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diff CSP2/CSP2_env/env-d9b9114564458d9d-741b3de822f2aaca6c6caa4325c4afce/share/doc/libtextstyle/libtextstyle_1.html @ 68:5028fdace37b
planemo upload commit 2e9511a184a1ca667c7be0c6321a36dc4e3d116d
| author | jpayne |
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| date | Tue, 18 Mar 2025 16:23:26 -0400 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/CSP2/CSP2_env/env-d9b9114564458d9d-741b3de822f2aaca6c6caa4325c4afce/share/doc/libtextstyle/libtextstyle_1.html Tue Mar 18 16:23:26 2025 -0400 @@ -0,0 +1,186 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html401/loose.dtd"> +<html> +<!-- Created on February, 21 2024 by texi2html 1.78a --> +<!-- +Written by: Lionel Cons <Lionel.Cons@cern.ch> (original author) + Karl Berry <karl@freefriends.org> + Olaf Bachmann <obachman@mathematik.uni-kl.de> + and many others. +Maintained by: Many creative people. +Send bugs and suggestions to <texi2html-bug@nongnu.org> + +--> +<head> +<title>GNU libtextstyle: 1. Introduction</title> + +<meta name="description" content="GNU libtextstyle: 1. Introduction"> +<meta name="keywords" content="GNU libtextstyle: 1. Introduction"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="texi2html 1.78a"> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +pre.display {font-family: serif} +pre.format {font-family: serif} +pre.menu-comment {font-family: serif} +pre.menu-preformatted {font-family: serif} +pre.smalldisplay {font-family: serif; font-size: smaller} +pre.smallexample {font-size: smaller} +pre.smallformat {font-family: serif; font-size: smaller} +pre.smalllisp {font-size: smaller} +span.roman {font-family:serif; font-weight:normal;} +span.sansserif {font-family:sans-serif; font-weight:normal;} +ul.toc {list-style: none} +--> +</style> + + +</head> + +<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> + +<table cellpadding="1" cellspacing="1" border="0"> +<tr><td valign="middle" align="left">[ << ]</td> +<td valign="middle" align="left">[<a href="libtextstyle_2.html#SEC4" title="Next chapter"> >> </a>]</td> +<td valign="middle" align="left"> </td> +<td valign="middle" align="left"> </td> +<td valign="middle" align="left"> </td> +<td valign="middle" align="left"> </td> +<td valign="middle" align="left"> </td> +<td valign="middle" align="left">[<a href="libtextstyle_toc.html#SEC_Top" title="Cover (top) of document">Top</a>]</td> +<td valign="middle" align="left">[<a href="libtextstyle_toc.html#SEC_Contents" title="Table of contents">Contents</a>]</td> +<td valign="middle" align="left">[<a href="libtextstyle_5.html#SEC46" title="Index">Index</a>]</td> +<td valign="middle" align="left">[<a href="libtextstyle_abt.html#SEC_About" title="About (help)"> ? </a>]</td> +</tr></table> + +<hr size="2"> +<a name="Introduction"></a> +<a name="SEC1"></a> +<h1 class="chapter"> <a href="libtextstyle_toc.html#TOC1">1. Introduction</a> </h1> + +<p>Text is easier to read when it is accompanied with styling information, +such as color, font attributes (weight, posture), or underlining, and +this styling is customized appropriately for the output device. +</p> +<p>GNU libtextstyle provides an easy way to add styling to programs that +produce output to a console or terminal emulator window. It does this +in a way that allows the end user to customize the styling using the +industry standard, namely Cascading Style Sheets (CSS). +</p> + + +<a name="Style-definitions"></a> +<a name="SEC2"></a> +<h2 class="section"> <a href="libtextstyle_toc.html#TOC2">1.1 Style definitions</a> </h2> + +<p>Let's look at the traditional way styling is done for specific programs. +</p> +<p>Browsers, when they render HTML, use CSS styling. +</p> +<p>The older approach to user-customizable text styling is that the user +associates patterns with escape sequences in an environment variable or a +command-line argument. This is the approach used, for example, by the +GNU ‘<samp>ls</samp>’ program in combination with the ‘<samp>dircolors</samp>’ program. +The processing is distributed across several steps: +</p><ol> +<li> +There is default style definition that is hard-coded in the +‘<samp>dircolors</samp>’ program. The user can also define their own definitions +in a file such as ‘<tt>~/.dir_colors</tt>’. This style definition contains +explicit terminal escape sequences; thus, it can only be used with +consoles and terminal emulators, and each style definition applies only +to a certain class of mostly-compatible terminal emulators. +</li><li> +The <code>dircolors</code> program, when invoked, translates such a style +definition to a sequence of shell statements that sets an environment +variable <code>LS_COLORS</code>. +</li><li> +The shell executes these statements, and thus sets the environment +variable <code>LS_COLORS</code>. +</li><li> +The program looks at the environment variable and emits the listed escape +sequences. +</li></ol> + +<p>In contrast, this library implements styling as follows: +</p><ol> +<li> +There is a default style definition in a CSS file that is part of the +same package as the stylable program. The user can also define their own +definitions in a CSS file, and set an environment environment variable to +point to it. +</li><li> +The program looks at the environment variable, parses the CSS file, +translates the styling specifications to the form that is appropriate for +the output device (escape sequences for terminal emulators, inline CSS +and <code><span></code> elements for HTML output), and emits it. +</li></ol> + +<p>Thus, with GNU libtextstyle, the styling has the following properties: +</p><ul> +<li> +It is easier for the user to define their own styling, because the file +format is standardized and supported by numerous syntax aware editors. +</li><li> +A styling file does not depend on the particular output device. An HTML +output and a black-on-white terminal emulator can use the same styling +file. A white-on-black (or even green-on-black) terminal emulator will +need different styling, though. +</li><li> +It is simpler: There is no need for a program that converts the style +specification from one format to another. +</li></ul> + + +<a name="Built_002din-versus-separate-styling"></a> +<a name="SEC3"></a> +<h2 class="section"> <a href="libtextstyle_toc.html#TOC3">1.2 Built-in versus separate styling</a> </h2> + +<p>There are generally two approaches for adding styling to text: +</p><ul> +<li> +The program that generates the text adds the styling. It does so through +interleaved statements that turn on or off specific attributes. +</li><li> +The styling gets added by a separate program, that postprocesses the +output. This separate program usually uses regular expressions to +determine which text regions to style with a certain set of text +attributes. +</li></ul> + +<p>The first approach produces a styling that is 100% correct, regardless of +the complexity of the text that is being output. This is the preferred +approach for example for JSON, XML, or programming language text. +</p> +<p>The second approach works well if the output has a simple, easy-to-parse +format. It may produce wrong styling in some cases when the text format +is more complex. This approach is often used for viewing log files. +</p> +<p>GNU libtextstyle supports both approaches; it includes an example program +for each of the two approaches. +</p> + +<table cellpadding="1" cellspacing="1" border="0"> +<tr><td valign="middle" align="left">[<a href="#SEC1" title="Beginning of this chapter or previous chapter"> << </a>]</td> +<td valign="middle" align="left">[<a href="libtextstyle_2.html#SEC4" title="Next chapter"> >> </a>]</td> +<td valign="middle" align="left"> </td> +<td valign="middle" align="left"> </td> +<td valign="middle" align="left"> </td> +<td valign="middle" align="left"> </td> +<td valign="middle" align="left"> </td> +<td valign="middle" align="left">[<a href="libtextstyle_toc.html#SEC_Top" title="Cover (top) of document">Top</a>]</td> +<td valign="middle" align="left">[<a href="libtextstyle_toc.html#SEC_Contents" title="Table of contents">Contents</a>]</td> +<td valign="middle" align="left">[<a href="libtextstyle_5.html#SEC46" title="Index">Index</a>]</td> +<td valign="middle" align="left">[<a href="libtextstyle_abt.html#SEC_About" title="About (help)"> ? </a>]</td> +</tr></table> +<p> + <font size="-1"> + This document was generated by <em>Bruno Haible</em> on <em>February, 21 2024</em> using <a href="https://www.nongnu.org/texi2html/"><em>texi2html 1.78a</em></a>. + </font> + <br> + +</p> +</body> +</html>