docs/xml/pango-engine-lang.xml

   1 <refentry id="PangoEngineLang">
   2 <refmeta>
   3 <refentrytitle role="top_of_page" id="PangoEngineLang.top_of_page">PangoEngineLang</refentrytitle>
   4 <manvolnum>3</manvolnum>
   5 <refmiscinfo>PANGO Library</refmiscinfo>
   6 </refmeta>
   7
   8 <refnamediv>
   9 <refname>PangoEngineLang</refname>
  10 <refpurpose>Rendering-system independent script engines</refpurpose>
  11 </refnamediv>
  12 <refsect1 id="PangoEngineLang.stability-level">
  13 <title>Stability Level</title>
  14 Unstable, unless otherwise indicated
  15 </refsect1>
  16
  17 <refsynopsisdiv id="PangoEngineLang.synopsis" role="synopsis">
  18 <title role="synopsis.title">Synopsis</title>
  19
  20 <synopsis>
  21                     <link linkend="PangoEngineLang-struct">PangoEngineLang</link>;
  22                     <link linkend="PangoEngineLangClass">PangoEngineLangClass</link>;
  23 #define             <link linkend="PANGO-ENGINE-TYPE-LANG--CAPS">PANGO_ENGINE_TYPE_LANG</link>
  24 #define             <link linkend="PANGO-ENGINE-LANG-DEFINE-TYPE--CAPS">PANGO_ENGINE_LANG_DEFINE_TYPE</link>       (name, prefix, class_init, instance_init)
  25 </synopsis>
  26 </refsynopsisdiv>
  27
  28 <refsect1 id="PangoEngineLang.object-hierarchy" role="object_hierarchy">
  29 <title role="object_hierarchy.title">Object Hierarchy</title>
  30 <synopsis>
  31   <link linkend="GObject">GObject</link>
  32    +----<link linkend="PangoEngine">PangoEngine</link>
  33          +----PangoEngineLang
  34 </synopsis>
  35 </refsect1>
  36
  37
  38
  39
  40
  41
  42
  43
  44 <refsect1 id="PangoEngineLang.description" role="desc">
  45 <title role="desc.title">Description</title>
  46 <para>
  47 The <firstterm>language engines</firstterm> are rendering-system independent
  48 engines that determine line, word, and character breaks for character strings.
  49 These engines are used in <link linkend="pango-break"><function>pango_break()</function></link>.
  50 </para>
  51 </refsect1>
  52
  53 <refsect1 id="PangoEngineLang.details" role="details">
  54 <title role="details.title">Details</title>
  55 <refsect2 id="PangoEngineLang-struct" role="struct">
  56 <title>PangoEngineLang</title>
  57 <indexterm zone="PangoEngineLang-struct"><primary sortas="PangoEngineLang">PangoEngineLang</primary></indexterm><programlisting>typedef struct _PangoEngineLang PangoEngineLang;</programlisting>
  58 <para>
  59 The <link linkend="PangoEngineLang"><type>PangoEngineLang</type></link> class is implemented by engines that
  60 customize the rendering-system independent part of the
  61 Pango pipeline for a particular script or language. For
  62 instance, a custom <link linkend="PangoEngineLang"><type>PangoEngineLang</type></link> could be provided for
  63 Thai to implement the dictionary-based word boundary
  64 lookups needed for that language.</para>
  65 <para>
  66 </para></refsect2>
  67 <refsect2 id="PangoEngineLangClass" role="struct">
  68 <title>PangoEngineLangClass</title>
  69 <indexterm zone="PangoEngineLangClass"><primary sortas="PangoEngineLangClass">PangoEngineLangClass</primary></indexterm><programlisting>typedef struct {
  70   void (*script_break) (PangoEngineLang *engine,
  71                         const char    *text,
  72                         int            len,
  73                         PangoAnalysis *analysis,
  74                         PangoLogAttr  *attrs,
  75                         int            attrs_len);
  76 } PangoEngineLangClass;
  77 </programlisting>
  78 <para>
  79 Class structure for <link linkend="PangoEngineLang"><type>PangoEngineLang</type></link></para>
  80 <para>
  81 </para><variablelist role="struct">
  82 <varlistentry>
  83 <term><structfield>script_break</structfield>&#160;()</term>
  84 <listitem><simpara> Provides a custom implementation of <link linkend="pango-break"><function>pango_break()</function></link>.
  85 If <link linkend="NULL--CAPS"><literal>NULL</literal></link>, <link linkend="pango-default-break"><function>pango_default_break()</function></link> is used instead. If not <link linkend="NULL--CAPS"><literal>NULL</literal></link>, for
  86 Pango versions before 1.16 (module interface version before 1.6.0),
  87 this was called instead of <link linkend="pango-default-break"><function>pango_default_break()</function></link>, but in newer versions,
  88 <link linkend="pango-default-break"><function>pango_default_break()</function></link> is always called and this is called after that to
  89 allow tailoring the breaking results.
  90 </simpara></listitem>
  91 </varlistentry>
  92 </variablelist></refsect2>
  93 <refsect2 id="PANGO-ENGINE-TYPE-LANG--CAPS" role="macro">
  94 <title>PANGO_ENGINE_TYPE_LANG</title>
  95 <indexterm zone="PANGO-ENGINE-TYPE-LANG--CAPS"><primary sortas="PANGO_ENGINE_TYPE_LANG">PANGO_ENGINE_TYPE_LANG</primary></indexterm><programlisting>#define PANGO_ENGINE_TYPE_LANG "PangoEngineLang"
  96 </programlisting>
  97 <para>
  98 A string constant defining the engine type
  99 for language engines.
 100 These engines derive from <link linkend="PangoEngineLang"><type>PangoEngineLang</type></link>.
 101 </para></refsect2>
 102 <refsect2 id="PANGO-ENGINE-LANG-DEFINE-TYPE--CAPS" role="macro">
 103 <title>PANGO_ENGINE_LANG_DEFINE_TYPE()</title>
 104 <indexterm zone="PANGO-ENGINE-LANG-DEFINE-TYPE--CAPS"><primary sortas="PANGO_ENGINE_LANG_DEFINE_TYPE">PANGO_ENGINE_LANG_DEFINE_TYPE</primary></indexterm><programlisting>#define             PANGO_ENGINE_LANG_DEFINE_TYPE(name, prefix, class_init, instance_init)</programlisting>
 105 <para>
 106 Outputs the necessary code for GObject type registration for a
 107 <link linkend="PangoEngineLang"><type>PangoEngineLang</type></link> class defined in a module. Two static symbols
 108 are defined.
 109 </para>
 110 <para>
 111 <programlisting>
 112  static GType <replaceable>prefix</replaceable>_type;
 113  static void <replaceable>prefix</replaceable>_register_type (GTypeModule module);
 114 </programlisting>
 115 </para>
 116 <para>
 117 The <function><replaceable>prefix</replaceable><link linkend="register-type"><function>_register_type()</function></link></function>
 118 function should be called in your <link linkend="script-engine-init"><function>script_engine_init()</function></link> function for
 119 each type that your module implements, and then your <link linkend="script-engine-create"><function>script_engine_create()</function></link>
 120 function can create instances of the object as follows:
 121 </para>
 122 <para>
 123 <informalexample><programlisting>
 124  PangoEngine *engine = g_object_new (<replaceable>prefix</replaceable>_type, NULL);
 125 </programlisting></informalexample></para>
 126 <para>
 127 </para><variablelist role="params">
 128 <varlistentry><term><parameter>name</parameter>&#160;:</term>
 129 <listitem><simpara> Name of the the type to register (for example:, <literal>ArabicEngineFc</literal>
 130 </simpara></listitem></varlistentry>
 131 <varlistentry><term><parameter>prefix</parameter>&#160;:</term>
 132 <listitem><simpara> Prefix for symbols that will be defined (for example:, <literal>arabic_engine_fc</literal>
 133 </simpara></listitem></varlistentry>
 134 <varlistentry><term><parameter>class_init</parameter>&#160;:</term>
 135 <listitem><simpara> Class initialization function for the new type, or <link linkend="NULL--CAPS"><literal>NULL</literal></link>
 136 </simpara></listitem></varlistentry>
 137 <varlistentry><term><parameter>instance_init</parameter>&#160;:</term>
 138 <listitem><simpara> Instance initialization function for the new type, or <link linkend="NULL--CAPS"><literal>NULL</literal></link>
 139 </simpara></listitem></varlistentry>
 140 </variablelist></refsect2>
 141
 142 </refsect1>
 143
 144
 145
 146
 147 </refentry>