Running GTK+ Applications3GTK LibraryRunning GTK+ Applications
How to run and debug your GTK+ application
Running and debugging GTK+ ApplicationsEnvironment variables
GTK+ inspects a number of environment variables in addition to standard
variables like LANG, PATH, HOME
or DISPLAY; mostly to determine paths to look for certain
files. The X11,
Windows and
Broadway GDK backends use some
additional environment variables.
GTK_DEBUG
Unless GTK+ has been configured with ,
this variable can be set to a list of debug options, which cause GTK+
to print out different types of debugging information.
actionsActions and menu modelsbuilderGtkBuilder supportgeometrySize allocationiconthemeIcon themeskeybindingsKeybindingsmodulesLoading of modulesprintingPrinting supportsize-requestSize requeststextText widget internalstreeTree widget internals
A number of keys are influencing behavior instead of just logging:
interactiveOpen the interactive debuggerno-css-cacheBypass caching for CSS style propertiestouchscreenPretend the pointer is a touchscreen devicebaselinesShow baselinesupdatesVisual feedback about window updatesresizeHighlight resizing widgetslayoutShow layout borderssnapshotInclude debug render nodes in the generated snapshots
The special value all can be used to turn on all
debug options. The special value help can be used
to obtain a list of all supported debug options.
GTK3_MODULES
A list of modules to load. Note that GTK+ also allows to specify modules to load via a commandline option () and with the gtk-modules setting.
GTK_MODULES
A list of modules to load in addition to the ones in the GTK3_MODULES variable.
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 GTK3_MODULES for modules that are only compatible
with GTK+ 3.
GTK_PATH
Specifies a list of directories to search when GTK+ is looking for
dynamically loaded objects such as the modules specified by
GTK_MODULES, 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 GTK_PATH,
followed by the directory .gtk-4.0 in the user's
home directory, followed by the system default directory,
which is libdir/gtk-4.0/modules.
(If GTK_EXE_PREFIX is defined, libdir is
$GTK_EXE_PREFIX/lib. Otherwise it is the libdir
specified when GTK+ was configured, usually
/usr/lib, or
/usr/local/lib.)
For each directory in this list, GTK+ actually looks in a
subdirectory
directory/version/host/type
Where version is derived from the
version of GTK+ (use pkg-config
--variable=gtk_binary_version gtk+-3.0 to determine this from a
script), host is the architecture on
which GTK+ was built. (use pkg-config
--variable=gtk_host gtk+-3.0 to determine this from a
script), and type is a directory
specific to the type of modules; currently it can be
modules, engines,
immodules, filesystems or
printbackends, corresponding to the types of
modules mentioned above. Either version,
host, 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.
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.
GTK_IM_MODULE
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 XSETTINGS and has a value in
Gtk/IMModule, 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.
GTK_IM_MODULE_FILE
Specifies the file listing the IM modules to load. This environment
variable the default value
libdir/gtk-4.0/4.0.0/immodules.cache
(libdir has the same meaning here as explained for GTK_PATH).
The immodules.cache file is generated by the
gtk-query-immodules-3.0 utility.
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.
GTK_EXE_PREFIX
If set, GTK+ uses $GTK_EXE_PREFIX/lib instead of
the libdir configured when GTK+ was compiled.
GTK_DATA_PREFIX
If set, makes GTK+ use $GTK_DATA_PREFIX
instead of the prefix configured when GTK+ was compiled.
GTK_THEME
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.
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`.
The following environment variables are used by GdkPixbuf, GDK or
Pango, not by GTK+ itself, but we list them here for completeness
nevertheless.
GDK_PIXBUF_MODULE_FILE
Specifies the file listing the GdkPixbuf loader modules to load.
This environment variable overrides the default value
libdir/gtk-4.0/4.0.0/loaders.cache
(libdir is the sysconfdir specified when
GTK+ was configured, usually /usr/local/lib.)
The loaders.cache file is generated by the
gdk-pixbuf-query-loaders utility.
GDK_DEBUG
If GTK+ has been configured with ,
this variable can be set to a list of debug options, which cause GDK
to print out different types of debugging information.
cursorInformation about cursor objects (only win32)eventloopInformation about event loop operation (mostly Quartz)miscMiscellaneous informationframesInformation about the frame clocksettingsInformation about xsettingsselectionInformation about selectionsclipboardInformation about clipboardsdndInformation about drag-and-dropopenglInformation about OpenGLvulkanInformation about Vulkan
A number of options affect behavior instead of logging:
nograbsTurn off all pointer and keyboard grabsgl-disableDisable OpenGL supportgl-softwareForce OpenGL software renderinggl-texture-rectUse the OpenGL texture rectangle extension, if availablegl-legacyUse a legacy OpenGL contextgl-legacyUse a GLES OpenGL contextvulkan-disableDisable Vulkan supportvulkan-validateLoad the Vulkan validation layer, if availablecairo-imageUse image surfaces for cairo rendering. This essentially
turns off all hardware acceleration with the cairo renderer
The special value all can be used to turn on all
debug options. The special value help can be used
to obtain a list of all supported debug options.
GSK_DEBUG
If GTK+ has been configured with ,
this variable can be set to a list of debug options, which cause GSK
to print out different types of debugging information.
rendererGeneral renderer informationcairocairo renderer informationopenglOpenGL renderer informationvulkanVulkan renderer informationfallbackInformation about fallbacksglyphcacheInformation about glyph caching
A number of options affect behavior instead of logging:
geometryShow bordersfull-redrawForce full redraws for every framesyncSync after each framevulkan-staging-imageUse a staging image for Vulkan texture uploadvulkan-staging-bufferUse a staging buffer for Vulkan texture upload
The special value all can be used to turn on all
debug options. The special value help can be used
to obtain a list of all supported debug options.
GDK_BACKEND
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:
quartzSelects the native Quartz backendwin32Selects the native backend for Microsoft Windowsx11Selects the native backend for connecting to X11 servers.broadwaySelects the Broadway backend for display in web browserswaylandSelects the Wayland backend for connecting to Wayland display serversmirSelects the Mir backend for connecting to Mir display servers
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.
GDK_VULKAN_DEVICE
This variable can be set to the index of a Vulkan device to override the
default selection of the device that is used for Vulkan rendering.
The special value list can be used to obtain a list
of all Vulkan devices.
GTK_CSD
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.
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.
XDG_DATA_HOME, XDG_DATA_DIRS
GTK+ uses these environment variables to locate icon themes
and MIME information. For more information, see
Icon Theme Specification,
the Shared MIME-info Database
and the Base Directory Specification.
DESKTOP_STARTUP_ID
GTK+ uses this environment variable to provide startup notification
according to the Startup Notification Spec.
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().
Interactive debugging
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.
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.
To enable the GTK+ inspector, you can use the Control-Shift-I or
Control-Shift-D keyboard shortcuts, or set the
GTK_DEBUG=interactive environment variable.
There are a few more environment variables that can be set to influence
how the inspector renders its UI. GTK_INSPECTOR_DISPLAY and
GTK_INSPECTOR_RENDERER determine the GDK display and
the GSK renderer that the inspector is using.
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.