CINXE.COM
Unit 18 | Graphite
<!DOCTYPE html> <html lang="en-US"> <head> <meta charset="UTF-8"> <meta http-equiv="X-UA-Compatible" content="IE=Edge"> <link rel="stylesheet" href="/assets/css/just-the-docs-default.css"> <script src="/assets/js/vendor/lunr.min.js"></script> <script src="/assets/js/just-the-docs.js"></script> <meta name="viewport" content="width=device-width, initial-scale=1"> <link rel="icon" href="/assets/images/favicon.ico" type="image/x-icon"> <!-- Begin Jekyll SEO tag v2.8.0 --> <title>Unit 18 | Graphite</title> <meta name="generator" content="Jekyll v4.3.2" /> <meta property="og:title" content="Unit 18" /> <meta property="og:locale" content="en_US" /> <meta name="description" content="Site for Graphite" /> <meta property="og:description" content="Site for Graphite" /> <link rel="canonical" href="https://silnrsi.github.io/graphite/tutorial/graide_tutorial18.html" /> <meta property="og:url" content="https://silnrsi.github.io/graphite/tutorial/graide_tutorial18.html" /> <meta property="og:site_name" content="Graphite" /> <meta property="og:type" content="website" /> <meta name="twitter:card" content="summary" /> <meta property="twitter:title" content="Unit 18" /> <script type="application/ld+json"> {"@context":"https://schema.org","@type":"WebPage","description":"Site for Graphite","headline":"Unit 18","url":"https://silnrsi.github.io/graphite/tutorial/graide_tutorial18.html"}</script> <!-- End Jekyll SEO tag --> </head> <body> <a class="skip-to-main" href="#main-content">Skip to main content</a> <svg xmlns="http://www.w3.org/2000/svg" class="d-none"> <symbol id="svg-link" viewBox="0 0 24 24"> <title>Link</title> <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="feather feather-link"> <path d="M10 13a5 5 0 0 0 7.54.54l3-3a5 5 0 0 0-7.07-7.07l-1.72 1.71"></path><path d="M14 11a5 5 0 0 0-7.54-.54l-3 3a5 5 0 0 0 7.07 7.07l1.71-1.71"></path> </svg> </symbol> <symbol id="svg-menu" viewBox="0 0 24 24"> <title>Menu</title> <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="feather feather-menu"> <line x1="3" y1="12" x2="21" y2="12"></line><line x1="3" y1="6" x2="21" y2="6"></line><line x1="3" y1="18" x2="21" y2="18"></line> </svg> </symbol> <symbol id="svg-arrow-right" viewBox="0 0 24 24"> <title>Expand</title> <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="feather feather-chevron-right"> <polyline points="9 18 15 12 9 6"></polyline> </svg> </symbol> <!-- Feather. MIT License: https://github.com/feathericons/feather/blob/master/LICENSE --> <symbol id="svg-external-link" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="feather feather-external-link"> <title id="svg-external-link-title">(external link)</title> <path d="M18 13v6a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2V8a2 2 0 0 1 2-2h6"></path><polyline points="15 3 21 3 21 9"></polyline><line x1="10" y1="14" x2="21" y2="3"></line> </symbol> <symbol id="svg-doc" viewBox="0 0 24 24"> <title>Document</title> <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="feather feather-file"> <path d="M13 2H6a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h12a2 2 0 0 0 2-2V9z"></path><polyline points="13 2 13 9 20 9"></polyline> </svg> </symbol> <symbol id="svg-search" viewBox="0 0 24 24"> <title>Search</title> <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="feather feather-search"> <circle cx="11" cy="11" r="8"></circle><line x1="21" y1="21" x2="16.65" y2="16.65"></line> </svg> </symbol> <!-- Bootstrap Icons. MIT License: https://github.com/twbs/icons/blob/main/LICENSE.md --> <symbol id="svg-copy" viewBox="0 0 16 16"> <title>Copy</title> <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="bi bi-clipboard" viewBox="0 0 16 16"> <path d="M4 1.5H3a2 2 0 0 0-2 2V14a2 2 0 0 0 2 2h10a2 2 0 0 0 2-2V3.5a2 2 0 0 0-2-2h-1v1h1a1 1 0 0 1 1 1V14a1 1 0 0 1-1 1H3a1 1 0 0 1-1-1V3.5a1 1 0 0 1 1-1h1v-1z"/> <path d="M9.5 1a.5.5 0 0 1 .5.5v1a.5.5 0 0 1-.5.5h-3a.5.5 0 0 1-.5-.5v-1a.5.5 0 0 1 .5-.5h3zm-3-1A1.5 1.5 0 0 0 5 1.5v1A1.5 1.5 0 0 0 6.5 4h3A1.5 1.5 0 0 0 11 2.5v-1A1.5 1.5 0 0 0 9.5 0h-3z"/> </svg> </symbol> <symbol id="svg-copied" viewBox="0 0 16 16"> <title>Copied</title> <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="bi bi-clipboard-check-fill" viewBox="0 0 16 16"> <path d="M6.5 0A1.5 1.5 0 0 0 5 1.5v1A1.5 1.5 0 0 0 6.5 4h3A1.5 1.5 0 0 0 11 2.5v-1A1.5 1.5 0 0 0 9.5 0h-3Zm3 1a.5.5 0 0 1 .5.5v1a.5.5 0 0 1-.5.5h-3a.5.5 0 0 1-.5-.5v-1a.5.5 0 0 1 .5-.5h3Z"/> <path d="M4 1.5H3a2 2 0 0 0-2 2V14a2 2 0 0 0 2 2h10a2 2 0 0 0 2-2V3.5a2 2 0 0 0-2-2h-1v1A2.5 2.5 0 0 1 9.5 5h-3A2.5 2.5 0 0 1 4 2.5v-1Zm6.854 7.354-3 3a.5.5 0 0 1-.708 0l-1.5-1.5a.5.5 0 0 1 .708-.708L7.5 10.793l2.646-2.647a.5.5 0 0 1 .708.708Z"/> </svg> </symbol> </svg> <div class="side-bar"> <div class="site-header" role="banner"> <a href="/" class="site-title lh-tight"> Graphite </a> <button id="menu-button" class="site-button btn-reset" aria-label="Toggle menu" aria-pressed="false"> <svg viewBox="0 0 24 24" class="icon" aria-hidden="true"><use xlink:href="#svg-menu"></use></svg> </a> </div> <nav aria-label="Main" id="site-nav" class="site-nav"> <ul class="nav-list"><li class="nav-list-item"><a href="/" class="nav-list-link">Home</a></li><li class="nav-list-item"><button class="nav-list-expander btn-reset" aria-label="toggle items in About Graphite category" aria-pressed="false"> <svg viewBox="0 0 24 24" aria-hidden="true"><use xlink:href="#svg-arrow-right"></use></svg> </button><a href="/graphite_about.html" class="nav-list-link">About Graphite</a><ul class="nav-list"><li class="nav-list-item "><a href="/graphite_aboutWhy.html" class="nav-list-link">Why was Graphite developed?</a></li><li class="nav-list-item "><button class="nav-list-expander btn-reset" aria-label="toggle items in Graphite and OpenType category" aria-pressed="false"> <svg viewBox="0 0 24 24" aria-hidden="true"><use xlink:href="#svg-arrow-right"></use></svg> </button><a href="/graphite_aboutOT.html" class="nav-list-link">Graphite and OpenType</a><ul class="nav-list"><li class="nav-list-item "> <a href="/graphite_otcompare.html" class="nav-list-link">Comparison of OpenType and Graphite shaping speeds in a Nastaliq context</a> </li></ul></li><li class="nav-list-item "><a href="/graphite_techAbout.html" class="nav-list-link">Graphite technical overview</a></li></ul></li><li class="nav-list-item"><a href="/graphite_news.html" class="nav-list-link">News</a></li><li class="nav-list-item"><button class="nav-list-expander btn-reset" aria-label="toggle items in Using Graphite category" aria-pressed="false"> <svg viewBox="0 0 24 24" aria-hidden="true"><use xlink:href="#svg-arrow-right"></use></svg> </button><a href="/graphite_appsParent.html" class="nav-list-link">Using Graphite</a><ul class="nav-list"><li class="nav-list-item "><a href="/graphite_apps.html" class="nav-list-link">Applications that support Graphite</a></li><li class="nav-list-item "><a href="/graphite_firefox.html" class="nav-list-link">Graphite and Firefox</a></li><li class="nav-list-item "><a href="/graphite_fontdemo.html" class="nav-list-link">Graphite Font Demo</a></li><li class="nav-list-item "><a href="/graphite_fonts.html" class="nav-list-link">Graphite-enabled Fonts</a></li></ul></li><li class="nav-list-item active"><button class="nav-list-expander btn-reset" aria-label="toggle items in Developers category" aria-pressed="true"> <svg viewBox="0 0 24 24" aria-hidden="true"><use xlink:href="#svg-arrow-right"></use></svg> </button><a href="/graphite_dev.html" class="nav-list-link">Developers</a><ul class="nav-list"><li class="nav-list-item "><a href="/graphite_devFont.html" class="nav-list-link">Font Development</a></li><li class="nav-list-item "><a href="/graide.html" class="nav-list-link">Graide</a></li><li class="nav-list-item active"><button class="nav-list-expander btn-reset" aria-label="toggle items in Graphite Tutorial category" aria-pressed="true"> <svg viewBox="0 0 24 24" aria-hidden="true"><use xlink:href="#svg-arrow-right"></use></svg> </button><a href="/graide_tutorial.html" class="nav-list-link">Graphite Tutorial</a><ul class="nav-list"><li class="nav-list-item "> <a href="/tutorial/graide_tutorial1.html" class="nav-list-link">Unit 1</a> </li><li class="nav-list-item "> <a href="/tutorial/graide_tutorial2.html" class="nav-list-link">Unit 2</a> </li><li class="nav-list-item "> <a href="/tutorial/graide_tutorial3.html" class="nav-list-link">Unit 3</a> </li><li class="nav-list-item "> <a href="/tutorial/graide_tutorial4.html" class="nav-list-link">Unit 4</a> </li><li class="nav-list-item "> <a href="/tutorial/graide_tutorial5.html" class="nav-list-link">Unit 5</a> </li><li class="nav-list-item "> <a href="/tutorial/graide_tutorial6.html" class="nav-list-link">Unit 6</a> </li><li class="nav-list-item "> <a href="/tutorial/graide_tutorial7.html" class="nav-list-link">Unit 7</a> </li><li class="nav-list-item "> <a href="/tutorial/graide_tutorial8.html" class="nav-list-link">Unit 8</a> </li><li class="nav-list-item "> <a href="/tutorial/graide_tutorial8a.html" class="nav-list-link">Intermission</a> </li><li class="nav-list-item "> <a href="/tutorial/graide_tutorial9.html" class="nav-list-link">Unit 9</a> </li><li class="nav-list-item "> <a href="/tutorial/graide_tutorial10.html" class="nav-list-link">Unit 10</a> </li><li class="nav-list-item "> <a href="/tutorial/graide_tutorial11.html" class="nav-list-link">Unit 11</a> </li><li class="nav-list-item "> <a href="/tutorial/graide_tutorial12.html" class="nav-list-link">Unit 12</a> </li><li class="nav-list-item "> <a href="/tutorial/graide_tutorial13.html" class="nav-list-link">Unit 13</a> </li><li class="nav-list-item "> <a href="/tutorial/graide_tutorial14.html" class="nav-list-link">Unit 14</a> </li><li class="nav-list-item "> <a href="/tutorial/graide_tutorial15.html" class="nav-list-link">Unit 15</a> </li><li class="nav-list-item "> <a href="/tutorial/graide_tutorial16.html" class="nav-list-link">Unit 16</a> </li><li class="nav-list-item "> <a href="/tutorial/graide_tutorial17.html" class="nav-list-link">Unit 17</a> </li><li class="nav-list-item active"> <a href="/tutorial/graide_tutorial18.html" class="nav-list-link active">Unit 18</a> </li><li class="nav-list-item "> <a href="/tutorial/graide_tutorial_end.html" class="nav-list-link">Conclusion</a> </li><li class="nav-list-item "> <a href="/tutorial/graphite_tut_solutions.html" class="nav-list-link">Solutions to Tutorial Exercises</a> </li></ul></li><li class="nav-list-item "><a href="/graphite_codeSnippets.html" class="nav-list-link">GDL Code Snippets</a></li><li class="nav-list-item "><a href="/graphite_devApp.html" class="nav-list-link">Adding Graphite to Your Application</a></li></ul></li><li class="nav-list-item"><a href="/graphite_download.html" class="nav-list-link">Download</a></li><li class="nav-list-item"><a href="/graphite_support.html" class="nav-list-link">Support</a></li><li class="nav-list-item"><a href="/graphite_contact.html" class="nav-list-link">Contact</a></li></ul> </nav> <footer class="site-footer"> This site uses <a href="https://github.com/just-the-docs/just-the-docs">Just the Docs</a>, a documentation theme for Jekyll. </footer> </div> <div class="main" id="top"> <div id="main-header" class="main-header"> <div class="search" role="search"> <div class="search-input-wrap"> <input type="text" id="search-input" class="search-input" tabindex="0" placeholder="Search Graphite site" aria-label="Search Graphite site" autocomplete="off"> <label for="search-input" class="search-label"><svg viewBox="0 0 24 24" class="search-icon"><use xlink:href="#svg-search"></use></svg></label> </div> <div id="search-results" class="search-results"></div> </div> <nav aria-label="Auxiliary" class="aux-nav"> <ul class="aux-nav-list"> <li class="aux-nav-list-item"> <a href="https://github.com/silnrsi/graphite" class="site-button" > Repository </a> </li> </ul> </nav> </div> <div id="main-content-wrap" class="main-content-wrap"> <nav aria-label="Breadcrumb" class="breadcrumb-nav"> <ol class="breadcrumb-nav-list"> <li class="breadcrumb-nav-list-item"><a href="/graphite_dev.html">Developers</a></li> <li class="breadcrumb-nav-list-item"><a href="/graide_tutorial.html">Graphite Tutorial</a></li> <li class="breadcrumb-nav-list-item"><span>Unit 18</span></li> </ol> </nav> <div id="main-content" class="main-content"> <main> <div class="table-wrapper"><table class="tut-nav-bar"> <tbody> <tr> <td><a href="graide_tutorial17">◀ Unit 17: Optional items</a></td> <td><a href="../graide_tutorial#contents">▲ Contents</a></td> <td><a href="graide_tutorial_end">Conclusion ▶</a></td> </tr> </tbody> </table></div> <h1 id="unit-18-corresponding-classes-revisited"> <a href="#unit-18-corresponding-classes-revisited" class="anchor-heading" aria-labelledby="unit-18-corresponding-classes-revisited"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Unit 18: Corresponding classes revisited </h1> <p><a href="graide_tutorial18#exercise-18">Exercise</a></p> <h2 id="discussion"> <a href="#discussion" class="anchor-heading" aria-labelledby="discussion"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Discussion </h2> <p>In Unit 4 we saw that Graphite uses the mechanism of corresponding classes to select glyphs for output. In other words, the members of the input and output classes are assumed to correspond, and the glyph to be output is the one that is at the same position within the output class as the input glyph is within the input class.</p> <p>This idea can be extended to glyphs that are in different slots in the rule. The dollar sign ($) followed by a slot number indicates which slot in the input is to be used for the purposes of determining the relevant item position.</p> <p>For instance, suppose in your font you have different versions of a certain lower diacritic depending on whether it is to be positioned below a base glyph with a descender or without. We can use the corresponding-class approach by creating two classes of glyphs, one containing the list of base glyphs and another containing the corresponding diacritics.</p> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>table(glyph) clsBase = unicode(0x61..0x7a); clsDiacPositioned = (gNormal, gNormal, gNormal, // abc gNormal, gNormal, gNormal, gLowered, // defg gNormal, gNormal, gLowered, ...); // hij… endtable; </code></pre></div></div> <p>The two instances of <code class="language-plaintext highlighter-rouge">gLowered</code> in the <code class="language-plaintext highlighter-rouge">clsDiacPositioned</code> class correspond to the characters g and j, which have descenders.</p> <p>Then the following rule is used to select the proper form of the diacritic, depending on the preceeding base character:</p> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>clsBase clsDiac > @1 clsDiacPositioned$1; </code></pre></div></div> <p>Suppose the base glyph in the input is g. The $1 syntax tells us to determine which item g is within its input class (<code class="language-plaintext highlighter-rouge">clsBase</code>). The answer is 7, and so the seventh item of class <code class="language-plaintext highlighter-rouge">clsDiacPositioned</code> - which is <code class="language-plaintext highlighter-rouge">gLowered</code> - is selected as the glyph to put into the output in the place of the original diacritic. On the other hand, suppose the base glyph in the input is d. Again, the <code class="language-plaintext highlighter-rouge">$1</code> syntax tells us to determine which item d is within the <code class="language-plaintext highlighter-rouge">clsBase</code> class. The answer is 4, and so the fourth item of class <code class="language-plaintext highlighter-rouge">clsDiacPositioned</code> - <code class="language-plaintext highlighter-rouge">gNormal</code> - placed in the output.</p> <p>In both cases, <code class="language-plaintext highlighter-rouge">@1</code> causes the base character itself to be passed through unchanged.</p> <h2 id="exercise-18"> <a href="#exercise-18" class="anchor-heading" aria-labelledby="exercise-18"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Exercise 18 </h2> <p>Extend your program from Exercise 17 to adjust the capitalization of the reordered items. If the original consonant was uppercase, the reordered vowel should be uppercase in the rendering, and the consonant should become lowercase. In other words, “Cup” is rendered as “Ucp”.</p> <p><a href="graphite_tut_solutions#exercise-18">Solution</a></p> <div class="table-wrapper"><table class="tut-nav-bar"> <tbody> <tr> <td><a href="graide_tutorial17">◀ Unit 17: Optional items</a></td> <td><a href="../graide_tutorial#contents">▲ Contents</a></td> <td><a href="graide_tutorial_end">Conclusion ▶</a></td> </tr> </tbody> </table></div> </main> <hr> <footer> <p class="text-small text-grey-dk-100 mb-0">Copyright © 2012-2023 SIL International and released under the <a href="http://creativecommons.org/licenses/by-sa/3.0/">Creative Commons Attribution-ShareAlike 3.0 license (CC-BY-SA)</a> unless noted otherwise.</p> </footer> </div> </div> <div class="search-overlay"></div> </div> </body> </html>