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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>Buffers, language, script and direction: 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="pt01.html" title="Part I. User's manual"> <link rel="prev" href="object-model-blobs.html" title="Blobs"> <link rel="next" href="adding-text-to-the-buffer.html" title="Adding text to the buffer"> <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="pt01.html"><img src="up.png" width="16" height="16" border="0" alt="Up"></a></td> <td><a accesskey="p" href="object-model-blobs.html"><img src="left.png" width="16" height="16" border="0" alt="Prev"></a></td> <td><a accesskey="n" href="adding-text-to-the-buffer.html"><img src="right.png" width="16" height="16" border="0" alt="Next"></a></td> </tr></table> <div class="chapter"> <div class="titlepage"><div><div><h2 class="title"> <a name="buffers-language-script-and-direction"></a>Buffers, language, script and direction</h2></div></div></div> <div class="toc"><dl class="toc"> <dt><span class="section"><a href="buffers-language-script-and-direction.html#creating-and-destroying-buffers">Creating and destroying buffers</a></span></dt> <dt><span class="section"><a href="adding-text-to-the-buffer.html">Adding text to the buffer</a></span></dt> <dt><span class="section"><a href="setting-buffer-properties.html">Setting buffer properties</a></span></dt> <dt><span class="section"><a href="customizing-unicode-functions.html">Customizing Unicode functions</a></span></dt> </dl></div> <p> The input to the HarfBuzz shaper is a series of Unicode characters, stored in a buffer. In this chapter, we'll look at how to set up a buffer with the text that we want and how to customize the properties of the buffer. We'll also look at a piece of lower-level machinery that you will need to understand before proceeding: the functions that HarfBuzz uses to retrieve Unicode information. </p> <p> After shaping is complete, HarfBuzz puts its output back into the buffer. But getting that output requires setting up a face and a font first, so we will look at that in the next chapter instead of here. </p> <div class="section"> <div class="titlepage"><div><div><h2 class="title" style="clear: both"> <a name="creating-and-destroying-buffers"></a>Creating and destroying buffers</h2></div></div></div> <p> As we saw in our <span class="emphasis"><em>Getting Started</em></span> example, a buffer is created and initialized with <code class="function">hb_buffer_create()</code>. This produces a new, empty buffer object, instantiated with some default values and ready to accept your Unicode strings. </p> <p> HarfBuzz manages the memory of objects (such as buffers) that it creates, so you don't have to. When you have finished working on a buffer, you can call <code class="function">hb_buffer_destroy()</code>: </p> <pre class="programlisting"> hb_buffer_t *buf = hb_buffer_create(); ... hb_buffer_destroy(buf); </pre> <p> This will destroy the object and free its associated memory - unless some other part of the program holds a reference to this buffer. If you acquire a HarfBuzz buffer from another subsystem and want to ensure that it is not garbage collected by someone else destroying it, you should increase its reference count: </p> <pre class="programlisting"> void somefunc(hb_buffer_t *buf) { buf = hb_buffer_reference(buf); ... </pre> <p> And then decrease it once you're done with it: </p> <pre class="programlisting"> hb_buffer_destroy(buf); } </pre> <p> While we are on the subject of reference-counting buffers, it is worth noting that an individual buffer can only meaningfully be used by one thread at a time. </p> <p> To throw away all the data in your buffer and start from scratch, call <code class="function">hb_buffer_reset(buf)</code>. If you want to throw away the string in the buffer but keep the options, you can instead call <code class="function">hb_buffer_clear_contents(buf)</code>. </p> </div> </div> <div class="footer"> <hr>Generated by GTK-Doc V1.32</div> </body> </html>