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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-15 19:44:05 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-15 19:44:05 +0000 |
| commit | d318611dd6f23fcfedd50e9b9e24620b102ba96a (patch) | |
| tree | 8b9eef82ca40fdd5a8deeabf07572074c236095d /doc/groff.html.node/Using-Symbols.html | |
| parent | Initial commit. (diff) | |
| download | groff-upstream/1.23.0.tar.xz groff-upstream/1.23.0.zip | |
Adding upstream version 1.23.0.upstream/1.23.0upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
| -rw-r--r-- | doc/groff.html.node/Using-Symbols.html | 632 |
1 files changed, 632 insertions, 0 deletions
diff --git a/doc/groff.html.node/Using-Symbols.html b/doc/groff.html.node/Using-Symbols.html new file mode 100644 index 0000000..af4a7cf --- /dev/null +++ b/doc/groff.html.node/Using-Symbols.html @@ -0,0 +1,632 @@ +<!DOCTYPE html> +<html> +<!-- Created by GNU Texinfo 7.0.3, https://www.gnu.org/software/texinfo/ --> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> +<!-- This manual documents GNU troff version 1.23.0. + +Copyright © 1994-2023 Free Software Foundation, Inc. + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with no +Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A +copy of the license is included in the section entitled "GNU Free +Documentation License". --> +<title>Using Symbols (The GNU Troff Manual)</title> + +<meta name="description" content="Using Symbols (The GNU Troff Manual)"> +<meta name="keywords" content="Using Symbols (The GNU Troff Manual)"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta name="viewport" content="width=device-width,initial-scale=1"> + +<link href="index.html" rel="start" title="Top"> +<link href="Request-Index.html" rel="index" title="Request Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Using-Fonts.html" rel="up" title="Using Fonts"> +<link href="Character-Classes.html" rel="next" title="Character Classes"> +<link href="Font-Positions.html" rel="prev" title="Font Positions"> +<style type="text/css"> +<!-- +a.copiable-link {visibility: hidden; text-decoration: none; line-height: 0em} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +pre.display-preformatted {font-family: inherit} +span.r {font-family: initial; font-weight: normal; font-style: normal} +span:hover a.copiable-link {visibility: visible} +strong.def-name {font-family: monospace; font-weight: bold; font-size: larger} +ul.mark-bullet {list-style-type: disc} +--> +</style> + + +</head> + +<body lang="en"> +<div class="subsection-level-extent" id="Using-Symbols"> +<div class="nav-panel"> +<p> +Next: <a href="Character-Classes.html" accesskey="n" rel="next">Character Classes</a>, Previous: <a href="Font-Positions.html" accesskey="p" rel="prev">Font Positions</a>, Up: <a href="Using-Fonts.html" accesskey="u" rel="up">Using Fonts</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Request-Index.html" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<h4 class="subsection" id="Using-Symbols-1">5.19.4 Using Symbols</h4> +<a class="index-entry-id" id="index-using-symbols"></a> +<a class="index-entry-id" id="index-symbols_002c-using"></a> + +<a class="index-entry-id" id="index-glyph"></a> +<a class="index-entry-id" id="index-character"></a> +<a class="index-entry-id" id="index-glyph_002c-distinguished-from-character"></a> +<a class="index-entry-id" id="index-character_002c-distinguished-from-glyph"></a> +<a class="index-entry-id" id="index-ligature"></a> +<p>A <em class="dfn">glyph</em> is a graphical representation of a <em class="dfn">character</em>. While +a character is an abstraction of semantic information, a glyph is +something that can be seen on screen or paper. A character has many +possible representation forms (for example, the character ‘A’ can be +written in an upright or slanted typeface, producing distinct +glyphs). Sometimes, a sequence of characters map to a single glyph: +this is a <em class="dfn">ligature</em>—the most common is ‘fi’. +</p> +<p>Space characters never become glyphs in GNU <code class="code">troff</code>. If not +discarded (as when trailing on text lines), they are represented by +horizontal motions in the output. +</p> +<a class="index-entry-id" id="index-symbol"></a> +<a class="index-entry-id" id="index-special-fonts"></a> +<a class="index-entry-id" id="index-fonts"></a> +<a class="index-entry-id" id="index-DESC-2"></a> +<a class="index-entry-id" id="index-special-request_002c-and-glyph-search-order"></a> +<a class="index-entry-id" id="index-fspecial-request_002c-and-glyph-search-order"></a> +<p>A <em class="dfn">symbol</em> is simply a named glyph. Within <code class="code">gtroff</code>, all glyph +names of a particular font are defined in its font file. If the user +requests a glyph not available in this font, <code class="code">gtroff</code> looks up an +ordered list of <em class="dfn">special fonts</em>. By default, the PostScript output +device supports the two special fonts ‘<samp class="samp">SS</samp>’ (slanted symbols) and +‘<samp class="samp">S</samp>’ (symbols) (the former is looked up before the latter). Other +output devices use different names for special fonts. Fonts mounted +with the <code class="code">fonts</code> keyword in the <samp class="file">DESC</samp> file are globally +available. To install additional special fonts locally (i.e., for a +particular font), use the <code class="code">fspecial</code> request. +</p> +<p>Here are the exact rules how <code class="code">gtroff</code> searches a given symbol: +</p> +<ul class="itemize mark-bullet"> +<li>If the symbol has been defined with the <code class="code">char</code> request, use it. +This hides a symbol with the same name in the current font. + +</li><li>Check the current font. + +</li><li>If the symbol has been defined with the <code class="code">fchar</code> request, use it. + +</li><li>Check whether the current font has a font-specific list of special +fonts; test all fonts in the order of appearance in the last +<code class="code">fspecial</code> call if appropriate. + +</li><li>If the symbol has been defined with the <code class="code">fschar</code> request for the +current font, use it. + +</li><li>Check all fonts in the order of appearance in the last <code class="code">special</code> +call. + +</li><li>If the symbol has been defined with the <code class="code">schar</code> request, use it. + +</li><li>As a last resort, consult all fonts loaded up to now for special fonts +and check them, starting with the lowest font number. This can +sometimes lead to surprising results since the <code class="code">fonts</code> line in +the <samp class="file">DESC</samp> file often contains empty positions, which are filled +later on. For example, consider the following: + +<div class="example"> +<div class="group"><pre class="example-preformatted">fonts 3 0 0 FOO +</pre></div></div> + +<p>This mounts font <code class="code">foo</code> at font position 3. We assume that +<code class="code">FOO</code> is a special font, containing glyph <code class="code">foo</code>, and that no +font has been loaded yet. The line +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.fspecial BAR BAZ +</pre></div></div> + +<p>makes font <code class="code">BAZ</code> special only if font <code class="code">BAR</code> is active. We +further assume that <code class="code">BAZ</code> is really a special font, i.e., the font +description file contains the <code class="code">special</code> keyword, and that it also +contains glyph <code class="code">foo</code> with a special shape fitting to font +<code class="code">BAR</code>. After executing <code class="code">fspecial</code>, font <code class="code">BAR</code> is loaded +at font position 1, and <code class="code">BAZ</code> at position 2. +</p> +<p>We now switch to a new font <code class="code">XXX</code>, trying to access glyph +<code class="code">foo</code> that is assumed to be missing. There are neither +font-specific special fonts for <code class="code">XXX</code> nor any other fonts made +special with the <code class="code">special</code> request, so <code class="code">gtroff</code> starts the +search for special fonts in the list of already mounted fonts, with +increasing font positions. Consequently, it finds <code class="code">BAZ</code> before +<code class="code">FOO</code> even for <code class="code">XXX</code>, which is not the intended behaviour. +</p></li></ul> + +<p>See <a class="xref" href="Device-and-Font-Description-Files.html">Device and Font Description Files</a>, and <a class="ref" href="Special-Fonts.html">Special Fonts</a>, for +more details. +</p> +<a class="index-entry-id" id="index-list-of-special-characters-_0028groff_005fchar_00287_0029-man-page_0029"></a> +<a class="index-entry-id" id="index-special-characters_002c-list-of-_0028groff_005fchar_00287_0029-man-page_0029"></a> +<a class="index-entry-id" id="index-characters_002c-special_002c-list-of-_0028groff_005fchar_00287_0029-man-page_0029"></a> +<a class="index-entry-id" id="index-available-glyphs_002c-list-of-_0028groff_005fchar_00287_0029-man-page_0029"></a> +<a class="index-entry-id" id="index-glyphs_002c-available_002c-list-of-_0028groff_005fchar_00287_0029-man-page_0029"></a> +<p>The <cite class="cite">groff_char<span class="r">(7)</span></cite> man page houses a complete list of +predefined special character names, but the availability of any as a +glyph is device- and font-dependent. For example, say +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">man -Tdvi groff_char > groff_char.dvi +</pre></div></div> + +<p>to obtain those available with the DVI device and default font +configuration.<a class="footnote" id="DOCF77" href="groff.html_fot.html#FOOT77"><sup>77</sup></a> If you want to use an additional macro package to change +the fonts used, <code class="code">groff</code> (or <code class="code">gtroff</code>) must be run directly. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">groff -Tdvi -mec -man groff_char.7 > groff_char.dvi +</pre></div></div> + +<a class="index-entry-id" id="index-composite-glyph-names"></a> +<a class="index-entry-id" id="index-glyph-names_002c-composite"></a> +<a class="index-entry-id" id="index-groff-glyph-list-_0028GGL_0029"></a> +<a class="index-entry-id" id="index-GGL-_0028groff-glyph-list_0029"></a> +<a class="index-entry-id" id="index-Adobe-Glyph-List-_0028AGL_0029"></a> +<p>Special character names not listed in <cite class="cite">groff_char<span class="r">(7)</span></cite> are +derived algorithmically, using a simplified version of the Adobe Glyph +List (AGL) algorithm, which is described in +<a class="uref" href="https://github.com/adobe-type-tools/agl-aglfn">https://github.com/adobe-type-tools/agl-aglfn</a>. The (frozen) +set of names that can’t be derived algorithmically is called the +<em class="dfn"><code class="code">groff</code> glyph list (GGL)</em>. +</p> +<ul class="itemize mark-bullet"> +<li>A glyph for Unicode character U+<var class="var">XXXX</var>[<var class="var">X</var>[<var class="var">X</var>]], which is +not a composite character is named +<code class="code">u<var class="var">XXXX</var><span class="r">[</span><var class="var">X</var><span class="r">[</span><var class="var">X</var><span class="r">]]</span></code>. <var class="var">X</var> must be an +uppercase hexadecimal digit. Examples: <code class="code">u1234</code>, <code class="code">u008E</code>, +<code class="code">u12DB8</code>. The largest Unicode value is 0x10FFFF. There must be at +least four <code class="code">X</code> digits; if necessary, add leading zeroes (after the +‘<samp class="samp">u</samp>’). No zero padding is allowed for character codes greater than +0xFFFF. Surrogates (i.e., Unicode values greater than 0xFFFF +represented with character codes from the surrogate area U+D800-U+DFFF) +are not allowed either. + +</li><li>A glyph representing more than a single input character is named + +<div class="display"> +<pre class="display-preformatted">‘<samp class="samp">u</samp>’ <var class="var">component1</var> ‘<samp class="samp">_</samp>’ <var class="var">component2</var> ‘<samp class="samp">_</samp>’ <var class="var">component3</var> … +</pre></div> + +<p>Example: <code class="code">u0045_0302_0301</code>. +</p> +<p>For simplicity, all Unicode characters that are composites must be +maximally decomposed to NFD;<a class="footnote" id="DOCF78" href="groff.html_fot.html#FOOT78"><sup>78</sup></a> for example, +<code class="code">u00CA_0301</code> is not a valid glyph name since U+00CA (<small class="sc">LATIN +CAPITAL LETTER E WITH CIRCUMFLEX</small>) can be further decomposed into U+0045 +(<small class="sc">LATIN CAPITAL LETTER E</small>) and U+0302 (<small class="sc">COMBINING CIRCUMFLEX +ACCENT</small>). <code class="code">u0045_0302_0301</code> is thus the glyph name for U+1EBE, +<small class="sc">LATIN CAPITAL LETTER E WITH CIRCUMFLEX AND ACUTE</small>. +</p> +</li><li>groff maintains a table to decompose all algorithmically derived glyph +names that are composites itself. For example, <code class="code">u0100</code> (<small class="sc">LATIN +LETTER A WITH MACRON</small>) is automatically decomposed into +<code class="code">u0041_0304</code>. Additionally, a glyph name of the GGL is preferred +to an algorithmically derived glyph name; <code class="code">groff</code> also +automatically does the mapping. Example: The glyph <code class="code">u0045_0302</code> is +mapped to <code class="code">^E</code>. + +</li><li>glyph names of the GGL can’t be used in composite glyph names; for +example, <code class="code">^E_u0301</code> is invalid. +</li></ul> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_005c_0028nm"><span class="category-def">Escape sequence: </span><span><strong class="def-name"><code class="t">\(</code><span class="r"><i class="slanted">nm</i></span><code class="t"></code></strong><a class="copiable-link" href='#index-_005c_0028nm'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-_005c-1"></a> +</dd><dt class="deffnx def-cmd-deffn" id="index-_005c_005bname_005d"><span class="category-def">Escape sequence: </span><span><strong class="def-name"><code class="t">\[</code><span class="r"><i class="slanted">name</i></span><code class="t">]</code></strong><a class="copiable-link" href='#index-_005c_005bname_005d'> ¶</a></span></dt> +<dt class="deffnx def-cmd-deffn" id="index-_005c_005bbase_002dglyph-combining_002dcomponent-_2026_005d"><span class="category-def">Escape sequence: </span><span><strong class="def-name"><code class="t">\[</code><span class="r"><i class="slanted">base-glyph combining-component …</i></span><code class="t">]</code></strong><a class="copiable-link" href='#index-_005c_005bbase_002dglyph-combining_002dcomponent-_2026_005d'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-_005c_0028"></a> +<a class="index-entry-id" id="index-_005c_005b"></a> +<p>Typeset a special character <var class="var">name</var> (two-character name <var class="var">nm</var>) or +a composite glyph consisting of <var class="var">base-glyph</var> overlaid with one or +more <var class="var">combining-component</var>s. For example, ‘<samp class="samp">\[A ho]</samp>’ is a +capital letter “A” with a “hook accent” (ogonek). +</p> +<p>There is no special syntax for one-character names—the analogous form +‘<samp class="samp">\<var class="var">n</var></samp>’ would collide with other escape sequences. However, the +four escape sequences <code class="code">\'</code>, <code class="code">\-</code>, <code class="code">\_</code>, and <code class="code">\`</code>, +are translated on input to the special character escape sequences +<code class="code">\[aa]</code>, <code class="code">\[-]</code>, <code class="code">\[ul]</code>, and <code class="code">\[ga]</code>, respectively. +</p> +<p>A special character name of length one is not the same thing as an +ordinary character: that is, the character <code class="code">a</code> is not the same as +<code class="code">\[a]</code>. +</p> +<p>If <var class="var">name</var> is undefined, a warning in category ‘<samp class="samp">char</samp>’ is +produced and the escape is ignored. See <a class="xref" href="Warnings.html">Warnings</a>, for information +about the enablement and suppression of warnings. +</p> +<p>GNU <code class="code">troff</code> resolves <code class="code">\[<span class="r">…</span>]</code> with more than a single +component as follows: +</p> +<ul class="itemize mark-bullet"> +<li>Any component that is found in the GGL is converted to the +<code class="code">u<var class="var">XXXX</var></code> form. + +</li><li>Any component <code class="code">u<var class="var">XXXX</var></code> that is found in the list of +decomposable glyphs is decomposed. + +</li><li>The resulting elements are then concatenated with ‘<samp class="samp">_</samp>’ in between, +dropping the leading ‘<samp class="samp">u</samp>’ in all elements but the first. +</li></ul> + +<p>No check for the existence of any component (similar to <code class="code">tr</code> +request) is done. +</p> +<p>Examples: +</p> +<dl class="table"> +<dt><code class="code">\[A ho]</code></dt> +<dd><p>‘<samp class="samp">A</samp>’ maps to <code class="code">u0041</code>, ‘<samp class="samp">ho</samp>’ maps to <code class="code">u02DB</code>, thus the +final glyph name would be <code class="code">u0041_02DB</code>. This is not the expected +result: the ogonek glyph ‘<samp class="samp">ho</samp>’ is a spacing ogonek, but for a +proper composite a non-spacing ogonek (U+0328) is necessary. Looking +into the file <samp class="file">composite.tmac</samp>, one can find ‘<samp class="samp">.composite ho u0328</samp>’<!-- /@w -->, which changes the mapping of ‘<samp class="samp">ho</samp>’ while a composite glyph +name is constructed, causing the final glyph name to be +<code class="code">u0041_0328</code>. +</p> +</dd> +<dt><code class="code">\[^E u0301]</code></dt> +<dt><code class="code">\[^E aa]</code></dt> +<dt><code class="code">\[E a^ aa]</code></dt> +<dt><code class="code">\[E ^ <code class="code">'</code>]</code></dt> +<dd><p>‘<samp class="samp">^E</samp>’ maps to <code class="code">u0045_0302</code>, thus the final glyph name is +<code class="code">u0045_0302_0301</code> in all forms (assuming proper calls of the +<code class="code">composite</code> request). +</p></dd> +</dl> + +<p>It is not possible to define glyphs with names like ‘<samp class="samp">A ho</samp>’<!-- /@w --> +within a <code class="code">groff</code> font file. This is not really a limitation; +instead, you have to define <code class="code">u0041_0328</code>. +</p></dd></dl> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_005cC_0027xxx_0027"><span class="category-def">Escape sequence: </span><span><strong class="def-name"><code class="t">\C<code class="code">'</code></code><span class="r"><i class="slanted">xxx</i></span><code class="t"><code class="code">'</code></code></strong><a class="copiable-link" href='#index-_005cC_0027xxx_0027'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-_005cC"></a> +<a class="index-entry-id" id="index-named-character-_0028_005cC_0029"></a> +<a class="index-entry-id" id="index-character_002c-named-_0028_005cC_0029"></a> +<p>Typeset the glyph of the special character <var class="var">xxx</var>. Normally, it is +more convenient to use <code class="code">\[<var class="var">xxx</var>]</code>, but <code class="code">\C</code> has some +advantages: it is compatible with <abbr class="acronym">AT&T</abbr> device-independent +<code class="code">troff</code> (and therefore available in compatibility +mode<a class="footnote" id="DOCF79" href="groff.html_fot.html#FOOT79"><sup>79</sup></a>) and can interpolate special +characters with ‘<samp class="samp">]</samp>’ in their names. The delimiter need not be +a neutral apostrophe; see <a class="ref" href="Delimiters.html">Delimiters</a>. +</p></dd></dl> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_002ecomposite"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.composite</code></strong> <var class="def-var-arguments">id1 id2</var><a class="copiable-link" href='#index-_002ecomposite'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-composite"></a> +<a class="index-entry-id" id="index-composite_002etmac"></a> +<p>Map special character name <var class="var">id1</var> to <var class="var">id2</var> if <var class="var">id1</var> is used +in <code class="code">\[...]</code> with more than one component. See above for examples. +This is a strict rewriting of the special character name; no check is +performed for the existence of a glyph for either. A set of default +mappings for many accents can be found in the file +<samp class="file">composite.tmac</samp>, loaded by the default <samp class="file">troffrc</samp> at startup. +</p></dd></dl> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_005cN_0027n_0027"><span class="category-def">Escape sequence: </span><span><strong class="def-name"><code class="t">\N<code class="code">'</code></code><span class="r"><i class="slanted">n</i></span><code class="t"><code class="code">'</code></code></strong><a class="copiable-link" href='#index-_005cN_0027n_0027'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-_005cN"></a> +<a class="index-entry-id" id="index-numbered-glyph-_0028_005cN_0029-1"></a> +<a class="index-entry-id" id="index-glyph_002c-numbered-_0028_005cN_0029-1"></a> +<a class="index-entry-id" id="index-char-request_002c-used-with-_005cN"></a> +<a class="index-entry-id" id="index-Unicode-1"></a> +<p>Typeset the glyph with code <var class="var">n</var> in the current font +(<code class="code">n</code> is <em class="emph">not</em> the input character code). The number +<var class="var">n</var> can be any non-negative decimal integer. Most devices only +have glyphs with codes between 0 and 255; the Unicode output device +uses codes in the range 0–65535. If the current font does not contain +a glyph with that code, special fonts are <em class="emph">not</em> searched. The +<code class="code">\N</code> escape sequence can be conveniently used in conjunction with +the <code class="code">char</code> request: +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.char \[phone] \f[ZD]\N'37' +</pre></div></div> + +<a class="index-entry-id" id="index-DESC-3"></a> +<a class="index-entry-id" id="index-unnamed-glyphs"></a> +<a class="index-entry-id" id="index-glyphs_002c-unnamed"></a> +<p>The code of each glyph is given in the fourth column in the font +description file after the <code class="code">charset</code> command. It is possible to +include unnamed glyphs in the font description file by using a name of +‘<samp class="samp">---</samp>’; the <code class="code">\N</code> escape sequence is the only way to use these. +</p> +<p>No kerning is applied to glyphs accessed with <code class="code">\N</code>. The delimiter +need not be a neutral apostrophe; see <a class="ref" href="Delimiters.html">Delimiters</a>. +</p></dd></dl> + +<p>A few escape sequences are also special characters. +</p> +<dl class="first-deffn"> +<dt class="deffn" id="index-_005c_0027-1"><span class="category-def">Escape sequence: </span><span><strong class="def-name"><code class="t">\<code class="code">'</code></code><span class="r"><i class="slanted"></i></span><code class="t"></code></strong><a class="copiable-link" href='#index-_005c_0027-1'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-_005c_0027"></a> +<p>An escaped neutral apostrophe is a synonym for <code class="code">\[aa]</code> (acute +accent). +</p></dd></dl> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_005c_0060-1"><span class="category-def">Escape sequence: </span><span><strong class="def-name"><code class="t">\<code class="code">`</code></code><span class="r"><i class="slanted"></i></span><code class="t"></code></strong><a class="copiable-link" href='#index-_005c_0060-1'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-_005c_0060"></a> +<p>An escaped grave accent is a synonym for <code class="code">\[ga]</code> (grave accent). +</p></dd></dl> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_005c_002d-1"><span class="category-def">Escape sequence: </span><span><strong class="def-name"><code class="t">\-</code><span class="r"><i class="slanted"></i></span><code class="t"></code></strong><a class="copiable-link" href='#index-_005c_002d-1'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-_005c_002d"></a> +<p>An escaped hyphen-minus is a synonym for <code class="code">\[-]</code> (minus sign). +</p></dd></dl> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_005c_005f-1"><span class="category-def">Escape sequence: </span><span><strong class="def-name"><code class="t">\_</code><span class="r"><i class="slanted"></i></span><code class="t"></code></strong><a class="copiable-link" href='#index-_005c_005f-1'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-_005c_005f"></a> +<p>An escaped underscore (“low line”) is a synonym for <code class="code">\[ul]</code> +(underrule). On typesetting devices, the underrule is font-invariant +and drawn lower than the underscore ‘<samp class="samp">_</samp>’. +</p></dd></dl> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_002ecflags"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.cflags</code></strong> <var class="def-var-arguments">n c1 c2 …</var><a class="copiable-link" href='#index-_002ecflags'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-cflags"></a> +<a class="index-entry-id" id="index-glyph-properties-_0028cflags_0029"></a> +<a class="index-entry-id" id="index-character-properties-_0028cflags_0029"></a> +<a class="index-entry-id" id="index-properties-of-glyphs-_0028cflags_0029"></a> +<a class="index-entry-id" id="index-properties-of-characters-_0028cflags_0029"></a> +<p>Assign properties encoded by the number <var class="var">n</var> to characters <var class="var">c1</var>, +<var class="var">c2</var>, and so on. +</p> +<p>Input characters, including special characters introduced by an escape, +have certain properties associated with them.<a class="footnote" id="DOCF80" href="groff.html_fot.html#FOOT80"><sup>80</sup></a> +These properties can be modified with this request. The first argument +is the sum of the desired flags and the remaining arguments are the +characters to be assigned those properties. Spaces between the <var class="var">cn</var> +arguments are optional. Any argument <var class="var">cn</var> can be a character class +defined with the <code class="code">class</code> request rather than an individual +character. See <a class="xref" href="Character-Classes.html">Character Classes</a>. +</p> +<p>The non-negative integer <var class="var">n</var> is the sum of any of the following. +Some combinations are nonsensical, such as ‘<samp class="samp">33</samp>’ (1 + 32). +</p> +<dl class="table"> +<dt id='index-end_002dof_002dsentence-characters-1'><span><code class="code">1</code><a class="copiable-link" href='#index-end_002dof_002dsentence-characters-1'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-characters_002c-end_002dof_002dsentence"></a> +<p>Recognize the character as ending a sentence if followed by a newline +or two spaces. Initially, characters ‘<samp class="samp">.?!</samp>’ have this property. +</p> +</dd> +<dt id='index-hyphenating-characters'><span><code class="code">2</code><a class="copiable-link" href='#index-hyphenating-characters'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-characters_002c-hyphenation"></a> +<p>Enable breaks before the character. A line is not broken at a character +with this property unless the characters on each side both have non-zero +hyphenation codes. This exception can be overridden by adding 64. +Initially, no characters have this property. +</p> +</dd> +<dt id='index-_005c_002d-glyph_002c-and-cflags'><span><code class="code">4</code><a class="copiable-link" href='#index-_005c_002d-glyph_002c-and-cflags'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-hy-glyph_002c-and-cflags"></a> +<a class="index-entry-id" id="index-em-glyph_002c-and-cflags"></a> +<p>Enable breaks after the character. A line is not broken at a character +with this property unless the characters on each side both have non-zero +hyphenation codes. This exception can be overridden by adding 64. +Initially, characters ‘<samp class="samp">\-\[hy]\[em]</samp>’ have this property. +</p> +</dd> +<dt id='index-overlapping-characters'><span><code class="code">8</code><a class="copiable-link" href='#index-overlapping-characters'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-characters_002c-overlapping"></a> +<a class="index-entry-id" id="index-ul-glyph_002c-and-cflags"></a> +<a class="index-entry-id" id="index-rn-glyph_002c-and-cflags"></a> +<a class="index-entry-id" id="index-ru-glyph_002c-and-cflags"></a> +<a class="index-entry-id" id="index-radicalex-glyph_002c-and-cflags"></a> +<a class="index-entry-id" id="index-sqrtex-glyph_002c-and-cflags"></a> +<p>Mark the glyph associated with this character as overlapping other +instances of itself horizontally. Initially, characters +‘<samp class="samp">\[ul]\[rn]\[ru]\[radicalex]\[sqrtex]</samp>’ have this property. +</p> +</dd> +<dt id='index-br-glyph_002c-and-cflags'><span><code class="code">16</code><a class="copiable-link" href='#index-br-glyph_002c-and-cflags'> ¶</a></span></dt> +<dd><p>Mark the glyph associated with this character as overlapping other +instances of itself vertically. Initially, the character ‘<samp class="samp">\[br]</samp>’ +has this property. +</p> +</dd> +<dt id='index-transparent-characters'><span><code class="code">32</code><a class="copiable-link" href='#index-transparent-characters'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-character_002c-transparent"></a> +<a class="index-entry-id" id="index-_0022_002c-at-end-of-sentence-1"></a> +<a class="index-entry-id" id="index-_0027_002c-at-end-of-sentence-1"></a> +<a class="index-entry-id" id="index-_0029_002c-at-end-of-sentence-1"></a> +<a class="index-entry-id" id="index-_005d_002c-at-end-of-sentence-1"></a> +<a class="index-entry-id" id="index-_002a_002c-at-end-of-sentence-1"></a> +<a class="index-entry-id" id="index-dg-glyph_002c-at-end-of-sentence-1"></a> +<a class="index-entry-id" id="index-dd-glyph_002c-at-end-of-sentence-1"></a> +<a class="index-entry-id" id="index-rq-glyph_002c-at-end-of-sentence-1"></a> +<a class="index-entry-id" id="index-cq-glyph_002c-at-end-of-sentence-1"></a> +<p>Mark the character as transparent for the purpose of end-of-sentence +recognition. In other words, an end-of-sentence character followed by +any number of characters with this property is treated as the end of a +sentence if followed by a newline or two spaces. This is the same as +having a zero space factor in TeX. Initially, characters +‘<samp class="samp">"')]*\[dg]\[dd]\[rq]\[cq]</samp>’ have this property. +</p> +</dd> +<dt><code class="code">64</code></dt> +<dd><p>Ignore hyphenation codes of the surrounding characters. Use this in +combination with values 2 and 4 (initially, no characters have this +property). +</p> +<p>For example, if you need an automatic break point after the en-dash in +numeric ranges like “3000–5000”, insert +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.cflags 68 \[en] +</pre></div></div> + +<p>into your document. However, this practice can lead to bad layout if +done thoughtlessly; in most situations, a better solution instead of +changing the <code class="code">cflags</code> value is to insert <code class="code">\:</code> right after the +hyphen at the places that really need a break point. +</p></dd> +</dl> + +<p>The remaining values were implemented for East Asian language support; +those who use alphabetic scripts exclusively can disregard them. +</p> +<dl class="table"> +<dt><code class="code">128</code></dt> +<dd><p>Prohibit a line break before the character, but allow a line break after +the character. This works only in combination with flags 256 and 512 +and has no effect otherwise. Initially, no characters have this +property. +</p> +</dd> +<dt><code class="code">256</code></dt> +<dd><p>Prohibit a line break after the character, but allow a line break before +the character. This works only in combination with flags 128 and 512 +and has no effect otherwise. Initially, no characters have this +property. +</p> +</dd> +<dt><code class="code">512</code></dt> +<dd><p>Allow line break before or after the character. This works only in +combination with flags 128 and 256 and has no effect otherwise. +Initially, no characters have this property. +</p></dd> +</dl> + +<p>In contrast to values 2 and 4, the values 128, 256, and 512 work +pairwise. If, for example, the left character has value 512, and the +right character 128, no break will be automatically inserted between +them. If we use value 6 instead for the left character, a break +after the character can’t be suppressed since the neighboring character +on the right doesn’t get examined. +</p></dd></dl> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_002echar"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.char</code></strong> <var class="def-var-arguments">c [<span class="r"><i class="slanted">contents</i></span>]</var><a class="copiable-link" href='#index-_002echar'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-char"></a> +</dd><dt class="deffnx def-cmd-deffn" id="index-_002efchar"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.fchar</code></strong> <var class="def-var-arguments">c [<span class="r"><i class="slanted">contents</i></span>]</var><a class="copiable-link" href='#index-_002efchar'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-fchar"></a> +</dd><dt class="deffnx def-cmd-deffn" id="index-_002efschar"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.fschar</code></strong> <var class="def-var-arguments">f c [<span class="r"><i class="slanted">contents</i></span>]</var><a class="copiable-link" href='#index-_002efschar'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-fschar"></a> +</dd><dt class="deffnx def-cmd-deffn" id="index-_002eschar"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.schar</code></strong> <var class="def-var-arguments">c [<span class="r"><i class="slanted">contents</i></span>]</var><a class="copiable-link" href='#index-_002eschar'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-schar"></a> +<a class="index-entry-id" id="index-defining-character-_0028char_0029"></a> +<a class="index-entry-id" id="index-defining-fallback-character-_0028fchar_002c-fschar_002c-schar_0029"></a> +<a class="index-entry-id" id="index-character_002c-defining-_0028char_0029"></a> +<a class="index-entry-id" id="index-character_002c-defining-fallback-_0028fchar_002c-fschar_002c-schar_0029"></a> +<a class="index-entry-id" id="index-fallback-character_002c-defining-_0028fchar_002c-fschar_002c-schar_0029"></a> +<a class="index-entry-id" id="index-creating-new-characters-_0028char_0029"></a> +<a class="index-entry-id" id="index-defining-symbol-_0028char_0029"></a> +<a class="index-entry-id" id="index-symbol_002c-defining-_0028char_0029"></a> +<a class="index-entry-id" id="index-defining-glyph-_0028char_0029"></a> +<a class="index-entry-id" id="index-glyph_002c-defining-_0028char_0029"></a> +<a class="index-entry-id" id="index-escape-character_002c-while-defining-glyph"></a> +<a class="index-entry-id" id="index-character_002c-escape_002c-while-defining-glyph"></a> +<a class="index-entry-id" id="index-tr-request_002c-and-glyph-definitions"></a> +<a class="index-entry-id" id="index-cp-request_002c-and-glyph-definitions"></a> +<a class="index-entry-id" id="index-rc-request_002c-and-glyph-definitions"></a> +<a class="index-entry-id" id="index-lc-request_002c-and-glyph-definitions"></a> +<a class="index-entry-id" id="index-_005cl_002c-and-glyph-definitions"></a> +<a class="index-entry-id" id="index-_005cL_002c-and-glyph-definitions"></a> +<a class="index-entry-id" id="index-_005c_0026_002c-and-glyph-definitions"></a> +<a class="index-entry-id" id="index-_005ce_002c-and-glyph-definitions"></a> +<a class="index-entry-id" id="index-hcode-request_002c-and-glyph-definitions"></a> +<p>Define a new character or glyph <var class="var">c</var> to be <var class="var">contents</var>, which +can be empty. More precisely, <code class="code">char</code> defines a <code class="code">groff</code> object +(or redefines an existing one) that is accessed with the +name <var class="var">c</var> on input, and produces <var class="var">contents</var> on output. +Every time glyph <var class="var">c</var> needs to be printed, <var class="var">contents</var> is +processed in a temporary environment and the result is wrapped up into a +single object. Compatibility mode is turned off and the escape +character is set to <code class="code">\</code> while <var class="var">contents</var> is processed. +Any emboldening, constant spacing, or track kerning is applied to this +object rather than to individual glyphs in <var class="var">contents</var>. +</p> +<p>An object defined by these requests can be used just like a normal glyph +provided by the output device. In particular, other characters can be +translated to it with the <code class="code">tr</code> or <code class="code">trin</code> requests; it can be +made the leader character with the <code class="code">lc</code> request; repeated patterns +can be drawn with it using the <code class="code">\l</code> and <code class="code">\L</code> escape sequences; +and words containing <var class="var">c</var> can be hyphenated correctly if the +<code class="code">hcode</code> request is used to give the object a hyphenation code. +</p> +<p>There is a special anti-recursion feature: use of the object within its +own definition is handled like a normal character (not +defined with <code class="code">char</code>). +</p> +<p>The <code class="code">tr</code> and <code class="code">trin</code> requests take precedence if <code class="code">char</code> +accesses the same symbol. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.tr XY +X + ⇒ Y +.char X Z +X + ⇒ Y +.tr XX +X + ⇒ Z +</pre></div></div> + +<p>The <code class="code">fchar</code> request defines a fallback glyph: <code class="code">gtroff</code> only +checks for glyphs defined with <code class="code">fchar</code> if it cannot find the glyph +in the current font. <code class="code">gtroff</code> carries out this test before +checking special fonts. +</p> +<p><code class="code">fschar</code> defines a fallback glyph for font <var class="var">f</var>: +<code class="code">gtroff</code> checks for glyphs defined with <code class="code">fschar</code> after the +list of fonts declared as font-specific special fonts with the +<code class="code">fspecial</code> request, but before the list of fonts declared as global +special fonts with the <code class="code">special</code> request. +</p> +<p>Finally, the <code class="code">schar</code> request defines a global fallback glyph: +<code class="code">gtroff</code> checks for glyphs defined with <code class="code">schar</code> after the list +of fonts declared as global special fonts with the <code class="code">special</code> +request, but before the already mounted special fonts. +</p> +<p>See <a class="xref" href="Character-Classes.html">Character Classes</a>. +</p></dd></dl> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_002erchar"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.rchar</code></strong> <var class="def-var-arguments">c …</var><a class="copiable-link" href='#index-_002erchar'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-rchar"></a> +</dd><dt class="deffnx def-cmd-deffn" id="index-_002erfschar"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.rfschar</code></strong> <var class="def-var-arguments">f c …</var><a class="copiable-link" href='#index-_002erfschar'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-rfschar"></a> +<a class="index-entry-id" id="index-removing-glyph-definition-_0028rchar_002c-rfschar_0029"></a> +<a class="index-entry-id" id="index-glyph_002c-removing-definition-_0028rchar_002c-rfschar_0029"></a> +<a class="index-entry-id" id="index-fallback-glyph_002c-removing-definition-_0028rchar_002c-rfschar_0029"></a> +<p>Remove definition of each ordinary or special character <var class="var">c</var>, +undoing the effect of a <code class="code">char</code>, <code class="code">fchar</code>, or <code class="code">schar</code> +request. Those supplied by font description files cannot be removed. +Spaces and tabs may separate <var class="var">c</var> arguments. +</p> +<p>The request <code class="code">rfschar</code> removes glyph definitions defined with +<code class="code">fschar</code> for font <var class="var">f</var>. +</p></dd></dl> + + +</div> +<hr> +<div class="nav-panel"> +<p> +Next: <a href="Character-Classes.html">Character Classes</a>, Previous: <a href="Font-Positions.html">Font Positions</a>, Up: <a href="Using-Fonts.html">Using Fonts</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Request-Index.html" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html> |