Date: Thu, 30 Nov 2006 09:20:41 +0100
From: Maxence Guesdon <maxence.guesdon at inria.fr>
To: Olivier Andrieu <oandrieu at nerim.net>
Cc: lablgtk at math.nagoya-u.ac.jp
Subject: Re: strange behaviour of GMain.Main.main / GMain.Main.quit
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On Wed, 29 Nov 2006 19:49:53 +0100
Olivier Andrieu <oandrieu at nerim.net> wrote:

> Salut Maxence,

Salut Olivier,

>  Maxence Guesdon [Wednesday 29 November 2006] :
>  >
>  > Hello,
>  > 
>  > I'm experiencing problems while using GMain.Main.main and
>  > GMain.Main.quit. Here is a program to reproduce the problem. It
>  > creates a window. When "Return" is pressed, the nb_waits counter in
>  > incrementend, then GMain.Main.main is called to wait for a
>  > GMain.Main.quit, then "pop!" is displayed (that is, when
>  > GMain.Main.main returns). When "Escape" is pressed, GMain.Main.quit is
>  > called nb_waits times. I thought that then all waiting "pop!" would be
>  > displayed one after the other but it works only when there is only one
>  > GMain.Main.main waiting. Is this a bug or a feature ?
> 
> It's not a bug, that's just how the glib event loop API works. A
> GMainLoop has a is_running boolean flag. g_main_loop_run basically
> does a:
>   while (loop->is_running) process_events (loop);
> and g_main_loop_quit simply sets loop->is_running to FALSE.
> 
> To get this multiple level of loops, you'd need to create a new loop
> object or something (but lablgtk doesn't wrap all the necessary
> functions). 

Looking at the code in GtkMain, I see:
  let loops = ref []
  let default_main () =
    let loop = (Main.create true) in
    loops := loop :: !loops;
    while Main.is_running loop do Main.iteration true done;
    if !loops <> [] then loops := List.tl !loops
  let main_func = ref default_main
  let main () = !main_func ()
  let quit () = if !loops <> [] then Main.quit (List.hd !loops)

So it seems that when I call GMain.Main.main () a new loop is created and
it is destroyed when I call GMain.Main.quit (). Am I missnig something ?
What happens to the code after the call to GMain.Main.main () in my
example ?

Maxence

-- 
Maxence Guesdon
http://yquem.inria.fr/~guesdon/
http://devel.inria.fr/rocq/