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aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> GDL Code Snippets </h1> <ul> <li><a href="graphite_codeSnippets#diacritic-attachment">Diacritic attachment</a> <ul> <li><a href="graphite_codeSnippets#diacritics-with-calculated-attachment-points">Diacritics with calculated attachment points</a></li> <li><a href="graphite_codeSnippets#stacking-diacritics">Stacking diacritics</a></li> <li><a href="graphite_codeSnippets#bridging-diacritics">Bridging diacritics</a></li> </ul> </li> <li><a href="graphite_codeSnippets#ligatures-conjuncts">Ligatures (conjuncts)</a> <ul> <li><a href="graphite_codeSnippets#ligatures-with-components">Ligatures with components</a></li> </ul> </li> <li><a href="graphite_codeSnippets#contextual-shaping">Contextual shaping</a> <ul> <li><a href="graphite_codeSnippets#word-contextual-shaping">Word-contextual shaping</a></li> </ul> </li> <li><a href="graphite_codeSnippets#reordering">Reordering</a></li> <li><a href="graphite_codeSnippets#splitting">Splitting</a></li> <li><a href="graphite_codeSnippets#font-features-variations">Font features (variations)</a> <ul> <li><a href="graphite_codeSnippets#boolean-feature">Boolean feature</a></li> <li><a href="graphite_codeSnippets#multi-valued-feature">Multi-valued feature</a></li> </ul> </li> </ul> <p>These snippets are intended as a quick reference. For complete documentation of the GDL language, download the reference paper:</p> <p><a href="assets/resources/GDL.pdf" class="btn btn-blue">Download GDL.pdf</a></p> <h2 id="diacritic-attachment"> <a href="#diacritic-attachment" class="anchor-heading" aria-labelledby="diacritic-attachment"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Diacritic attachment </h2> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>table(glyph) // These can also be classes, in which case the attachment point(s) // must be defined on each element of the class: base = glyphid(34) {TopS = point(130m, 512m); BottomS = point(130m, 0m)}; upperdiac = glyphid(101) {TopM = point(86m, -12m)} lowerdiac = glyphid(102) {BottomM = point(86m, 43m)}; endtable; // glyph table(positioning) base upperdiac {attach {to=@1; at=TopS; with=TopM}}; base lowerdiac {attach {to=@1; at=BottomS; with=BottomM}}; endtable; // positioning </code></pre></div></div> <h3 id="diacritics-with-calculated-attachment-points"> <a href="#diacritics-with-calculated-attachment-points" class="anchor-heading" aria-labelledby="diacritics-with-calculated-attachment-points"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Diacritics with calculated attachment points </h3> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>table(glyph) base = glyphid(...) {TopS = point(bb.lsb + bb.width/2, bb.top); BottomS = point(bb.lsb + bb.width/2, bb.bottom)}; upperdiac = glyphid(...) {TopM = point(bb.width/2, bb.bottom - 10m)} lowerdiac = glyphid(...) {BottomM = point(bb.width/2, bb.top + 10m)}; endtable; // glyph table(positioning) base upperdiac {attach {to=@1; at=TopS; with=TopM}}; base lowerdiac {attach {to=@1; at=BottomS; with=BottomM}}; endtable; // positioning </code></pre></div></div> <h3 id="stacking-diacritics"> <a href="#stacking-diacritics" class="anchor-heading" aria-labelledby="stacking-diacritics"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Stacking diacritics </h3> <p>The following example shows how to handle a stack/chain of both upper and lower diacritic attachments. Note that, as specified by the Unicode standard, lower diacritics are first.</p> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>table(glyph) base1 = glyphid(34) {TopS = point(130m, 512m); BottomS = point(130m, 0m)}; base1 = glyphid(35) {TopS = point(130m, 5108m); BottomS = point(130m, -18m)}; upperdiac1 = glyphid(101) {TopM = point(86m, -12m); TopS = point(86m, 43m)}; upperdiac2 = glyphid(105) {TopM = point(81m, -10m); TopS = point(81m, 52m)}; lowerdiac1 = glyphid(102) {BottomM = point(79m, 43m); BottomS = point(79m, -3m)}; lowerdiac2 = glyphid(103) {BottomM = point(77m, 48m); BottomS = point(77m, -5m)}; // etc. base = (base1, base2, ...); upperdiac = (upperdiac1, upperdiac2, ...); lowerdiac = (lowerdiac1, lowerdiac2, ...); takes_lower = (base, lowerdiac); // lower diacritics can be attached to bases or other lower diacs takes_upper = (base, upperdiac); // upper diacritics can be attached to bases or other upper diacs endtable; // glyph table(positioning) // Optionally permit up to three intervening lower diacritics: #define LOWERSEQ [ lowerdiac [ lowerdiac lowerdiac? ]? ]? takes_lower lowerdiac {attach {to=@1; at=BottomS; with=BottomM}} / _ ^ _; takes_upper upperdiac {attach {to=@1; at=TopS; with=TopM}} / _ LOWERSEQ ^ _; endtable; // positioning </code></pre></div></div> <h3 id="bridging-diacritics"> <a href="#bridging-diacritics" class="anchor-heading" aria-labelledby="bridging-diacritics"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Bridging diacritics </h3> <p>Bridging diacritics must be centered over the two bases they bridge and must be higher than the tallest.</p> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>table(glyph) base1 = ...; base2 = ...; bridgediac = ...; endtable; // glyph table(positioning) bridgediac {shift.y = max(@B1.boundingbox.top, @B2.boundingbox.top) - @D.boundingbox.bottom + 100m ; // gap of 100m shift.x = (@B2.boundingbox.width - @B1.boundingbox.width)/2} / base1=B1 _=D base2=B2; endtable; // positioning If the base glyphs have other diacritics attached, using @B1.boundingbox.top.1 will give the bounding box of the base plus diacritics. </code></pre></div></div> <h2 id="ligatures-conjuncts"> <a href="#ligatures-conjuncts" class="anchor-heading" aria-labelledby="ligatures-conjuncts"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Ligatures (conjuncts) </h2> <p>Ligatures or conjuncts occur when multiple characters combine to form a single glyph shape.</p> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>table(glyph) char1 = ...; char2 = ...; ligature = ...; endtable; // glyph table(substitution) char1 char2 > ligature:(1 2) _ ; endtable; // substitution </code></pre></div></div> <h3 id="ligatures-with-components"> <a href="#ligatures-with-components" class="anchor-heading" aria-labelledby="ligatures-with-components"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Ligatures with components </h3> <p>Ligature components correspond to sub-regions of the ligature glyph that visually correspond to the original characters. Selecting and manipulating the visual components allows manipulating the underlying characters.</p> <blockquote class="blue-note"> <p><strong>Note</strong></p> <p>This feature is only supported by the original Graphite engine; it is not supported by Graphite2.</p> </blockquote> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>table(glyph) char1 = ...; char2 = ...; ligature = ... // <-- specify which glyph // Define the visual components of the conjunct. // This conjunct has three components: // the top-left, the bottom-left, and the right side. { component {cTL= box(0, bb.height/2, aw/2, bb.top); cBL= box(0, bb.bottom, aw/2, bb.height/2); cR = box(aw/2, bb.bottom, aw, bb.top) } }; endtable; // glyph table(substitution) char1 char2 char3 > ligature:(1 2 3) {component {cTL.ref=@1; cBL.ref=@2; cR=@3}} _ _; endtable; // substitution </code></pre></div></div> <h2 id="contextual-shaping"> <a href="#contextual-shaping" class="anchor-heading" aria-labelledby="contextual-shaping"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Contextual shaping </h2> <p>Many scripts have characters that must use alternate forms depending on neighboring letters.</p> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>table(glyph) // Define the glyphs and classes: matraI = ...; matraI_wide = ...; matraI_wider = ...; matraI_widest = ...; class_wide = ...; class_wider = ...; class_widest = ...; endtable; // glyph table(substitution) // Choose the width of the matra-I that matches the width of the neighboring letter: matraI class_wide > matraI_wide @2; matraI class_wider > matraI_wider @2; matraI class_widest > matraI_widest @2; endtable; </code></pre></div></div> <h3 id="word-contextual-shaping"> <a href="#word-contextual-shaping" class="anchor-heading" aria-labelledby="word-contextual-shaping"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Word-contextual shaping </h3> <p>Arabic is an example of a script whose characters take on alternate forms depending on their location within the word: initial, medial, final, isolate.</p> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>table(glyph) // All characters are initially isolate forms. // Define the individual glyphs: beh = ...; behInit = ...; // etc. // Elements of these four classes must correspond: class_isolate = (beh, teh, theh, peh, teheh, ...); class_initial = (behInit, tehInit, thehInit, pehInit, tehehInit, ...); class_medial = (behMed, behMed, thehMed, pehMed, tehehMed, ...); class_final = (behFin, behFin, thehFin, pehFin, tehehFin, ...); endtable; // glyph table(substitution) // For any contiguous pair of word-forming letters: // turn the first from isolate to initial, or from final to medial // turn the second to final // back up and treat the second as the first of the next pair to consider // Any unprocessed letters are left as isolates. (class_isolate class_final) (class_isolate) > (class_initial class_medial) (class_final) / _ ^ _; endtable; // substitution </code></pre></div></div> <h2 id="reordering"> <a href="#reordering" class="anchor-heading" aria-labelledby="reordering"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Reordering </h2> <p>Many scripts of south and southeast Asia have characters that are rendered in an order that is different from their order in the data.</p> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>table(glyph) // Define the glyphs or classes: consonants = ...; vowelLeftSide = ...; endtable; // glyph table(substitution) consonant vowelLeftSide > @2 @1; endtable; // substitution </code></pre></div></div> <h2 id="splitting"> <a href="#splitting" class="anchor-heading" aria-labelledby="splitting"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Splitting </h2> <p>Many scripts of south and southeast Asia have characters that are rendered by two or more non-contiguous glyphs.</p> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>table(glyph) // Define the glyphs or classes: consonants = ...; // If these are classes, the elements of the classes must correspond: vowelSplit = (vowel1, vowel2, vowel3, ...); vowelLeftHalf = (vowel1Left, vowel2Left, vowel3Left, ...); vowelRightHalf = (vowel1Right, vowel2Right, vowel3Right, ...); endtable; // glyph table(substitution) _ consonant vowelSplit > vowelLeftHalf$3:3 @2 vowelRightHalf:3; end-table; // substitution </code></pre></div></div> <h2 id="font-features-variations"> <a href="#font-features-variations" class="anchor-heading" aria-labelledby="font-features-variations"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Font features (variations) </h2> <p>Font features provide a way to define alterative renderings that can be selected by the user.</p> <h3 id="boolean-feature"> <a href="#boolean-feature" class="anchor-heading" aria-labelledby="boolean-feature"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Boolean feature </h3> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>table(feature) altk { id = "altk"; // can be integer or 4-char string name.1033 = string("Alternate K"); // 1033 = LG_USENG, US English default = 0; settings { off { value = 0; name.1033 = string("False"); } on { value = 1; name.1033 = string("True"); } } }; endtable; // feature table(glyph) g_k = ...; g_k_alt = ...; endtable; // glyph table(substitution) if (altk) g_k > g_k_alt endif; endtable; // substitution </code></pre></div></div> <h3 id="multi-valued-feature"> <a href="#multi-valued-feature" class="anchor-heading" aria-labelledby="multi-valued-feature"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Multi-valued feature </h3> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>table(feature) altk { id = "altk"; // can be integer or 4-char string name.1033 = string("Alternate K"); // 1033 = LG_USENG, US English default = 0; settings { form1 { value = 0; name.1033 = string("Form 1"); } form2 { value = 1; name.1033 = string("Form 2"); } form3 { value = 2; name.1033 = string("Form 3"); } form4 { value = 3; name.1033 = string("Form 4"); } } }; endtable; // feature table(glyph) g_k = ...; g_k1 = ...; g_k2 = ...; g_k3 = ...; g_k4 = ...; endtable; // glyph table(substitution) // Note that for mutually exclusive conditions, successive // 'if' statements are more efficient than 'elseif'. if (altk == form1) g_k > g_k1; endif; if (altk == form2) g_k > g_k2; endif; if (altk == form3) g_k > g_k3; endif; if (altk == form4) g_k > g_k3; endif; endtable; // substitution </code></pre></div></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>