/*  $Id$

    Part of XPCE --- The SWI-Prolog GUI toolkit

    Author:        Jan Wielemaker and Anjo Anjewierden
    E-mail:        J.Wielemaker@cs.vu.nl
    WWW:           http://www.swi-prolog.org/packages/xpce/
    Copyright (C): 2009, University of Amsterdam

    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License
    as published by the Free Software Foundation; either version 2
    of the License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    As a special exception, if you link this library with other files,
    compiled with a Free Software compiler, to produce an executable, this
    library does not by itself cause the resulting executable to be covered
    by the GNU General Public License. This exception does not however
    invalidate any other reasons why the executable file might be covered by
    the GNU General Public License.
*/

:- module(pce_dispatch,
	  [ pce_dispatch/1,		% +Options
	    pce_end_dispatch/0,
	    pce_call/1			% :Goal
	  ]).
:- use_module(library(pce)).

:- meta_predicate
	pce_call(0).

/** <module> Run XPCE in a separate thread

This module allows one to run XPCE in   a separate thread =pce=. This is
especially  nice  if  xpce  is  only  used  to  support  the  SWI-Prolog
development tools because it ensures that   the  tools remain responsive
while the main thread executes long-running goals.

This module can be activated automatically if   xpce is loaded using the
prolog flag xpce_threaded:

  ==
  :- set_prolog_flag(xpce_threaded, true).
  ==

@tbd	This module is highly experimental and has only be tested
	somewhat on Linux systems.
*/

%%	pce_dispatch(+Options) is det.
%
%	Create a new thread =pce= that takes   care  of the XPCE message
%	loop. This predicate has no effect  if dispatching is already on
%	another thread than the =main=.  The   loop  can  be ended using
%	pce_end_dispatch/0.

pce_dispatch(Options) :-
	with_mutex(pce_dispatch, pce_dispatch_(Options)).

pce_dispatch_(Options) :-
	pce_thread(main), !,
	thread_self(Me),
	thread_create(pce_dispatcher(Me), _, [alias(pce)|Options]),
	thread_get_message(pce_dispatch).
pce_dispatch_(_).

:- dynamic
	end_pce_dispatcher/1.

pce_dispatcher(Origin) :-
	set_pce_thread,
	thread_self(Me),
	retractall(pce:pce_thread(_)),
	assert(pce:pce_thread(Me)),
	thread_send_message(Origin, pce_dispatch),
	repeat,
	    catch(pce_dispatch, E, true),
	    (	var(E)
	    ->	true
	    ;	print_message(error, E)
	    ),
	retract(end_pce_dispatcher(Sender)), !,
	thread_send_message(Sender, end_pce_dispatcher).

end(Requester) :-
	assert(end_pce_dispatcher(Requester)).

%%	pce_end_dispatch is det.
%
%	End the XPCE dispatcher loop started with pce_dispatch/1.

pce_end_dispatch :-
	thread_self(Me),
	in_pce_thread(end(Me)),
	thread_get_message(end_pce_dispatcher),
	set_pce_thread,
	thread_self(Me),
	retractall(pce:pce_thread(_)),
	assert(pce:pce_thread(Me)).

%%	pce_call(:Goal) is det.
%
%	Run Goal in the XPCE thread.
%
%	@deprecated New code should used in_pce_thread/1.

pce_call(Goal) :-
	in_pce_thread(Goal).
