<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 WindowSystem 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 specifiedin 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 someadditional 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 certainaspects of the X Window System surprising. This section introducessome basic X concepts at a high level. For more details, the book mostpeople use is called the <citetitle pubwork="book">Xlib ProgrammingManual</citetitle> by Adrian Nye; this book is volume one in theO'Reilly X Window System series.</para><para>Standards are another important resource if you're poking in low-levelX11 details, in particular the ICCCM and the Extended Window ManagerHints specifications. <ulinkurl="http://www.freedesktop.org/standards/">freedesktop.org</ulink>has links to many relevant specifications.</para><para>The GDK manual covers <linklinkend="gdk-X-Window-System-Interaction">using Xlib in a GTKprogram</link>.</para><refsect2><title>Server, client, window manager</title><para>Other window systems typically put all their functionality in theapplication itself. With X, each application involves three differentprograms: the <firstterm>X server</firstterm>, the application (calleda <firstterm>client</firstterm> because it's a client of the Xserver), and a special client called the <firstterm>windowmanager</firstterm>.</para><para>The X server is in charge of managing resources, processing drawingrequests, and dispatching events such as keyboard and mouse events tointerested applications. So client applications can ask the X serverto create a window, draw a circle, or move windows around.</para><para>The window manager is in charge of rendering the frame or bordersaround 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 yourbehalf, using an established  <ulinkurl="http://www.freedesktop.org/standards/">convention</ulink>.</para><para>GTK+ has functions for asking the window manager to do various things;see for example <linklinkend="gtk-window-iconify">gtk_window_iconify()</link> or <linklinkend="gtk-window-maximize">gtk_window_maximize()</link> or <linklinkend="gtk-window-set-decorated">gtk_window_set_decorated()</link>.Keep in mind that <linklinkend="gtk-window-move">gtk_window_move()</link> and window sizingare ultimately controlled by the window manager as well and mostwindow managers <emphasis>will</emphasis> ignore certain requests fromtime 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>