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<refentry id="gtk-running">
<refmeta>
<refentrytitle>Running GTK+ Applications</refentrytitle>
<manvolnum>3</manvolnum>
<refmiscinfo>GTK Library</refmiscinfo>
</refmeta>

<refnamediv>
<refname>Running GTK+ Applications</refname>
<refpurpose>
How to run and debug your GTK+ application
</refpurpose>
</refnamediv>

<refsect1>
<title>Running and debugging GTK+ Applications</title>

<refsect2>
<title>Common commandline options</title>

<para>
All GTK+ applications support a number of standard commandline
options. These are removed from <literal>argv</literal> by gtk_init().
Modules may parse and remove further options. The
<link linkend="x11-cmdline">X11</link> and
<link linkend="win32-cmdline">Windows</link> GDK backends parse
some additional commandline options.
</para>

<formalpara>
<title><systemitem>--gtk-module <replaceable>module</replaceable></systemitem></title>

<para>
A list of modules to load in addition to those specified in the
<envar>GTK3_MODULES</envar> environment variable and the
<literal>gtk-modules</literal> setting.
</para>
</formalpara>

<formalpara>
<title><systemitem>--g-fatal-warnings</systemitem></title>

<para>
Make GTK+ abort on all warnings. This is useful to stop on the first
warning in a debugger, if your application is printing multiple
warnings.  It's almost always best to start debugging with the first
warning that occurs.
</para>
</formalpara>

<formalpara>
<title><systemitem>--gtk-debug <replaceable>options</replaceable></systemitem></title>

<para>
A list of <link linkend="GTK-Debug-Options">debug options</link>
to turn on in addition to those specified in the <envar>GTK_DEBUG</envar>
environment variable. This option is not available if GTK+ has been
configured with <option>--enable-debug=no</option>.
</para>
</formalpara>

<formalpara>
<title><systemitem>--gtk-no-debug <replaceable>options</replaceable></systemitem></title>

<para>
A list of <link linkend="GTK-Debug-Options">debug options</link>
to turn off. This option is only available if GTK+ has been configured with
<option>--enable-debug=yes</option>.
</para>
</formalpara>

<para>
The following options are really used by GDK, not by GTK+, but we
list them here for completeness nevertheless.
</para>

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

<para>
Sets the program class; see gdk_set_program_class().
</para>
</formalpara>

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

<para>
Sets the program name.
</para>
</formalpara>

<formalpara>
<title><systemitem>--gdk-debug <replaceable>options</replaceable></systemitem></title>

<para>
A list of <link linkend="GDK-Debug-Options">debug options</link>
to turn on in addition to those specified in the <envar>GDK_DEBUG</envar>
environment variable. This option is only available if GTK+ has been
configured with <option>--enable-debug=yes</option>.
</para>
</formalpara>

<formalpara>
<title><systemitem>--gdk-no-debug <replaceable>options</replaceable></systemitem></title>

<para>
A list of <link linkend="GDK-Debug-Options">debug options</link>
to turn off. This option is only available if GTK+ has been configured with
<option>--enable-debug=yes</option>.
</para>
</formalpara>

</refsect2>

<refsect2>
<title>Environment variables</title>

<para>
GTK+ inspects a number of environment variables in addition to standard
variables like <envar>LANG</envar>, <envar>PATH</envar>, <envar>HOME</envar>
or <envar>DISPLAY</envar>; mostly to determine paths to look for certain
files. The <link linkend="x11-envar">X11</link>,
<link linkend="win32-envar">Windows</link> and
<link linkend="broadway-envar">Broadway</link> GDK backends use some
additional environment variables.
</para>

<formalpara id="GTK-Debug-Options">
  <title><envar>GTK_DEBUG</envar></title>

  <para>
  Unless GTK+ has been configured with <option>--enable-debug=no</option>,
  this variable can be set to a list of debug options, which cause GTK+
  to print out different types of debugging information.
  <variablelist>
    <varlistentry>
      <term>actions</term>
      <listitem><para>Actions and menu models</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>baselines</term>
      <listitem><para>Show baselines</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>builder</term>
      <listitem><para>GtkBuilder support</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>geometry</term>
      <listitem><para>Size allocation</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>icontheme</term>
      <listitem><para>Icon themes</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>interactive</term>
      <listitem><para>Open the <link linkend="interactive-debugging">interactive debugger</link></para></listitem>
    </varlistentry>
    <varlistentry>
      <term>keybindings</term>
      <listitem><para>Keybindings</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>misc</term>
      <listitem><para>Miscellaneous information</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>modules</term>
      <listitem><para>Loading of modules</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>no-css-cache</term>
      <listitem><para>Bypass caching for CSS style properties</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>no-pixel-cache</term>
      <listitem><para>Disable the pixel cache</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>plugsocket</term>
      <listitem><para>Cross-process embedding</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>pixel-cache</term>
      <listitem><para>Pixel cache</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>printing</term>
      <listitem><para>Printing support</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>size-request</term>
      <listitem><para>Size requests</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>text</term>
      <listitem><para>Text widget internals</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>touchscreen</term>
      <listitem><para>Pretend the pointer is a touchscreen device</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>tree</term>
      <listitem><para>Tree widget internals</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>updates</term>
      <listitem><para>Visual feedback about window updates</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>resize</term>
      <listitem><para>Highlight resizing widgets</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>layout</term>
      <listitem><para>Show layout borders</para></listitem>
    </varlistentry>
  </variablelist>
  The special value <literal>all</literal> can be used to turn on all
  debug options. The special value <literal>help</literal> can be used
  to obtain a list of all supported debug options.
  </para>
</formalpara>

<formalpara>
  <title><envar>GTK3_MODULES</envar></title>

  <para>
    A list of modules to load. Note that GTK+ also allows to specify modules to load via a commandline option (<option>--gtk-module</option>) and with the <literal>gtk-modules</literal> setting.
  </para>
</formalpara>

<formalpara>
  <title><envar>GTK_MODULES</envar></title>

  <para>
    A list of modules to load in addition to the ones in the <envar>GTK3_MODULES</envar> variable.
  </para>
  <warning>
    Note that this environment variable is read by GTK+ 2.x too,
    which may not have the same set of modules available for loading.
    Use <envar>GTK3_MODULES</envar> for modules that are only compatible
    with GTK+ 3.
  </warning>
</formalpara>

<formalpara id="gtk-path">
  <title><envar>GTK_PATH</envar></title>

  <para>
    Specifies a list of directories to search when GTK+ is looking for
    dynamically loaded objects such as the modules specified by
    <envar>GTK_MODULES</envar>, theme engines, input method
    modules, file system backends and print backends. If the path to
    the dynamically loaded object is given as an absolute path name,
    then GTK+ loads it directly.
    Otherwise, GTK+ goes in turn through the directories in <envar>GTK_PATH</envar>,
    followed by the directory <filename>.gtk-3.0</filename> in the user's
    home directory, followed by the system default directory,
    which is <filename><replaceable>libdir</replaceable>/gtk-3.0/modules</filename>.
    (If <envar>GTK_EXE_PREFIX</envar> is defined, <replaceable>libdir</replaceable> is
    <filename>$GTK_EXE_PREFIX/lib</filename>. Otherwise it is the libdir
    specified when GTK+ was configured, usually
    <filename>/usr/lib</filename>, or
    <filename>/usr/local/lib</filename>.)
    For each directory in this list, GTK+ actually looks in a
    subdirectory
    <filename><replaceable>directory</replaceable>/<replaceable>version</replaceable>/<replaceable>host</replaceable>/<replaceable>type</replaceable></filename>
    Where <replaceable>version</replaceable> is derived from the
    version of GTK+ (use <literal>pkg-config
    --variable=gtk_binary_version gtk+-3.0</literal> to determine this from a
    script), <replaceable>host</replaceable> is the architecture on
    which GTK+ was built. (use <literal>pkg-config
    --variable=gtk_host gtk+-3.0</literal> to determine this from a
    script), and <replaceable>type</replaceable> is a directory
    specific to the type of modules; currently it can be
    <literal>modules</literal>, <literal>engines</literal>,
    <literal>immodules</literal>, <literal>filesystems</literal> or
    <literal>printbackends</literal>, corresponding to the types of
    modules mentioned above. Either <replaceable>version</replaceable>,
    <replaceable>host</replaceable>, or both may be omitted. GTK+ looks
    first in the most specific directory, then in directories with
    fewer components.
    The components of GTK_PATH are separated by the ':' character on
    Linux and Unix, and the ';' character on Windows.
  </para>
  <warning>
    Note that this environment variable is read by GTK+ 2.x too, which
    makes it unsuitable for setting it system-wide (or session-wide),
    since doing so will cause either GTK+ 2.x applications or GTK+ 3
    applications to see incompatible modules.
  </warning>
</formalpara>

<formalpara>
  <title><envar>GTK_IM_MODULE</envar></title>

  <para>
    Specifies an IM module to use in preference to the one determined
    from the locale. If this isn't set and you are running on the system
    that enables <literal>XSETTINGS</literal> and has a value in
    <literal>Gtk/IMModule</literal>, that will be used for the default
    IM module.
    This also can be a colon-separated list of input-methods, which
    GTK+ will try in turn until it finds one available on the system.
  </para>
</formalpara>

<formalpara id="gtk-im-module-file">
  <title><envar>GTK_IM_MODULE_FILE</envar></title>

  <para>
    Specifies the file listing the IM modules to load. This environment
    variable the default value
    <filename><replaceable>libdir</replaceable>/gtk-3.0/3.0.0/immodules.cache</filename>
    (<replaceable>libdir</replaceable> has the same meaning here as explained for <envar>GTK_PATH</envar>).
  </para>
  <para>
    The <filename>immodules.cache</filename> file is generated by the
    <command>gtk-query-immodules-3.0</command> utility.
  </para>
  <warning>
    Note that this environment variable is read by GTK+ 2.x too, which
    makes it unsuitable for setting it system-wide (or session-wide),
    since doing so will cause either GTK+ 2.x applications or GTK+ 3
    applications to see the wrong list of IM modules.
  </warning>
</formalpara>

<formalpara>
  <title><envar>GTK_EXE_PREFIX</envar></title>

  <para>
    If set, GTK+ uses <filename>$GTK_EXE_PREFIX/lib</filename> instead of
    the libdir configured when GTK+ was compiled.
  </para>
</formalpara>

<formalpara>
  <title><envar>GTK_DATA_PREFIX</envar></title>

  <para>
    If set, makes GTK+ use <filename>$GTK_DATA_PREFIX</filename>
    instead of the prefix configured when GTK+ was compiled.
  </para>
</formalpara>

<formalpara>
  <title><envar>GTK_THEME</envar></title>

  <para>
    If set, makes GTK+ use the named theme instead of the theme
    that is specified by the gtk-theme-name setting. This is intended
    mainly for easy debugging of theme issues.
  </para>
  <para>
    It is also possible to specify a theme variant to load, by appending
    the variant name with a colon, like this: `GTK_THEME=Adwaita:dark`.
  </para>
</formalpara>

<para>
The following environment variables are used by GdkPixbuf, GDK or
Pango, not by GTK+ itself, but we list them here for completeness
nevertheless.
</para>

<formalpara>
  <title><envar>GDK_PIXBUF_MODULE_FILE</envar></title>

  <para>
    Specifies the file listing the GdkPixbuf loader modules to load.
    This environment variable overrides the default value
    <filename><replaceable>libdir</replaceable>/gtk-3.0/3.0.0/loaders.cache</filename>
    (<replaceable>libdir</replaceable> is the sysconfdir specified when
    GTK+ was configured, usually <filename>/usr/local/lib</filename>.)
  </para>
  <para>
    The <filename>loaders.cache</filename> file is generated by the
    <command>gdk-pixbuf-query-loaders</command> utility.
  </para>
 </formalpara>

<formalpara id="GDK-Debug-Options">
  <title><envar>GDK_DEBUG</envar></title>

  <para>
  If GTK+ has been configured with <option>--enable-debug=yes</option>,
  this variable can be set to a list of debug options, which cause GDK
  to print out different types of debugging information.
  <variablelist>
    <varlistentry>
      <term>cursor</term>
      <listitem><para>Information about cursor objects (only win32)</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>dnd</term>
      <listitem><para>Information about drag-and-drop</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>draw</term>
      <listitem><para>Information about drawing operations (only win32)</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>eventloop</term>
      <listitem><para>Information about event loop operation (mostly Quartz)</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>misc</term>
      <listitem><para>Miscellaneous information</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>nogl</term>
      <listitem><para>Turn off OpenGL. GDK will behave as if OpenGL support was not available.</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>nograbs</term>
      <listitem><para>Turn off all pointer and keyboard grabs</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>xinerama</term>
      <listitem><para>Simulate a multi-monitor setup</para></listitem>
    </varlistentry>
    <varlistentry>
      <term>xim</term>
      <listitem><para>Information about XIM support</para></listitem>
    </varlistentry>

  </variablelist>
  The special value <literal>all</literal> can be used to turn on all
  debug options.
  </para>
</formalpara>

<formalpara>
  <title><envar>GDK_RENDERING</envar></title>

  <para>
    If set, selects the way how GDK creates similar surfaces. This affects both the
    functionality of the function gdk_window_create_similar_surface() as well as the
    way GDK creates backing surfaces for double buffering. The following values can
    be used:
    <variablelist>

      <varlistentry>
        <term>similar</term>
        <listitem><para>Create similar surfaces to the window in use. This is the
          default behavior when the variable is not set.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term>image</term>
        <listitem><para>Always create image surfaces. This essentially turns off
          all hardware acceleration inside GTK.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term>recording</term>
        <listitem><para>Always create recording surfaces. This causes bare rendering
          to the backend without the creation of intermediate surfaces (Pixmaps in X)
          and will likely cause flicker.</para></listitem>
      </varlistentry>

    </variablelist>
    All other values will be ignored and fall back to the default behavior. More
    values might be added in the future. 
  </para>
</formalpara>

<formalpara>
  <title><envar>GDK_BACKEND</envar></title>

  <para>
    If set, selects the GDK backend to use. Selecting a backend requires that
    GTK+ is compiled with support for that backend. The following backends can
    be selected, provided they are included in the GDK libraries you are using:
    <variablelist>

      <varlistentry>
        <term>quartz</term>
        <listitem><para>Selects the native Quartz backend</para></listitem>
      </varlistentry>

      <varlistentry>
        <term>win32</term>
        <listitem><para>Selects the native backend for Microsoft Windows</para></listitem>
      </varlistentry>

      <varlistentry>
        <term>x11</term>
        <listitem><para>Selects the native backend for connecting to X11 servers.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term>broadway</term>
        <listitem><para>Selects the Broadway backend for display in web browsers</para></listitem>
      </varlistentry>

      <varlistentry>
        <term>wayland</term>
        <listitem><para>Selects the Wayland backend for connecting to Wayland display servers</para></listitem>
      </varlistentry>

      <varlistentry>
        <term>mir</term>
        <listitem><para>Selects the Mir backend for connecting to Mir display servers</para></listitem>
      </varlistentry>

    </variablelist>
    Since 3.10, this environment variable can contain a comma-separated list
    of backend names, which are tried in order. The list may also contain
    a *, which means: try all remaining backends. The special value "help" can
    be used to make GDK print out a list of all available backends.
    For more information about selecting backends, see the gdk_display_manager_get() function.
  </para>
</formalpara>

<formalpara>
  <title><envar>GTK_CSD</envar></title>

  <para>
    The default value of this environment variable is 1. If changed to 0, this
    disables the default use of client-side decorations on GTK+ windows, thus
    making the window manager responsible for drawing the decorations of
    windows that do not have a custom titlebar widget.
  </para>
  <para>
    CSD is always used for windows with a custom titlebar widget set, as the WM
    should not draw another titlebar or other decorations around the custom one.
  </para>
</formalpara>

<formalpara>
  <title><envar>XDG_DATA_HOME</envar>, <envar>XDG_DATA_DIRS</envar></title>

  <para>
    GTK+ uses these environment variables to locate icon themes
    and MIME information. For more information, see
    <ulink url="https://freedesktop.org/Standards/icon-theme-spec">Icon Theme Specification</ulink>,
    the <ulink url="https://freedesktop.org/Standards/shared-mime-info-spec">Shared MIME-info Database</ulink>
    and the <ulink url="https://freedesktop.org/Standards/basedir-spec">Base Directory Specification</ulink>.
  </para>
</formalpara>

<formalpara>
  <title><envar>DESKTOP_STARTUP_ID</envar></title>

  <para>
    GTK+ uses this environment variable to provide startup notification
    according to the <ulink url="https://standards.freedesktop.org/startup-notification-spec/startup-notification-latest.txt">Startup Notification Spec</ulink>.
    Following the specification, GTK+ unsets this variable after reading
    it (to keep it from leaking to child processes). So, if you need its
    value for your own purposes, you have to read it before calling
    gtk_init().
  </para>
</formalpara>

</refsect2>

<refsect2 id="interactive-debugging">
<title>Interactive debugging</title>

  <inlinegraphic fileref="inspector.png" format="PNG"></inlinegraphic>

  <para>
    GTK+ includes an interactive debugger, called the GTK+ Inspector, which
    lets you explore the widget tree of any GTK+ application at runtime, as
    well as tweak the theme and trigger visual debugging aids. You can
    easily try out changes at runtime before putting them into the code.
  </para>
  <para>
    Note that the GTK+ inspector can only show GTK+ internals. It can not
    understand the application-specific logic of a GTK+ application. Also,
    the fact that the GTK+ inspector is running in the application process
    limits what it can do. It is meant as a complement to full-blown debuggers
    and system tracing facilities such as DTrace, not as a replacement.
  </para>
  <para>
    To enable the GTK+ inspector, you can use the Control-Shift-I or
    Control-Shift-D keyboard shortcuts, or set the
    <envar>GTK_DEBUG=interactive</envar> environment variable.
  </para>
  <para>
    In some situations, it may be inappropriate to give users access to the
    GTK+ inspector. The keyboard shortcuts can be disabled with the
    `enable-inspector-keybinding` key in the `org.gtk.Settings.Debug`
    GSettings schema.
  </para>
 
</refsect2>

</refsect1>

</refentry>
