1/*  Part of XPCE --- The SWI-Prolog GUI toolkit
    2
    3    Author:        Jan Wielemaker and Anjo Anjewierden
    4    E-mail:        J.Wielemaker@cs.vu.nl
    5    WWW:           http://www.swi-prolog.org/packages/xpce/
    6    Copyright (c)  2009-2015, University of Amsterdam
    7                              VU University Amsterdam
    8    All rights reserved.
    9
   10    Redistribution and use in source and binary forms, with or without
   11    modification, are permitted provided that the following conditions
   12    are met:
   13
   14    1. Redistributions of source code must retain the above copyright
   15       notice, this list of conditions and the following disclaimer.
   16
   17    2. Redistributions in binary form must reproduce the above copyright
   18       notice, this list of conditions and the following disclaimer in
   19       the documentation and/or other materials provided with the
   20       distribution.
   21
   22    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   23    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   24    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   25    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   26    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   27    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   28    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   29    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   30    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   31    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   32    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   33    POSSIBILITY OF SUCH DAMAGE.
   34*/
   35
   36:- module(pce_dispatch,
   37          [ pce_dispatch/1,             % +Options
   38            pce_end_dispatch/0,
   39            pce_call/1                  % :Goal
   40          ]).   41:- use_module(library(pce)).   42
   43:- meta_predicate
   44    pce_call(0).   45
   46/** <module> Run XPCE in a separate thread
   47
   48This module allows one to run XPCE in   a separate thread =pce=. This is
   49especially  nice  if  xpce  is  only  used  to  support  the  SWI-Prolog
   50development tools because it ensures that   the  tools remain responsive
   51while the main thread executes long-running goals.
   52
   53This module can be deactivated by setting the flag `xpce_threaded`:
   54
   55  ==
   56  :- set_prolog_flag(xpce_threaded, false).
   57  ==
   58*/
   59
   60:- predicate_options(pce_dispatch/1, 1,
   61                     [ pass_to(system:thread_create/3, 3)
   62                     ]).   63
   64%!  pce_dispatch(+Options) is det.
   65%
   66%   Create a new thread =pce= that takes   care  of the XPCE message
   67%   loop. This predicate has no effect  if dispatching is already on
   68%   another thread than the =main=.  The   loop  can  be ended using
   69%   pce_end_dispatch/0.
   70
   71pce_dispatch(Options) :-
   72    with_mutex(pce_dispatch, pce_dispatch_(Options)).
   73
   74pce_dispatch_(_) :-
   75    pce_thread(pce),
   76    !.
   77pce_dispatch_(Options) :-
   78    thread_self(Me),
   79    thread_create(pce_dispatcher(Me), _,
   80                  [ alias(pce),
   81                    debug(false)
   82                  | Options
   83                  ]),
   84    thread_get_message(pce_dispatch).
   85
   86:- dynamic
   87    end_pce_dispatcher/1.   88
   89pce_dispatcher(Origin) :-
   90    set_pce_thread,
   91    thread_self(Me),
   92    retractall(pce:pce_thread(_)),
   93    assert(pce:pce_thread(Me)),
   94    thread_send_message(Origin, pce_dispatch),
   95    set_prolog_flag(debug_on_error, false),         % avoid the debugger
   96    set_prolog_flag(generate_debug_info, true),     % Started with false
   97    repeat,
   98        catch(pce_dispatch, E, true),
   99        (   var(E)
  100        ->  true
  101        ;   print_message(error, E)
  102        ),
  103    retract(end_pce_dispatcher(Sender)),
  104    !,
  105    thread_send_message(Sender, end_pce_dispatcher).
  106
  107end(Requester) :-
  108    assert(end_pce_dispatcher(Requester)).
  109
  110%!  pce_end_dispatch is det.
  111%
  112%   End the XPCE dispatcher loop started with pce_dispatch/1.
  113
  114pce_end_dispatch :-
  115    thread_self(Me),
  116    in_pce_thread(end(Me)),
  117    thread_get_message(end_pce_dispatcher),
  118    set_pce_thread,
  119    thread_self(Me),
  120    retractall(pce:pce_thread(_)),
  121    assert(pce:pce_thread(Me)).
  122
  123%!  pce_call(:Goal) is det.
  124%
  125%   Run Goal in the XPCE thread.
  126%
  127%   @deprecated New code should used in_pce_thread/1.
  128
  129pce_call(Goal) :-
  130    in_pce_thread(Goal).
  131
  132:- public start_dispatch/0.  133
  134start_dispatch :-
  135    (   current_prolog_flag(xpce_threaded, true),
  136        current_predicate(pce_dispatch/1)
  137    ->  pce_dispatch([])
  138    ;   true
  139    )