1/*  Part of SWI-Prolog
    2
    3    Author:        Jan Wielemaker
    4    E-mail:        J.Wielemaker@vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (c)  2006-2015, 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(www_browser,
   37          [ www_open_url/1,             % +UrlOrSpec
   38            expand_url_path/2           % +Spec, -URL
   39          ]).   40:- autoload(library(lists),[member/2]).   41
   42:- if(exists_source(library(process))).   43:- autoload(library(process), [process_create/3]).   44:- endif.   45
   46:- multifile
   47    known_browser/2.

?- www_open_url(swipl(.)).

 www_open_url(+Url)

Open URL in running version of the users' browser or start a new browser. This predicate tries the following steps:

1. If a prolog flag (see set_prolog_flag/2) browser is set and this is the name of a known executable, use this. The flag may be set to Command-Mode, where mode is one of fg or bg, requesting Command to run in foreground or background mode. Default is bg.
2. On Windows, use win_shell(open, URL)
3. Find a generic `open' comment. Candidates are xdg-open, open or gnome-open.
4. If a environment variable BROWSER is set and this is the name of a known executable, use this.
5. Try to find a known browser. @tbd Figure out the right tool in step 3 as it is not uncommon that multiple are installed.

   85www_open_url(Spec) :-                   % user configured
   86    expand_url_path(Spec, URL),
   87    open_url(URL).
   88
   89open_url(URL) :-
   90    current_prolog_flag(browser, Browser),
   91    expand_browser_flag(Browser, Command, Mode),
   92    has_command(Command),
   93    !,
   94    run_command(Command, [URL], Mode).
   95:- if(current_predicate(win_shell/2)).   96open_url(URL) :-                        % Windows shell
   97    win_shell(open, URL),
   98    !.
   99:- endif.  100open_url(URL) :-                        % Unix `open document'
  101    open_command(Open),
  102    has_command(Open),
  103    !,
  104    run_command(Open, [URL], fg).
  105open_url(URL) :-                        % user configured
  106    getenv('BROWSER', Browser),
  107    has_command(Browser),
  108    !,
  109    run_browser(Browser, URL).
  110open_url(URL) :-                        % something we know
  111    known_browser(Browser, _),
  112    has_command(Browser),
  113    !,
  114    run_browser(Browser, URL).
  115
  116expand_browser_flag(Command-Mode, Command, Mode) :- !.
  117expand_browser_flag(Command, Command, bg) :- atomic(Command).
  118
  119open_command(open) :-                   % Apples open command
  120    current_prolog_flag(apple, true).
  121open_command('xdg-open').               % Free desktop
  122open_command('gnome-open').             % Gnome (deprecated in favour of xdg-open
  123open_command(open).                     % Who knows

 run_browser(+Browser, +URL) is det

Open a page using a browser.

  129run_browser(Browser, URL) :-
  130    run_command(Browser, [URL], bg).

 run_command(+Command, +Args, +Background)

Run OS command Command using Args, silencing the error output because many browsers are rather verbose.

  137:- if(current_predicate(process_create/3)).  138run_command(Command, Args, fg) :-
  139    !,
  140    process_create(path(Command), Args, [stderr(null)]).
  141:- endif.  142:- if(current_prolog_flag(unix, true)).  143run_command(Command, [Arg], fg) :-
  144    format(string(Cmd), "\"~w\" \"~w\" &> /dev/null", [Command, Arg]),
  145    shell(Cmd).
  146run_command(Command, [Arg], bg) :-
  147    format(string(Cmd), "\"~w\" \"~w\" &> /dev/null &", [Command, Arg]),
  148    shell(Cmd).
  149:- else.  150run_command(Command, [Arg], fg) :-
  151    format(string(Cmd), "\"~w\" \"~w\"", [Command, Arg]),
  152    shell(Cmd).
  153run_command(Command, [Arg], bg) :-
  154    format(string(Cmd), "\"~w\" \"~w\" &", [Command, Arg]),
  155    shell(Cmd).
  156:- endif.

 known_browser(+FileBaseName, -Compatible)

True if browser FileBaseName has a remote protocol compatible to Compatible.

  163known_browser(firefox,   netscape).
  164known_browser(mozilla,   netscape).
  165known_browser(netscape,  netscape).
  166known_browser(konqueror, -).
  167known_browser(opera,     -).

 has_command(+Command)

Succeeds if Command is in $PATH. Works for Unix systems. For Windows we have to test for executable extensions.

  175:- dynamic
  176    command_cache/2.  177:- volatile
  178    command_cache/2.  179
  180has_command(Command) :-
  181    command_cache(Command, Path),
  182    !,
  183    Path \== (-).
  184has_command(Command) :-
  185    (   getenv('PATH', Path),
  186        (   current_prolog_flag(windows, true)
  187        ->  Sep = (;)
  188        ;   Sep = (:)
  189        ),
  190        atomic_list_concat(Parts, Sep, Path),
  191        member(Part, Parts),
  192        prolog_to_os_filename(PlPart, Part),
  193        atomic_list_concat([PlPart, Command], /, Exe),
  194        access_file(Exe, execute)
  195    ->  assert(command_cache(Command, Exe))
  196    ;   assert(command_cache(Command, -)),
  197        fail
  198    ).
  199
  200
  201                 /*******************************
  202                 *            NET PATHS         *
  203                 *******************************/

 url_path(+Alias, -Expansion) is nondet

Define URL path aliases. This multifile predicate is defined in module user. Expansion is either a URL, or a term Alias(Sub).

  210:- multifile
  211    user:url_path/2.  212
  213user:url_path(swipl,          'http://www.swi-prolog.org').
  214user:url_path(swipl_book,     'http://books.google.nl/books/about/\c
  215                               SWI_Prolog_Reference_Manual_6_2_2.html?\c
  216                               id=q6R3Q3B-VC4C&redir_esc=y').
  217
  218user:url_path(swipl_faq,      swipl('FAQ')).
  219user:url_path(swipl_man,      swipl('pldoc/doc_for?object=manual')).
  220user:url_path(swipl_mail,     swipl('Mailinglist.html')).
  221user:url_path(swipl_download, swipl('Download.html')).
  222user:url_path(swipl_pack,     swipl('pack/list')).
  223user:url_path(swipl_bugs,     swipl('bug.html')).
  224user:url_path(swipl_quick,    swipl('man/quickstart.html')).

 expand_url_path(+Spec, -URL)

Expand URL specifications similar to absolute_file_name/3. The predicate url_path/2 plays the role of file_search_path/2.

Errors

- existence_error(url_path, Spec) if the location is not defined.

  234expand_url_path(URL, URL) :-
  235    atomic(URL),
  236    !.                 % Allow atom and string
  237expand_url_path(Spec, URL) :-
  238    Spec =.. [Path, Local],
  239    (   user:url_path(Path, Spec2)
  240    ->  expand_url_path(Spec2, URL0),
  241        (   Local == '.'
  242        ->  URL = URL0
  243        ;   sub_atom(Local, 0, _, _, #)
  244        ->  atom_concat(URL0, Local, URL)
  245        ;   atomic_list_concat([URL0, Local], /, URL)
  246        )
  247    ;   throw(error(existence_error(url_path, Path), expand_url_path/2))
  248    )