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)  2010-2025, VU University Amsterdam
    7                              CWI, Amsterdam
    8                              SWI-Prolog Solutions b.v.
    9    All rights reserved.
   10
   11    Redistribution and use in source and binary forms, with or without
   12    modification, are permitted provided that the following conditions
   13    are met:
   14
   15    1. Redistributions of source code must retain the above copyright
   16       notice, this list of conditions and the following disclaimer.
   17
   18    2. Redistributions in binary form must reproduce the above copyright
   19       notice, this list of conditions and the following disclaimer in
   20       the documentation and/or other materials provided with the
   21       distribution.
   22
   23    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   24    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   25    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   26    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   27    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   28    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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   31    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   33    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   34    POSSIBILITY OF SUCH DAMAGE.
   35*/
   36
   37:- module(ansi_term,
   38          [ ansi_format/3,              % +Attr, +Format, +Args
   39            ansi_format/4,              % +Stream, +Attr, +Format, +Args
   40            ansi_get_color/2,           % +Which, -rgb(R,G,B)
   41            ansi_hyperlink/2,           % +Stream,+Location
   42            ansi_hyperlink/3            % +Stream,+URL,+Label
   43          ]).   44:- autoload(library(error), [domain_error/2, must_be/2, instantiation_error/1]).   45:- autoload(library(lists), [append/3]).   46:- autoload(library(utf8), [utf8_codes/3]).

   71:- multifile
   72    prolog:console_color/2,                     % +Term, -AnsiAttrs
   73    supports_get_color/0,
   74    hyperlink/2,                                % +Stream, +Spec
   75    tty_url_hook/2.                             % +For, -URL
   76
   77color_term_flag_default(true) :-
   78    stream_property(user_input, tty(true)),
   79    stream_property(user_error, tty(true)),
   80    stream_property(user_output, tty(true)),
   81    \+ getenv('TERM', dumb),
   82    !.
   83color_term_flag_default(false).
   84
   85init_color_term_flag :-
   86    color_term_flag_default(Default),
   87    create_prolog_flag(color_term, Default,
   88                       [ type(boolean),
   89                         keep(true)
   90                       ]),
   91    create_prolog_flag(hyperlink_term, false,
   92                       [ type(boolean),
   93                         keep(true)
   94                       ]).
   95
   96:- initialization
   97    init_color_term_flag.   98
   99:- meta_predicate
  100    keep_line_pos(+, 0).  101
  102:- multifile
  103    user:message_property/2.

 ansi_format(+ClassOrAttributes, +Format, +Args) is det

 ansi_format(+Stream, +ClassOrAttributes, +Format, +Args) is det

Format text with ANSI attributes. This predicate behaves as format/2 using Format and Args, but if the current_output is a terminal, it adds ANSI escape sequences according to Attributes. For example, to print a text in bold cyan, do

?- ansi_format([bold,fg(cyan)], 'Hello ~w', [world]).

Attributes is either a single attribute, a list thereof or a term that is mapped to concrete attributes based on the current theme (see prolog:console_color/2). The attribute names are derived from the ANSI specification. See the source for sgr_code/2 for details. Some commonly used attributes are:

bold

underline

fg(Color),bg(Color),hfg(Color),hbg(Color)

For fg(Color) and bg(Color), the colour name can be '#RGB' or '#RRGGBB'

fg8(Spec),bg8(Spec)

8-bit color specification. Spec is a colour name, h(Color) or an integer 0..255.

fg(R,G,B),bg(R,G,B)

24-bit (direct color) specification. The components are integers in the range 0..255.

Defined color constants are below. default can be used to access the default color of the terminal.

• black, red, green, yellow, blue, magenta, cyan, white

ANSI sequences are sent if and only if

• The current_output has the property tty(true) (see stream_property/2).
• The Prolog flag color_term is true.

  146ansi_format(Attr, Format, Args) :-
  147    ansi_format(current_output, Attr, Format, Args).
  148
  149ansi_format(Stream, Class, Format, Args) :-
  150    stream_property(Stream, tty(true)),
  151    current_prolog_flag(color_term, true),
  152    class_attrs(Class, Attr),
  153    Attr \== [],
  154    !,
  155    phrase(sgr_codes_ex(Attr), Codes),
  156    atomic_list_concat(Codes, ;, Code),
  157    with_output_to(
  158        Stream,
  159        (   keep_line_pos(current_output, format('\e[~wm', [Code])),
  160            format(Format, Args),
  161            keep_line_pos(current_output, format('\e[0m'))
  162        )
  163    ),
  164    flush_output.
  165ansi_format(Stream, _Attr, Format, Args) :-
  166    format(Stream, Format, Args).
  167
  168sgr_codes_ex(X) -->
  169    { var(X),
  170      !,
  171      instantiation_error(X)
  172    }.
  173sgr_codes_ex([]) -->
  174    !.
  175sgr_codes_ex([H|T]) -->
  176    !,
  177    sgr_codes_ex(H),
  178    sgr_codes_ex(T).
  179sgr_codes_ex(Attr) -->
  180    (   { sgr_code(Attr, Code) }
  181    ->  (   { is_list(Code) }
  182        ->  list(Code)
  183        ;   [Code]
  184        )
  185    ;   { domain_error(sgr_code, Attr) }
  186    ).
  187
  188list([]) --> [].
  189list([H|T]) --> [H], list(T).

 sgr_code(+Name, -Code)

True when code is the Select Graphic Rendition code for Name. The defined names are given below. Note that most terminals only implement this partially.

reset	all attributes off
bold
faint
italic
underline
blink(slow)
blink(rapid)
negative
conceal
crossed_out
font(primary)
font(N)	Alternate font (1..8)
fraktur
underline(double)
intensity(normal)
fg(Name)	Color name
bg(Name)	Color name
framed
encircled
overlined
ideogram(underline)
right_side_line
ideogram(underline(double))
right_side_line(double)
ideogram(overlined)
left_side_line
ideogram(stress_marking)
-Off	Switch attributes off
hfg(Name)	Color name
hbg(Name)	Color name

See also

- http://en.wikipedia.org/wiki/ANSI_escape_code

  231sgr_code(reset, 0).
  232sgr_code(bold,  1).
  233sgr_code(faint, 2).
  234sgr_code(italic, 3).
  235sgr_code(underline, 4).
  236sgr_code(blink(slow), 5).
  237sgr_code(blink(rapid), 6).
  238sgr_code(negative, 7).
  239sgr_code(conceal, 8).
  240sgr_code(crossed_out, 9).
  241sgr_code(font(primary), 10) :- !.
  242sgr_code(font(N), C) :-
  243    C is 10+N.
  244sgr_code(fraktur, 20).
  245sgr_code(underline(double), 21).
  246sgr_code(intensity(normal), 22).
  247sgr_code(fg(Name), C) :-
  248    (   ansi_color(Name, N)
  249    ->  C is N+30
  250    ;   rgb(Name, R, G, B)
  251    ->  sgr_code(fg(R,G,B), C)
  252    ).
  253sgr_code(bg(Name), C) :-
  254    !,
  255    (   ansi_color(Name, N)
  256    ->  C is N+40
  257    ;   rgb(Name, R, G, B)
  258    ->  sgr_code(bg(R,G,B), C)
  259    ).
  260sgr_code(framed, 51).
  261sgr_code(encircled, 52).
  262sgr_code(overlined, 53).
  263sgr_code(ideogram(underline), 60).
  264sgr_code(right_side_line, 60).
  265sgr_code(ideogram(underline(double)), 61).
  266sgr_code(right_side_line(double), 61).
  267sgr_code(ideogram(overlined), 62).
  268sgr_code(left_side_line, 62).
  269sgr_code(ideogram(stress_marking), 64).
  270sgr_code(-X, Code) :-
  271    off_code(X, Code).
  272sgr_code(hfg(Name), C) :-
  273    ansi_color(Name, N),
  274    C is N+90.
  275sgr_code(hbg(Name), C) :-
  276    !,
  277    ansi_color(Name, N),
  278    C is N+100.
  279sgr_code(fg8(Name), [38,5,N]) :-
  280    ansi_color8(Name, N).
  281sgr_code(bg8(Name), [48,5,N]) :-
  282    ansi_color8(Name, N).
  283sgr_code(fg(R,G,B), [38,2,R,G,B]) :-
  284    between(0, 255, R),
  285    between(0, 255, G),
  286    between(0, 255, B).
  287sgr_code(bg(R,G,B), [48,2,R,G,B]) :-
  288    between(0, 255, R),
  289    between(0, 255, G),
  290    between(0, 255, B).
  291
  292off_code(italic_and_franktur, 23).
  293off_code(underline, 24).
  294off_code(blink, 25).
  295off_code(negative, 27).
  296off_code(conceal, 28).
  297off_code(crossed_out, 29).
  298off_code(framed, 54).
  299off_code(overlined, 55).
  300
  301ansi_color8(h(Name), N) :-
  302    !,
  303    ansi_color(Name, N0),
  304    N is N0+8.
  305ansi_color8(Name, N) :-
  306    atom(Name),
  307    !,
  308    ansi_color(Name, N).
  309ansi_color8(N, N) :-
  310    between(0, 255, N).
  311
  312ansi_color(black,   0).
  313ansi_color(red,     1).
  314ansi_color(green,   2).
  315ansi_color(yellow,  3).
  316ansi_color(blue,    4).
  317ansi_color(magenta, 5).
  318ansi_color(cyan,    6).
  319ansi_color(white,   7).
  320ansi_color(default, 9).
  321
  322rgb(Name, R, G, B) :-
  323    atom_codes(Name, [0'#,R1,R2,G1,G2,B1,B2]),
  324    hex_color(R1,R2,R),
  325    hex_color(G1,G2,G),
  326    hex_color(B1,B2,B).
  327rgb(Name, R, G, B) :-
  328    atom_codes(Name, [0'#,R1,G1,B1]),
  329    hex_color(R1,R),
  330    hex_color(G1,G),
  331    hex_color(B1,B).
  332
  333hex_color(D1,D2,V) :-
  334    code_type(D1, xdigit(V1)),
  335    code_type(D2, xdigit(V2)),
  336    V is 16*V1+V2.
  337
  338hex_color(D1,V) :-
  339    code_type(D1, xdigit(V1)),
  340    V is 16*V1+V1.

 prolog:console_color(+Term, -AnsiAttributes) is semidet

Hook that allows for mapping abstract terms to concrete ANSI attributes. This hook is used by theme files to adjust the rendering based on user preferences and context. Defaults are defined in the file boot/messages.pl, default_theme/2.

See also

- library(theme/dark) for an example implementation and the Term values used by the system messages.

  353                 /*******************************
  354                 *             HOOK             *
  355                 *******************************/

 prolog:message_line_element(+Stream, +Term) is semidet

Hook implementation that deals with ansi(+Attr, +Fmt, +Args) in message specifications.

  362prolog:message_line_element(S, ansi(Class, Fmt, Args)) :-
  363    class_attrs(Class, Attr),
  364    ansi_format(S, Attr, Fmt, Args).
  365prolog:message_line_element(S, ansi(Class, Fmt, Args, Ctx)) :-
  366    class_attrs(Class, Attr),
  367    ansi_format(S, Attr, Fmt, Args),
  368    (   nonvar(Ctx),
  369        Ctx = ansi(_, RI-RA)
  370    ->  keep_line_pos(S, format(S, RI, RA))
  371    ;   true
  372    ).
  373prolog:message_line_element(S, url(Location)) :-
  374    ansi_hyperlink(S, Location).
  375prolog:message_line_element(S, url(URL, Label)) :-
  376    ansi_hyperlink(S, URL, Label).
  377prolog:message_line_element(S, begin(Level, Ctx)) :-
  378    level_attrs(Level, Attr),
  379    stream_property(S, tty(true)),
  380    current_prolog_flag(color_term, true),
  381    !,
  382    (   is_list(Attr)
  383    ->  sgr_codes(Attr, Codes),
  384        atomic_list_concat(Codes, ;, Code)
  385    ;   sgr_code(Attr, Code)
  386    ),
  387    keep_line_pos(S, format(S, '\e[~wm', [Code])),
  388    Ctx = ansi('\e[0m', '\e[0m\e[~wm'-[Code]).
  389prolog:message_line_element(S, end(Ctx)) :-
  390    nonvar(Ctx),
  391    Ctx = ansi(Reset, _),
  392    keep_line_pos(S, write(S, Reset)).
  393
  394sgr_codes([], []).
  395sgr_codes([H0|T0], [H|T]) :-
  396    sgr_code(H0, H),
  397    sgr_codes(T0, T).
  398
  399level_attrs(Level,         Attrs) :-
  400    user:message_property(Level, color(Attrs)),
  401    !.
  402level_attrs(Level,         Attrs) :-
  403    class_attrs(message(Level), Attrs).
  404
  405class_attrs(Class, Attrs) :-
  406    user:message_property(Class, color(Attrs)),
  407    !.
  408class_attrs(Class, Attrs) :-
  409    prolog:console_color(Class, Attrs),
  410    !.
  411class_attrs(Class, Attrs) :-
  412    '$messages':default_theme(Class, Attrs),
  413    !.
  414class_attrs(Attrs, Attrs).

 ansi_hyperlink(+Stream, +Location) is det

 ansi_hyperlink(+Stream, +URL, +Label) is det

Create a hyperlink for a terminal emulator. The file is fairly easy, but getting the line and column across is not as there seems to be no established standard. The current implementation emits, i.e., inserting a capital L before the line.

``file://AbsFileName[#LLine[:Column]]``

See also

- https://gist.github.com/egmontkob/eb114294efbcd5adb1944c9f3cb5feda

  428ansi_hyperlink(Stream, Location) :-
  429    hyperlink(Stream, url(Location)),
  430    !.
  431ansi_hyperlink(Stream, Location) :-
  432    location_label(Location, Label),
  433    ansi_hyperlink(Stream, Location, Label).
  434
  435location_label(File:Line:Column, Label) =>
  436    format(string(Label), '~w:~w:~w', [File,Line,Column]).
  437location_label(File:Line, Label) =>
  438    format(string(Label), '~w:~w', [File,Line]).
  439location_label(File, Label) =>
  440    format(string(Label), '~w', [File]).
  441
  442ansi_hyperlink(Stream, Location, Label),
  443    hyperlink(Stream, url(Location, Label)) =>
  444    true.
  445ansi_hyperlink(Stream, Location, Label) =>
  446    (   location_url(Location, URL)
  447    ->  keep_line_pos(Stream,
  448                      format(Stream, '\e]8;;~w\e\\', [URL])),
  449        format(Stream, '~w', [Label]),
  450        keep_line_pos(Stream,
  451                      format(Stream, '\e]8;;\e\\', []))
  452    ;   format(Stream, '~w', [Label])
  453    ).
  454
  455is_url(URL) :-
  456    (   atom(URL)
  457    ->  true
  458    ;   string(URL)
  459    ),
  460    url_prefix(Prefix),
  461    sub_string(URL, 0, _, _, Prefix).
  462
  463url_prefix('http://').
  464url_prefix('https://').
  465url_prefix('file://').

 location_url(+Location, -URL) is det

Translate Location into a (file) URL. This predicate is hooked by tty_url_hook/2 with the same signature to allow for actions, location specifiers or URL schemes.

  473location_url(Location, URL),
  474    tty_url_hook(Location, URL0) =>
  475    URL = URL0.
  476location_url(File:Line:Column, URL) =>
  477    url_file_name(FileURL, File),
  478    format(string(URL), '~w#~d:~d', [FileURL, Line, Column]).
  479location_url(File:Line, URL) =>
  480    url_file_name(FileURL, File),
  481    format(string(URL), '~w#~w', [FileURL, Line]).
  482location_url(File, URL) =>
  483    url_file_name(URL, File).

 tty_url_hook(+Location, -URL)

Hook for location_url/2.

 url_file_name(-URL, +File) is semidet

Same as uri_file_name/2 in mode (-,+), but as a core library we do not wish to depend on the clib package and its foreign support.

  495url_file_name(URL, File) :-
  496    is_url(File), !,
  497    current_prolog_flag(hyperlink_term, true),
  498    URL = File.
  499url_file_name(URL, File) :-
  500    current_prolog_flag(hyperlink_term, true),
  501    absolute_file_name(File, AbsFile),
  502    ensure_leading_slash(AbsFile, AbsFile1),
  503    url_encode_path(AbsFile1, Encoded),
  504    format(string(URL), 'file://~s', [Encoded]).
  505
  506ensure_leading_slash(Path, SlashPath) :-
  507    (   sub_atom(Path, 0, _, _, /)
  508    ->  SlashPath = Path
  509    ;   atom_concat(/, Path, SlashPath)
  510    ).
  511
  512url_encode_path(Name, Encoded) :-
  513    atom_codes(Name, Codes),
  514    phrase(utf8_codes(Codes), UTF8),
  515    phrase(encode(UTF8), Encoded).
  516
  517encode([]) --> [].
  518encode([H|T]) --> encode1(H), encode(T).
  519
  520encode1(C) -->
  521    { reserved(C),
  522      !,
  523      format(codes([C1,C2]), '~`0t~16r~2|', [C])
  524    },
  525    "%", [C1,C2].
  526encode1(C) -->
  527    [C].
  528
  529reserved(C) :- C =< 0'\s.
  530reserved(C) :- C >= 127.
  531reserved(0'#).

 keep_line_pos(+Stream, :Goal)

Run goal without changing the position information on Stream. This is used to avoid that the exchange of ANSI sequences modifies the notion of, notably, the line_pos notion.

  539keep_line_pos(S, G) :-
  540    stream_property(S, position(Pos)),
  541    !,
  542    setup_call_cleanup(
  543        stream_position_data(line_position, Pos, LPos),
  544        G,
  545        set_stream(S, line_position(LPos))).
  546keep_line_pos(_, G) :-
  547    call(G).

 ansi_get_color(+Which, -RGB) is semidet

Obtain the RGB color for an ANSI color parameter. Which is either a color alias or an integer ANSI color id. Defined aliases are foreground and background. This predicate sends a request to the console (user_output) and reads the reply. This assumes an xterm compatible terminal.

Arguments:

RGB	- is a term rgb(Red,Green,Blue). The color components are integers in the range 0..65535.

  560ansi_get_color(Which0, RGB) :-
  561    \+ current_prolog_flag(console_menu, true),
  562    stream_property(user_input, tty(true)),
  563    stream_property(user_output, tty(true)),
  564    stream_property(user_error, tty(true)),
  565    supports_get_color,
  566    (   color_alias(Which0, Which)
  567    ->  true
  568    ;   must_be(between(0,15),Which0)
  569    ->  Which = Which0
  570    ),
  571    catch(keep_line_pos(user_output,
  572                        ansi_get_color_(Which, RGB)),
  573          error(timeout_error(_,_), _),
  574          no_xterm).
  575
  576supports_get_color :-
  577    getenv('TERM', Term),
  578    sub_atom(Term, 0, _, _, xterm),
  579    \+ getenv('TERM_PROGRAM', 'Apple_Terminal').
  580
  581color_alias(foreground, 10).
  582color_alias(background, 11).
  583
  584ansi_get_color_(Which, rgb(R,G,B)) :-
  585    format(codes(Id), '~w', [Which]),
  586    hex4(RH),
  587    hex4(GH),
  588    hex4(BH),
  589    phrase(("\e]", Id, ";rgb:", RH, "/", GH, "/", BH, "\a"), Pattern),
  590    stream_property(user_input, timeout(Old)),
  591    setup_call_cleanup(
  592        set_stream(user_input, timeout(0.05)),
  593        with_tty_raw(exchange_pattern(Which, Pattern)),
  594        set_stream(user_input, timeout(Old))),
  595    !,
  596    hex_val(RH, R),
  597    hex_val(GH, G),
  598    hex_val(BH, B).
  599
  600no_xterm :-
  601    print_message(warning, ansi(no_xterm_get_colour)),
  602    fail.
  603
  604hex4([_,_,_,_]).
  605
  606hex_val([D1,D2,D3,D4], V) :-
  607    code_type(D1, xdigit(V1)),
  608    code_type(D2, xdigit(V2)),
  609    code_type(D3, xdigit(V3)),
  610    code_type(D4, xdigit(V4)),
  611    V is (V1<<12)+(V2<<8)+(V3<<4)+V4.
  612
  613exchange_pattern(Which, Pattern) :-
  614    format(user_output, '\e]~w;?\a', [Which]),
  615    flush_output(user_output),
  616    read_pattern(user_input, Pattern, []).
  617
  618read_pattern(From, Pattern, NotMatched0) :-
  619    copy_term(Pattern, TryPattern),
  620    append(Skip, Rest, NotMatched0),
  621    append(Rest, RestPattern, TryPattern),
  622    !,
  623    echo(Skip),
  624    try_read_pattern(From, RestPattern, NotMatched, Done),
  625    (   Done == true
  626    ->  Pattern = TryPattern
  627    ;   read_pattern(From, Pattern, NotMatched)
  628    ).

 try_read_pattern(+From, +Pattern, -NotMatched)

  632try_read_pattern(_, [], [], true) :-
  633    !.
  634try_read_pattern(From, [H|T], [C|RT], Done) :-
  635    get_code(C),
  636    (   C = H
  637    ->  try_read_pattern(From, T, RT, Done)
  638    ;   RT = [],
  639        Done = false
  640    ).
  641
  642echo([]).
  643echo([H|T]) :-
  644    put_code(user_output, H),
  645    echo(T).
  646
  647:- multifile prolog:message//1.  648
  649prolog:message(ansi(no_xterm_get_colour)) -->
  650    [ 'Terminal claims to be xterm compatible,'-[], nl,
  651      'but does not report colour info'-[]
  652    ]