glib-standard-macros.html

glid编写实例

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<span class="term"><em class="parameter"><code>b</code></em>&#160;:</span></td>
<td>a numeric value.
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<span class="term"><span class="emphasis"><em>Returns</em></span>&#160;:</span></td>
<td>the maximum of <em class="parameter"><code>a</code></em> and <em class="parameter"><code>b</code></em>.


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<div class="refsect2" lang="en">
<a name="id2824958"></a><h3>
<a name="ABS:CAPS"></a>ABS()</h3>
<a class="indexterm" name="id2824968"></a><pre class="programlisting">#define ABS(a)	   (((a) &lt; 0) ? -(a) : (a))
</pre>
<p>
Calculates the absolute value of <em class="parameter"><code>a</code></em>.
The absolute value is simply the number with any negative sign taken away.
</p>
<p>
For example,
</p>
<div class="itemizedlist"><ul type="disc">
<li><p>
ABS(-10) is 10.
</p></li>
<li><p>
ABS(10) is also 10.
</p></li>
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<span class="term"><em class="parameter"><code>a</code></em>&#160;:</span></td>
<td>a numeric value.
</td>
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<td>
<span class="term"><span class="emphasis"><em>Returns</em></span>&#160;:</span></td>
<td>the absolute value of <em class="parameter"><code>a</code></em>.


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<div class="refsect2" lang="en">
<a name="id2825040"></a><h3>
<a name="CLAMP:CAPS"></a>CLAMP()</h3>
<a class="indexterm" name="id2825050"></a><pre class="programlisting">#define CLAMP(x, low, high)  (((x) &gt; (high)) ? (high) : (((x) &lt; (low)) ? (low) : (x)))
</pre>
<p>
Ensures that <em class="parameter"><code>x</code></em> is between the limits set by <em class="parameter"><code>low</code></em> and <em class="parameter"><code>high</code></em>.
</p>
<p>
For example,
</p>
<div class="itemizedlist"><ul type="disc">
<li><p>
CLAMP(5, 10, 15) is 10.
</p></li>
<li><p>
CLAMP(15, 5, 10) is 10.
</p></li>
<li><p>
CLAMP(20, 15, 25) is 20.
</p></li>
</ul></div>
<p>
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<span class="term"><em class="parameter"><code>x</code></em>&#160;:</span></td>
<td>the value to clamp.
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<span class="term"><em class="parameter"><code>low</code></em>&#160;:</span></td>
<td>the minimum value allowed.
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<span class="term"><em class="parameter"><code>high</code></em>&#160;:</span></td>
<td>the maximum value allowed.
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<span class="term"><span class="emphasis"><em>Returns</em></span>&#160;:</span></td>
<td>the value of <em class="parameter"><code>x</code></em> clamped to the range between <em class="parameter"><code>low</code></em> and <em class="parameter"><code>high</code></em>.


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<div class="refsect2" lang="en">
<a name="id2825182"></a><h3>
<a name="G-STRUCT-MEMBER:CAPS"></a>G_STRUCT_MEMBER()</h3>
<a class="indexterm" name="id2825192"></a><pre class="programlisting">#define     G_STRUCT_MEMBER(member_type, struct_p, struct_offset)</pre>
<p>
Returns a member of a structure at a given offset, using the given type.
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<span class="term"><em class="parameter"><code>member_type</code></em>&#160;:</span></td>
<td>the type of the struct field.
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<span class="term"><em class="parameter"><code>struct_p</code></em>&#160;:</span></td>
<td>a pointer to a struct.
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<span class="term"><em class="parameter"><code>struct_offset</code></em>&#160;:</span></td>
<td>the offset of the field from the start of the struct, in bytes.
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<span class="term"><span class="emphasis"><em>Returns</em></span>&#160;:</span></td>
<td>the struct member.


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<div class="refsect2" lang="en">
<a name="id2825267"></a><h3>
<a name="G-STRUCT-MEMBER-P:CAPS"></a>G_STRUCT_MEMBER_P()</h3>
<a class="indexterm" name="id2825278"></a><pre class="programlisting">#define     G_STRUCT_MEMBER_P(struct_p, struct_offset)</pre>
<p>
Returns an untyped pointer to a given offset of a struct.
</p>
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<span class="term"><em class="parameter"><code>struct_p</code></em>&#160;:</span></td>
<td>a pointer to a struct.
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<span class="term"><em class="parameter"><code>struct_offset</code></em>&#160;:</span></td>
<td>the offset from the start of the struct, in bytes.
</td>
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<td>
<span class="term"><span class="emphasis"><em>Returns</em></span>&#160;:</span></td>
<td>an untyped pointer to <em class="parameter"><code>struct_p</code></em> plus <em class="parameter"><code>struct_offset</code></em> bytes.


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<div class="refsect2" lang="en">
<a name="id2825350"></a><h3>
<a name="G-STRUCT-OFFSET:CAPS"></a>G_STRUCT_OFFSET()</h3>
<a class="indexterm" name="id2825361"></a><pre class="programlisting">#define     G_STRUCT_OFFSET(struct_type, member)</pre>
<p>
Returns the offset, in bytes, of a member of a struct.
</p>
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<span class="term"><em class="parameter"><code>struct_type</code></em>&#160;:</span></td>
<td>a structure type, e.g. <span class="structname">GtkWidget</span>.
</td>
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<span class="term"><em class="parameter"><code>member</code></em>&#160;:</span></td>
<td>a field in the structure, e.g. <em class="structfield"><code>window</code></em>.
</td>
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<td>
<span class="term"><span class="emphasis"><em>Returns</em></span>&#160;:</span></td>
<td>the offset of <em class="parameter"><code>member</code></em> from the start of <em class="parameter"><code>struct_type</code></em>.


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<div class="refsect2" lang="en">
<a name="id2825439"></a><h3>
<a name="G-MEM-ALIGN:CAPS"></a>G_MEM_ALIGN</h3>
<a class="indexterm" name="id2825450"></a><pre class="programlisting">#define     G_MEM_ALIGN</pre>
<p>
Indicates the number of bytes to which memory will be aligned on the
current platform.
</p>
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<div class="refsect2" lang="en">
<a name="id2825466"></a><h3>
<a name="G-CONST-RETURN:CAPS"></a>G_CONST_RETURN</h3>
<a class="indexterm" name="id2825476"></a><pre class="programlisting">#define     G_CONST_RETURN</pre>
<p>
If <code class="literal">G_DISABLE_CONST_RETURNS</code> is defined, this macro expands to nothing.
By default, the macro expands to <code class="literal">const</code>. The macro 
should be used in place of <code class="literal">const</code> for functions that 
return a value that should not be modified. The purpose of this macro is 
to allow us to turn on <code class="literal">const</code> for returned constant 
strings by default, while allowing programmers who find that annoying to 
turn it off. This macro should only be used for return values and for
<span class="emphasis"><em>out</em></span> parameters, it doesn't make sense for 
<span class="emphasis"><em>in</em></span> parameters. 
</p>
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