SWI-Prolog -- Manual

This library allows for exploiting the color and attribute facilities of most modern terminals using ANSI escape sequences. This library provides the following:

ansi_format/3 allows writing messages to the terminal with ansi attributes.
It defines the hook prolog:message_line_element/2, which provides ansi attributes and hyperlinks for print_message/2.

The behavior of this library is controlled by two Prolog flags:

[|](99, [111,108,111,114,95,116,101,114,109]): When true, activate the color output for this library. Otherwise simply call format/3.
[|](104, [121,112,101,114,108,105,110,107,95,116,101,114,109]): Emit terminal hyperlinks for url(Location) and url(URL, Label) elements of Prolog messages.

[det]ansi_format(+ClassOrAttributes, +Format, +Args)

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.

[semidet,multifile]prolog:console_color(+Term, -AnsiAttributes)

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.

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

[semidet,multifile]prolog:message_line_element(+Stream, +Term)

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

[det]ansi_hyperlink(+Stream, +Location)

[det]ansi_hyperlink(+Stream, +URL, +Label)

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

[semidet,multifile]hyperlink(+Stream, +Spec)

Multifile hook that may be used to redefine ansi_hyperlink/2,3. If this predicate succeeds the system assumes the link has been written to Stream.

Spec is either url(Location) or url(URL, Label). See ansi_hyperlink/2,3 for details.

[semidet]ansi_get_color(+Which, -RGB)

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.

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

A.2 library(ansi_term): Print decorated text to ANSI consoles