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<h2><span class="refentrytitle">Multi-head Support Overview</span></h2>
<p>Multi-head Support Overview — Overview of GdkDisplay and GdkScreen</p>
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<td class="gallery_image" valign="top" align="right"></td>
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<div class="refsect1">
<a name="id-1.2.3.3"></a><h2>Overview</h2>
<p>
Multihead support is based around two main object types:
</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem"><p>GdkDisplay</p></li>
<li class="listitem"><p>GdkScreen</p></li>
</ul></div>
<p>
</p>
<p>
GdkDisplay objects are the GDK
representation of the X Display which can be described as <span class="emphasis"><em>a
workstation consisting of a keyboard a pointing device (such as a
mouse) and one or more screens</em></span>.
It is used to open and keep track of various GdkScreen objects currently
instanciated by the application. It is also used to grab and release
the keyboard and the mouse pointer.
</p>
<p>
GdkScreen objects are the GDK
representation of a physical screen. It is used throughout GDK and GTK+
to specify which screen the top level windows are to be displayed on.
It is also used to query the screen specification and default settings such as
the default colormap (<a class="link" href="GdkScreen.html#gdk-screen-get-default-colormap" title="gdk_screen_get_default_colormap ()">gdk_screen_get_default_colormap</a>()),
the screen width (<a class="link" href="GdkScreen.html#gdk-screen-get-width" title="gdk_screen_get_width ()">gdk_screen_get_width</a>()), etc.
</p>
<p>
The following code samples demonstrate common usage of the objects described above.
</p>
<div class="example">
<a name="id-1.2.3.3.6"></a><p class="title"><b>Example 1. Testing the number of screen on the current display</b></p>
<div class="example-contents">
<table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
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<td class="listing_code"><pre class="programlisting">gint num_screen <span class="gtkdoc opt">=</span> <span class="number">0</span><span class="gtkdoc opt">;</span>
gchar <span class="gtkdoc opt">*</span>displayname <span class="gtkdoc opt">=</span> NULL<span class="gtkdoc opt">;</span>
GdkScreen <span class="gtkdoc opt">**</span>screen_list<span class="gtkdoc opt">;</span>
GdkDisplay <span class="gtkdoc opt">*</span>display<span class="gtkdoc opt">;</span>
<span class="function"><a href="../gtk4/gtk4-General.html#gtk-init">gtk_init</a></span> <span class="gtkdoc opt">(&</span>argc<span class="gtkdoc opt">, &</span>argv<span class="gtkdoc opt">);</span>
display <span class="gtkdoc opt">=</span> <span class="function"><a href="GdkDisplay.html#gdk-display-get-default">gdk_display_get_default</a></span> <span class="gtkdoc opt">();</span>
num_screen <span class="gtkdoc opt">=</span> <span class="function"><a href="GdkDisplay.html#gdk-display-get-n-screens">gdk_display_get_n_screens</a></span> <span class="gtkdoc opt">(</span>display<span class="gtkdoc opt">);</span>
displayname <span class="gtkdoc opt">=</span> <span class="function"><a href="GdkDisplay.html#gdk-display-get-name">gdk_display_get_name</a></span> <span class="gtkdoc opt">(</span>display<span class="gtkdoc opt">);</span>
<span class="keyword">if</span> <span class="gtkdoc opt">(</span>num_screen <span class="gtkdoc opt"><=</span> <span class="number">1</span><span class="gtkdoc opt">)</span>
<span class="gtkdoc opt">{</span>
<span class="function">printf</span> <span class="gtkdoc opt">(</span><span class="string">"This Xserver (%s) manages only one screen. exiting...</span><span class="gtkdoc esc">\n</span><span class="string">"</span><span class="gtkdoc opt">,</span>
displayname<span class="gtkdoc opt">);</span>
<span class="function">exit</span> <span class="gtkdoc opt">(</span><span class="number">1</span><span class="gtkdoc opt">);</span>
<span class="gtkdoc opt">}</span>
<span class="keyword">else</span>
<span class="gtkdoc opt">{</span>
<span class="function">printf</span> <span class="gtkdoc opt">(</span><span class="string">"This Xserver (%s) manages %d screens.</span><span class="gtkdoc esc">\n</span><span class="string">"</span><span class="gtkdoc opt">,</span> displayname<span class="gtkdoc opt">,</span>
num_screen<span class="gtkdoc opt">);</span>
<span class="gtkdoc opt">}</span></pre></td>
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</tbody>
</table>
</div>
</div>
<br class="example-break"><div class="example">
<a name="id-1.2.3.3.7"></a><p class="title"><b>Example 2. Opening a second display</b></p>
<div class="example-contents">
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<td class="listing_code"><pre class="programlisting">gchar <span class="gtkdoc opt">*</span>second_screen_name<span class="gtkdoc opt">;</span>
GdkDisplay <span class="gtkdoc opt">*</span>second_display<span class="gtkdoc opt">;</span>
GdkScreen <span class="gtkdoc opt">*</span>second_screen<span class="gtkdoc opt">;</span>
GtkWidget <span class="gtkdoc opt">*</span>window<span class="gtkdoc opt">;</span>
<span class="function"><a href="../gtk4/gtk4-General.html#gtk-init">gtk_init</a></span> <span class="gtkdoc opt">(&</span>argc<span class="gtkdoc opt">, &</span>argv<span class="gtkdoc opt">);</span>
<span class="comment">/* screen2_name needs to be initialized before calling </span>
<span class="comment">/* gdk_display_new() */</span>
second_display <span class="gtkdoc opt">=</span> <span class="function">gdk_display_new</span> <span class="gtkdoc opt">(&</span>argc<span class="gtkdoc opt">, &</span>argv<span class="gtkdoc opt">,</span> second_screen_name<span class="gtkdoc opt">);</span>
<span class="keyword">if</span> <span class="gtkdoc opt">(</span>second_display<span class="gtkdoc opt">)</span>
second_screen <span class="gtkdoc opt">=</span> <span class="function"><a href="GdkDisplay.html#gdk-display-get-default-screen">gdk_display_get_default_screen</a></span> <span class="gtkdoc opt">(</span>second_display<span class="gtkdoc opt">);</span>
<span class="keyword">else</span>
<span class="gtkdoc opt">{</span>
<span class="function"><a href="../glib/glib-Warnings-and-Assertions.html#g-print">g_print</a></span> <span class="gtkdoc opt">(</span><span class="string">"Can't open display :</span><span class="gtkdoc esc">\n\t</span><span class="string">%s</span><span class="gtkdoc esc">\n\n</span><span class="string">"</span><span class="gtkdoc opt">,</span>
second_screen_name<span class="gtkdoc opt">);</span>
<span class="function">exit</span> <span class="gtkdoc opt">(</span><span class="number">1</span><span class="gtkdoc opt">);</span>
<span class="gtkdoc opt">}</span>
<span class="comment">/* now GdkScreen can be assigned to GtkWindows */</span>
window <span class="gtkdoc opt">=</span> <span class="function"><a href="../gtk4/GtkWindow.html#gtk-window-new">gtk_window_new</a></span> <span class="gtkdoc opt">(</span>GTK_WINDOW_TOPLEVEL<span class="gtkdoc opt">);</span>
<span class="function">gtk_window_set_screen</span> <span class="gtkdoc opt">(</span>window<span class="gtkdoc opt">,</span> second_screen<span class="gtkdoc opt">);</span></pre></td>
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</div>
</div>
<br class="example-break">
</div>
<div class="refsect1">
<a name="id-1.2.3.4"></a><h2>See Also</h2>
<p>
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term">GdkDisplay</span></p></td>
<td><p>the GDK Object used to represent and manipulate display
related data</p></td>
</tr>
<tr>
<td><p><span class="term">GdkScreen</span></p></td>
<td><p>the GDK Object used to represent and query screen related
data</p></td>
</tr>
</tbody>
</table></div>
<p>
</p>
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