<refentry id="gtk-x11" revision="17 Jan 2002">
<refmeta>
<refentrytitle>Using GTK+ on the X Window System</refentrytitle>
<manvolnum>3</manvolnum>
<refmiscinfo>GTK Library</refmiscinfo>
</refmeta>

<refnamediv>
<refname>Using GTK+ on the X Window System</refname>
<refpurpose>
X11 aspects of using GTK+
</refpurpose>
</refnamediv>

<refsect1>
<title>GTK+ for the X Window System</title>

<para>
On UNIX, the X backend is the default build for GTK+. So 
you don't need to do anything special when compiling it,
and everything should "just work."
</para>

<para>
To mix low-level Xlib routines into a GTK program, 
see <link linkend="gdk-X-Window-System-Interaction">GDK X Window
System interaction</link> in the GDK manual.
</para>

<refsect2 id="x11-cmdline">
<title>X11-specific commandline options</title>

<para>
The X backend understands some additional command line 
arguments.
</para>

<formalpara>
<title><systemitem>--display <replaceable>display</replaceable></systemitem></title>

<para>
The name of the X display to open instead of the one specified
in the <envar>DISPLAY</envar> environment variable. 
</para>
</formalpara>

<formalpara>
<title><systemitem>--screen <replaceable>screen_number</replaceable></systemitem></title>

<para>
  The number of the screen within the default display. This overrides
  any screen number specified in the display name specified by
  by he <systemitem>--display</systemitem> command line option or
  the <envar>DISPLAY</envar> environment variable. If this screen
  cannot be opened, then GTK+ will fall back to the screen
  specified in the display name. This option is not useful
  interactively; the intended purposes is that when a program
  registers its command line with a <firstterm>session
  manager</firstterm> for later restarting, it can save the
  screen it is on, without having to worry if it might be
  restarted on a different display.
</para>
</formalpara>

<formalpara>
<title><systemitem>--sync</systemitem></title>

<para>
Makes all X requests synchronously. This is a useful option for 
debugging, but it will slow down the performance considerably.
</para>
</formalpara>

<formalpara>
<title><systemitem>--gxid-host <replaceable>host</replaceable></systemitem></title>

<para>
The host to contact the <application>gxid</application> daemon on; overrides 
the <link linkend="GXID"><envar>GXID_HOST</envar></link> environment variable.
</para>
</formalpara>

<formalpara>
<title><systemitem>--gxid-port <replaceable>port</replaceable></systemitem></title>

<para>
The port for the connection to <application>gxid</application>; overrides 
the <link linkend="GXID"><envar>GXID_PORT</envar></link> environment variable.
This option is only available if GTK+ has been configured with
<option>--gdk-target=x11</option>.
</para>
</formalpara>

</refsect2>

<refsect2 id="x11-envar">
<title>X11-specific environment variables</title>

<para>
The X backend can be influenced with some
additional environment variables.
</para>

<formalpara id="GXID">
  <title><envar>GXID_HOST</envar>, <envar>GXID_PORT</envar></title>

  <para>
    The host and port to contact the <application>gxid</application> daemon 
    on. <application>gxid</application> is only necessary on X servers which 
    don't support using the pointer and extension devices at once, and is
    only built if GTK+ is configured with <option>--with-xinput=gxi</option>. 
    The <application>XFree86</application> and <application>Xorg</application>
    X servers don't have this 
    restriction.
  </para>
</formalpara>

<formalpara>
  <title><envar>GDK_USE_XFT</envar></title>

  <para>
    If this variable is set to 1, GTK+ will use the Pango Xft backend instead
    of the X backend when possible (i.e. when the X server supports the XRender
    extension and Pango has been built with Xft support). 
  </para>
</formalpara>

</refsect2>

</refsect1>

<refsect1 id="gtk-X11-arch">
<title>Understanding the X11 architecture</title>

<para>
People coming from a Windows or MacOS background often find certain
aspects of the X Window System surprising. This section introduces
some basic X concepts at a high level. For more details, the book most
people use is called the <citetitle pubwork="book">Xlib Programming
Manual</citetitle> by Adrian Nye; this book is volume one in the
O'Reilly X Window System series.
</para>
<para>
Standards are another important resource if you're poking in low-level
X11 details, in particular the ICCCM and the Extended Window Manager
Hints specifications. <ulink
url="http://www.freedesktop.org/standards/">freedesktop.org</ulink>
has links to many relevant specifications.
</para>
<para>
The GDK manual covers <link
linkend="gdk-X-Window-System-Interaction">using Xlib in a GTK
program</link>.
</para>

<refsect2>
<title>Server, client, window manager</title>

<para>
Other window systems typically put all their functionality in the
application itself. With X, each application involves three different
programs: the <firstterm>X server</firstterm>, the application (called
a <firstterm>client</firstterm> because it's a client of the X
server), and a special client called the <firstterm>window
manager</firstterm>.
</para>

<para>
The X server is in charge of managing resources, processing drawing
requests, and dispatching events such as keyboard and mouse events to
interested applications. So client applications can ask the X server
to create a window, draw a circle, or move windows around.
</para>

<para>
The window manager is in charge of rendering the frame or borders
around windows; it also has final say on the size of each window,
and window states such as minimized, maximized, and so forth.
On Windows and MacOS the application handles most of this.
On X11, if you wish to modify the window's state, or 
change its frame, you must ask the window manager to do so on your
behalf, using an established  <ulink
url="http://www.freedesktop.org/standards/">convention</ulink>.
</para>

<para>
GTK+ has functions for asking the window manager to do various things;
see for example <link
linkend="gtk-window-iconify">gtk_window_iconify()</link> or <link
linkend="gtk-window-maximize">gtk_window_maximize()</link> or <link
linkend="gtk-window-set-decorated">gtk_window_set_decorated()</link>.
Keep in mind that <link
linkend="gtk-window-move">gtk_window_move()</link> and window sizing
are ultimately controlled by the window manager as well and most
window managers <emphasis>will</emphasis> ignore certain requests from
time to time, in the interests of good user interface.
</para>

<!--
May also want to explain DESKTOP_STARTUP_ID here. 
http://www.freedesktop.org/Standards/startup-notification-spec
-->

</refsect2>

</refsect1>

</refentry>
