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Running GTK ApplicationsRunning 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.
GTK_DEBUG
.
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 |
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.
GTK_PATH
.
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
.
(If libdir
/gtk-4.0/modulesGTK_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
Where directory
/version
/host
/type
version
is derived from the
version of GTK (use pkg-config
--variable=gtk_binary_version gtk4
to determine this from a
script), host
is the architecture on
which GTK was built. (use pkg-config
--variable=gtk_host gtk4
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.
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_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.cachelibdir
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 --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-gles |
Use a GLES OpenGL context |
vulkan-disable |
Disable Vulkan support |
vulkan-validate |
Load the Vulkan validation layer, if available |
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 --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 |
shaders |
Shaders |
ssurface |
Surfaces |
vulkan |
Vulkan renderer information |
fallback |
Information about fallbacks |
glyphcache |
Information about glyph caching |
A number of options affect behavior instead of logging:
diff |
Show differences |
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.
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:
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 |
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.
GSK_RENDERER
.
If set, selects the GSK renderer to use. The following renderers can
be selected, provided they are included in the GTK library you are using
and the GDK backend supports them:
help |
Prints information about available options |
broadway |
Selects the Broadway-backend specific renderer |
cairo |
Selects the fallback Cairo renderer |
gl |
Selects the default OpenGL renderer |
vulkan |
Selects the Vulkan renderer |
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().
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.
GTK supports profiling with sysprof. It exports timing information about frameclock phases and various characteristics of GskRenders in a format that can be displayed by sysprof or GNOME Builder.
A simple way to capture data is to set the GTK_TRACE
environment variable. When it is set, GTK will write profiling
data to a file called
gtk.
.
PID
.syscap
When launching the application from sysprof, it will set the
SYSPROF_TRACE_FD
environment variable to point
GTK at a file descriptor to write profiling data to.
When GtkApplication registers with D-Bus, it exports the
org.gnome.Sysprof2.Profiler
interface
that lets sysprof request profiling data at runtime.