Class
GioSettings
Description
class Gio.Settings : GObject.Object
{
priv: GSettingsPrivate*
}
The GSettings
class provides a convenient API for storing and retrieving
application settings.
Reads and writes can be considered to be non-blocking. Reading
settings with GSettings
is typically extremely fast: on
approximately the same order of magnitude (but slower than) a
GHashTable
lookup. Writing settings is also extremely fast in terms
of time to return to your application, but can be extremely expensive
for other threads and other processes. Many settings backends
(including dconf) have lazy initialisation which means in the common
case of the user using their computer without modifying any settings
a lot of work can be avoided. For dconf, the D-Bus service doesn’t
even need to be started in this case. For this reason, you should
only ever modify GSettings
keys in response to explicit user action.
Particular care should be paid to ensure that modifications are not
made during startup — for example, when setting the initial value
of preferences widgets. The built-in g_settings_bind()
functionality
is careful not to write settings in response to notify signals as a
result of modifications that it makes to widgets.
When creating a GSettings instance, you have to specify a schema that describes the keys in your settings and their types and default values, as well as some other information.
Normally, a schema has a fixed path that determines where the settings are stored in the conceptual global tree of settings. However, schemas can also be ‘[relocatable][gsettings-relocatable]’, i.e. not equipped with a fixed path. This is useful e.g. when the schema describes an ‘account’, and you want to be able to store a arbitrary number of accounts.
Paths must start with and end with a forward slash character (‘/’) and must not contain two sequential slash characters. Paths should be chosen based on a domain name associated with the program or library to which the settings belong. Examples of paths are “/org/gtk/settings/file-chooser/” and “/ca/desrt/dconf-editor/”. Paths should not start with “/apps/”, “/desktop/” or “/system/” as they often did in GConf.
Unlike other configuration systems (like GConf), GSettings does not
restrict keys to basic types like strings and numbers. GSettings stores
values as GVariant
, and allows any GVariantType
for keys. Key names
are restricted to lowercase characters, numbers and ‘-‘. Furthermore,
the names must begin with a lowercase character, must not end
with a ‘-‘, and must not contain consecutive dashes.
Similar to GConf, the default values in GSettings schemas can be
localized, but the localized values are stored in gettext catalogs
and looked up with the domain that is specified in the
gettext-domain
attribute of the l10n
attribute of
the
The l10n
attribute must be set to messages
or time
, and sets the
locale category for
translation.
The messages
category should be used by default; use time
for
translatable date or time formats. A translation comment can be added as an
XML comment immediately above the context
attribute can be set on the
For example:
<!-- Translators: A list of words which are not allowed to be typed, in
GVariant serialization syntax.
See: https://developer.gnome.org/glib/stable/gvariant-text.html -->
<default l10n='messages' context='Banned words'>['bad', 'words']</default>
Translations of default values must remain syntactically valid serialized
GVariants
(e.g. retaining any surrounding quotation marks) or runtime
errors will occur.
GSettings uses schemas in a compact binary form that is created by the [glib-compile-schemas][glib-compile-schemas] utility. The input is a schema description in an XML format.
A DTD for the gschema XML format can be found here: gschema.dtd
The [glib-compile-schemas][glib-compile-schemas] tool expects schema
files to have the extension .gschema.xml
.
At runtime, schemas are identified by their id (as specified in the
id attribute of the
In addition to GVariant
types, keys can have types that have
enumerated types. These can be described by a g_settings_set_flags()
access the numeric values
corresponding to the string value of enum and flags keys.
An example for default value:
<schemalist>
<schema id="org.gtk.Test" path="/org/gtk/Test/" gettext-domain="test">
<key name="greeting" type="s">
<default l10n="messages">"Hello, earthlings"</default>
<summary>A greeting</summary>
<description>
Greeting of the invading martians
</description>
</key>
<key name="box" type="(ii)">
<default>(20,30)</default>
</key>
<key name="empty-string" type="s">
<default>""</default>
<summary>Empty strings have to be provided in GVariant form</summary>
</key>
</schema>
</schemalist>
An example for ranges, choices and enumerated types:
<schemalist>
<enum id="org.gtk.Test.myenum">
<value nick="first" value="1"/>
<value nick="second" value="2"/>
</enum>
<flags id="org.gtk.Test.myflags">
<value nick="flag1" value="1"/>
<value nick="flag2" value="2"/>
<value nick="flag3" value="4"/>
</flags>
<schema id="org.gtk.Test">
<key name="key-with-range" type="i">
<range min="1" max="100"/>
<default>10</default>
</key>
<key name="key-with-choices" type="s">
<choices>
<choice value='Elisabeth'/>
<choice value='Annabeth'/>
<choice value='Joe'/>
</choices>
<aliases>
<alias value='Anna' target='Annabeth'/>
<alias value='Beth' target='Elisabeth'/>
</aliases>
<default>'Joe'</default>
</key>
<key name='enumerated-key' enum='org.gtk.Test.myenum'>
<default>'first'</default>
</key>
<key name='flags-key' flags='org.gtk.Test.myflags'>
<default>["flag1","flag2"]</default>
</key>
</schema>
</schemalist>
Vendor overrides
Default values are defined in the schemas that get installed by an application. Sometimes, it is necessary for a vendor or distributor to adjust these defaults. Since patching the XML source for the schema is inconvenient and error-prone, [glib-compile-schemas][glib-compile-schemas] reads so-called vendor override’ files. These are keyfiles in the same directory as the XML schema sources which can override default values. The schema id serves as the group name in the key file, and the values are expected in serialized GVariant form, as in the following example:
[org.gtk.Example]
key1='string'
key2=1.5
glib-compile-schemas expects schema files to have the extension
.gschema.override
.
Binding
A very convenient feature of GSettings lets you bind GObject
properties
directly to settings, using g_settings_bind(). Once a GObject property
has been bound to a setting, changes on either side are automatically
propagated to the other side. GSettings handles details like mapping
between GObject and GVariant types, and preventing infinite cycles.
This makes it very easy to hook up a preferences dialog to the
underlying settings. To make this even more convenient, GSettings
looks for a boolean property with the name “sensitivity” and
automatically binds it to the writability of the bound setting.
If this ‘magic’ gets in the way, it can be suppressed with the
G_SETTINGS_BIND_NO_SENSITIVITY
flag.
Relocatable schemas # {#gsettings-relocatable}
A relocatable schema is one with no path
attribute specified on its
GSettings
object
can be instantiated for a relocatable schema, assigning a path to the
instance. Paths passed to g_settings_new_with_path()
will typically be
constructed dynamically from a constant prefix plus some form of instance
identifier; but they must still be valid GSettings paths. Paths could also
be constant and used with a globally installed schema originating from a
dependency library.
For example, a relocatable schema could be used to store geometry information
for different windows in an application. If the schema ID was
org.foo.MyApp.Window
, it could be instantiated for paths
/org/foo/MyApp/main/
, /org/foo/MyApp/document-1/
,
/org/foo/MyApp/document-2/
, etc. If any of the paths are well-known
they can be specified as
<schema id="org.foo.MyApp" path="/org/foo/MyApp/">
<child name="main" schema="org.foo.MyApp.Window"/>
</schema>
Build system integration # {#gsettings-build-system}
GSettings comes with autotools integration to simplify compiling and
installing schemas. To add GSettings support to an application, add the
following to your configure.ac
:
GLIB_GSETTINGS
In the appropriate Makefile.am
, use the following snippet to compile and
install the named schema:
gsettings_SCHEMAS = org.foo.MyApp.gschema.xml
EXTRA_DIST = $(gsettings_SCHEMAS)
@GSETTINGS_RULES@
No changes are needed to the build system to mark a schema XML file for
translation. Assuming it sets the gettext-domain
attribute, a schema may
be marked for translation by adding it to POTFILES.in
, assuming gettext
0.19 is in use (the preferred method for translation):
data/org.foo.MyApp.gschema.xml
Alternatively, if intltool 0.50.1 is in use:
[type: gettext/gsettings]data/org.foo.MyApp.gschema.xml
GSettings will use gettext to look up translations for the l10n
attribute set. Translations must not be included in the .gschema.xml
file
by the build system, for example by using intltool XML rules with a
.gschema.xml.in
template.
If an enumerated type defined in a C header file is to be used in a GSettings
schema, it can either be defined manually using an Makefile.am
:
gsettings_ENUM_NAMESPACE = org.foo.MyApp
gsettings_ENUM_FILES = my-app-enums.h my-app-misc.h
gsettings_ENUM_NAMESPACE
specifies the schema namespace for the enum files,
which are specified in gsettings_ENUM_FILES
. This will generate a
org.foo.MyApp.enums.xml
file containing the extracted enums, which will be
automatically included in the schema compilation, install and uninstall
rules. It should not be committed to version control or included in
EXTRA_DIST
.
Constructors
g_settings_new_full
Creates a new GSettings
object with a given schema, backend and path.
since: 2.32
g_settings_new_with_backend
Creates a new GSettings
object with the schema specified by
schema_id
and a given GSettingsBackend
.
since: 2.26
g_settings_new_with_backend_and_path
Creates a new GSettings
object with the schema specified by
schema_id
and a given GSettingsBackend
and path.
since: 2.26
g_settings_new_with_path
Creates a new GSettings
object with the relocatable schema specified
by schema_id
and a given path.
since: 2.26
Instance methods
g_settings_apply
Applies any changes that have been made to the settings. This
function does nothing unless settings
is in ‘delay-apply’ mode;
see g_settings_delay(). In the normal case settings are always
applied immediately.
g_settings_bind
Create a binding between the key
in the settings
object
and the property property
of object
.
since: 2.26
g_settings_bind_with_mapping
Create a binding between the key
in the settings
object
and the property property
of object
.
since: 2.26
g_settings_bind_writable
Create a binding between the writability of key
in the
settings
object and the property property
of object
.
The property must be boolean; “sensitive” or “visible”
properties of widgets are the most likely candidates.
since: 2.26
g_settings_delay
Changes the GSettings
object into ‘delay-apply’ mode. In this
mode, changes to settings
are not immediately propagated to the
backend, but kept locally until g_settings_apply()
is called.
since: 2.26
g_settings_get_child
Creates a child settings object which has a base path of
base-path/
name`, where
base-pathis the base path of
settings`.
since: 2.26
g_settings_get_enum
Gets the value that is stored in settings
for key
and converts it
to the enum value that it represents.
since: 2.26
g_settings_get_flags
Gets the value that is stored in settings
for key
and converts it
to the flags value that it represents.
since: 2.26
g_settings_get_has_unapplied
Returns whether the GSettings
object has any unapplied
changes. This can only be the case if it is in ‘delayed-apply’ mode.
since: 2.26
g_settings_get_mapped
Gets the value that is stored at key
in settings
, subject to
application-level validation/mapping.
g_settings_range_check
Checks if the given value
is of the correct type and within the
permitted range for key
.
deprecated: 2.40 since: 2.28
g_settings_revert
Reverts all non-applied changes to the settings. This function
does nothing unless settings
is in ‘delay-apply’ mode; see
g_settings_delay(). In the normal case settings are always applied immediately.
g_settings_set_enum
Looks up the enumerated type nick for value
and writes it to key
,
within settings
.
g_settings_set_flags
Looks up the flags type nicks for the bits specified by value
, puts
them in an array of strings and writes the array to key
, within
settings
.
Properties
Gio.Settings:delay-apply
Whether the GSettings
object is in ‘delay-apply’ mode. See
g_settings_delay()
for details.
since: 2.28
Gio.Settings:has-unapplied
If this property is TRUE
, the GSettings
object has outstanding
changes that will be applied when g_settings_apply()
is called.
Gio.Settings:schema
The name of the schema that describes the types of keys
for this GSettings
object.
deprecated: 2.32
Gio.Settings:schema-id
The name of the schema that describes the types of keys
for this GSettings
object.
Gio.Settings:settings-schema
The GSettingsSchema
describing the types of keys for this
GSettings
object.
Signals
Gio.Settings::change-event
The “change-event” signal is emitted once per change event that affects this settings object. You should connect to this signal only if you are interested in viewing groups of changes before they are split out into multiple emissions of the “changed” signal. For most use cases it is more appropriate to use the “changed” signal.
Gio.Settings::changed
The “changed” signal is emitted when a key has potentially changed.
You should call one of the g_settings_get()
calls to check the new value.
Gio.Settings::writable-change-event
The “writable-change-event” signal is emitted once per writability change event that affects this settings object. You should connect to this signal if you are interested in viewing groups of changes before they are split out into multiple emissions of the “writable-changed” signal. For most use cases it is more appropriate to use the “writable-changed” signal.
Gio.Settings::writable-changed
The “writable-changed” signal is emitted when the writability of a
key has potentially changed. You should call
g_settings_is_writable()
in order to determine the new status.
Signals inherited from GObject (1)
GObject::notify
The notify signal is emitted on an object when one of its properties has its value set through g_object_set_property(), g_object_set(), et al.
Class structure
struct GioSettingsClass {
GObjectClass parent_class;
void (* writable_changed) (
GSettings* settings,
const gchar* key
);
void (* changed) (
GSettings* settings,
const gchar* key
);
gboolean (* writable_change_event) (
GSettings* settings,
GQuark key
);
gboolean (* change_event) (
GSettings* settings,
const GQuark* keys,
gint n_keys
);
None padding;
}
Class members
parent_class: GObjectClass
- No description available.
writable_changed: void (* writable_changed) ( GSettings* settings, const gchar* key )
- No description available.
changed: void (* changed) ( GSettings* settings, const gchar* key )
- No description available.
writable_change_event: gboolean (* writable_change_event) ( GSettings* settings, GQuark key )
- No description available.
change_event: gboolean (* change_event) ( GSettings* settings, const GQuark* keys, gint n_keys )
- No description available.
padding: None
- No description available.