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<h2><span class="refentrytitle"><a name="gobject-Generic-values.top_of_page"></a>Generic values</span></h2>
<p>Generic values — A polymorphic type that can hold values of any
    other type</p>
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<div class="refsynopsisdiv">
<a name="gobject-Generic-values.synopsis"></a><h2>Synopsis</h2>
<pre class="synopsis">
#include &lt;glib-object.h&gt;

#define             <a class="link" href="gobject-Generic-values.html#G-VALUE-INIT:CAPS" title="G_VALUE_INIT">G_VALUE_INIT</a>
#define             <a class="link" href="gobject-Generic-values.html#G-VALUE-HOLDS:CAPS" title="G_VALUE_HOLDS()">G_VALUE_HOLDS</a>                       (value,
                                                         type)
#define             <a class="link" href="gobject-Generic-values.html#G-VALUE-TYPE:CAPS" title="G_VALUE_TYPE()">G_VALUE_TYPE</a>                        (value)
#define             <a class="link" href="gobject-Generic-values.html#G-VALUE-TYPE-NAME:CAPS" title="G_VALUE_TYPE_NAME()">G_VALUE_TYPE_NAME</a>                   (value)
#define             <a class="link" href="gobject-Generic-values.html#G-TYPE-IS-VALUE:CAPS" title="G_TYPE_IS_VALUE()">G_TYPE_IS_VALUE</a>                     (type)
#define             <a class="link" href="gobject-Generic-values.html#G-TYPE-IS-VALUE-ABSTRACT:CAPS" title="G_TYPE_IS_VALUE_ABSTRACT()">G_TYPE_IS_VALUE_ABSTRACT</a>            (type)
#define             <a class="link" href="gobject-Generic-values.html#G-IS-VALUE:CAPS" title="G_IS_VALUE()">G_IS_VALUE</a>                          (value)
                    <a class="link" href="gobject-Generic-values.html#GValue" title="GValue">GValue</a>;
#define             <a class="link" href="gobject-Generic-values.html#G-TYPE-VALUE:CAPS" title="G_TYPE_VALUE">G_TYPE_VALUE</a>
#define             <a class="link" href="gobject-Generic-values.html#G-TYPE-VALUE-ARRAY:CAPS" title="G_TYPE_VALUE_ARRAY">G_TYPE_VALUE_ARRAY</a>
<a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="returnvalue">GValue</span></a> *            <a class="link" href="gobject-Generic-values.html#g-value-init" title="g_value_init ()">g_value_init</a>                        (<em class="parameter"><code><a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *value</code></em>,
                                                         <em class="parameter"><code><a class="link" href="gobject-Type-Information.html#GType" title="GType"><span class="type">GType</span></a> g_type</code></em>);
<span class="returnvalue">void</span>                <a class="link" href="gobject-Generic-values.html#g-value-copy" title="g_value_copy ()">g_value_copy</a>                        (<em class="parameter"><code>const <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *src_value</code></em>,
                                                         <em class="parameter"><code><a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *dest_value</code></em>);
<a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="returnvalue">GValue</span></a> *            <a class="link" href="gobject-Generic-values.html#g-value-reset" title="g_value_reset ()">g_value_reset</a>                       (<em class="parameter"><code><a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *value</code></em>);
<span class="returnvalue">void</span>                <a class="link" href="gobject-Generic-values.html#g-value-unset" title="g_value_unset ()">g_value_unset</a>                       (<em class="parameter"><code><a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *value</code></em>);
<span class="returnvalue">void</span>                <a class="link" href="gobject-Generic-values.html#g-value-set-instance" title="g_value_set_instance ()">g_value_set_instance</a>                (<em class="parameter"><code><a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *value</code></em>,
                                                         <em class="parameter"><code><a href="./../glib/glib/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> instance</code></em>);
<a href="./../glib/glib/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>            <a class="link" href="gobject-Generic-values.html#g-value-fits-pointer" title="g_value_fits_pointer ()">g_value_fits_pointer</a>                (<em class="parameter"><code>const <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *value</code></em>);
<a href="./../glib/glib/glib-Basic-Types.html#gpointer"><span class="returnvalue">gpointer</span></a>            <a class="link" href="gobject-Generic-values.html#g-value-peek-pointer" title="g_value_peek_pointer ()">g_value_peek_pointer</a>                (<em class="parameter"><code>const <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *value</code></em>);
<a href="./../glib/glib/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>            <a class="link" href="gobject-Generic-values.html#g-value-type-compatible" title="g_value_type_compatible ()">g_value_type_compatible</a>             (<em class="parameter"><code><a class="link" href="gobject-Type-Information.html#GType" title="GType"><span class="type">GType</span></a> src_type</code></em>,
                                                         <em class="parameter"><code><a class="link" href="gobject-Type-Information.html#GType" title="GType"><span class="type">GType</span></a> dest_type</code></em>);
<a href="./../glib/glib/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>            <a class="link" href="gobject-Generic-values.html#g-value-type-transformable" title="g_value_type_transformable ()">g_value_type_transformable</a>          (<em class="parameter"><code><a class="link" href="gobject-Type-Information.html#GType" title="GType"><span class="type">GType</span></a> src_type</code></em>,
                                                         <em class="parameter"><code><a class="link" href="gobject-Type-Information.html#GType" title="GType"><span class="type">GType</span></a> dest_type</code></em>);
<a href="./../glib/glib/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>            <a class="link" href="gobject-Generic-values.html#g-value-transform" title="g_value_transform ()">g_value_transform</a>                   (<em class="parameter"><code>const <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *src_value</code></em>,
                                                         <em class="parameter"><code><a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *dest_value</code></em>);
<span class="returnvalue">void</span>                (<a class="link" href="gobject-Generic-values.html#GValueTransform" title="GValueTransform ()">*GValueTransform</a>)                  (<em class="parameter"><code>const <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *src_value</code></em>,
                                                         <em class="parameter"><code><a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *dest_value</code></em>);
<span class="returnvalue">void</span>                <a class="link" href="gobject-Generic-values.html#g-value-register-transform-func" title="g_value_register_transform_func ()">g_value_register_transform_func</a>     (<em class="parameter"><code><a class="link" href="gobject-Type-Information.html#GType" title="GType"><span class="type">GType</span></a> src_type</code></em>,
                                                         <em class="parameter"><code><a class="link" href="gobject-Type-Information.html#GType" title="GType"><span class="type">GType</span></a> dest_type</code></em>,
                                                         <em class="parameter"><code><a class="link" href="gobject-Generic-values.html#GValueTransform" title="GValueTransform ()"><span class="type">GValueTransform</span></a> transform_func</code></em>);
<a href="./../glib/glib/glib-Basic-Types.html#gchar"><span class="returnvalue">gchar</span></a> *             <a class="link" href="gobject-Generic-values.html#g-strdup-value-contents" title="g_strdup_value_contents ()">g_strdup_value_contents</a>             (<em class="parameter"><code>const <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *value</code></em>);
</pre>
</div>
<div class="refsect1">
<a name="gobject-Generic-values.description"></a><h2>Description</h2>
<p>
The <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure is basically a variable container that consists
of a type identifier and a specific value of that type.
The type identifier within a <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure always determines the
type of the associated value.
To create a undefined <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure, simply create a zero-filled
<a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure. To initialize the <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a>, use the <a class="link" href="gobject-Generic-values.html#g-value-init" title="g_value_init ()"><code class="function">g_value_init()</code></a>
function. A <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> cannot be used until it is initialized.
The basic type operations (such as freeing and copying) are determined
by the <a class="link" href="gobject-Type-Information.html#GTypeValueTable" title="struct GTypeValueTable"><span class="type">GTypeValueTable</span></a> associated with the type ID stored in the <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a>.
Other <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> operations (such as converting values between types) are
provided by this interface.
</p>
<p>
The code in the example program below demonstrates <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a>'s
features.
</p>
<p>
</p>
<div class="informalexample">
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        <td class="listing_code"><pre class="programlisting"><span class="preproc">#include</span><span class="normal"> </span><span class="string">&lt;glib-object.h&gt;</span>

<span class="keyword">static</span><span class="normal"> </span><span class="type">void</span>
<span class="function">int2string</span><span class="normal"> </span><span class="symbol">(</span><span class="keyword">const</span><span class="normal"> </span><span class="usertype">GValue</span><span class="normal"> </span><span class="symbol">*</span><span class="normal">src_value</span><span class="symbol">,</span>
<span class="normal">            </span><span class="usertype">GValue</span><span class="normal">       </span><span class="symbol">*</span><span class="normal">dest_value</span><span class="symbol">)</span>
<span class="cbracket">{</span>
<span class="normal">  </span><span class="keyword">if</span><span class="normal"> </span><span class="symbol">(</span><span class="function"><a href="gobject-Standard-Parameter-and-Value-Types.html#g-value-get-int">g_value_get_int</a></span><span class="normal"> </span><span class="symbol">(</span><span class="normal">src_value</span><span class="symbol">)</span><span class="normal"> </span><span class="symbol">==</span><span class="normal"> </span><span class="number">42</span><span class="symbol">)</span>
<span class="normal">    </span><span class="function"><a href="gobject-Standard-Parameter-and-Value-Types.html#g-value-set-static-string">g_value_set_static_string</a></span><span class="normal"> </span><span class="symbol">(</span><span class="normal">dest_value</span><span class="symbol">,</span><span class="normal"> </span><span class="string">"An important number"</span><span class="symbol">);</span>
<span class="normal">  </span><span class="keyword">else</span>
<span class="normal">    </span><span class="function"><a href="gobject-Standard-Parameter-and-Value-Types.html#g-value-set-static-string">g_value_set_static_string</a></span><span class="normal"> </span><span class="symbol">(</span><span class="normal">dest_value</span><span class="symbol">,</span><span class="normal"> </span><span class="string">"What's that?"</span><span class="symbol">);</span>
<span class="cbracket">}</span>

<span class="type">int</span>
<span class="function">main</span><span class="normal"> </span><span class="symbol">(</span><span class="type">int</span><span class="normal">   argc</span><span class="symbol">,</span>
<span class="normal">      </span><span class="type">char</span><span class="normal"> </span><span class="symbol">*</span><span class="normal">argv</span><span class="symbol">[])</span>
<span class="cbracket">{</span>
<span class="normal">  </span><span class="comment">/* GValues must be initialized */</span>
<span class="normal">  </span><span class="usertype">GValue</span><span class="normal"> a </span><span class="symbol">=</span><span class="normal"> <a href="gobject-Generic-values.html#G-VALUE-INIT:CAPS">G_VALUE_INIT</a></span><span class="symbol">;</span>
<span class="normal">  </span><span class="usertype">GValue</span><span class="normal"> b </span><span class="symbol">=</span><span class="normal"> <a href="gobject-Generic-values.html#G-VALUE-INIT:CAPS">G_VALUE_INIT</a></span><span class="symbol">;</span>
<span class="normal">  </span><span class="keyword">const</span><span class="normal"> </span><span class="usertype">gchar</span><span class="normal"> </span><span class="symbol">*</span><span class="normal">message</span><span class="symbol">;</span>

<span class="normal">  </span><span class="function"><a href="gobject-Type-Information.html#g-type-init">g_type_init</a></span><span class="normal"> </span><span class="symbol">();</span>

<span class="normal">  </span><span class="comment">/* The GValue starts empty */</span>
<span class="normal">  </span><span class="function"><a href="./../glib/glib/glib-Testing.html#g-assert">g_assert</a></span><span class="normal"> </span><span class="symbol">(!</span><span class="function"><a href="gobject-Standard-Parameter-and-Value-Types.html#G-VALUE-HOLDS-STRING:CAPS">G_VALUE_HOLDS_STRING</a></span><span class="normal"> </span><span class="symbol">(&amp;</span><span class="normal">a</span><span class="symbol">));</span>

<span class="normal">  </span><span class="comment">/* Put a string in it */</span>
<span class="normal">  </span><span class="function"><a href="gobject-Generic-values.html#g-value-init">g_value_init</a></span><span class="normal"> </span><span class="symbol">(&amp;</span><span class="normal">a</span><span class="symbol">,</span><span class="normal"> <a href="gobject-Type-Information.html#G-TYPE-STRING:CAPS">G_TYPE_STRING</a></span><span class="symbol">);</span>
<span class="normal">  </span><span class="function"><a href="./../glib/glib/glib-Testing.html#g-assert">g_assert</a></span><span class="normal"> </span><span class="symbol">(</span><span class="function"><a href="gobject-Standard-Parameter-and-Value-Types.html#G-VALUE-HOLDS-STRING:CAPS">G_VALUE_HOLDS_STRING</a></span><span class="normal"> </span><span class="symbol">(&amp;</span><span class="normal">a</span><span class="symbol">));</span>
<span class="normal">  </span><span class="function"><a href="gobject-Standard-Parameter-and-Value-Types.html#g-value-set-static-string">g_value_set_static_string</a></span><span class="normal"> </span><span class="symbol">(&amp;</span><span class="normal">a</span><span class="symbol">,</span><span class="normal"> </span><span class="string">"Hello, world!"</span><span class="symbol">);</span>
<span class="normal">  </span><span class="function"><a href="./../glib/glib/glib-String-Utility-Functions.html#g-printf">g_printf</a></span><span class="normal"> </span><span class="symbol">(</span><span class="string">"%s</span><span class="specialchar">\n</span><span class="string">"</span><span class="symbol">,</span><span class="normal"> </span><span class="function"><a href="gobject-Standard-Parameter-and-Value-Types.html#g-value-get-string">g_value_get_string</a></span><span class="normal"> </span><span class="symbol">(&amp;</span><span class="normal">a</span><span class="symbol">));</span>

<span class="normal">  </span><span class="comment">/* Reset it to its pristine state */</span>
<span class="normal">  </span><span class="function"><a href="gobject-Generic-values.html#g-value-unset">g_value_unset</a></span><span class="normal"> </span><span class="symbol">(&amp;</span><span class="normal">a</span><span class="symbol">);</span>

<span class="normal">  </span><span class="comment">/* It can then be reused for another type */</span>
<span class="normal">  </span><span class="function"><a href="gobject-Generic-values.html#g-value-init">g_value_init</a></span><span class="normal"> </span><span class="symbol">(&amp;</span><span class="normal">a</span><span class="symbol">,</span><span class="normal"> <a href="gobject-Type-Information.html#G-TYPE-INT:CAPS">G_TYPE_INT</a></span><span class="symbol">);</span>
<span class="normal">  </span><span class="function"><a href="gobject-Standard-Parameter-and-Value-Types.html#g-value-set-int">g_value_set_int</a></span><span class="normal"> </span><span class="symbol">(&amp;</span><span class="normal">a</span><span class="symbol">,</span><span class="normal"> </span><span class="number">42</span><span class="symbol">);</span>

<span class="normal">  </span><span class="comment">/* Attempt to transform it into a GValue of type STRING */</span>
<span class="normal">  </span><span class="function"><a href="gobject-Generic-values.html#g-value-init">g_value_init</a></span><span class="normal"> </span><span class="symbol">(&amp;</span><span class="normal">b</span><span class="symbol">,</span><span class="normal"> <a href="gobject-Type-Information.html#G-TYPE-STRING:CAPS">G_TYPE_STRING</a></span><span class="symbol">);</span>

<span class="normal">  </span><span class="comment">/* An INT is transformable to a STRING */</span>
<span class="normal">  </span><span class="function"><a href="./../glib/glib/glib-Testing.html#g-assert">g_assert</a></span><span class="normal"> </span><span class="symbol">(</span><span class="function"><a href="gobject-Generic-values.html#g-value-type-transformable">g_value_type_transformable</a></span><span class="normal"> </span><span class="symbol">(</span><span class="normal"><a href="gobject-Type-Information.html#G-TYPE-INT:CAPS">G_TYPE_INT</a></span><span class="symbol">,</span><span class="normal"> <a href="gobject-Type-Information.html#G-TYPE-STRING:CAPS">G_TYPE_STRING</a></span><span class="symbol">));</span>

<span class="normal">  </span><span class="function"><a href="gobject-Generic-values.html#g-value-transform">g_value_transform</a></span><span class="normal"> </span><span class="symbol">(&amp;</span><span class="normal">a</span><span class="symbol">,</span><span class="normal"> </span><span class="symbol">&amp;</span><span class="normal">b</span><span class="symbol">);</span>
<span class="normal">  </span><span class="function"><a href="./../glib/glib/glib-String-Utility-Functions.html#g-printf">g_printf</a></span><span class="normal"> </span><span class="symbol">(</span><span class="string">"%s</span><span class="specialchar">\n</span><span class="string">"</span><span class="symbol">,</span><span class="normal"> </span><span class="function"><a href="gobject-Standard-Parameter-and-Value-Types.html#g-value-get-string">g_value_get_string</a></span><span class="normal"> </span><span class="symbol">(&amp;</span><span class="normal">b</span><span class="symbol">));</span>

<span class="normal">  </span><span class="comment">/* Attempt to transform it again using a custom transform function */</span>
<span class="normal">  </span><span class="function"><a href="gobject-Generic-values.html#g-value-register-transform-func">g_value_register_transform_func</a></span><span class="normal"> </span><span class="symbol">(</span><span class="normal"><a href="gobject-Type-Information.html#G-TYPE-INT:CAPS">G_TYPE_INT</a></span><span class="symbol">,</span><span class="normal"> <a href="gobject-Type-Information.html#G-TYPE-STRING:CAPS">G_TYPE_STRING</a></span><span class="symbol">,</span><span class="normal"> int2string</span><span class="symbol">);</span>
<span class="normal">  </span><span class="function"><a href="gobject-Generic-values.html#g-value-transform">g_value_transform</a></span><span class="normal"> </span><span class="symbol">(&amp;</span><span class="normal">a</span><span class="symbol">,</span><span class="normal"> </span><span class="symbol">&amp;</span><span class="normal">b</span><span class="symbol">);</span>
<span class="normal">  </span><span class="function"><a href="./../glib/glib/glib-String-Utility-Functions.html#g-printf">g_printf</a></span><span class="normal"> </span><span class="symbol">(</span><span class="string">"%s</span><span class="specialchar">\n</span><span class="string">"</span><span class="symbol">,</span><span class="normal"> </span><span class="function"><a href="gobject-Standard-Parameter-and-Value-Types.html#g-value-get-string">g_value_get_string</a></span><span class="normal"> </span><span class="symbol">(&amp;</span><span class="normal">b</span><span class="symbol">));</span>
<span class="normal">  </span><span class="keyword">return</span><span class="normal"> </span><span class="number">0</span><span class="symbol">;</span>
<span class="cbracket">}</span></pre></td>
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    </tbody>
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</div>

<p>
</p>
</div>
<div class="refsect1">
<a name="gobject-Generic-values.details"></a><h2>Details</h2>
<div class="refsect2">
<a name="G-VALUE-INIT:CAPS"></a><h3>G_VALUE_INIT</h3>
<pre class="programlisting">#define G_VALUE_INIT  { 0, { { 0 } } }
</pre>
<p>
A <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> must be initialized before it can be used.
This macro can be used as initializer instead of an explicit
<code class="literal">{ 0 }</code> when declaring a variable,
but it cannot be assigned to a variable.
</p>
<p>
</p>
<div class="informalexample">
  <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
    <tbody>
      <tr>
        <td class="listing_lines" align="right"><pre>1</pre></td>
        <td class="listing_code"><pre class="programlisting"><span class="usertype">GValue</span><span class="normal"> value </span><span class="symbol">=</span><span class="normal"> <a href="gobject-Generic-values.html#G-VALUE-INIT:CAPS">G_VALUE_INIT</a></span><span class="symbol">;</span></pre></td>
      </tr>
    </tbody>
  </table>
</div>

<p>
</p>
<p class="since">Since 2.30</p>
</div>
<hr>
<div class="refsect2">
<a name="G-VALUE-HOLDS:CAPS"></a><h3>G_VALUE_HOLDS()</h3>
<pre class="programlisting">#define G_VALUE_HOLDS(value,type) (G_TYPE_CHECK_VALUE_TYPE ((value), (type)))
</pre>
<p>
Checks if <em class="parameter"><code>value</code></em> holds (or contains) a value of <em class="parameter"><code>type</code></em>.
This macro will also check for <em class="parameter"><code>value</code></em> != <a href="./../glib/glib/glib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a> and issue a
warning if the check fails.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>value</code></em> :</span></p></td>
<td>A <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>type</code></em> :</span></p></td>
<td>A <a class="link" href="gobject-Type-Information.html#GType" title="GType"><span class="type">GType</span></a> value.</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>
<a href="./../glib/glib/glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> if <em class="parameter"><code>value</code></em> holds the <em class="parameter"><code>type</code></em>.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="G-VALUE-TYPE:CAPS"></a><h3>G_VALUE_TYPE()</h3>
<pre class="programlisting">#define G_VALUE_TYPE(value)		(((GValue*) (value))-&gt;g_type)
</pre>
<p>
Get the type identifier of <em class="parameter"><code>value</code></em>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>value</code></em> :</span></p></td>
<td>A <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure.</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>the <a class="link" href="gobject-Type-Information.html#GType" title="GType"><span class="type">GType</span></a>.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="G-VALUE-TYPE-NAME:CAPS"></a><h3>G_VALUE_TYPE_NAME()</h3>
<pre class="programlisting">#define G_VALUE_TYPE_NAME(value) (g_type_name (G_VALUE_TYPE (value)))
</pre>
<p>
Gets the type name of <em class="parameter"><code>value</code></em>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>value</code></em> :</span></p></td>
<td>A <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure.</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>the type name.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="G-TYPE-IS-VALUE:CAPS"></a><h3>G_TYPE_IS_VALUE()</h3>
<pre class="programlisting">#define G_TYPE_IS_VALUE(type)		(g_type_check_is_value_type (type))
</pre>
<p>
Checks whether the passed in type ID can be used for <a class="link" href="gobject-Generic-values.html#g-value-init" title="g_value_init ()"><code class="function">g_value_init()</code></a>.
That is, this macro checks whether this type provides an implementation
of the <a class="link" href="gobject-Type-Information.html#GTypeValueTable" title="struct GTypeValueTable"><span class="type">GTypeValueTable</span></a> functions required for a type to create a <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> of.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>type</code></em> :</span></p></td>
<td>A <a class="link" href="gobject-Type-Information.html#GType" title="GType"><span class="type">GType</span></a> value.</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>Whether <em class="parameter"><code>type</code></em> is suitable as a <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> type.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="G-TYPE-IS-VALUE-ABSTRACT:CAPS"></a><h3>G_TYPE_IS_VALUE_ABSTRACT()</h3>
<pre class="programlisting">#define G_TYPE_IS_VALUE_ABSTRACT(type)          (g_type_test_flags ((type), G_TYPE_FLAG_VALUE_ABSTRACT))
</pre>
<p>
Checks if <em class="parameter"><code>type</code></em> is an abstract value type.  An abstract value type introduces
a value table, but can't be used for <a class="link" href="gobject-Generic-values.html#g-value-init" title="g_value_init ()"><code class="function">g_value_init()</code></a> and is normally used as
an abstract base type for derived value types.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>type</code></em> :</span></p></td>
<td>A <a class="link" href="gobject-Type-Information.html#GType" title="GType"><span class="type">GType</span></a> value.</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>
<a href="./../glib/glib/glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> on success.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="G-IS-VALUE:CAPS"></a><h3>G_IS_VALUE()</h3>
<pre class="programlisting">#define G_IS_VALUE(value)		(G_TYPE_CHECK_VALUE (value))
</pre>
<p>
Checks if <em class="parameter"><code>value</code></em> is a valid and initialized <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>value</code></em> :</span></p></td>
<td>A <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure.</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>
<a href="./../glib/glib/glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> on success.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="GValue"></a><h3>GValue</h3>
<pre class="programlisting">typedef struct {
} GValue;
</pre>
<p>
An opaque structure used to hold different types of values.
The data within the structure has protected scope: it is accessible only
to functions within a <a class="link" href="gobject-Type-Information.html#GTypeValueTable" title="struct GTypeValueTable"><span class="type">GTypeValueTable</span></a> structure, or implementations of
the g_value_*() API. That is, code portions which implement new fundamental
types.
<a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> users cannot make any assumptions about how data is stored
within the 2 element <em class="parameter"><code>data</code></em> union, and the <em class="parameter"><code>g_type</code></em> member should
only be accessed through the <a class="link" href="gobject-Generic-values.html#G-VALUE-TYPE:CAPS" title="G_VALUE_TYPE()"><code class="function">G_VALUE_TYPE()</code></a> macro.
</p>
</div>
<hr>
<div class="refsect2">
<a name="G-TYPE-VALUE:CAPS"></a><h3>G_TYPE_VALUE</h3>
<pre class="programlisting">#define G_TYPE_VALUE (g_value_get_type ())
</pre>
<p>
The type ID of the "GValue" type which is a boxed type,
used to pass around pointers to GValues.
</p>
</div>
<hr>
<div class="refsect2">
<a name="G-TYPE-VALUE-ARRAY:CAPS"></a><h3>G_TYPE_VALUE_ARRAY</h3>
<pre class="programlisting">#define G_TYPE_VALUE_ARRAY (g_value_array_get_type ())
</pre>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Warning</h3>
<p><code class="literal">G_TYPE_VALUE_ARRAY</code> has been deprecated since version 2.32 and should not be used in newly-written code. Use <a href="./../glib/glib/glib-Arrays.html#GArray"><span class="type">GArray</span></a> instead of <a class="link" href="gobject-Value-arrays.html#GValueArray" title="struct GValueArray"><span class="type">GValueArray</span></a></p>
</div>
<p>
The type ID of the "GValueArray" type which is a boxed type,
used to pass around pointers to GValueArrays.
</p>
</div>
<hr>
<div class="refsect2">
<a name="g-value-init"></a><h3>g_value_init ()</h3>
<pre class="programlisting"><a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="returnvalue">GValue</span></a> *            g_value_init                        (<em class="parameter"><code><a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *value</code></em>,
                                                         <em class="parameter"><code><a class="link" href="gobject-Type-Information.html#GType" title="GType"><span class="type">GType</span></a> g_type</code></em>);</pre>
<p>
Initializes <em class="parameter"><code>value</code></em> with the default value of <em class="parameter"><code>type</code></em>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>value</code></em> :</span></p></td>
<td>A zero-filled (uninitialized) <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>g_type</code></em> :</span></p></td>
<td>Type the <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> should hold values of.</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>the <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure that has been passed in. <span class="annotation">[<acronym title="Don't free data after the code is done."><span class="acronym">transfer none</span></acronym>]</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="g-value-copy"></a><h3>g_value_copy ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>                g_value_copy                        (<em class="parameter"><code>const <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *src_value</code></em>,
                                                         <em class="parameter"><code><a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *dest_value</code></em>);</pre>
<p>
Copies the value of <em class="parameter"><code>src_value</code></em> into <em class="parameter"><code>dest_value</code></em>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>src_value</code></em> :</span></p></td>
<td>An initialized <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>dest_value</code></em> :</span></p></td>
<td>An initialized <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure of the same type as <em class="parameter"><code>src_value</code></em>.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="g-value-reset"></a><h3>g_value_reset ()</h3>
<pre class="programlisting"><a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="returnvalue">GValue</span></a> *            g_value_reset                       (<em class="parameter"><code><a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *value</code></em>);</pre>
<p>
Clears the current value in <em class="parameter"><code>value</code></em> and resets it to the default value
(as if the value had just been initialized).
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>value</code></em> :</span></p></td>
<td>An initialized <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure.</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>the <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure that has been passed in</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="g-value-unset"></a><h3>g_value_unset ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>                g_value_unset                       (<em class="parameter"><code><a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *value</code></em>);</pre>
<p>
Clears the current value in <em class="parameter"><code>value</code></em> and "unsets" the type,
this releases all resources associated with this GValue.
An unset value is the same as an uninitialized (zero-filled)
<a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody><tr>
<td><p><span class="term"><em class="parameter"><code>value</code></em> :</span></p></td>
<td>An initialized <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure.</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="g-value-set-instance"></a><h3>g_value_set_instance ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>                g_value_set_instance                (<em class="parameter"><code><a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *value</code></em>,
                                                         <em class="parameter"><code><a href="./../glib/glib/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> instance</code></em>);</pre>
<p>
Sets <em class="parameter"><code>value</code></em> from an instantiatable type via the
value_table's <code class="function">collect_value()</code> function.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>value</code></em> :</span></p></td>
<td>An initialized <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>instance</code></em> :</span></p></td>
<td>the instance. <span class="annotation">[<acronym title="NULL is ok, both for passing and for returning."><span class="acronym">allow-none</span></acronym>]</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="g-value-fits-pointer"></a><h3>g_value_fits_pointer ()</h3>
<pre class="programlisting"><a href="./../glib/glib/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>            g_value_fits_pointer                (<em class="parameter"><code>const <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *value</code></em>);</pre>
<p>
Determines if <em class="parameter"><code>value</code></em> will fit inside the size of a pointer value.
This is an internal function introduced mainly for C marshallers.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>value</code></em> :</span></p></td>
<td>An initialized <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure.</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>
<a href="./../glib/glib/glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> if <em class="parameter"><code>value</code></em> will fit inside a pointer value.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="g-value-peek-pointer"></a><h3>g_value_peek_pointer ()</h3>
<pre class="programlisting"><a href="./../glib/glib/glib-Basic-Types.html#gpointer"><span class="returnvalue">gpointer</span></a>            g_value_peek_pointer                (<em class="parameter"><code>const <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *value</code></em>);</pre>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>value</code></em> :</span></p></td>
<td>An initialized <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> structure.</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>the value contents as pointer. This
function asserts that <a class="link" href="gobject-Generic-values.html#g-value-fits-pointer" title="g_value_fits_pointer ()"><code class="function">g_value_fits_pointer()</code></a> returned <a href="./../glib/glib/glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> for the
passed in value.  This is an internal function introduced mainly
for C marshallers. <span class="annotation">[<acronym title="Don't free data after the code is done."><span class="acronym">transfer none</span></acronym>]</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="g-value-type-compatible"></a><h3>g_value_type_compatible ()</h3>
<pre class="programlisting"><a href="./../glib/glib/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>            g_value_type_compatible             (<em class="parameter"><code><a class="link" href="gobject-Type-Information.html#GType" title="GType"><span class="type">GType</span></a> src_type</code></em>,
                                                         <em class="parameter"><code><a class="link" href="gobject-Type-Information.html#GType" title="GType"><span class="type">GType</span></a> dest_type</code></em>);</pre>
<p>
Returns whether a <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> of type <em class="parameter"><code>src_type</code></em> can be copied into
a <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> of type <em class="parameter"><code>dest_type</code></em>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>src_type</code></em> :</span></p></td>
<td>source type to be copied.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>dest_type</code></em> :</span></p></td>
<td>destination type for copying.</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>
<a href="./../glib/glib/glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> if <a class="link" href="gobject-Generic-values.html#g-value-copy" title="g_value_copy ()"><code class="function">g_value_copy()</code></a> is possible with <em class="parameter"><code>src_type</code></em> and <em class="parameter"><code>dest_type</code></em>.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="g-value-type-transformable"></a><h3>g_value_type_transformable ()</h3>
<pre class="programlisting"><a href="./../glib/glib/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>            g_value_type_transformable          (<em class="parameter"><code><a class="link" href="gobject-Type-Information.html#GType" title="GType"><span class="type">GType</span></a> src_type</code></em>,
                                                         <em class="parameter"><code><a class="link" href="gobject-Type-Information.html#GType" title="GType"><span class="type">GType</span></a> dest_type</code></em>);</pre>
<p>
Check whether <a class="link" href="gobject-Generic-values.html#g-value-transform" title="g_value_transform ()"><code class="function">g_value_transform()</code></a> is able to transform values
of type <em class="parameter"><code>src_type</code></em> into values of type <em class="parameter"><code>dest_type</code></em>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>src_type</code></em> :</span></p></td>
<td>Source type.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>dest_type</code></em> :</span></p></td>
<td>Target type.</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>
<a href="./../glib/glib/glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> if the transformation is possible, <a href="./../glib/glib/glib-Standard-Macros.html#FALSE:CAPS"><code class="literal">FALSE</code></a> otherwise.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="g-value-transform"></a><h3>g_value_transform ()</h3>
<pre class="programlisting"><a href="./../glib/glib/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>            g_value_transform                   (<em class="parameter"><code>const <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *src_value</code></em>,
                                                         <em class="parameter"><code><a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *dest_value</code></em>);</pre>
<p>
Tries to cast the contents of <em class="parameter"><code>src_value</code></em> into a type appropriate
to store in <em class="parameter"><code>dest_value</code></em>, e.g. to transform a <a class="link" href="gobject-Type-Information.html#G-TYPE-INT:CAPS" title="G_TYPE_INT"><code class="literal">G_TYPE_INT</code></a> value
into a <a class="link" href="gobject-Type-Information.html#G-TYPE-FLOAT:CAPS" title="G_TYPE_FLOAT"><code class="literal">G_TYPE_FLOAT</code></a> value. Performing transformations between
value types might incur precision lossage. Especially
transformations into strings might reveal seemingly arbitrary
results and shouldn't be relied upon for production code (such
as rcfile value or object property serialization).
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>src_value</code></em> :</span></p></td>
<td>Source value.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>dest_value</code></em> :</span></p></td>
<td>Target value.</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>Whether a transformation rule was found and could be applied.
Upon failing transformations, <em class="parameter"><code>dest_value</code></em> is left untouched.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="GValueTransform"></a><h3>GValueTransform ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>                (*GValueTransform)                  (<em class="parameter"><code>const <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *src_value</code></em>,
                                                         <em class="parameter"><code><a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *dest_value</code></em>);</pre>
<p>
The type of value transformation functions which can be registered with
<a class="link" href="gobject-Generic-values.html#g-value-register-transform-func" title="g_value_register_transform_func ()"><code class="function">g_value_register_transform_func()</code></a>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>src_value</code></em> :</span></p></td>
<td>Source value.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>dest_value</code></em> :</span></p></td>
<td>Target value.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="g-value-register-transform-func"></a><h3>g_value_register_transform_func ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>                g_value_register_transform_func     (<em class="parameter"><code><a class="link" href="gobject-Type-Information.html#GType" title="GType"><span class="type">GType</span></a> src_type</code></em>,
                                                         <em class="parameter"><code><a class="link" href="gobject-Type-Information.html#GType" title="GType"><span class="type">GType</span></a> dest_type</code></em>,
                                                         <em class="parameter"><code><a class="link" href="gobject-Generic-values.html#GValueTransform" title="GValueTransform ()"><span class="type">GValueTransform</span></a> transform_func</code></em>);</pre>
<p>
Registers a value transformation function for use in <a class="link" href="gobject-Generic-values.html#g-value-transform" title="g_value_transform ()"><code class="function">g_value_transform()</code></a>.
A previously registered transformation function for <em class="parameter"><code>src_type</code></em> and <em class="parameter"><code>dest_type</code></em>
will be replaced.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>src_type</code></em> :</span></p></td>
<td>Source type.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>dest_type</code></em> :</span></p></td>
<td>Target type.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>transform_func</code></em> :</span></p></td>
<td>a function which transforms values of type <em class="parameter"><code>src_type</code></em>
into value of type <em class="parameter"><code>dest_type</code></em>
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="g-strdup-value-contents"></a><h3>g_strdup_value_contents ()</h3>
<pre class="programlisting"><a href="./../glib/glib/glib-Basic-Types.html#gchar"><span class="returnvalue">gchar</span></a> *             g_strdup_value_contents             (<em class="parameter"><code>const <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> *value</code></em>);</pre>
<p>
Return a newly allocated string, which describes the contents of a
<a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a>.  The main purpose of this function is to describe <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a>
contents for debugging output, the way in which the contents are
described may change between different GLib versions.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>value</code></em> :</span></p></td>
<td>
<a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> which contents are to be described.</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>Newly allocated string.</td>
</tr>
</tbody>
</table></div>
</div>
</div>
<div class="refsect1">
<a name="gobject-Generic-values.see-also"></a><h2>See Also</h2>
The fundamental types which all support <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a>
    operations and thus can be used as a type initializer for
    <a class="link" href="gobject-Generic-values.html#g-value-init" title="g_value_init ()"><code class="function">g_value_init()</code></a> are defined by a separate interface.  See the <a class="link" href="gobject-Standard-Parameter-and-Value-Types.html" title="Parameters and Values">Standard
    Values API</a> for details.
</div>
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