Running GTK+ Applications 3 GTK Library Running GTK+ Applications How to run and debug your GTK+ application 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. Unless GTK+ has been configured with --enable-debug=no, this variable can be set to a list of debug options, which cause GTK+ to print out different types of debugging information. actions Actions and menu models builder GtkBuilder support geometry Size allocation icontheme Icon themes keybindings Keybindings modules Loading of modules printing Printing support size-request Size requests text Text widget internals tree Tree widget internals A number of keys are influencing behavior instead of just logging: interactive Open the interactive debugger no-css-cache Bypass caching for CSS style properties touchscreen Pretend the pointer is a touchscreen device baselines Show baselines updates Visual feedback about window updates resize Highlight resizing widgets layout Show layout borders snapshot Include 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. Specifies a list of directories to search when GTK+ is looking for dynamically loaded objects such as input method modules 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. 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. If set, GTK+ uses $GTK_EXE_PREFIX/lib instead of the libdir configured when GTK+ was compiled. If set, makes GTK+ use $GTK_DATA_PREFIX instead of the prefix configured when GTK+ was compiled. 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. 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. If GTK+ has been configured with --enable-debug=yes, this variable can be set to a list of debug options, which cause GDK to print out different types of debugging information. cursor Information about cursor objects (only win32) eventloop Information about event loop operation (mostly Quartz) misc Miscellaneous information frames Information about the frame clock settings Information about xsettings selection Information about selections clipboard Information about clipboards dnd Information about drag-and-drop opengl Information about OpenGL vulkan Information about Vulkan A number of options affect behavior instead of logging: nograbs Turn off all pointer and keyboard grabs gl-disable Disable OpenGL support gl-software Force OpenGL software rendering gl-texture-rect Use the OpenGL texture rectangle extension, if available gl-legacy Use a legacy OpenGL context gl-legacy Use a GLES OpenGL context vulkan-disable Disable Vulkan support vulkan-validate Load the Vulkan validation layer, if available cairo-image Use 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. If GTK+ has been configured with --enable-debug=yes, this variable can be set to a list of debug options, which cause GSK to print out different types of debugging information. renderer General renderer information cairo cairo renderer information opengl OpenGL renderer information vulkan Vulkan renderer information fallback Information about fallbacks glyphcache Information about glyph caching A number of options affect behavior instead of logging: geometry Show borders full-redraw Force full redraws for every frame sync Sync after each frame vulkan-staging-image Use a staging image for Vulkan texture upload vulkan-staging-buffer Use 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. 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: quartz Selects the native Quartz backend win32 Selects the native backend for Microsoft Windows x11 Selects the native backend for connecting to X11 servers. broadway Selects the Broadway backend for display in web browsers wayland Selects the Wayland backend for connecting to Wayland display servers mir Selects 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. 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. 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. 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. 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(). 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.