Mercurial > repos > rliterman > csp2

comparison CSP2/CSP2_env/env-d9b9114564458d9d-741b3de822f2aaca6c6caa4325c4afce/share/doc/libtextstyle/libtextstyle_1.html @ 68:5028fdace37b

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
planemo upload commit 2e9511a184a1ca667c7be0c6321a36dc4e3d116d
author jpayne
date Tue, 18 Mar 2025 16:23:26 -0400
parents
children
comparison
equal deleted inserted replaced
67:0e9998148a16 68:5028fdace37b
1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html401/loose.dtd">
2 <html>
3 <!-- Created on February, 21 2024 by texi2html 1.78a -->
4 <!--
5 Written by: Lionel Cons <Lionel.Cons@cern.ch> (original author)
6 Karl Berry <karl@freefriends.org>
7 Olaf Bachmann <obachman@mathematik.uni-kl.de>
8 and many others.
9 Maintained by: Many creative people.
10 Send bugs and suggestions to <texi2html-bug@nongnu.org>
11
12 -->
13 <head>
14 <title>GNU libtextstyle: 1. Introduction</title>
15
16 <meta name="description" content="GNU libtextstyle: 1. Introduction">
17 <meta name="keywords" content="GNU libtextstyle: 1. Introduction">
18 <meta name="resource-type" content="document">
19 <meta name="distribution" content="global">
20 <meta name="Generator" content="texi2html 1.78a">
21 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
22 <style type="text/css">
23 <!--
24 a.summary-letter {text-decoration: none}
25 pre.display {font-family: serif}
26 pre.format {font-family: serif}
27 pre.menu-comment {font-family: serif}
28 pre.menu-preformatted {font-family: serif}
29 pre.smalldisplay {font-family: serif; font-size: smaller}
30 pre.smallexample {font-size: smaller}
31 pre.smallformat {font-family: serif; font-size: smaller}
32 pre.smalllisp {font-size: smaller}
33 span.roman {font-family:serif; font-weight:normal;}
34 span.sansserif {font-family:sans-serif; font-weight:normal;}
35 ul.toc {list-style: none}
36 -->
37 </style>
38
39
40 </head>
41
42 <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
43
44 <table cellpadding="1" cellspacing="1" border="0">
45 <tr><td valign="middle" align="left">[ &lt;&lt; ]</td>
46 <td valign="middle" align="left">[<a href="libtextstyle_2.html#SEC4" title="Next chapter"> &gt;&gt; </a>]</td>
47 <td valign="middle" align="left"> &nbsp; </td>
48 <td valign="middle" align="left"> &nbsp; </td>
49 <td valign="middle" align="left"> &nbsp; </td>
50 <td valign="middle" align="left"> &nbsp; </td>
51 <td valign="middle" align="left"> &nbsp; </td>
52 <td valign="middle" align="left">[<a href="libtextstyle_toc.html#SEC_Top" title="Cover (top) of document">Top</a>]</td>
53 <td valign="middle" align="left">[<a href="libtextstyle_toc.html#SEC_Contents" title="Table of contents">Contents</a>]</td>
54 <td valign="middle" align="left">[<a href="libtextstyle_5.html#SEC46" title="Index">Index</a>]</td>
55 <td valign="middle" align="left">[<a href="libtextstyle_abt.html#SEC_About" title="About (help)"> ? </a>]</td>
56 </tr></table>
57
58 <hr size="2">
59 <a name="Introduction"></a>
60 <a name="SEC1"></a>
61 <h1 class="chapter"> <a href="libtextstyle_toc.html#TOC1">1. Introduction</a> </h1>
62
63 <p>Text is easier to read when it is accompanied with styling information,
64 such as color, font attributes (weight, posture), or underlining, and
65 this styling is customized appropriately for the output device.
66 </p>
67 <p>GNU libtextstyle provides an easy way to add styling to programs that
68 produce output to a console or terminal emulator window. It does this
69 in a way that allows the end user to customize the styling using the
70 industry standard, namely Cascading Style Sheets (CSS).
71 </p>
72
73
74 <a name="Style-definitions"></a>
75 <a name="SEC2"></a>
76 <h2 class="section"> <a href="libtextstyle_toc.html#TOC2">1.1 Style definitions</a> </h2>
77
78 <p>Let's look at the traditional way styling is done for specific programs.
79 </p>
80 <p>Browsers, when they render HTML, use CSS styling.
81 </p>
82 <p>The older approach to user-customizable text styling is that the user
83 associates patterns with escape sequences in an environment variable or a
84 command-line argument. This is the approach used, for example, by the
85 GNU &lsquo;<samp>ls</samp>&rsquo; program in combination with the &lsquo;<samp>dircolors</samp>&rsquo; program.
86 The processing is distributed across several steps:
87 </p><ol>
88 <li>
89 There is default style definition that is hard-coded in the
90 &lsquo;<samp>dircolors</samp>&rsquo; program. The user can also define their own definitions
91 in a file such as &lsquo;<tt>~/.dir_colors</tt>&rsquo;. This style definition contains
92 explicit terminal escape sequences; thus, it can only be used with
93 consoles and terminal emulators, and each style definition applies only
94 to a certain class of mostly-compatible terminal emulators.
95 </li><li>
96 The <code>dircolors</code> program, when invoked, translates such a style
97 definition to a sequence of shell statements that sets an environment
98 variable <code>LS_COLORS</code>.
99 </li><li>
100 The shell executes these statements, and thus sets the environment
101 variable <code>LS_COLORS</code>.
102 </li><li>
103 The program looks at the environment variable and emits the listed escape
104 sequences.
105 </li></ol>
106
107 <p>In contrast, this library implements styling as follows:
108 </p><ol>
109 <li>
110 There is a default style definition in a CSS file that is part of the
111 same package as the stylable program. The user can also define their own
112 definitions in a CSS file, and set an environment environment variable to
113 point to it.
114 </li><li>
115 The program looks at the environment variable, parses the CSS file,
116 translates the styling specifications to the form that is appropriate for
117 the output device (escape sequences for terminal emulators, inline CSS
118 and <code>&lt;span&gt;</code> elements for HTML output), and emits it.
119 </li></ol>
120
121 <p>Thus, with GNU libtextstyle, the styling has the following properties:
122 </p><ul>
123 <li>
124 It is easier for the user to define their own styling, because the file
125 format is standardized and supported by numerous syntax aware editors.
126 </li><li>
127 A styling file does not depend on the particular output device. An HTML
128 output and a black-on-white terminal emulator can use the same styling
129 file. A white-on-black (or even green-on-black) terminal emulator will
130 need different styling, though.
131 </li><li>
132 It is simpler: There is no need for a program that converts the style
133 specification from one format to another.
134 </li></ul>
135
136
137 <a name="Built_002din-versus-separate-styling"></a>
138 <a name="SEC3"></a>
139 <h2 class="section"> <a href="libtextstyle_toc.html#TOC3">1.2 Built-in versus separate styling</a> </h2>
140
141 <p>There are generally two approaches for adding styling to text:
142 </p><ul>
143 <li>
144 The program that generates the text adds the styling. It does so through
145 interleaved statements that turn on or off specific attributes.
146 </li><li>
147 The styling gets added by a separate program, that postprocesses the
148 output. This separate program usually uses regular expressions to
149 determine which text regions to style with a certain set of text
150 attributes.
151 </li></ul>
152
153 <p>The first approach produces a styling that is 100% correct, regardless of
154 the complexity of the text that is being output. This is the preferred
155 approach for example for JSON, XML, or programming language text.
156 </p>
157 <p>The second approach works well if the output has a simple, easy-to-parse
158 format. It may produce wrong styling in some cases when the text format
159 is more complex. This approach is often used for viewing log files.
160 </p>
161 <p>GNU libtextstyle supports both approaches; it includes an example program
162 for each of the two approaches.
163 </p>
164
165 <table cellpadding="1" cellspacing="1" border="0">
166 <tr><td valign="middle" align="left">[<a href="#SEC1" title="Beginning of this chapter or previous chapter"> &lt;&lt; </a>]</td>
167 <td valign="middle" align="left">[<a href="libtextstyle_2.html#SEC4" title="Next chapter"> &gt;&gt; </a>]</td>
168 <td valign="middle" align="left"> &nbsp; </td>
169 <td valign="middle" align="left"> &nbsp; </td>
170 <td valign="middle" align="left"> &nbsp; </td>
171 <td valign="middle" align="left"> &nbsp; </td>
172 <td valign="middle" align="left"> &nbsp; </td>
173 <td valign="middle" align="left">[<a href="libtextstyle_toc.html#SEC_Top" title="Cover (top) of document">Top</a>]</td>
174 <td valign="middle" align="left">[<a href="libtextstyle_toc.html#SEC_Contents" title="Table of contents">Contents</a>]</td>
175 <td valign="middle" align="left">[<a href="libtextstyle_5.html#SEC46" title="Index">Index</a>]</td>
176 <td valign="middle" align="left">[<a href="libtextstyle_abt.html#SEC_About" title="About (help)"> ? </a>]</td>
177 </tr></table>
178 <p>
179 <font size="-1">
180 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>.
181 </font>
182 <br>
183
184 </p>
185 </body>
186 </html>