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Article contents:[[toc:]] == chibi-term Chibi Scheme's term library === Module: (chibi term ansi) A library to use ANSI escape codes to format text and background color, font weight, and underlining. ==== Foreground colors ===== Standard 8-color foreground escape strings <procedure>(black-escape)</procedure> <procedure>(red-escape)</procedure> <procedure>(green-escape)</procedure> <procedure>(yellow-escape)</procedure> <procedure>(blue-escape)</procedure> <procedure>(magenta-escape)</procedure> <procedure>(cyan-escape)</procedure> <procedure>(white-escape)</procedure> Return a string consisting of an ANSI escape code to select the specified text color. ===== {{rgb-escape}} <procedure>(rgb-escape red-level green-level blue-level)</procedure> Return a string consisting of an ANSI escape code to select the text color specified by the {{red-level}}, {{green-level}}, and {{blue-level}} arguments, each of which must be an exact integer in the range [0, 5]. The caller is resonsible for verifying that the terminal supports 256 colors. ===== {{gray-escape}} <procedure>(gray-escape gray-level)</procedure> Return a string consisting of an ANSI escape code to select the text color specified by the {{gray-level}} argument, which must be an exact integer in the range [0, 23]. The caller is resonsible for verifying that the terminal supports 256 colors. ===== {{rgb24-escape}} <procedure>(rgb24-escape red-level green-level blue-level)</procedure> The true-color equivalent of {{rgb-escape}}. Return a string consisting of an ANSI escape code to select the text color specified by the {{red-level}},{{green-level}}, and {{blue-level}} arguments, each of which must be an exact integer in the range [0, 255]. ===== {{reset-color-escape}} <constant>(reset-color-escape)</constant> Return a string consisting of an ANSI escape code to select the default text color. ===== Standard 8-color foreground format procedures <procedure>(black str)</procedure> <procedure>(red str)</procedure> <procedure>(green str)</procedure> <procedure>(yellow str)</procedure> <procedure>(blue str)</procedure> <procedure>(magenta str)</procedure> <procedure>(cyan str)</procedure> <procedure>(white str)</procedure> If ANSI escapes are enabled, return a string consisting of the string {{str}} with a prefix that selects specified text color and a suffix that selects the default text color. If ANSI escapes are not enabled, return {{str}}. ===== {{rgb}} <procedure>(rgb red-level green-level blue-level)</procedure> Returns a procedure which takes a single argument, a string, and which when called behaves as follows. If ANSI escapes are enabled, the procedure returns a string consisting of its argument with a prefix that selects specified text color (obtained by calling the {{rgb-escape}} procedure with the values of the {{red-level}}, {{green-level}}, and {{blue-level}} arguments) and a suffix that selects the default text color. If ANSI escapes are not enabled, the procedure returns its argument. The caller is resonsible for verifying that the terminal supports 256 colors. ===== {{gray}} <procedure>(gray gray-level)</procedure> Returns a procedure which takes a single argument, a string, and which when called behaves as follows. If ANSI escapes are enabled, the procedure returns a string consisting of its argument with a prefix that selects specified text color (obtained by calling the {{gray-escape}} procedure with the values of the {{gray-level}} argument) and a suffix that selects the default text color. If ANSI escapes are not enabled, the procedure returns its argument. The caller is resonsible for verifying that the terminal supports 256 colors. ===== {{rgb24}} <procedure>(rgb24 red-level green-level blue-level)</procedure> The true-color equivalent of {{rbg}}, extending the ranges to [0, 255]. ==== Background colors ===== Standard 8-color background escape strings <procedure>(black-background-escape)</procedure> <procedure>(red-background-escape)</procedure> <procedure>(green-background-escape)</procedure> <procedure>(yellow-background-escape)</procedure> <procedure>(blue-background-escape)</procedure> <procedure>(magenta-background-escape)</procedure> <procedure>(cyan-background-escape)</procedure> <procedure>(white-background-escape)</procedure> Return a string consisting of an ANSI escape code to select the specified background color. ===== {{rgb-background-escape}} <procedure>(rgb-background-escape red-level green-level blue-level)</procedure> Return a string consisting of an ANSI escape code to select the background color specified by the {{red-level}}, {{green-level}}, and {{blue-level}} arguments, each of which must be an exact integer in the range [0, 5]. The caller is resonsible for verifying that the terminal supports 256 colors. ===== {{gray-background-escape}} <procedure>(gray-background-escape gray-level)</procedure> Return a string consisting of an ANSI escape code to select the background color specified by the {{gray-level}} argument, which must be an exact integer in the range [0, 23]. The caller is resonsible for verifying that the terminal supports 256 colors. ===== {{rgb24-background-escape}} <procedure>(rgb24-background-escape red-level green-level blue-level)</procedure> The true-color equivalent of {{rgb-background-escape}}. Return a string consisting of an ANSI escape code to select the text color specified by the {{red-level}}, {{green-level}},and {{blue-level}} arguments, each of which must be an exact integer in the range [0, 255]. ===== {{reset-background-color-escape}} <constant>(reset-background-color-escape)</constant> Return a string consisting of an ANSI escape code to select the default background color. ===== Standard 8-color background format procedures <procedure>(black-background)</procedure> <procedure>(red-background)</procedure> <procedure>(green-background)</procedure> <procedure>(yellow-background)</procedure> <procedure>(blue-background)</procedure> <procedure>(magenta-background)</procedure> <procedure>(cyan-background)</procedure> <procedure>(white-background)</procedure> If ANSI escapes are enabled, return a string consisting of the string {{str}} with a prefix that selects specified background color and a suffix that selects the default background color. If ANSI escapes are not enabled, return {{str}}. ===== {{rgb-background}} <procedure>(rgb-background red-level green-level blue-level)</procedure> Returns a procedure which takes a single argument, a string, and which when called behaves as follows. If ANSI escapes are enabled, the procedure returns a string consisting of its argument with a prefix that selects specified background color (obtained by calling the {{rgb-background-escape}} procedure with the values of the {{red-level}}, {{green-level}},and {{blue-level}} arguments) and a suffix that selects the default background color. If ANSI escapes are not enabled, the procedure returns its argument. The caller is resonsible for verifying that the terminal supports 256 colors. ===== {{gray-background}} <procedure>(gray-background gray-level)</procedure> Returns a procedure which takes a single argument, a string, and which when called behaves as follows. If ANSI escapes are enabled, the procedure returns a string consisting of its argument with a prefix that selects specified background color (obtained by calling the {{gray-background-escape}} procedure with the values of the {{gray-level}} argument) and a suffix that selects the default background color. If ANSI escapes are not enabled, the procedure returns its argument. The caller is resonsible for verifying that the terminal supports 256 colors. ===== {{rgb24-background}} <procedure>(rgb24-background red-level green-level blue-level)</procedure> The true-color equivalent of {{rbg-background}}, extending the ranges to [0, 255]. ==== Other properties ===== {{bold-escape}} <procedure>(bold-escape)</procedure> Return a string consisting of an ANSI escape code to select bold style. ===== {{reset-bold-escape}} <procedure>(reset-bold-escape)</procedure> Return a string consisting of an ANSI escape code to select non-bold style. ===== {{bold}} <procedure>(bold str)</procedure> If ANSI escapes are enabled, return a string consisting of the string {{str}} with a prefix that selects bold style and a suffix that selects non-bold style. If ANSI escapes are not enabled, return {{str}}. ===== {{underline-escape}} <procedure>(underline-escape)</procedure> Return a string consisting of an ANSI escape code to select underlined style. ===== {{reset-underline-escape}} <procedure>(reset-underline-escape)</procedure> Return a string consisting of an ANSI escape code to select non-underlined style. ===== {{underline}} <procedure>(underline str)</procedure> If ANSI escapes are enabled, return a string consisting of the string {{str}} with a prefix that selects underlined style and a suffix that selects non-underlined style. If ANSI escapes are not enabled, return {{str}}. ===== {{italic-escape}} <procedure>(italic-escape)</procedure> Return a string consisting of an ANSI escape code to select italic style. ===== {{reset-italic-escape}} <procedure>(reset-italic-escape)</procedure> Return a string consisting of an ANSI escape code to select non-italic style. ===== {{italic}} <constant>(italic str)</constant> Returns {{str}} optionally wrapped in italic escapes. ===== {{strikethrough-escape}} <procedure>(strikethrough-escape)</procedure> Return a string consisting of an ANSI escape code to select strikethrough style. ===== {{reset-strike-through-escape}} <procedure>(reset-strike-through-escape)</procedure> Return a string consisting of an ANSI escape code to select non-strikethrough style. ===== {{strikethrough}} <procedure>(strikethrough str)</procedure> Returns {{str}} optionally wrapped in strikethrough escapes. ===== {{negative-escape}} <procedure>(negative-escape)</procedure> Return a string consisting of an ANSI escape code to select negative style (text in the background color and background in the text color). ===== {{reset-negative-escape}} <procedure>(reset-negative-escape)</procedure> Return a string consisting of an ANSI escape code to select positive style (text in the text color and background in the background color). ===== {{negative}} <procedure>(negative str)</procedure> If ANSI escapes are enabled, return a string consisting of the string {{str}} with a prefix that selects negative style (text in the background color and background in the text color) and a suffix that selects positive style (text in the text color and background in the background color). If ANSI escapes are not enabled, return {{str}}. ==== Enabling or disabling ANSI escapes ===== {{ansi-escapes-enabled?}} <parameter>(ansi-escapes-enabled? #!optional value)</parameter> A parameter object that determines whether ANSI escapes are enabled in some of the preceding procedures. They are disabled if {{(ansi-escapes-enabled?)}} returns {{#f}}, and otherwise they are enabled. The initial value returned by {{(ansi-escapes-enabled?)}} is determined by the environment. If the environment variable {{NO_COLOR}} is set, the initial value is {{#f}} If the environment variable {{ANSI_ESCAPES_ENABLED}} is set, its value determines the initial value returned by {{(ansi-escapes-enabled?)}}. If the value of {{ANSI_ESCAPES_ENABLED}} is {{"0"}}, the initial value is {{#f}},otherwise the initial value is {{#t}}. If the environment variable {{ANSI_ESCAPES_ENABLED}} is not set and the environment variable {{TERM}} is set to {{dumb}}, the initial value is {{#f}}. If neither of the environment variables {{NO_COLOR}}, {{ANSI_ESCAPES_ENABLED}} are set and {{TERM}} is not {{dumb}}, the initial value returned by {{(ansi-escapes-enabled?)}} is {{#t}}. '''Note:''' The initial value logic has been modifien in the CHICKEN implementation. Chibi's original library did not support {{NO_COLOR}} and used a hard-coded list of known {{TERM}} values to set the initial value to {{#t}} and otherwise default to {{#f}}. ==== Notes It is important to remember that the formatting procedures apply a prefix to set a particular graphics parameter and a suffix to reset the parameter to its default value. This can lead to surprises. For example, on an ANSI terminal, one might mistakenly expect the following to display GREEN in green text and then RED in red text: <enscript highlight="scheme"> (display (red (string-append (green "GREEN") "RED"))) </enscript> However, it will actually display GREEN in green text and then RED in the default text color. This is a limitation of ANSI control codes; graphics attributes are not saved to and restored from a stack, but instead are simply set. One way to display GREEN in green text and then RED in red text is: <enscript highlight="scheme"> (display (string-append (green "GREEN") (red "RED"))) </enscript> On the other hand, text color, background color, font weight (bold or default), underline (on or off), image (positive or negative) are orthogonal. So, for example, on an ANSI terminal the following should display GREEN in green text and then RED in red text, with both in bold and GREEN underlined. <enscript highlight="scheme"> (display (bold (string-append (underline (green "GREEN")) (red "RED")))) </enscript> === Maintainer Diego A. Mundo === Author Alex Shinn === Version History ; 0.1.0 : Initial library port === License BSD Copyright (c) 2009-2021 Alex Shinn All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 3. The name of the author may not be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 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