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diff --git a/doc/groff.html.node/Font-Description-File-Format.html b/doc/groff.html.node/Font-Description-File-Format.html new file mode 100644 index 0000000..a44cf20 --- /dev/null +++ b/doc/groff.html.node/Font-Description-File-Format.html @@ -0,0 +1,280 @@ +<!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>Font Description File Format (The GNU Troff Manual)</title> + +<meta name="description" content="Font Description File Format (The GNU Troff Manual)"> +<meta name="keywords" content="Font Description File Format (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="Device-and-Font-Description-Files.html" rel="up" title="Device and Font Description Files"> +<link href="DESC-File-Format.html" rel="prev" title="DESC File Format"> +<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} +--> +</style> + + +</head> + +<body lang="en"> +<div class="subsection-level-extent" id="Font-Description-File-Format"> +<div class="nav-panel"> +<p> +Previous: <a href="DESC-File-Format.html" accesskey="p" rel="prev"><samp class="file">DESC</samp> File Format</a>, Up: <a href="Device-and-Font-Description-Files.html" accesskey="u" rel="up">Device and Font Description Files</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="Font-Description-File-Format-1">6.2.2 Font Description File Format</h4> +<a class="index-entry-id" id="index-font-file_002c-format"></a> +<a class="index-entry-id" id="index-font-description-file_002c-format"></a> +<a class="index-entry-id" id="index-format-of-font-files"></a> +<a class="index-entry-id" id="index-format-of-font-description-files"></a> + +<p>On typesetting output devices, each font is typically available at +multiple sizes. While paper measurements in the device description file +are in absolute units, measurements applicable to fonts must be +proportional to the type size. <code class="code">groff</code> achieves this using the +precedent set by <abbr class="acronym">AT&T</abbr> device-independent <code class="code">troff</code>: one +font size is chosen as a norm, and all others are scaled linearly +relative to that basis. The “unit width” is the number of basic units +per point when the font is rendered at this nominal size. +</p> +<p>For instance, <code class="code">groff</code>’s <code class="code">lbp</code> device uses a <code class="code">unitwidth</code> +of 800. Its Times roman font ‘<samp class="samp">TR</samp>’ has a <code class="code">spacewidth</code> +of 833; this is also the width of its comma, period, centered +period, and mathematical asterisk, while its ‘<samp class="samp">M</samp>’ is 2,963 basic +units. Thus, an ‘<samp class="samp">M</samp>’ on the <code class="code">lbp</code> device is 2,963 basic units +wide at a notional type size of 800 points.<a class="footnote" id="DOCF126" href="groff.html_fot.html#FOOT126"><sup>126</sup></a> +</p> +<p>A font description file has two sections. The first is a sequence of +directives, and is parsed similarly to the <samp class="file">DESC</samp> file described +above. Except for the directive names that begin the second section, +their ordering is immaterial. Later directives of the same name +override earlier ones, spaces and tabs are handled in the same way, +<a class="index-entry-id" id="index-comments-in-font-description-files"></a> +<a class="index-entry-id" id="index-font-description-files_002c-comments"></a> +<a class="index-entry-id" id="index-_0023-1"></a> +and the same comment syntax is supported. Empty lines are ignored +throughout. +</p> +<dl class="table"> +<dt id='index-name'><span><code class="code">name <var class="var">f</var></code><a class="copiable-link" href='#index-name'> ¶</a></span></dt> +<dd><p>The name of the font is <var class="var">f</var>. ‘<samp class="samp">DESC</samp>’ is an invalid font +name. Simple integers are valid, but their use is +discouraged.<a class="footnote" id="DOCF127" href="groff.html_fot.html#FOOT127"><sup>127</sup></a> +</p> +</dd> +<dt id='index-spacewidth'><span><code class="code">spacewidth <var class="var">n</var></code><a class="copiable-link" href='#index-spacewidth'> ¶</a></span></dt> +<dd><p>The width of an unadjusted inter-word space is <var class="var">n</var> basic units. +</p></dd> +</dl> + +<p>The directives above must appear in the first section; those below are +optional. +</p> +<dl class="table"> +<dt id='index-slant'><span><code class="code">slant <var class="var">n</var></code><a class="copiable-link" href='#index-slant'> ¶</a></span></dt> +<dd><p>The font’s glyphs have a slant of <var class="var">n</var> degrees; a positive +<var class="var">n</var> slants in the direction of text flow. +</p> +</dd> +<dt id='index-ligatures'><span><code class="code">ligatures <var class="var">lig1</var> <span class="r">…</span> <var class="var">lign</var> <span class="r">[</span>0<span class="r">]</span></code><a class="copiable-link" href='#index-ligatures'> ¶</a></span></dt> +<dd><p>Glyphs <var class="var">lig1</var>, …, <var class="var">lign</var> are ligatures; possible ligatures +are ‘<samp class="samp">ff</samp>’, ‘<samp class="samp">fi</samp>’, ‘<samp class="samp">fl</samp>’, ‘<samp class="samp">ffi</samp>’ and ‘<samp class="samp">ffl</samp>’. For +compatibility with other <code class="code">troff</code> implementations, the list of +ligatures may be terminated with a <code class="code">0</code>. The list of ligatures +must not extend over more than one line. +</p> +</dd> +<dt id='index-special-fonts-2'><span><code class="code">special</code><a class="copiable-link" href='#index-special-fonts-2'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-special-1"></a> +<p>The font is <em class="dfn">special</em>: when a glyph is requested that is not present +in the current font, it is sought in any mounted fonts that bear this +property. +</p></dd> +</dl> + +<p>Other directives in this section are ignored by GNU <code class="code">troff</code>, but +may be used by postprocessors to obtain further information about the +font. +</p> +<p>The second section contains one or two subsections. These can appear in +either order; the first one encountered commences the second section. +Each starts with a directive on a line by itself. A <code class="code">charset</code> +subsection is mandatory unless the associated <samp class="file">DESC</samp> file contains +the <code class="code">unicode</code> directive. Another subsection, <code class="code">kernpairs</code>, +is optional. +</p> +<a class="index-entry-id" id="index-charset-1"></a> +<p>The directive <code class="code">charset</code> starts the character set +subsection.<a class="footnote" id="DOCF128" href="groff.html_fot.html#FOOT128"><sup>128</sup></a> It precedes a series +of glyph descriptions, one per line. Each such glyph description +comprises a set of fields separated by spaces or tabs and organized as +follows. +</p> +<blockquote class="quotation"> +<p><var class="var">name</var> <var class="var">metrics</var> <var class="var">type</var> <var class="var">code</var> [<var class="var">entity-name</var>] +[<code class="code">--</code> <var class="var">comment</var>] +</p></blockquote> + +<a class="index-entry-id" id="index-8_002dbit-input"></a> +<a class="index-entry-id" id="index-input_002c-8_002dbit"></a> +<a class="index-entry-id" id="index-accessing-unnamed-glyphs-with-_005cN"></a> +<a class="index-entry-id" id="index-unnamed-glyphs_002c-accessing-with-_005cN"></a> +<a class="index-entry-id" id="index-characters_002c-unnamed_002c-accessing-with-_005cN"></a> +<a class="index-entry-id" id="index-glyphs_002c-unnamed_002c-accessing-with-_005cN"></a> +<a class="index-entry-id" id="index-_002d_002d_002d"></a> +<p><var class="var">name</var> identifies the glyph: +if <var class="var">name</var> is a printable character <var class="var">c</var>, it corresponds to +the <code class="code">troff</code> ordinary character <var class="var">c</var>. If <var class="var">name</var> is a +multi-character sequence not beginning with <code class="code">\</code>, it corresponds to +the GNU <code class="code">troff</code> special character escape sequence +‘<samp class="samp">\[<var class="var">name</var>]</samp>’. A name consisting of three minus signs, +‘<samp class="samp">---</samp>’, is special and indicates that the glyph is unnamed: such +glyphs can be accessed only by the <code class="code">\N</code> escape sequence in +<code class="code">troff</code>. A special character named ‘<samp class="samp">---</samp>’ can still be defined +using <code class="code">char</code> and similar requests. The <var class="var">name</var> ‘<samp class="samp">\-</samp>’ +defines the minus sign glyph. Finally, <var class="var">name</var> can be the +unbreakable one-sixth and one-twelfth space escape sequences, <code class="code">\|</code> +and <code class="code">\^</code> (“thin” and “hair” spaces, respectively), in which +case only the width metric described below is interpreted; a font can +thus customize the widths of these spaces. +</p> +<p>The form of the <var class="var">metrics</var> field is as follows. +</p> +<div class="display"> +<div class="group"><pre class="display-preformatted"><var class="var">width</var>[<code class="code">,</code>[<var class="var">height</var>[<code class="code">,</code>[<var class="var">depth</var>[<code class="code">,</code>[<var class="var">italic-correction</var> + [<code class="code">,</code>[<var class="var">left-italic-correction</var>[<code class="code">,</code>[<var class="var">subscript-correction</var>]]]]]]]]]] +</pre></div></div> + +<p>There must not be any spaces, tabs, or newlines between these +<em class="dfn">subfields</em> (which have been split here into two lines only for +better legibility). The subfields are in basic units expressed as +decimal integers. Unspecified subfields default to <code class="code">0</code>. +Since there is no associated binary format, these values are not +required to fit into the C language data type ‘<samp class="samp">char</samp>’ as they are in +<abbr class="acronym">AT&T</abbr> device-independent <code class="code">troff</code>. +</p> +<p>The <var class="var">width</var> subfield gives the width of the glyph. The <var class="var">height</var> +subfield gives the height of the glyph (upward is positive); if a glyph +does not extend above the baseline, it should be given a zero height, +rather than a negative height. The <var class="var">depth</var> subfield gives the depth +of the glyph, that is, the distance below the baseline to which the +glyph extends (downward is positive); if a glyph does not extend below +the baseline, it should be given a zero depth, rather than a negative +depth. Italic corrections are relevant to glyphs in italic or oblique +styles. The <var class="var">italic-correction</var> is the amount of space that should +be added after an oblique glyph to be followed immediately by an upright +glyph. The <var class="var">left-italic-correction</var> is the amount of space that +should be added before an oblique glyph to be preceded immediately by an +upright glyph. The <var class="var">subscript-correction</var> is the amount of space +that should be added after an oblique glyph to be followed by a +subscript; it should be less than the italic correction. +</p> +<p>For fonts used with typesetting devices, the <var class="var">type</var> field gives a +featural description of the glyph: it is a bit mask recording whether +the glyph is an ascender, descender, both, or neither. When a <code class="code">\w</code> +escape sequence is interpolated, these values are bitwise or-ed +together for each glyph and stored in the <code class="code">nr</code> register. In font +descriptions for terminal devices, all glyphs might have a type of zero, +regardless of their appearance. +</p> +<dl class="table"> +<dt><code class="code">0</code></dt> +<dd><p>means the glyph lies entirely between the baseline and a horizontal line +at the “x-height” of the font; typical examples are ‘<samp class="samp">a</samp>’, +‘<samp class="samp">c</samp>’, and ‘<samp class="samp">x</samp>’; +</p> +</dd> +<dt><code class="code">1</code></dt> +<dd><p>means the glyph descends below the baseline, like ‘<samp class="samp">p</samp>’; +</p> +</dd> +<dt><code class="code">2</code></dt> +<dd><p>means the glyph ascends above the font’s x-height, like ‘<samp class="samp">A</samp>’ or +‘<samp class="samp">b</samp>’; and +</p> +</dd> +<dt><code class="code">3</code></dt> +<dd><p>means the glyph is both an ascender and a descender—this is true of +parentheses in some fonts. +</p></dd> +</dl> + +<p>The <var class="var">code</var> field gives a numeric identifier that the postprocessor +uses to render the glyph. The glyph can be specified to <code class="code">troff</code> +using this code by means of the <code class="code">\N</code> escape sequence. <var class="var">code</var> +can be any integer.<a class="footnote" id="DOCF129" href="groff.html_fot.html#FOOT129"><sup>129</sup></a> +</p> +<p>The <var class="var">entity-name</var> field defines an identifier for the glyph that the +postprocessor uses to print the GNU <code class="code">troff</code> glyph <var class="var">name</var>. This +field is optional; it was introduced so that the <code class="code">grohtml</code> output +driver could encode its character set. For example, the glyph +‘<samp class="samp">\[Po]</samp>’ is represented by ‘<samp class="samp">&pound;</samp>’ in <abbr class="acronym">HTML</abbr> 4.0. +For efficiency, these data are now compiled directly into +<code class="code">grohtml</code>. <code class="code">grops</code> uses the field to build sub-encoding +arrays for PostScript fonts containing more than 256 glyphs. Anything +on the line after the <var class="var">entity-name</var> field or ‘<samp class="samp">--</samp>’ is ignored. +</p> +<p>A line in the <code class="code">charset</code> section can also have the form +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted"><var class="var">name</var> " +</pre></div></div> + +<p>identifying <var class="var">name</var> as another name for the glyph mentioned in the +preceding line. Such aliases can be chained. +</p> +<a class="index-entry-id" id="index-kernpairs"></a> +<p>The directive <code class="code">kernpairs</code> starts a list of kerning adjustments to +be made to adjacent glyph pairs from this font. It contains a sequence +of lines formatted as follows. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted"><var class="var">g1</var> <var class="var">g2</var> <var class="var">n</var> +</pre></div></div> + +<p>The foregoing means that when glyph <var class="var">g1</var> is typeset immediately +before <var class="var">g2</var>, the space between them should be increased +by <var class="var">n</var>. Most kerning pairs should have a negative value +for <var class="var">n</var>. +</p> + + + + +</div> +<hr> +<div class="nav-panel"> +<p> +Previous: <a href="DESC-File-Format.html"><samp class="file">DESC</samp> File Format</a>, Up: <a href="Device-and-Font-Description-Files.html">Device and Font Description Files</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> |