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kc3-lang/harfbuzz/docs/usermanual-buffers-language-script-and-direction.xml

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  • Author : Nathan Willis
    Date : 2018-10-29 17:10:53
    Hash : 9f4b375e
    Message : Usermanual: minor wording updates, build fixes.

  • docs/usermanual-buffers-language-script-and-direction.xml
  • <?xml version="1.0"?>
    <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
                   "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd" [
      <!ENTITY % local.common.attrib "xmlns:xi  CDATA  #FIXED 'http://www.w3.org/2003/XInclude'">
      <!ENTITY version SYSTEM "version.xml">
    ]>
    <chapter id="buffers-language-script-and-direction">
      <title>Buffers, language, script and direction</title>
      <para>
        The input to HarfBuzz 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 then customize the properties of the
        buffer.
      </para>
      <section id="creating-and-destroying-buffers">
        <title>Creating and destroying buffers</title>
        <para>
          As we saw in our initial example, a buffer is created and
          initialized with <literal>hb_buffer_create()</literal>. This
          produces a new, empty buffer object, instantiated with some
          default values and ready to accept your Unicode strings.
        </para>
        <para>
          HarfBuzz manages the memory of objects that it creates (such as
          buffers), so you don't have to. When you have finished working on
          a buffer, you can call <literal>hb_buffer_destroy()</literal>:
        </para>
        <programlisting language="C">
      hb_buffer_t *buffer = hb_buffer_create();
      ...
      hb_buffer_destroy(buffer);
    </programlisting>
        <para>
          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:
        </para>
        <programlisting language="C">
    void somefunc(hb_buffer_t *buffer) {
      buffer = hb_buffer_reference(buffer);
      ...
    </programlisting>
        <para>
          And then decrease it once you're done with it:
        </para>
        <programlisting language="C">
      hb_buffer_destroy(buffer);
    }
    </programlisting>
        <para>
          To throw away all the data in your buffer and start from scratch,
          call <literal>hb_buffer_reset(buffer)</literal>. If you want to
          throw away the string in the buffer but keep the options, you can
          instead call <literal>hb_buffer_clear_contents(buffer)</literal>.
        </para>
      </section>
      <section id="adding-text-to-the-buffer">
        <title>Adding text to the buffer</title>
        <para>
          Now we have a brand new HarfBuzz buffer. Let's start filling it
          with text! From HarfBuzz's perspective, a buffer is just a stream
          of Unicode codepoints, but your input string is probably in one of
          the standard Unicode character encodings (UTF-8, UTF-16, UTF-32)
        </para>
      </section>
      <section id="setting-buffer-properties">
        <title>Setting buffer properties</title>
        <para>
        </para>
      </section>
      <section id="what-about-the-other-scripts">
        <title>What about the other scripts?</title>
        <para>
        </para>
      </section>
      <section id="customizing-unicode-functions">
        <title>Customizing Unicode functions</title>
        <para>
        </para>
      </section>
    </chapter>