your breath.
>
> Duncan


Duncan,

You are amazingly helpful and responsive.

Thanks,

David




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