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<title>Getting started with HarfBuzz: HarfBuzz Manual</title>
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<div class="chapter">
<div class="titlepage"><div><div><h2 class="title">
<a name="getting-started"></a>Getting started with HarfBuzz</h2></div></div></div>
<div class="toc"><dl class="toc">
<dt><span class="section"><a href="getting-started.html#id-1.2.4.2">An overview of the HarfBuzz shaping API</a></span></dt>
<dt><span class="section"><a href="ch03s02.html">Terminology</a></span></dt>
<dt><span class="section"><a href="ch03s03.html">A simple shaping example</a></span></dt>
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<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="id-1.2.4.2"></a>An overview of the HarfBuzz shaping API</h2></div></div></div>
<p>
The core of the HarfBuzz shaping API is the function
<code class="function">hb_shape()</code>. This function takes a font, a
buffer containing a string of Unicode codepoints and
(optionally) a list of font features as its input. It replaces
the codepoints in the buffer with the corresponding glyphs from
the font, correctly ordered and positioned, and with any of the
optional font features applied.
</p>
<p>
In addition to holding the pre-shaping input (the Unicode
codepoints that comprise the input string) and the post-shaping
output (the glyphs and positions), a HarfBuzz buffer has several
properties that affect shaping. The most important are the
text-flow direction (e.g., left-to-right, right-to-left,
top-to-bottom, or bottom-to-top), the script tag, and the
language tag.
</p>
<p>
For input string buffers, flags are available to denote when the
buffer represents the beginning or end of a paragraph, to
indicate whether or not to visibly render Unicode <code class="literal">Default
Ignorable</code> codepoints, and to modify the cluster-merging
behavior for the buffer. For shaped output buffers, the
individual X and Y offsets and <code class="literal">advances</code>
(the logical dimensions) of each glyph are
accessible. HarfBuzz also flags glyphs as
<code class="literal">UNSAFE_TO_BREAK</code> if breaking the string at
that glyph (e.g., in a line-breaking or hyphenation process)
would require re-shaping the text.
</p>
<p>
HarfBuzz also provides methods to compare the contents of
buffers, join buffers, normalize buffer contents, and handle
invalid codepoints, as well as to determine the state of a
buffer (e.g., input codepoints or output glyphs). Buffer
lifecycles are managed and all buffers are reference-counted.
</p>
<p>
Although the default <code class="function">hb_shape()</code> function is
sufficient for most use cases, a variant is also provide that
lets you specify which of HarfBuzz's shapers to use on a buffer.
</p>
<p>
HarfBuzz can read TrueType fonts, TrueType collections, OpenType
fonts, and OpenType collections. Functions are provided to query
font objects about metrics, Unicode coverage, available tables and
features, and variation selectors. Individual glyphs can also be
queried for metrics, variations, and glyph names. OpenType
variable fonts are supported, and HarfBuzz allows you to set
variation-axis coordinates on font objects.
</p>
<p>
HarfBuzz provides glue code to integrate with various other
libraries, including FreeType, GObject, and CoreText. Support
for integrating with Uniscribe and DirectWrite is experimental
at present.
</p>
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