bug#19688: [patch] add support for emacs daemon on Windows

[Eli Zaretskii]

> Date: Sat, 14 Feb 2015 22:37:55 +0900
> From: Mark Laws <mdl@60hz.org>
> Cc: 19688@debbugs.gnu.org
> 
> On Sat, Feb 14, 2015 at 10:28 PM, Eli Zaretskii <eliz@gnu.org> wrote:
> > I don't see why 'WaitForInputIdle' wouldn't work.  Can you explain?
> > AFAIU, it waits until the process is idle, which means it did all the
> > initialization and is ready for accepting connections.  Am I missing
> > something?
> 
> http://blogs.msdn.com/b/oldnewthing/archive/2010/03/26/9985422.aspx

Thanks, it's good to know about those subtleties.

However, after looking at the Emacs initialization code, I think those
problems will not affect Emacs, because we only start the thread that
reads Windows messages inside the call to Frecursive_edit, and by that
time the daemon initialization is already done.

OTOH, there's one other caveat in the documentation of
'WaitForInputIdle': it returns immediately "if the process is a
console application or does not have a message queue".  Emacs is built
as a console application, and I'm not sure at which point it begins to
"have a message queue", as far as this function is concerned.

> I can try it if you want, but it seems fragile compared to the event thing.

Please do try it, I think it will either work reliably or not at all.

The reason I'd prefer to use it if it works is because doing so
side-steps the entire issue of how to pass the event ID, which,
together with the code which handles the event, adds non-trivial
amount of code to your patch.  It would be nice to avoid that, if
possible.

Thanks.