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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><html lang="en"><HEAD><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><TITLE>Appendix C: Implementation and performance notes</TITLE><link rel="stylesheet" href="style/default.css" type="text/css"><link rel="prev" href="changes.html"><link rel="next" href="grammar.html"><link rel="contents" href="cover.html#minitoc"><link rel="CSS-properties" href="propidx.html" title="properties"><link rel="index" href="indexlist.html" title="index"></HEAD><BODY><div class="navbar" align="center"><p><a href="changes.html">previous</a> <a href="grammar.html">next</a> <a href="cover.html#minitoc">contents</a> <a href="propidx.html">properties</a> <a href="indexlist.html">index</a> </div><hr class="navbar"><H1 align="center">Appendix C. Implementation and performancenotes for fonts</H1><div class="subtoc"><p><strong>Contents</strong> <ul class="toc"> <li class="tocline2"><a href="notes.html#q1" class="tocxref">C.1 Glossary of font terms</a> <li class="tocline2"><a href="notes.html#coneg" class="tocxref">C.2 Font retrieval</a> <li class="tocline2"><a href="notes.html#panose" class="tocxref">C.3 Meaning of the Panose Digits</a> <li class="tocline2"><a href="notes.html#truetype-unicode" class="tocxref">C.4 Deducing Unicode Ranges for TrueType</a> <li class="tocline2"><a href="notes.html#autodescgen" class="tocxref">C.5 Automatic descriptor generation</a> </ul></div><P><em>This appendix is informative, not normative.</em></P><H2><a name="q1">C.1 Glossary of font terms</a></H2><dl><DT><a name="definingDocLock"><b>DocLock™</b></a><dd>Bitstream's <i>DocLock™</i> technology ensures that TrueDocPFRs can only be used with the site they are published for. A TrueDocPFR moved to a different site or referenced from another site will notwork.<dt><a name="definingDSIG"><b>Digital Signature</b></a><dd>Part of a trust management technology, used to provide signedassertions about a resource. <dt><a name="definingFontCaching"></A><b>Font Caching</b></dt><dd><i>Font caching</i> allows for a temporary copy of fonts on the clientsystem. They are often stored on disk with other cached items such asgraphics specifically for the UA.</dd><DT><a name="definingFontFace"><b>Font Face</b></A><DD>A "handle" that refers to a specific face of a font, excludingthe font size.<dt><a name="definingFontMatching"></A><b>Font Matching</b></dt><dd><i>Font matching</i> is a process of selecting a similar font basedon using one or more attributes of the primary font. Common attribute includeserif, sans-serif, weight, cap height, x-height, spacing, language, andposture. Font matching is dependent on the algorithm and the variety ofcandidate fonts.</dd><dt><a name="definingSubsetting"></A><b>Glyph Representation Sub-setting</b></dt><dd><i>Glyph Representation sub-setting</i> is the process by whichunwanted glyph representations (together with their side bearings andkerning information) are removed from a primary font to produce asmaller subset font that covers a particular document or set ofdocuments. This is a particular win for documents that use ideographicscripts, where the glyph complement of the base font can be verylarge. Glyph representation sub-setting for documents using scriptsthat require ligatures, such as Arabic, is difficult without knowingthe ligature formation rules of the final display system.</dd><dt><a name="definingIntellifont"><b>Intellifont</b></a><dd>Intellifont technology was developed by Agfa and is the nativeformat for Hewlett-Packard and other printers that use the PCL5language. It is also the native font format on the Amigacomputers.<dt><a name="defininginfinifont"><b>Infinifont</b></a><dd>A font synthesis technique which, given a Panose-1 number (and,optionally, additional font description data) can generate a faux fontwithout extrapolating from a single master outline or interpolatingbetween two or more outlines (see <a href="refs.html#ref-INFINIFONT" rel="biblioentry" class="noxref"><span class="informref">[INFINIFONT]</span></a>).<dt><a name="definingItalic"><b>Italic</b></a><dd>A class of letter forms for Latin scripts, that are more cursivethan roman letter forms but less so than script forms. Often, a pair offonts are designed to be used together; one is a serifed roman and oneis italic. Other terms to describe this class of letter forms includecursive and, for Cyrillic scripts, kursiv. For sans-serif faces, thecompanion face is often a slanted or oblique variant rather than adifferent class of letter form.<br><P><img src="./images/italic-40.gif" alt="Italic forms"><SPAN class="dlink"> <A name="img-italic-40" href="images/longdesc/italic-40-desc.html" title="Long description for italic forms">[D]</A></SPAN></p><dt><a name="definingKern"><b>Kerning</b></a><dd>Altering the spacing between selected glyph representations, whichwould otherwise appear to be too close or too far apart, to obtain amore even typographical color.<p><img src="./images/kern-22.gif" alt="Illustration of kerning"><SPAN class="dlink"> <A name="img-kern-22" href="images/longdesc/kern-22-desc.html" title="Long description for kerning">[D]</A></SPAN></p><dt><a name="definingMultiMaster"></A><b>Multiple Master Font</b></dt><dd>A <i>Multiple Master Font</i> contain two primary fonts that are usedwith special rendering software to provide an interpolated result. AdobeSystems provides a mechanism that allows for parameters to be used to controlthe output or the interpolated output font. These parameters generally describethe characteristics of an original font and the multiple master resultis referred to as a "synthesized font."</dd><dt><a name="definingOpenType"><b> Open Type</b></a><dd>Open Type is an extension to the TrueType font format thatcontains additional information that extends the capabilities of thefonts to support high-quality international typography. Open Type canassociate a single character with multiple glyph representations, andcombinations of characters with a single glyph representation(ligature formation). Open Type includes two-dimensional informationto support features for complex positioning and glyph attachment.TrueType Open and OpenType contain explicit script and languageinformation, so a text-processing application can adjust its behavioraccordingly (see <a href="refs.html#ref-OPENTYPE" rel="biblioentry" class="noxref"><span class="informref">[OPENTYPE]</span></a>).<dt><a name="definingServerFont"></A><b>Server Font</b></dt><dd>A <i>Server Font</i> is a font resource located on the web serverthat is referenced by the WebFont definition. The user agent may usethis resource for rendering the page.</dd><dt><a name="definingSpeedo"><b>Speedo</b></a><dd><i>Speedo</i> font technology was developed by Bitstream and isthe native font format on the Atari ST and Falcon computers. It isalso used by computers running the X window system.<dt><a name="definingTrueDoc"></A><b>TrueDoc</b></dt><dd><i>TrueDoc</i> technology was developed by Bitstream for thecreation, transport, and imaging of platform independent scalablefont objects on the web. Creation of font objects is done by theTrueDoc character shape recorder (CSR) and the rendering of the fontobjects is done by TrueDoc's character shape player (CSP). Thetechnology is intended to be used on the web for viewing andprinting.</dd><dt><a name="definingTrueDocPFR"></A><b>TrueDoc Portable Font Resource</b></dt><dd>A <i>TrueDoc Portable font resource</i> (or, <b>PFR</b>) is aplatform-independent scalable font object that is produced by acharacter shape player. Input may be either TrueType or Type 1 of anyflavor on either Windows, Mac, or Unix. TrueDoc Portable FontResources provide good compression ratios, are platformindependent, and because they are not in an native font format(TrueType or Type 1) they can not be easily installed.</dd><dt><a name="definingTT"></A><b>TrueType</b></dt><dd><i>TrueType </i> is a font format developed by Apple and licensedto Microsoft. TrueType is the native operating system font format forWindows and Macintosh. TrueType contains a hierarchical set of tablesand glyph representations. Characters can be hinted on a percharacter and point size basis yielding excellent quality at screenresolutions. TrueType fonts for Windows and Mac have few differences,though they can be different enough to prevent cross platformusage. </dd><dt><a name="definingTTC"></A><b>TrueType Collection</b></dt><dd>A <i>TrueType Collection</i> (or <b>TTC</b>) is an extension tothe TrueType format that includes tables that allow for multipleTrueType fonts to be contained within a single TrueType font file.TrueType collection files are relatively rare at this time. </dd><dt><a name="definingTTGX"></A><b>TrueType GX Fonts</b></dt><dd><i>TrueType GX Fonts</i> contain extensions to the standardTrueType format that allow for mutable fonts, similar to MultipleMaster fonts. There may be several mutation axis such as weight,height, and slant. The axis can be defined to obtain almost anyeffect. TrueType GX can also supports alternate glyph representationsubstitution for ligatures, contextual forms, fractions, etc. To date,TrueType GX is available only on the Mac (see <a href="refs.html#ref-TRUETYPEGX" rel="biblioentry" class="noxref"><span class="informref">[TRUETYPEGX]</span></a>).<dt><a name="definingT1"></A><b>Type 1 font</b></dt><dd><i>Type 1 fonts</i>, developed by Adobe Systems, were one of firstscalable formats available. Type 1 fonts generally contain 228characters with the glyph representations described using third degreebezier curves. Mac, Windows, and X have similar but separate formats;Adobe provides Adobe Type Manager for all three platforms. Type1c is amore recent losslessly-compressed storage form for Type 1 glyphrepresentations.</dd><dt><a name="definingURIbound"><b>URI Binding</b></a><dd>A process of locking a particular font resource to a given Website by embedding an encrypted URI or a digitally signed usageassertion into the font resource.</dl><h2>C.2 <a name=coneg>Font retrieval</a></h2><p>There are many different font formats in use by many differentplatforms. To select a preferred font format, transparent contentnegotiation is used (see <a href="refs.html#ref-NEGOT" rel="biblioentry" class="noxref"><span class="informref">[NEGOT]</span></a>). It is always possible totell when a font is being dereferenced, because the URI is inside afont description. A given implementation will know which downloadable font formats it supports and can thus use the format hint to avoid downloading fonts in an unsupported format.<h2>C.3 <a name="panose">Meaning of the Panose Digits</a></h2><p><img src="./images/panose-16.gif" alt="Illustration of Panose-1"><SPAN class="dlink"> <A name="img-panose-16" href="images/longdesc/panose-16-desc.html" title="Long description for screen shot of Windows 95 font description GUI">[D]</A></SPAN></p><p>The Family, Serif Style and Proportion numbers are used byWindows95 for font selection and matching.<p>The meaning of the ten numbers and the allowable values (given inparentheses) are given below for the most common case, where the "family" digit is <tt>2, Text and Display</tt>. (If the first digit has a different value, the remaining nine digits have different meanings). For further details on Panose-1, see <a href="refs.html#ref-PANOSE" rel="biblioentry" class="noxref"><span class="informref">[PANOSE]</span></a>.<dl><dt>Family<dd><ul><li>Any (0)<li>No Fit (1)<li><a href="refs.html#ref-PANOSE" rel="biblioentry" class="noxref"><span class="informref">[PANOSE]</span></a> <b>Latin Text and Display</b> (2)<li><a href="refs.html#ref-PANOSE" rel="biblioentry" class="noxref"><span class="informref">[PANOSE]</span></a> <b>Latin Script</b> (3)<li><a href="refs.html#ref-PANOSE" rel="biblioentry" class="noxref"><span class="informref">[PANOSE]</span></a> <b>Latin Decorative</b> (4)<li><a href="refs.html#ref-PANOSE" rel="biblioentry" class="noxref"><span class="informref">[PANOSE]</span></a> <b>Latin Pictorial</b> (5)</ul><dt>Serif Style<dd><ul><li>Any (0)<li>No Fit (1)<li>Cove (2)<li>Obtuse Cove (3)<li>Square Cove (4)<li>Obtuse Square Cove (5)<li>Square (6)<li>Thin (7)<li>Bone (8)<li>Exaggerated (9)<li>Triangle (10)<li>Normal Sans (11)<li>Obtuse Sans (12)<li>Perp Sans (13)<li>Flared (14)<li>Rounded (15)</ul><dt>Weight<dd><ul><li>Any (0)<li>No Fit (1)<li>Very Light (2)[100]<li>Light (3) [200]<li>Thin (4) [300]<li>Book (5) [400] <i>same as CSS1 'normal'</i><li>Medium (6) [500]<li>Demi (7) [600]<li>Bold (8) [700] <i>same as CSS1 'bold'</i><li>Heavy (9) [800]<li>Black (10) [900]<li>Extra Black / Nord (11) [900] <i>force mapping to CSS1 100-900 scale</i></ul><dt>Proportion<dd><ul><li>Any (0)<li>No Fit (1)⌨️ 快捷键说明
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