Table of Contents

1 library(editline): 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.

While reading a line, the binding surrounds the prompt and the input with the OSC 133 semantic prompt marks of FinalTerm: ESC]133;A before the prompt, ESC]133;B before the input, ESC]133;C after the line was entered and ESC]133;D where its output ends, which is just before the next line is asked for. A term that takes more than one line is read a line at a time; the prompt of each line after the first is marked ESC]133;A;k=s, which says it continues an input rather than starting one, so that a terminal can keep the whole term together. A terminal that understands them (Epilog, iTerm2, kitty, WezTerm, VS Code) can tell prompt, input and output apart, which is what lets it jump between prompts, act on the output of one command or, in Epilog, move the caret to a click in the line being edited. A read that asks for a single character, as get_single_char/1 and the debugger do, is not marked: there is no line being edited there. A terminal that does not know the marks ignores them; one that prints them instead can be spared them with el_set/2 using prompt_marks(false).

[det]el_wrap

[det]el_wrap(+Options)

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.

[det]el_wrap(+ProgName:atom, +In:stream, +Out:stream, +Error:stream)

[det]el_wrap(+ProgName:atom, +In:stream, +Out:stream, +Error:stream, +Options)

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.

ProgName

is the name of the invoking program, used when reading the editrc(5) file to determine which settings to use.

[nondet,multifile]el_setup(+In:stream)

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.

[semidet]el_wrapped(+In:stream)

True if In is a stream wrapped by el_wrap/3.

[det]el_unwrap(+In:stream)

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.

[det]el_source(+In:stream, +File)

Initialise editline by reading the contents of File. If File is unbound try $HOME/.editrc

[det]el_bind(+In:stream, +Args)

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.

[det]el_addfn(+Input:stream, +Command, +Help, :Goal)

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.

[semidet]el_set(+Input:stream, +Action)

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.

prompt_marks(+Boolean)

Enable or disable the OSC 133 prompt marks described with this module. They are enabled by default and are ignored by a terminal that does not know them; disable them for a terminal that prints them instead. Note that Epilog then has neither mark nor bracketed paste to tell it that a line is being edited if bracketed paste is disabled as well, and a click no longer moves the caret.

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

[semidet]el_get(+Input:stream, ?Property)

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.

prompt_marks(-Boolean)

Whether the prompt and the input are marked with OSC 133; see el_set/2.

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

[det]el_line(+Input:stream, -Line)

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.

[det]el_cursor(+Input:stream, +Move:integer)

Move the cursor Move character forwards (positive) or backwards (negative).

[det]el_insertstr(+Input:stream, +Text)

Insert Text at the cursor.

[det]el_deletestr(+Input:stream, +Count)

Delete Count characters before the cursor.

[det]el_history(+In:stream, ?Action)

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.

[det]el_history_events(+In:stream, -Events:list(pair))

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.

[det]el_add_history(+In:stream, +Line:text)

Add a line to the command line history.

[det]el_read_history(+In:stream, +File:file)

Read the history saved using el_write_history/2.

File	is a file specification for absolute_file_name/3.

[det]el_write_history(+In:stream, +File:file)

Save editline history to File. The history may be reloaded using el_read_history/2.

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.

[semidet,multifile]prolog:history(+Input, ?Action)

Provide the plugable interface into the system command line management.

[det,multifile]prolog:line_editor_attributes(+Off, +On)

Tell libedit how to switch the decoration of the line being edited off and on again. The toplevel leaves the attributes of the colour class input in effect while the user is typing (see decorate_prompt/2 in boot/toplevel.pl). Erasing part of the screen paints it with the current background colour, so libedit must switch these attributes off before it erases the rows the line no longer uses, e.g. after unwrapping a long line or moving from a multi-line history entry to a shorter one. See EL_ATTRS in libedit.

The toplevel calls this each time it builds a prompt, so a theme loaded at run time is picked up. Does nothing if libedit is too old to support this.

Index

?

el_add_history/2

el_addfn/4

el_bind/2

el_cursor/2

el_deletestr/2

el_get/2

el_history/2

el_history_events/2

el_insertstr/2

el_line/2

el_read_history/2

el_set/2

el_setup/1

el_source/2

el_unwrap/1

el_version/1

el_wrap/0

el_wrap/1

el_wrap/4

el_wrap/5

el_wrapped/1

el_write_history/2

prolog:history/2

prolog:line_editor_attributes/2