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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Working with OpenType Variable Fonts: HarfBuzz Manual</title> <meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> <link rel="home" href="index.html" title="HarfBuzz Manual"> <link rel="up" href="fonts-and-faces.html" title="Fonts, faces, and output"> <link rel="prev" href="fonts-and-faces-native-opentype.html" title="Font objects and HarfBuzz's native OpenType implementation"> <link rel="next" href="shaping-and-shape-plans.html" title="Shaping and shape plans"> <meta name="generator" content="GTK-Doc V1.32 (XML mode)"> <link rel="stylesheet" href="style.css" type="text/css"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table class="navigation" id="top" width="100%" summary="Navigation header" cellpadding="2" cellspacing="5"><tr valign="middle"> <td width="100%" align="left" class="shortcuts"></td> <td><a accesskey="h" href="index.html"><img src="home.png" width="16" height="16" border="0" alt="Home"></a></td> <td><a accesskey="u" href="fonts-and-faces.html"><img src="up.png" width="16" height="16" border="0" alt="Up"></a></td> <td><a accesskey="p" href="fonts-and-faces-native-opentype.html"><img src="left.png" width="16" height="16" border="0" alt="Prev"></a></td> <td><a accesskey="n" href="shaping-and-shape-plans.html"><img src="right.png" width="16" height="16" border="0" alt="Next"></a></td> </tr></table> <div class="section"> <div class="titlepage"><div><div><h2 class="title" style="clear: both"> <a name="fonts-and-faces-variable"></a>Working with OpenType Variable Fonts</h2></div></div></div> <p> If you are working with OpenType Variable Fonts, there are a few additional functions you should use to specify the variation-axis settings of your font object. Without doing so, your variable font's font object can still be used, but only at the default setting for every axis (which, of course, is sometimes what you want, but does not cover general usage). </p> <p> HarfBuzz manages variation settings in the <span class="type">hb_variation_t</span> data type, which holds a <span class="property">tag</span> for the variation-axis identifier tag and a <span class="property">value</span> for its setting. You can retrieve the list of variation axes in a font binary from the face object (not from a font object, notably) by calling <code class="function">hb_ot_var_get_axis_count(face)</code> to find the number of axes, then using <code class="function">hb_ot_var_get_axis_infos()</code> to collect the axis structures: </p> <pre class="programlisting"> axes = hb_ot_var_get_axis_count(face); ... hb_ot_var_get_axis_infos(face, 0, axes, axes_array); </pre> <p> For each axis returned in the array, you can can access the identifier in its <span class="property">tag</span>. HarfBuzz also has tag definitions predefined for the five standard axes specified in OpenType (<code class="literal">ital</code> for italic, <code class="literal">opsz</code> for optical size, <code class="literal">slnt</code> for slant, <code class="literal">wdth</code> for width, and <code class="literal">wght</code> for weight). Each axis also has a <span class="property">min_value</span>, a <span class="property">default_value</span>, and a <span class="property">max_value</span>. </p> <p> To set your font object's variation settings, you call the <code class="function">hb_font_set_variations()</code> function with an array of <span class="type">hb_variation_t</span> variation settings. Let's say our font has weight and width axes. We need to specify each of the axes by tag and assign a value on the axis: </p> <pre class="programlisting"> unsigned int variation_count = 2; hb_variation_t variation_data[variation_count]; variation_data[0].tag = HB_OT_TAG_VAR_AXIS_WIDTH; variation_data[1].tag = HB_OT_TAG_VAR_AXIS_WEIGHT; variation_data[0].value = 80; variation_data[1].value = 750; ... hb_font_set_variations(font, variation_data, variation_count); </pre> <p> That should give us a slightly condensed font ("normal" on the <code class="literal">wdth</code> axis is 100) at a noticeably bolder weight ("regular" is 400 on the <code class="literal">wght</code> axis). </p> <p> In practice, though, you should always check that the value you want to set on the axis is within the [<span class="property">min_value</span>,<span class="property">max_value</span>] range actually implemented in the font's variation axis. After all, a font might only provide lighter-than-regular weights, and setting a heavier value on the <code class="literal">wght</code> axis will not change that. </p> <p> Once your variation settings are specified on your font object, however, shaping with a variable font is just like shaping a static font. </p> </div> <div class="footer"> <hr>Generated by GTK-Doc V1.32</div> </body> </html>