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<title>Using Symbols (The GNU Troff Manual)</title>
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<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>
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<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>
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