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 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:

1
2
3

[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.

GSettings

typedef struct _GSettings GSettings;

g_settings_new ()

GSettings *              g_settings_new                 (const gchar *schema);

Creates a new GSettings object with a given schema.

Signals on the newly created GSettings object will be dispatched via the thread-default GMainContext in effect at the time of the call to g_settings_new(). The new GSettings will hold a reference on the context. See g_main_context_push_thread_default().

Since 2.26

g_settings_new_with_path ()

GSettings *              g_settings_new_with_path       (const gchar *schema,
                                                         const gchar *path);

Creates a new GSettings object with a given schema and path.

You only need to do this if you want to directly create a settings object with a schema that doesn't have a specified path of its own. That's quite rare.

It is a programmer error to call this function for a schema that has an explicitly specified path.

Since 2.26

g_settings_new_with_backend ()

GSettings *              g_settings_new_with_backend    (const gchar *schema,
                                                         GSettingsBackend *backend);

Creates a new GSettings object with a given schema and backend.

Creating settings objects with an different backend allows accessing settings from a database other than the usual one. For example, it may make sense to pass a backend corresponding to the "defaults" settings database on the system to get a settings object that modifies the system default settings instead of the settings for this user.

Since 2.26

g_settings_new_with_backend_and_path ()

GSettings *              g_settings_new_with_backend_and_path
                                                        (const gchar *schema,
                                                         GSettingsBackend *backend,
                                                         const gchar *path);

Creates a new GSettings object with a given schema, backend and path.

This is a mix of g_settings_new_with_backend() and g_settings_new_with_path().

Since 2.26

g_settings_sync ()

void                g_settings_sync                     (void);

Ensures that all pending operations for the given are complete for the default backend.

Writes made to a GSettings are handled asynchronously. For this reason, it is very unlikely that the changes have it to disk by the time g_settings_set() returns.

This call will block until all of the writes have made it to the backend. Since the mainloop is not running, no change notifications will be dispatched during this call (but some may be queued by the time the call is done).

g_settings_get_value ()

GVariant *               g_settings_get_value           (GSettings *settings,
                                                         const gchar *key);

Gets the value that is stored in settings for key.

It is a programmer error to give a key that isn't contained in the schema for settings.

Since 2.26

g_settings_set_value ()

gboolean            g_settings_set_value                (GSettings *settings,
                                                         const gchar *key,
                                                         GVariant *value);

Sets key in settings to value.

It is a programmer error to give a key that isn't contained in the schema for settings or for value to have the incorrect type, per the schema.

If value is floating then this function consumes the reference.

Since 2.26

g_settings_is_writable ()

gboolean            g_settings_is_writable              (GSettings *settings,
                                                         const gchar *name);

Finds out if a key can be written or not

Since 2.26

g_settings_delay ()

void                g_settings_delay                    (GSettings *settings);

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_apply ()

void                g_settings_apply                    (GSettings *settings);

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_revert ()

void                g_settings_revert                   (GSettings *settings);

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.

Change notifications will be emitted for affected keys.

g_settings_get_has_unapplied ()

gboolean            g_settings_get_has_unapplied        (GSettings *settings);

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_child ()

GSettings *              g_settings_get_child           (GSettings *settings,
                                                         const gchar *name);

Creates a 'child' settings object which has a base path of base-path/name, where base-path is the base path of settings.

The schema for the child settings object must have been declared in the schema of settings using a <child> element.

Since 2.26

g_settings_reset ()

void                g_settings_reset                    (GSettings *settings,
                                                         const gchar *key);

Resets key to its default value.

This call resets the key, as much as possible, to its default value. That might the value specified in the schema or the one set by the administrator.

g_settings_list_schemas ()

const gchar * const * g_settings_list_schemas           (void);

Gets a list of the GSettings schemas installed on the system. The returned list is exactly the list of schemas for which you may call g_settings_new() without adverse effects.

This function does not list the schemas that do not provide their own paths (ie: schemas for which you must use g_settings_new_with_path()). See g_settings_list_relocatable_schemas() for that.

Since 2.26

g_settings_list_relocatable_schemas ()

const gchar * const * g_settings_list_relocatable_schemas
                                                        (void);

Gets a list of the relocatable GSettings schemas installed on the system. These are schemas that do not provide their own path. It is usual to instantiate these schemas directly, but if you want to you can use g_settings_new_with_path() to specify the path.

The output of this function, tTaken together with the output of g_settings_list_schemas() represents the complete list of all installed schemas.

Since 2.28

g_settings_list_keys ()

gchar **                 g_settings_list_keys           (GSettings *settings);

Introspects the list of keys on settings.

You should probably not be calling this function from "normal" code (since you should already know what keys are in your schema). This function is intended for introspection reasons.

You should free the return value with g_strfreev() when you are done with it.

g_settings_list_children ()

gchar **                 g_settings_list_children       (GSettings *settings);

Gets the list of children on settings.

The list is exactly the list of strings for which it is not an error to call g_settings_get_child().

For GSettings objects that are lists, this value can change at any time and you should connect to the "children-changed" signal to watch for those changes. Note that there is a race condition here: you may request a child after listing it only for it to have been destroyed in the meantime. For this reason, g_settings_get_child() may return NULL even for a child that was listed by this function.

For GSettings objects that are not lists, you should probably not be calling this function from "normal" code (since you should already know what children are in your schema). This function may still be useful there for introspection reasons, however.

You should free the return value with g_strfreev() when you are done with it.

g_settings_get_range ()

GVariant *               g_settings_get_range           (GSettings *settings,
                                                         const gchar *key);

Queries the range of a key.

This function will return a GVariant that fully describes the range of values that are valid for key.

The type of GVariant returned is (sv). The string describes the type of range restriction in effect. The type and meaning of the value contained in the variant depends on the string.

If the string is 'type' then the variant contains an empty array. The element type of that empty array is the expected type of value and all values of that type are valid.

If the string is 'enum' then the variant contains an array enumerating the possible values. Each item in the array is a possible valid value and no other values are valid.

If the string is 'flags' then the variant contains an array. Each item in the array is a value that may appear zero or one times in an array to be used as the value for this key. For example, if the variant contained the array ['x', 'y'] then the valid values for the key would be [], ['x'], ['y'], ['x', 'y'] and ['y', 'x'].

Finally, if the string is 'range' then the variant contains a pair of like-typed values -- the minimum and maximum permissible values for this key.

This information should not be used by normal programs. It is considered to be a hint for introspection purposes. Normal programs should already know what is permitted by their own schema. The format may change in any way in the future -- but particularly, new forms may be added to the possibilities described above.

It is a programmer error to give a key that isn't contained in the schema for settings.

You should free the returned value with g_variant_unref() when it is no longer needed.

Since 2.28

g_settings_range_check ()

gboolean            g_settings_range_check              (GSettings *settings,
                                                         const gchar *key,
                                                         GVariant *value);

Checks if the given value is of the correct type and within the permitted range for key.

This API is not intended to be used by normal programs -- they should already know what is permitted by their own schemas. This API is meant to be used by programs such as editors or commandline tools.

It is a programmer error to give a key that isn't contained in the schema for settings.

Since 2.28

g_settings_get ()

void                g_settings_get                      (GSettings *settings,
                                                         const gchar *key,
                                                         const gchar *format,
                                                         ...);

Gets the value that is stored at key in settings.

A convenience function that combines g_settings_get_value() with g_variant_get().

It is a programmer error to give a key that isn't contained in the schema for settings or for the GVariantType of format to mismatch the type given in the schema.

Since 2.26

g_settings_set ()

gboolean            g_settings_set                      (GSettings *settings,
                                                         const gchar *key,
                                                         const gchar *format,
                                                         ...);

Sets key in settings to value.

A convenience function that combines g_settings_set_value() with g_variant_new().

It is a programmer error to give a key that isn't contained in the schema for settings or for the GVariantType of format to mismatch the type given in the schema.

Since 2.26

g_settings_get_boolean ()

gboolean            g_settings_get_boolean              (GSettings *settings,
                                                         const gchar *key);

Gets the value that is stored at key in settings.

A convenience variant of g_settings_get() for booleans.

It is a programmer error to give a key that isn't specified as having a boolean type in the schema for settings.

Since 2.26

g_settings_set_boolean ()

gboolean            g_settings_set_boolean              (GSettings *settings,
                                                         const gchar *key,
                                                         gboolean value);

Sets key in settings to value.

A convenience variant of g_settings_set() for booleans.

It is a programmer error to give a key that isn't specified as having a boolean type in the schema for settings.

Since 2.26

g_settings_get_int ()

gint                g_settings_get_int                  (GSettings *settings,
                                                         const gchar *key);

Gets the value that is stored at key in settings.

A convenience variant of g_settings_get() for 32-bit integers.

It is a programmer error to give a key that isn't specified as having a int32 type in the schema for settings.

Since 2.26

g_settings_set_int ()

gboolean            g_settings_set_int                  (GSettings *settings,
                                                         const gchar *key,
                                                         gint value);

Sets key in settings to value.

A convenience variant of g_settings_set() for 32-bit integers.

It is a programmer error to give a key that isn't specified as having a int32 type in the schema for settings.

Since 2.26

g_settings_get_double ()

gdouble             g_settings_get_double               (GSettings *settings,
                                                         const gchar *key);

Gets the value that is stored at key in settings.

A convenience variant of g_settings_get() for doubles.

It is a programmer error to give a key that isn't specified as having a 'double' type in the schema for settings.

Since 2.26

g_settings_set_double ()

gboolean            g_settings_set_double               (GSettings *settings,
                                                         const gchar *key,
                                                         gdouble value);

Sets key in settings to value.

A convenience variant of g_settings_set() for doubles.

It is a programmer error to give a key that isn't specified as having a 'double' type in the schema for settings.

Since 2.26

g_settings_get_string ()

gchar *                  g_settings_get_string          (GSettings *settings,
                                                         const gchar *key);

Gets the value that is stored at key in settings.

A convenience variant of g_settings_get() for strings.

It is a programmer error to give a key that isn't specified as having a string type in the schema for settings.

Since 2.26

g_settings_set_string ()

gboolean            g_settings_set_string               (GSettings *settings,
                                                         const gchar *key,
                                                         const gchar *value);

Sets key in settings to value.

A convenience variant of g_settings_set() for strings.

It is a programmer error to give a key that isn't specified as having a string type in the schema for settings.

Since 2.26

g_settings_get_strv ()

gchar **                 g_settings_get_strv            (GSettings *settings,
                                                         const gchar *key);

A convenience variant of g_settings_get() for string arrays.

It is a programmer error to give a key that isn't specified as having an array of strings type in the schema for settings.

Since 2.26

g_settings_set_strv ()

gboolean            g_settings_set_strv                 (GSettings *settings,
                                                         const gchar *key,
                                                         const gchar *const *value);

Sets key in settings to value.

A convenience variant of g_settings_set() for string arrays. If value is NULL, then key is set to be the empty array.

It is a programmer error to give a key that isn't specified as having an array of strings type in the schema for settings.

Since 2.26

g_settings_get_enum ()

gint                g_settings_get_enum                 (GSettings *settings,
                                                         const gchar *key);

Gets the value that is stored in settings for key and converts it to the enum value that it represents.

In order to use this function the type of the value must be a string and it must be marked in the schema file as an enumerated type.

It is a programmer error to give a key that isn't contained in the schema for settings or is not marked as an enumerated type.

If the value stored in the configuration database is not a valid value for the enumerated type then this function will return the default value.

Since 2.26

g_settings_set_enum ()

gboolean            g_settings_set_enum                 (GSettings *settings,
                                                         const gchar *key,
                                                         gint value);

Looks up the enumerated type nick for value and writes it to key, within settings.

It is a programmer error to give a key that isn't contained in the schema for settings or is not marked as an enumerated type, or for value not to be a valid value for the named type.

After performing the write, accessing key directly with g_settings_get_string() will return the 'nick' associated with value.

g_settings_get_flags ()

guint               g_settings_get_flags                (GSettings *settings,
                                                         const gchar *key);

Gets the value that is stored in settings for key and converts it to the flags value that it represents.

In order to use this function the type of the value must be an array of strings and it must be marked in the schema file as an flags type.

It is a programmer error to give a key that isn't contained in the schema for settings or is not marked as a flags type.

If the value stored in the configuration database is not a valid value for the flags type then this function will return the default value.

Since 2.26

g_settings_set_flags ()

gboolean            g_settings_set_flags                (GSettings *settings,
                                                         const gchar *key,
                                                         guint value);

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, withing settings.

It is a programmer error to give a key that isn't contained in the schema for settings or is not marked as a flags type, or for value to contain any bits that are not value for the named type.

After performing the write, accessing key directly with g_settings_get_strv() will return an array of 'nicks'; one for each bit in value.

GSettingsGetMapping ()

gboolean            (*GSettingsGetMapping)              (GVariant *value,
                                                         gpointer *result,
                                                         gpointer user_data);

The type of the function that is used to convert from a value stored in a GSettings to a value that is useful to the application.

If the value is successfully mapped, the result should be stored at result and TRUE returned. If mapping fails (for example, if value is not in the right format) then FALSE should be returned.

If value is NULL then it means that the mapping function is being given a "last chance" to successfully return a valid value. TRUE must be returned in this case.

g_settings_get_mapped ()

gpointer            g_settings_get_mapped               (GSettings *settings,
                                                         const gchar *key,
                                                         GSettingsGetMapping mapping,
                                                         gpointer user_data);

Gets the value that is stored at key in settings, subject to application-level validation/mapping.

You should use this function when the application needs to perform some processing on the value of the key (for example, parsing). The mapping function performs that processing. If the function indicates that the processing was unsuccessful (due to a parse error, for example) then the mapping is tried again with another value.

This allows a robust 'fall back to defaults' behaviour to be implemented somewhat automatically.

The first value that is tried is the user's setting for the key. If the mapping function fails to map this value, other values may be tried in an unspecified order (system or site defaults, translated schema default values, untranslated schema default values, etc).

If the mapping function fails for all possible values, one additional attempt is made: the mapping function is called with a NULL value. If the mapping function still indicates failure at this point then the application will be aborted.

The result parameter for the mapping function is pointed to a gpointer which is initially set to NULL. The same pointer is given to each invocation of mapping. The final value of that gpointer is what is returned by this function. NULL is valid; it is returned just as any other value would be.

enum GSettingsBindFlags

typedef enum
{
  G_SETTINGS_BIND_DEFAULT,
  G_SETTINGS_BIND_GET            = (1<<0),
  G_SETTINGS_BIND_SET            = (1<<1),
  G_SETTINGS_BIND_NO_SENSITIVITY = (1<<2),
  G_SETTINGS_BIND_GET_NO_CHANGES = (1<<3),
  G_SETTINGS_BIND_INVERT_BOOLEAN = (1<<4)
} GSettingsBindFlags;

Flags used when creating a binding. These flags determine in which direction the binding works. The default is to synchronize in both directions.

g_settings_bind ()

void                g_settings_bind                     (GSettings *settings,
                                                         const gchar *key,
                                                         gpointer object,
                                                         const gchar *property,
                                                         GSettingsBindFlags flags);

Create a binding between the key in the settings object and the property property of object.

The binding uses the default GIO mapping functions to map between the settings and property values. These functions handle booleans, numeric types and string types in a straightforward way. Use g_settings_bind_with_mapping() if you need a custom mapping, or map between types that are not supported by the default mapping functions.

Unless the flags include G_SETTINGS_BIND_NO_SENSITIVITY, this function also establishes a binding between the writability of key and the "sensitive" property of object (if object has a boolean property by that name). See g_settings_bind_writable() for more details about writable bindings.

Note that the lifecycle of the binding is tied to the object, and that you can have only one binding per object property. If you bind the same property twice on the same object, the second binding overrides the first one.

Since 2.26

g_settings_bind_with_mapping ()

void                g_settings_bind_with_mapping        (GSettings *settings,
                                                         const gchar *key,
                                                         gpointer object,
                                                         const gchar *property,
                                                         GSettingsBindFlags flags,
                                                         GSettingsBindGetMapping get_mapping,
                                                         GSettingsBindSetMapping set_mapping,
                                                         gpointer user_data,
                                                         GDestroyNotify destroy);

Create a binding between the key in the settings object and the property property of object.

The binding uses the provided mapping functions to map between settings and property values.

Note that the lifecycle of the binding is tied to the object, and that you can have only one binding per object property. If you bind the same property twice on the same object, the second binding overrides the first one.

Since 2.26

g_settings_bind_writable ()

void                g_settings_bind_writable            (GSettings *settings,
                                                         const gchar *key,
                                                         gpointer object,
                                                         const gchar *property,
                                                         gboolean inverted);

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.

Writable bindings are always uni-directional; changes of the writability of the setting will be propagated to the object property, not the other way.

When the inverted argument is TRUE, the binding inverts the value as it passes from the setting to the object, i.e. property will be set to TRUE if the key is not writable.

Note that the lifecycle of the binding is tied to the object, and that you can have only one binding per object property. If you bind the same property twice on the same object, the second binding overrides the first one.

Since 2.26

g_settings_unbind ()

void                g_settings_unbind                   (gpointer object,
                                                         const gchar *property);

Removes an existing binding for property on object.

Note that bindings are automatically removed when the object is finalized, so it is rarely necessary to call this function.

Since 2.26

GSettingsBindSetMapping ()

GVariant *          (*GSettingsBindSetMapping)          (const GValue *value,
                                                         const GVariantType *expected_type,
                                                         gpointer user_data);

The type for the function that is used to convert an object property value to a GVariant for storing it in GSettings.

GSettingsBindGetMapping ()

gboolean            (*GSettingsBindGetMapping)          (GValue *value,
                                                         GVariant *variant,
                                                         gpointer user_data);

The type for the function that is used to convert from GSettings to an object property. The value is already initialized to hold values of the appropriate type.

The "backend" property

  "backend"                  GSettingsBackend*     : Read / Write / Construct Only

The GSettingsBackend for this settings object.

The "delay-apply" property

  "delay-apply"              gboolean              : Read

Whether the GSettings object is in 'delay-apply' mode. See g_settings_delay() for details.

Default value: FALSE

Since 2.28

The "has-unapplied" property

  "has-unapplied"            gboolean              : Read

If this property is TRUE, the GSettings object has outstanding changes that will be applied when g_settings_apply() is called.

Default value: FALSE

The "path" property

  "path"                     gchar*                : Read / Write / Construct Only

The path within the backend where the settings are stored.

Default value: NULL

The "schema" property

  "schema"                   gchar*                : Read / Write / Construct Only

The name of the schema that describes the types of keys for this GSettings object.

Default value: NULL

The "change-event" signal

gboolean            user_function                      (GSettings *settings,
                                                        gpointer   keys,
                                                        gint       n_keys,
                                                        gpointer   user_data)      : Run Last

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.

In the event that the change event applies to one or more specified keys, keys will be an array of GQuark of length n_keys. In the event that the change event applies to the GSettings object as a whole (ie: potentially every key has been changed) then keys will be NULL and n_keys will be 0.

The default handler for this signal invokes the "changed" signal for each affected key. If any other connected handler returns TRUE then this default functionality will be supressed.

The "changed" signal

void                user_function                      (GSettings *settings,
                                                        gchar     *key,
                                                        gpointer   user_data)      : Has Details

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.

This signal supports detailed connections. You can connect to the detailed signal "changed::x" in order to only receive callbacks when key "x" changes.

The "writable-change-event" signal

gboolean            user_function                      (GSettings *settings,
                                                        guint      key,
                                                        gpointer   user_data)      : Run Last

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.

In the event that the writability change applies only to a single key, key will be set to the GQuark for that key. In the event that the writability change affects the entire settings object, key will be 0.

The default handler for this signal invokes the "writable-changed" and "changed" signals for each affected key. This is done because changes in writability might also imply changes in value (if for example, a new mandatory setting is introduced). If any other connected handler returns TRUE then this default functionality will be supressed.

The "writable-changed" signal

void                user_function                      (GSettings *settings,
                                                        gchar     *key,
                                                        gpointer   user_data)      : Has Details

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.

This signal supports detailed connections. You can connect to the detailed signal "writable-changed::x" in order to only receive callbacks when the writability of "x" changes.