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In-Reply-To: <20061130092041.1d52a40d at tintin.inria.fr>
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Date: Thu, 30 Nov 2006 10:16:48 +0100 (CET)
Subject: Re: strange behaviour of GMain.Main.main / GMain.Main.quit
From: "Olivier Andrieu" <oandrieu at nerim.net>
To: "Maxence Guesdon" <maxence.guesdon at inria.fr>
Cc: lablgtk at math.nagoya-u.ac.jp
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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 ?

Oh right, I forgot lablgtk was doing its own thing with loops rather than
wrapping g_main_loop run.

Well what's happening in your code is that you're repeatedly calling
GtkMain.Main.quit() in a for loop, but that turns into repeated calls to
Glib.Main.quit() to the *same* loop object on top of the loops "stack". As
you can see in the code above, loops are not pop'ed by GtkMain.Main.quit()
but when GtkMain.Main.main() returns.

[C'est de mémoire, je n'ai plus ton exemple sous les yeux là].
-- 
  Olivier