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    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)  2017-2025, 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,
   29    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   30    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   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(editline,
   38          [ el_wrap/0,                          % wrap user_input, etc.
   39            el_wrap/1,                          % +Options
   40            el_wrap/4,                          % +Prog, +Input, +Output, +Error
   41            el_wrap/5,                          % +Prog, +Input, +Output, +Error, +Options
   42            el_wrapped/1,                       % +Input
   43            el_unwrap/1,                        % +Input
   44
   45            el_source/2,                        % +Input, +File
   46            el_bind/2,                          % +Input, +Args
   47            el_set/2,                           % +Input, +Action
   48            el_get/2,                           % +Input, ?Property
   49            el_addfn/4,                         % +Input, +Name, +Help, :Goal
   50            el_cursor/2,                        % +Input, +Move
   51            el_line/2,                          % +Input, -Line
   52            el_insertstr/2,                     % +Input, +Text
   53            el_deletestr/2,                     % +Input, +Count
   54
   55            el_history/2,                       % +Input, ?Action
   56            el_history_events/2,                % +Input, -Events
   57            el_add_history/2,                   % +Input, +Line
   58            el_write_history/2,                 % +Input, +FileName
   59            el_read_history/2,                  % +Input, +FileName
   60
   61	    el_version/1			% -Version:integer
   62          ]).   63:- autoload(library(apply),[maplist/2,maplist/3]).   64:- autoload(library(lists),[reverse/2,max_list/2,append/3,member/2]).   65:- autoload(library(solution_sequences),[call_nth/2]).   66:- autoload(library(option), [merge_options/3]).   67
   68:- use_foreign_library(foreign(libedit4pl)).   69
   70:- initialization el_wrap_if_ok.   71
   72:- meta_predicate
   73    el_addfn(+,+,+,3).   74
   75:- multifile
   76    el_setup/1,                         % +Input
   77    prolog:complete_input/4.

BSD libedit based command line editing

This library wraps the BSD libedit command line editor. The binding provides a high level API to enable command line editing on the Prolog user streams and low level predicates to apply the library on other streams and program the library. */

   88el_wrap_if_ok :-
   89    \+ current_prolog_flag(readline, readline),
   90    stream_property(user_input, tty(true)),
   91    !,
   92    el_wrap.
   93el_wrap_if_ok.
 el_wrap is det
 el_wrap(+Options) is det
Enable using editline on the standard user streams if user_input is connected to a terminal. This is the high level predicate used for most purposes. The remainder of the library interface deals with low level predicates that allows for applying and programming libedit in non-standard situations.

The library is registered with ProgName set to swipl (see el_wrap/4).

Options processed:

pipes(+Boolean)
Used by Epilog windows to indicate we are reading from a Windows named pipe in overlapped mode. Ignored on other platforms.
history(+Size)
Size of the history. Default is defined by the Prolog flag history or 100 if this flag is not defined.
alert_signo(+Integer)
Signal used for making thread_signal/2 work while the thread is in a blocking system call.
  119el_wrap :-
  120    el_wrap([]).
  121
  122el_wrap(_) :-
  123    el_wrapped(user_input),
  124    !.
  125el_wrap(Options) :-
  126    stream_property(user_input, tty(true)), !,
  127    findall(Opt, el_default(Opt), Defaults),
  128    merge_options(Options, Defaults, Options1),
  129    el_wrap(swipl, user_input, user_output, user_error, Options1),
  130    add_prolog_commands(user_input),
  131    ignore(el_set(user_input, wordchars("_"))),
  132    forall(el_setup(user_input), true),
  133    enable_bracketed_paste(user_input),
  134    enable_word_motion(user_input),
  135    enable_windows_eof(user_input).
  136el_wrap(_).
  137
  138el_default(history(Size)) :-
  139    current_prolog_flag(history, Value),
  140    (   integer(Value),
  141        Value >= 0
  142    ->  Size = Value
  143    ;   Value == false
  144    ->  Size = 0
  145    ).
  146:- if(current_predicate(prolog_alert_signal/2)).  147el_default(alert_signo(SigNo)) :-
  148    prolog_alert_signal(SigName, SigName),
  149    current_signal(SigName, SigNo, _Handler).
  150:- endif.  151
  152add_prolog_commands(Input) :-
  153    el_addfn(Input, complete, 'Complete atoms and files', complete),
  154    el_addfn(Input, show_completions, 'List completions', show_completions),
  155    el_addfn(Input, electric, 'Indicate matching bracket', electric),
  156    el_addfn(Input, isearch_history, 'Incremental search in history',
  157             isearch_history),
  158    el_addfn(Input, bracketed_paste, 'Handle bracketed paste', bracketed_paste),
  159    el_bind(Input, ["^I",  complete]),
  160    el_bind(Input, ["^[?", show_completions]),
  161    el_bind(Input, ["^R",  isearch_history]),
  162    bind_electric(Input),
  163    add_paste_quoted(Input),
  164    el_source(Input, _).
 enable_bracketed_paste(+Input) is det
Sync bracketed paste mode with the current editor: bind ESC[200~ to bracketed_paste/3 and enable the mode in emacs, unbind and disable it in vi. In vi mode ESC leaves insert mode, so the ESC[200~ start marker cannot be dispatched as a key binding. Called from el_wrap/1 after the el_setup/1 hook, since that hook may switch editor with el_bind/2 -v or -e.
  175enable_bracketed_paste(Input) :-
  176    (   el_get(Input, editor(vi))
  177    ->  el_bind(Input, ['-r', "\e[200~"]),
  178        el_set(Input, bracketed_paste(false))
  179    ;   el_bind(Input, ["\e[200~", bracketed_paste]),
  180        el_set(Input, bracketed_paste(true))
  181    ).
 enable_word_motion(+Input) is det
Bind the xterm Ctrl+Left/Ctrl+Right escape sequences to word motion. The Epilog terminal sends ESC[1;5D and ESC[1;5C for these key combinations (see packages/xpce/src/txt/terminal.c); most xterm-compatible terminals use the same sequences. In vi mode the binding is installed in both the insert keymap and the command (alternative) keymap. Called after the el_setup/1 hooks since those may switch editor.

This complements the readline emulation, which already binds these sequences in its initialisation.

  196enable_word_motion(Input) :-
  197    el_bind(Input, ["\e[1;5D", 'ed-prev-word']),
  198    el_bind(Input, ["\e[1;5C", 'em-next-word']),
  199    (   el_get(Input, editor(vi))
  200    ->  el_bind(Input, ['-a', "\e[1;5D", 'vi-prev-word']),
  201        el_bind(Input, ['-a', "\e[1;5C", 'vi-next-word'])
  202    ;   true
  203    ).
 enable_windows_eof(+Input) is det
Bind ^Z to send end-of-file on Windows, matching the platform convention (compare with ^D on Unix). Routed through libedit's built-in em-delete-or-list (emacs) or vi-list-or-eof (vi), both of which return EOF on an empty line.
  212enable_windows_eof(Input) :-
  213    current_prolog_flag(windows, true),
  214    !,
  215    (   el_get(Input, editor(vi))
  216    ->  el_bind(Input, ["^Z", 'vi-list-or-eof'])
  217    ;   el_bind(Input, ["^Z", 'em-delete-or-list'])
  218    ).
  219enable_windows_eof(_).
 el_wrap(+ProgName:atom, +In:stream, +Out:stream, +Error:stream) is det
 el_wrap(+ProgName:atom, +In:stream, +Out:stream, +Error:stream, +Options) is det
Enable editline on the stream-triple <In,Out,Error>. From this moment on In is a handle to the command line editor. Options:
pipes(true)
Windows only. Assume the I/O is using pipes rather than a console. This is used for the Epilog terminal.
Arguments:
ProgName- is the name of the invoking program, used when reading the editrc(5) file to determine which settings to use.
  234el_wrap(ProgName, In, Out, Error) :-
  235    el_wrap(ProgName, In, Out, Error, []).
 el_setup(+In:stream) is nondet
This hooks is called as forall(el_setup(Input), true) after the input stream has been wrapped, the default Prolog commands have been added and the default user setup file has been sourced using el_source/2. It can be used to define and bind additional commands.
 el_wrapped(+In:stream) is semidet
True if In is a stream wrapped by el_wrap/3.
 el_unwrap(+In:stream) is det
Remove the libedit wrapper for In and the related output and error streams.
bug
- The wrapper creates FILE* handles that cannot be closed and thus wrapping and unwrapping implies a (modest) memory leak.
 el_source(+In:stream, +File) is det
Initialise editline by reading the contents of File. If File is unbound try $HOME/.editrc
 el_bind(+In:stream, +Args) is det
Invoke the libedit bind command with the given arguments. The example below lists the current key bindings.
?- el_bind(user_input, ['-a']).

The predicate el_bind/2 is typically used to bind commands defined using el_addfn/4. Note that the C proxy function has only the last character of the command as context to find the Prolog binding. This implies we cannot both bind e.g., "^[?" and "?" to a Prolog function.

See also
- editrc(5) for more information.
 el_addfn(+Input:stream, +Command, +Help, :Goal) is det
Add a new command to the command line editor associated with Input. Command is the name of the command, Help is the help string printed with e.g. bind -a (see el_bind/2) and Goal is called of the associated key-binding is activated. Goal is called as
call(:Goal, +Input, +Char, -Continue)

where Input is the input stream providing access to the editor, Char the activating character and Continue must be instantated with one of the known continuation codes as defined by libedit: norm, newline, eof, arghack, refresh, refresh_beep, cursor, redisplay, error or fatal. In addition, the following Continue code is provided.

electric(Move, TimeOut, Continue)
Show electric caret at Move positions to the left of the normal cursor positions for the given TimeOut. Continue as defined by the Continue value.

The registered Goal typically used el_line/2 to fetch the input line and el_cursor/2, el_insertstr/2 and/or el_deletestr/2 to manipulate the input line.

Normally el_bind/2 is used to associate the defined command with a keyboard sequence.

See also
- el_set(3) EL_ADDFN for details.
 el_set(+Input:stream, +Action) is semidet
Interface to el_set() and el_wset(). Currently provided values for Action are:
wordchars(+Text)
Set the characters considered part of a word. This feature depends on el_wsey() EL_WORDCHARS, which is only provided in some recent versions of libedit.
bracketed_paste(+Boolean)
Enable or disable bracketed paste mode. When enabled, the terminal is asked to bracket pasted text with ESC[200~ / ESC[201~ before each prompt, which the default bindings route through bracketed_paste/3. Disabling sends the matching ESC[?2004l sequence immediately. enable_bracketed_paste/1 manages this based on the current editor; you normally do not need to set it directly.

This predicate fails silently of Action is not implemented. Illegal input raises in an exception.

 el_get(+Input:stream, ?Property) is semidet
Interface to el_get(). Currently supported Property terms:
editor(-Editor)
Editor is unified with emacs or vi, reflecting the current keymap selected via el_bind/2 with -e / -v.
bracketed_paste(-Boolean)
Whether bracketed paste mode is currently enabled; see el_set/2.

Any other Property raises a domain_error(editline_property, _).

 el_line(+Input:stream, -Line) is det
Fetch the currently buffered input line. Line is a term line(Before, After), where Before is a string holding the text before the cursor and After is a string holding the text after the cursor.
 el_cursor(+Input:stream, +Move:integer) is det
Move the cursor Move character forwards (positive) or backwards (negative).
 el_insertstr(+Input:stream, +Text) is det
Insert Text at the cursor.
 el_deletestr(+Input:stream, +Count) is det
Delete Count characters before the cursor.
 el_history(+In:stream, ?Action) is det
Perform a generic action on the history. This provides an incomplete interface to history() from libedit. Supported actions are:
clear
Clear the history.
setsize(+Integer)
Set size of history to size elements.
getsize(-Integer)
Unify Integer with the maximum size of the history. Note that this is not the same as el_history() using H_GETSIZE, which returns the number of currently saved events. The number of saved events may be computed from first and last or using el_history_events/2.
setunique(+Boolean)
Set flag that adjacent identical event strings should not be entered into the history.
first(-Num, -String)
last(-Num, -String)
curr(-Num, -String)
prev(-Num, -String)
next(-Num, -String)
Retrieve an event. Num is the event number and String is the event string. Note that first is the most recent event and last the oldest.
set(Num)
Set the notion of current to Num.
prev_str(+Search, -Num, -String)
next_str(+Search, -Num, -String)
Retrieve the previous or next event whose String starts with Search.
event(+Num, -String)
True when String represents event Num. This is an extension to the history() API, retrieving a numbered event without changing the current notion.
 el_history_events(+In:stream, -Events:list(pair)) is det
Unify Events with a list of pairs of the form Num-String, where Num is the event number and String is the associated string without terminating newline.
 el_add_history(+In:stream, +Line:text) is det
Add a line to the command line history.
 el_read_history(+In:stream, +File:file) is det
Read the history saved using el_write_history/2.
Arguments:
File- is a file specification for absolute_file_name/3.
 el_write_history(+In:stream, +File:file) is det
Save editline history to File. The history may be reloaded using el_read_history/2.
Arguments:
File- is a file specification for absolute_file_name/3.
 el_version(-Version)
True when Version is LIBEDIT_MAJOR*10000 + LIBEDIT_MINOR*100. The version is generated from the include file histedit.h, which implies that the actual version of the shared library may be different.
 prolog:history(+Input, ?Action) is semidet
Provide the plugable interface into the system command line management.
  434:- multifile
  435    prolog:history/2.  436
  437prolog:history(Input, enabled) :-
  438    !,
  439    el_wrapped(Input),
  440    el_history(Input, getsize(Size)),
  441    Size > 0.
  442prolog:history(Input, add(Line)) :-
  443    !,
  444    el_add_history(Input, Line).
  445prolog:history(Input, load(File)) :-
  446    !,
  447    compat_read_history(Input, File).
  448prolog:history(Input, save(File)) :-
  449    !,
  450    el_write_history(Input, File).
  451prolog:history(Input, events(Events)) :-
  452    !,
  453    el_history_events(Input, Events).
  454prolog:history(Input, Command) :-
  455    public_command(Command),
  456    !,
  457    el_history(Input, Command).
  458
  459public_command(first(_Num, _String)).
  460public_command(curr(_Num, _String)).
  461public_command(event(_Num, _String)).
  462public_command(prev_str(_Search, _Num, _String)).
  463public_command(clear).
 compat_read_history(+Input, +File) is det
Read the saved history. This loads both the LibEdit and old history format used by swipl-win.exe before migrating to SDL.
  470compat_read_history(Input, File) :-
  471    catch(el_read_history(Input, File), error(editline(_),_), fail),
  472    !.
  473compat_read_history(Input, File) :-
  474    access_file(File, read),
  475    setup_call_cleanup(
  476        open(File, read, In, [encoding(utf8)]),
  477        read_old_history(Input, In),
  478        close(In)),
  479    !.
  480compat_read_history(_, _).
  481
  482read_old_history(Input, From) :-
  483    catch('$raw_read'(From, Line), error(_,_), fail),
  484    (   Line == end_of_file
  485    ->  true
  486    ;   string_concat(Line, '.', Event),
  487        el_add_history(Input, Event),
  488        read_old_history(Input, From)
  489    ).
  490
  491		 /*******************************
  492		 *        ELECTRIC CARET	*
  493		 *******************************/
 bind_electric(+Input) is det
Bind known close statements for electric input
  499bind_electric(Input) :-
  500    forall(bracket(_Open, Close), bind_code(Input, Close, electric)),
  501    forall(quote(Close), bind_code(Input, Close, electric)).
  502
  503bind_code(Input, Code, Command) :-
  504    string_codes(Key, [Code]),
  505    el_bind(Input, [Key, Command]).
 electric(+Input, +Char, -Continue) is det
  510electric(Input, Char, Continue) :-
  511    string_codes(Str, [Char]),
  512    el_insertstr(Input, Str),
  513    el_line(Input, line(Before, _)),
  514    (   string_codes(Before, Codes),
  515        nesting(Codes, 0, Nesting),
  516        reverse(Nesting, [Close|RevNesting])
  517    ->  (   Close = open(_,_)                   % open quote
  518        ->  Continue = refresh
  519        ;   matching_open(RevNesting, Close, _, Index)
  520        ->  string_length(Before, Len),         % Proper match
  521            Move is Index-Len,
  522            Continue = electric(Move, 500, refresh)
  523        ;   Continue = refresh_beep             % Not properly nested
  524        )
  525    ;   Continue = refresh_beep
  526    ).
  527
  528matching_open_index(String, Index) :-
  529    string_codes(String, Codes),
  530    nesting(Codes, 0, Nesting),
  531    reverse(Nesting, [Close|RevNesting]),
  532    matching_open(RevNesting, Close, _, Index).
  533
  534matching_open([Open|Rest], Close, Rest, Index) :-
  535    Open = open(Index,_),
  536    match(Open, Close),
  537    !.
  538matching_open([Close1|Rest1], Close, Rest, Index) :-
  539    Close1 = close(_,_),
  540    matching_open(Rest1, Close1, Rest2, _),
  541    matching_open(Rest2, Close, Rest, Index).
  542
  543match(open(_,Open),close(_,Close)) :-
  544    (   bracket(Open, Close)
  545    ->  true
  546    ;   Open == Close,
  547        quote(Open)
  548    ).
  549
  550bracket(0'(, 0')).
  551bracket(0'[, 0']).
  552bracket(0'{, 0'}).
  553
  554quote(0'\').
  555quote(0'\").
  556quote(0'\`).
  557
  558nesting([], _, []).
  559nesting([H|T], I, Nesting) :-
  560    (   bracket(H, _Close)
  561    ->  Nesting = [open(I,H)|Nest]
  562    ;   bracket(_Open, H)
  563    ->  Nesting = [close(I,H)|Nest]
  564    ),
  565    !,
  566    I2 is I+1,
  567    nesting(T, I2, Nest).
  568nesting([0'0, 0'\'|T], I, Nesting) :-
  569    !,
  570    phrase(skip_code, T, T1),
  571    difflist_length(T, T1, Len),
  572    I2 is I+Len+2,
  573    nesting(T1, I2, Nesting).
  574nesting([H|T], I, Nesting) :-
  575    quote(H),
  576    !,
  577    (   phrase(skip_quoted(H), T, T1)
  578    ->  difflist_length(T, T1, Len),
  579        I2 is I+Len+1,
  580        Nesting = [open(I,H),close(I2,H)|Nest],
  581        nesting(T1, I2, Nest)
  582    ;   Nesting = [open(I,H)]                   % Open quote
  583    ).
  584nesting([_|T], I, Nesting) :-
  585    I2 is I+1,
  586    nesting(T, I2, Nesting).
  587
  588difflist_length(List, Tail, Len) :-
  589    difflist_length(List, Tail, 0, Len).
  590
  591difflist_length(List, Tail, Len0, Len) :-
  592    List == Tail,
  593    !,
  594    Len = Len0.
  595difflist_length([_|List], Tail, Len0, Len) :-
  596    Len1 is Len0+1,
  597    difflist_length(List, Tail, Len1, Len).
  598
  599skip_quoted(H) -->
  600    [H],
  601    !.
  602skip_quoted(H) -->
  603    "\\", [H],
  604    !,
  605    skip_quoted(H).
  606skip_quoted(H) -->
  607    [_],
  608    skip_quoted(H).
  609
  610skip_code -->
  611    "\\", [_],
  612    !.
  613skip_code -->
  614    [_].
  615
  616
  617		 /*******************************
  618		 *           COMPLETION		*
  619		 *******************************/
 complete(+Input, +Char, -Continue) is det
Implementation of the registered complete editline function. The predicate is called with three arguments, the first being the input stream used to access the libedit functions and the second the activating character. The last argument tells libedit what to do. Consult el_set(3), EL_ADDFN for details.
  630:- dynamic
  631    last_complete/2.  632
  633complete(Input, _Char, Continue) :-
  634    el_line(Input, line(Before, After)),
  635    ensure_input_completion,
  636    prolog:complete_input(Before, After, Delete, Completions),
  637    (   Completions = [One]
  638    ->  string_length(Delete, Len),
  639        el_deletestr(Input, Len),
  640        complete_text(One, Text),
  641        el_insertstr(Input, Text),
  642        Continue = refresh
  643    ;   Completions == []
  644    ->  Continue = refresh_beep
  645    ;   get_time(Now),
  646        retract(last_complete(TLast, Before)),
  647        Now - TLast < 2
  648    ->  nl(user_error),
  649        list_alternatives(Completions),
  650        Continue = redisplay
  651    ;   retractall(last_complete(_,_)),
  652        get_time(Now),
  653        asserta(last_complete(Now, Before)),
  654        common_competion(Completions, Extend),
  655        (   Delete == Extend
  656        ->  Continue = refresh_beep
  657        ;   string_length(Delete, Len),
  658            el_deletestr(Input, Len),
  659            el_insertstr(Input, Extend),
  660            Continue = refresh
  661        )
  662    ).
  663
  664:- dynamic
  665    input_completion_loaded/0.  666
  667ensure_input_completion :-
  668    input_completion_loaded,
  669    !.
  670ensure_input_completion :-
  671    predicate_property(prolog:complete_input(_,_,_,_),
  672                       number_of_clauses(N)),
  673    N > 0,
  674    !.
  675ensure_input_completion :-
  676    exists_source(library(console_input)),
  677    !,
  678    use_module(library(console_input), []),
  679    asserta(input_completion_loaded).
  680ensure_input_completion.
 show_completions(+Input, +Char, -Continue) is det
Editline command to show possible completions.
  687show_completions(Input, _Char, Continue) :-
  688    el_line(Input, line(Before, After)),
  689    prolog:complete_input(Before, After, _Delete, Completions),
  690    nl(user_error),
  691    list_alternatives(Completions),
  692    Continue = redisplay.
  693
  694complete_text(Text-_Comment, Text) :- !.
  695complete_text(Text, Text).
 common_competion(+Alternatives, -Common) is det
True when Common is the common prefix of all candidate Alternatives.
  701common_competion(Alternatives, Common) :-
  702    maplist(atomic, Alternatives),
  703    !,
  704    common_prefix(Alternatives, Common).
  705common_competion(Alternatives, Common) :-
  706    maplist(complete_text, Alternatives, AltText),
  707    !,
  708    common_prefix(AltText, Common).
 common_prefix(+Atoms, -Common) is det
True when Common is the common prefix of all Atoms.
  714common_prefix([A1|T], Common) :-
  715    common_prefix_(T, A1, Common).
  716
  717common_prefix_([], Common, Common).
  718common_prefix_([H|T], Common0, Common) :-
  719    common_prefix(H, Common0, Common1),
  720    common_prefix_(T, Common1, Common).
 common_prefix(+A1, +A2, -Prefix:string) is det
True when Prefix is the common prefix of the atoms A1 and A2
  726common_prefix(A1, A2, Prefix) :-
  727    sub_atom(A1, 0, _, _, A2),
  728    !,
  729    Prefix = A2.
  730common_prefix(A1, A2, Prefix) :-
  731    sub_atom(A2, 0, _, _, A1),
  732    !,
  733    Prefix = A1.
  734common_prefix(A1, A2, Prefix) :-
  735    atom_codes(A1, C1),
  736    atom_codes(A2, C2),
  737    list_common_prefix(C1, C2, C),
  738    string_codes(Prefix, C).
  739
  740list_common_prefix([H|T0], [H|T1], [H|T]) :-
  741    !,
  742    list_common_prefix(T0, T1, T).
  743list_common_prefix(_, _, []).
 list_alternatives(+Alternatives)
List possible completions at the current point.
To be done
- currently ignores the Comment in Text-Comment alternatives.
  753list_alternatives(Alternatives) :-
  754    maplist(atomic, Alternatives),
  755    !,
  756    length(Alternatives, Count),
  757    maplist(atom_length, Alternatives, Lengths),
  758    max_list(Lengths, Max),
  759    tty_size(_, Cols),
  760    ColW is Max+2,
  761    Columns is max(1, Cols // ColW),
  762    RowCount is (Count+Columns-1)//Columns,
  763    length(Rows, RowCount),
  764    to_matrix(Alternatives, Rows, Rows),
  765    (   RowCount > 11
  766    ->  length(First, 10),
  767        Skipped is RowCount - 10,
  768        append(First, _, Rows),
  769        maplist(write_row(ColW), First),
  770        format(user_error, '... skipped ~D rows~n', [Skipped])
  771    ;   maplist(write_row(ColW), Rows)
  772    ).
  773list_alternatives(Alternatives) :-
  774    maplist(complete_text, Alternatives, AltText),
  775    list_alternatives(AltText).
  776
  777to_matrix([], _, Rows) :-
  778    !,
  779    maplist(close_list, Rows).
  780to_matrix([H|T], [RH|RT], Rows) :-
  781    !,
  782    add_list(RH, H),
  783    to_matrix(T, RT, Rows).
  784to_matrix(List, [], Rows) :-
  785    to_matrix(List, Rows, Rows).
  786
  787add_list(Var, Elem) :-
  788    var(Var), !,
  789    Var = [Elem|_].
  790add_list([_|T], Elem) :-
  791    add_list(T, Elem).
  792
  793close_list(List) :-
  794    append(List, [], _),
  795    !.
  796
  797write_row(ColW, Row) :-
  798    length(Row, Columns),
  799    make_format(Columns, ColW, Format),
  800    format(user_error, Format, Row).
  801
  802make_format(N, ColW, Format) :-
  803    format(string(PerCol), '~~w~~t~~~d+', [ColW]),
  804    Front is N - 1,
  805    length(LF, Front),
  806    maplist(=(PerCol), LF),
  807    append(LF, ['~w~n'], Parts),
  808    atomics_to_string(Parts, Format).
  809
  810
  811		 /*******************************
  812		 *             SEARCH		*
  813		 *******************************/
 isearch_history(+Input, +Char, -Continue) is det
Incremental search through the history. The behavior is based on GNU readline.
  820isearch_history(Input, _Char, Continue) :-
  821    el_line(Input, line(Before, After)),
  822    string_concat(Before, After, Current),
  823    string_length(Current, Len),
  824    search_print('', "", Current),
  825    search(Input, "", Current, 1, Line),
  826    el_deletestr(Input, Len),
  827    el_insertstr(Input, Line),
  828    Continue = redisplay.
  829
  830search(Input, For, Current, Nth, Line) :-
  831    el_getc(Input, Next),
  832    Next \== -1,
  833    !,
  834    search(Next, Input, For, Current, Nth, Line).
  835search(_Input, _For, _Current, _Nth, "").
  836
  837search(7, _Input, _, Current, _, Current) :-    % C-g: abort
  838    !,
  839    clear_line.
  840search(18, Input, For, Current, Nth, Line) :-   % C-r: search previous
  841    !,
  842    N2 is Nth+1,
  843    search_(Input, For, Current, N2, Line).
  844search(19, Input, For, Current, Nth, Line) :-   % C-s: search next
  845    !,
  846    N2 is max(1,Nth-1),
  847    search_(Input, For, Current, N2, Line).
  848search(127, Input, For, Current, _Nth, Line) :- % DEL/BS: shorten search
  849    sub_string(For, 0, _, 1, For1),
  850    !,
  851    search_(Input, For1, Current, 1, Line).
  852search(Char, Input, For, Current, Nth, Line) :-
  853    code_type(Char, cntrl),
  854    !,
  855    search_end(Input, For, Current, Nth, Line),
  856    el_push(Input, Char).
  857search(Char, Input, For, Current, _Nth, Line) :-
  858    format(string(For1), '~w~c', [For,Char]),
  859    search_(Input, For1, Current, 1, Line).
  860
  861search_(Input, For1, Current, Nth, Line) :-
  862    (   find_in_history(Input, For1, Current, Nth, Candidate)
  863    ->  search_print('', For1, Candidate)
  864    ;   search_print('failed ', For1, Current)
  865    ),
  866    search(Input, For1, Current, Nth, Line).
  867
  868search_end(Input, For, Current, Nth, Line) :-
  869    (   find_in_history(Input, For, Current, Nth, Line)
  870    ->  true
  871    ;   Line = Current
  872    ),
  873    clear_line.
  874
  875find_in_history(_, "", Current, _, Current) :-
  876    !.
  877find_in_history(Input, For, _, Nth, Line) :-
  878    el_history_events(Input, History),
  879    call_nth(( member(_N-Line, History),
  880               sub_string(Line, _, _, _, For)
  881             ),
  882             Nth),
  883    !.
  884
  885search_print(State, Search, Current) :-
  886    format(user_error, '\r(~wreverse-i-search)`~w\': ~w\e[0K',
  887           [State, Search, Current]).
  888
  889clear_line :-
  890    format(user_error, '\r\e[0K', []).
  891
  892
  893                /*******************************
  894                *         PASTE QUOTED         *
  895                *******************************/
  896
  897:- meta_predicate
  898    with_quote_flags(+,+,0).  899
  900add_paste_quoted(Input) :-
  901    current_prolog_flag(gui, true),
  902    !,
  903    el_addfn(Input, paste_quoted, 'Paste as quoted atom', paste_quoted),
  904    el_bind(Input, ["^Y",  paste_quoted]).
  905add_paste_quoted(_).
 paste_quoted(+Input, +Char, -Continue) is det
Paste the selection as quoted Prolog value. The quoting type depends on the quote before the caret. If there is no quote before the caret we paste as an atom.
  913paste_quoted(Input, _Char, Continue) :-
  914    clipboard_content(String),
  915    quote_text(Input, String, Quoted),
  916    el_insertstr(Input, Quoted),
  917    Continue = refresh.
  918
  919quote_text(Input, String, Value) :-
  920    el_line(Input, line(Before, _After)),
  921    (   sub_string(Before, _, 1, 0, Quote)
  922    ->  true
  923    ;   Quote = "'"
  924    ),
  925    quote_text(Input, Quote, String, Value).
  926
  927quote_text(Input, "'", Text, Quoted) =>
  928    format(string(Quoted), '~q', [Text]),
  929    el_deletestr(Input, 1).
  930quote_text(Input, "\"", Text, Quoted) =>
  931    atom_string(Text, String),
  932    with_quote_flags(
  933        string, codes,
  934        format(string(Quoted), '~q', [String])),
  935    el_deletestr(Input, 1).
  936quote_text(Input, "`", Text, Quoted) =>
  937    atom_string(Text, String),
  938    with_quote_flags(
  939        codes, string,
  940        format(string(Quoted), '~q', [String])),
  941    el_deletestr(Input, 1).
  942quote_text(_, _, Text, Quoted) =>
  943    format(string(Quoted), '~q', [Text]).
  944
  945with_quote_flags(Double, Back, Goal) :-
  946    current_prolog_flag(double_quotes, ODouble),
  947    current_prolog_flag(back_quotes, OBack),
  948    setup_call_cleanup(
  949        ( set_prolog_flag(double_quotes, Double),
  950          set_prolog_flag(back_quotes, Back) ),
  951        Goal,
  952        ( set_prolog_flag(double_quotes, ODouble),
  953          set_prolog_flag(back_quotes, OBack) )).
  954
  955clipboard_content(Text) :-
  956    current_prolog_flag(gui, true),
  957    !,
  958    autoload_call(in_pce_thread_sync(
  959                      autoload_call(
  960                          get(@(display), paste, primary, string(Text))))).
  961clipboard_content("").
  962
  963
  964                /*******************************
  965                *       BRACKETED PASTE        *
  966                *******************************/
 bracketed_paste(+Input, +Char, -Continue) is det
Handler for the bracketed paste start sequence ESC[200~. Reads characters until the end sequence ESC[201~ is received and inserts the collected text literally, bypassing per-character key dispatch.

The terminal is asked to enable bracketed paste mode (ESC[?2004h) from the C layer each time a prompt is issued.

  977bracketed_paste(Input, _Char, Continue) :-
  978    collect_paste(Input, [], RevCodes),
  979    reverse(RevCodes, Codes),
  980    string_codes(Text, Codes),
  981    el_insertstr(Input, Text),
  982    Continue = refresh.
 collect_paste(+Input, +RevAcc, -RevResult) is det
Read characters one at a time, accumulating them in reverse order. Stop when the reversed accumulator starts with the end sequence ESC[201~ (27,91,50,48,49,126) and return the reversed content that precedes it.
  991collect_paste(Input, RevCodes, Result) :-
  992    el_getc(Input, Char),
  993    (   Char == -1                          % EOF / error
  994    ->  Result = RevCodes
  995    ;   paste_char(Char, Char1),
  996        RevCodes1 = [Char1|RevCodes],
  997        (   RevCodes1 = [0'~,0'1,0'0,0'2,0'[,0'\e|Rest]  % ESC[201~ reversed
  998        ->  Result = Rest
  999        ;   collect_paste(Input, RevCodes1, Result)
 1000        )
 1001    ).
 paste_char(+Raw, -Char) is det
Translate a raw character code from bracketed paste to the intended code. The tty line discipline in edit mode has INLCR set, which maps LF (10) to CR (13) before libedit reads it. We reverse that here so pasted newlines are inserted as actual newlines.
 1010paste_char(0'\r, 0'\n) :- !.               % CR → LF (INLCR maps \n to \r in edit mode)
 1011paste_char(C,   C).
 1012
 1013
 1014                /*******************************
 1015                *           MESSAGE            *
 1016                *******************************/
 1017
 1018:- multifile prolog:error_message//1. 1019
 1020prolog:error_message(editline(Msg)) -->
 1021    [ 'editline: ~s'-[Msg] ]