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.

See also

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

 ansi_format(+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.

 sgr_code(+Name, -Code)[private]

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

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

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.

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

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

 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

 location_url(+Location, -URL) is det[private]

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.

 tty_url_hook(+Location, -URL)[multifile]

Hook for location_url/2.

 url_file_name(-URL, +File) is semidet[private]

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.

 keep_line_pos(+Stream, :Goal)[private]

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.

 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.

 try_read_pattern(+From, +Pattern, -NotMatched)[private]

Re-exported predicates

The following predicates are exported from this file while their implementation is defined in imported modules or non-module files loaded by this module.

 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