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The #GSettingsBackend interface defines a generic interface for non-strictly-typed data that is stored in a hierarchy. To implement an alternative storage backend for #GSettings, you need to implement the #GSettingsBackend interface and then make it implement the extension point %G_SETTINGS_BACKEND_EXTENSION_POINT_NAME.

The interface defines methods for reading and writing values, a method for determining if writing of certain values will fail (lockdown) and a change notification mechanism.

The semantics of the interface are very precisely defined and implementations must carefully adhere to the expectations of callers that are documented on each of the interface methods.

Some of the #GSettingsBackend functions accept or return a #GTree. These trees always have strings as keys and #GVariant as values. g_settings_backend_create_tree() is a convenience function to create suitable trees.

The #GSettingsBackend API is exported to allow third-party implementations, but does not carry the same stability guarantees as the public GIO API. For this reason, you have to define the C preprocessor symbol %G_SETTINGS_ENABLE_BACKEND before including gio/gsettingsbackend.h.

Hierarchy

Index

Constructors

Properties

gTypeInstance: TypeInstance
parentInstance: GObject.Object
name: string

Methods

  • Creates a binding between source_property on source and target_property on target.

    Whenever the source_property is changed the target_property is updated using the same value. For instance:

      g_object_bind_property (action, "active", widget, "sensitive", 0);
    

    Will result in the "sensitive" property of the widget #GObject instance to be updated with the same value of the "active" property of the action #GObject instance.

    If flags contains %G_BINDING_BIDIRECTIONAL then the binding will be mutual: if target_property on target changes then the source_property on source will be updated as well.

    The binding will automatically be removed when either the source or the target instances are finalized. To remove the binding without affecting the source and the target you can just call g_object_unref() on the returned #GBinding instance.

    Removing the binding by calling g_object_unref() on it must only be done if the binding, source and target are only used from a single thread and it is clear that both source and target outlive the binding. Especially it is not safe to rely on this if the binding, source or target can be finalized from different threads. Keep another reference to the binding and use g_binding_unbind() instead to be on the safe side.

    A #GObject can have multiple bindings.

    Parameters

    • sourceProperty: string

      the property on source to bind

    • target: GObject.Object

      the target #GObject

    • targetProperty: string

      the property on target to bind

    • flags: BindingFlags

      flags to pass to #GBinding

    Returns Binding

  • Creates a binding between source_property on source and target_property on target, allowing you to set the transformation functions to be used by the binding.

    This function is the language bindings friendly version of g_object_bind_property_full(), using #GClosures instead of function pointers.

    Parameters

    • sourceProperty: string

      the property on source to bind

    • target: GObject.Object

      the target #GObject

    • targetProperty: string

      the property on target to bind

    • flags: BindingFlags

      flags to pass to #GBinding

    • transformTo: TClosure<any, any>

      a #GClosure wrapping the transformation function from the source to the target, or %NULL to use the default

    • transformFrom: TClosure<any, any>

      a #GClosure wrapping the transformation function from the target to the source, or %NULL to use the default

    Returns Binding

  • changed(key: string, originTag: object): void
  • Signals that a single key has possibly changed. Backend implementations should call this if a key has possibly changed its value.

    key must be a valid key (ie starting with a slash, not containing '//', and not ending with a slash).

    The implementation must call this function during any call to g_settings_backend_write(), before the call returns (except in the case that no keys are actually changed and it cares to detect this fact). It may not rely on the existence of a mainloop for dispatching the signal later.

    The implementation may call this function at any other time it likes in response to other events (such as changes occurring outside of the program). These calls may originate from a mainloop or may originate in response to any other action (including from calls to g_settings_backend_write()).

    In the case that this call is in response to a call to g_settings_backend_write() then origin_tag must be set to the same value that was passed to that call.

    Parameters

    • key: string

      the name of the key

    • originTag: object

      the origin tag

    Returns void

  • changedTree(tree: GLib.Tree, originTag: object): void
  • This call is a convenience wrapper. It gets the list of changes from tree, computes the longest common prefix and calls g_settings_backend_changed().

    Parameters

    • tree: GLib.Tree

      a #GTree containing the changes

    • originTag: object

      the origin tag

    Returns void

  • connect(sigName: string, callback: ((...args: any[]) => void)): number
  • Parameters

    • sigName: string
    • callback: ((...args: any[]) => void)
        • (...args: any[]): void
        • Parameters

          • Rest ...args: any[]

          Returns void

    Returns number

  • emit(sigName: string, ...args: any[]): void
  • forceFloating(): void
  • This function is intended for #GObject implementations to re-enforce a [floating][floating-ref] object reference. Doing this is seldom required: all #GInitiallyUnowneds are created with a floating reference which usually just needs to be sunken by calling g_object_ref_sink().

    Returns void

  • freezeNotify(): void
  • Increases the freeze count on object. If the freeze count is non-zero, the emission of "notify" signals on object is stopped. The signals are queued until the freeze count is decreased to zero. Duplicate notifications are squashed so that at most one #GObject::notify signal is emitted for each property modified while the object is frozen.

    This is necessary for accessors that modify multiple properties to prevent premature notification while the object is still being modified.

    Returns void

  • getData(key?: string): object
  • Gets a named field from the objects table of associations (see g_object_set_data()).

    Parameters

    • Optional key: string

      name of the key for that association

    Returns object

  • getProperty(propertyName?: string, value?: any): void
  • Gets a property of an object.

    The value can be:

    • an empty #GValue initialized by %G_VALUE_INIT, which will be automatically initialized with the expected type of the property (since GLib 2.60)
    • a #GValue initialized with the expected type of the property
    • a #GValue initialized with a type to which the expected type of the property can be transformed

    In general, a copy is made of the property contents and the caller is responsible for freeing the memory by calling g_value_unset().

    Note that g_object_get_property() is really intended for language bindings, g_object_get() is much more convenient for C programming.

    Parameters

    • Optional propertyName: string

      the name of the property to get

    • Optional value: any

      return location for the property value

    Returns void

  • getQdata(quark: number): object
  • This function gets back user data pointers stored via g_object_set_qdata().

    Parameters

    • quark: number

      A #GQuark, naming the user data pointer

    Returns object

  • getv(names: string[], values: any[]): void
  • Gets n_properties properties for an object. Obtained properties will be set to values. All properties must be valid. Warnings will be emitted and undefined behaviour may result if invalid properties are passed in.

    Parameters

    • names: string[]

      the names of each property to get

    • values: any[]

      the values of each property to get

    Returns void

  • isFloating(): boolean
  • keysChanged(path: string, items: string[], originTag: object): void
  • Signals that a list of keys have possibly changed. Backend implementations should call this if keys have possibly changed their values.

    path must be a valid path (ie starting and ending with a slash and not containing '//'). Each string in items must form a valid key name when path is prefixed to it (ie: each item must not start or end with '/' and must not contain '//').

    The meaning of this signal is that any of the key names resulting from the contatenation of path with each item in items may have changed.

    The same rules for when notifications must occur apply as per g_settings_backend_changed(). These two calls can be used interchangeably if exactly one item has changed (although in that case g_settings_backend_changed() is definitely preferred).

    For efficiency reasons, the implementation should strive for path to be as long as possible (ie: the longest common prefix of all of the keys that were changed) but this is not strictly required.

    Parameters

    • path: string

      the path containing the changes

    • items: string[]

      the %NULL-terminated list of changed keys

    • originTag: object

      the origin tag

    Returns void

  • notify(propertyName: string): void
  • Emits a "notify" signal for the property property_name on object.

    When possible, eg. when signaling a property change from within the class that registered the property, you should use g_object_notify_by_pspec() instead.

    Note that emission of the notify signal may be blocked with g_object_freeze_notify(). In this case, the signal emissions are queued and will be emitted (in reverse order) when g_object_thaw_notify() is called.

    Parameters

    • propertyName: string

      the name of a property installed on the class of object.

    Returns void

  • Emits a "notify" signal for the property specified by pspec on object.

    This function omits the property name lookup, hence it is faster than g_object_notify().

    One way to avoid using g_object_notify() from within the class that registered the properties, and using g_object_notify_by_pspec() instead, is to store the GParamSpec used with g_object_class_install_property() inside a static array, e.g.:

      enum
    {
    PROP_0,
    PROP_FOO,
    PROP_LAST
    };

    static GParamSpec *properties[PROP_LAST];

    static void
    my_object_class_init (MyObjectClass *klass)
    {
    properties[PROP_FOO] = g_param_spec_int ("foo", "Foo", "The foo",
    0, 100,
    50,
    G_PARAM_READWRITE);
    g_object_class_install_property (gobject_class,
    PROP_FOO,
    properties[PROP_FOO]);
    }

    and then notify a change on the "foo" property with:

      g_object_notify_by_pspec (self, properties[PROP_FOO]);
    

    Parameters

    • pspec: ParamSpec

      the #GParamSpec of a property installed on the class of object.

    Returns void

  • off(sigName: string, callback: ((...args: any[]) => void)): EventEmitter
  • Parameters

    • sigName: string
    • callback: ((...args: any[]) => void)
        • (...args: any[]): void
        • Parameters

          • Rest ...args: any[]

          Returns void

    Returns EventEmitter

  • on(sigName: string, callback: ((...args: any[]) => void), after?: boolean): EventEmitter
  • Parameters

    • sigName: string
    • callback: ((...args: any[]) => void)
        • (...args: any[]): void
        • Parameters

          • Rest ...args: any[]

          Returns void

    • Optional after: boolean

    Returns EventEmitter

  • once(sigName: string, callback: ((...args: any[]) => void), after?: boolean): EventEmitter
  • Parameters

    • sigName: string
    • callback: ((...args: any[]) => void)
        • (...args: any[]): void
        • Parameters

          • Rest ...args: any[]

          Returns void

    • Optional after: boolean

    Returns EventEmitter

  • pathChanged(path: string, originTag: object): void
  • Signals that all keys below a given path may have possibly changed. Backend implementations should call this if an entire path of keys have possibly changed their values.

    path must be a valid path (ie starting and ending with a slash and not containing '//').

    The meaning of this signal is that any of the key which has a name starting with path may have changed.

    The same rules for when notifications must occur apply as per g_settings_backend_changed(). This call might be an appropriate reasponse to a 'reset' call but implementations are also free to explicitly list the keys that were affected by that call if they can easily do so.

    For efficiency reasons, the implementation should strive for path to be as long as possible (ie: the longest common prefix of all of the keys that were changed) but this is not strictly required. As an example, if this function is called with the path of "/" then every single key in the application will be notified of a possible change.

    Parameters

    • path: string

      the path containing the changes

    • originTag: object

      the origin tag

    Returns void

  • pathWritableChanged(path: string): void
  • Signals that the writability of all keys below a given path may have changed.

    Since GSettings performs no locking operations for itself, this call will always be made in response to external events.

    Parameters

    • path: string

      the name of the path

    Returns void

  • Increases the reference count of object.

    Since GLib 2.56, if GLIB_VERSION_MAX_ALLOWED is 2.56 or greater, the type of object will be propagated to the return type (using the GCC typeof() extension), so any casting the caller needs to do on the return type must be explicit.

    Returns GObject.Object

  • Increase the reference count of object, and possibly remove the [floating][floating-ref] reference, if object has a floating reference.

    In other words, if the object is floating, then this call "assumes ownership" of the floating reference, converting it to a normal reference by clearing the floating flag while leaving the reference count unchanged. If the object is not floating, then this call adds a new normal reference increasing the reference count by one.

    Since GLib 2.56, the type of object will be propagated to the return type under the same conditions as for g_object_ref().

    Returns GObject.Object

  • runDispose(): void
  • Releases all references to other objects. This can be used to break reference cycles.

    This function should only be called from object system implementations.

    Returns void

  • setData(key: string, data?: object): void
  • Each object carries around a table of associations from strings to pointers. This function lets you set an association.

    If the object already had an association with that name, the old association will be destroyed.

    Internally, the key is converted to a #GQuark using g_quark_from_string(). This means a copy of key is kept permanently (even after object has been finalized) — so it is recommended to only use a small, bounded set of values for key in your program, to avoid the #GQuark storage growing unbounded.

    Parameters

    • key: string

      name of the key

    • Optional data: object

      data to associate with that key

    Returns void

  • setProperty(propertyName: string, value?: any): void
  • Sets a property on an object.

    Parameters

    • propertyName: string

      the name of the property to set

    • Optional value: any

      the value

    Returns void

  • stealData(key?: string): object
  • Remove a specified datum from the object's data associations, without invoking the association's destroy handler.

    Parameters

    • Optional key: string

      name of the key

    Returns object

  • stealQdata(quark: number): object
  • This function gets back user data pointers stored via g_object_set_qdata() and removes the data from object without invoking its destroy() function (if any was set). Usually, calling this function is only required to update user data pointers with a destroy notifier, for example:

    void
    object_add_to_user_list (GObject *object,
    const gchar *new_string)
    {
    // the quark, naming the object data
    GQuark quark_string_list = g_quark_from_static_string ("my-string-list");
    // retrieve the old string list
    GList *list = g_object_steal_qdata (object, quark_string_list);

    // prepend new string
    list = g_list_prepend (list, g_strdup (new_string));
    // this changed 'list', so we need to set it again
    g_object_set_qdata_full (object, quark_string_list, list, free_string_list);
    }
    static void
    free_string_list (gpointer data)
    {
    GList *node, *list = data;

    for (node = list; node; node = node->next)
    g_free (node->data);
    g_list_free (list);
    }

    Using g_object_get_qdata() in the above example, instead of g_object_steal_qdata() would have left the destroy function set, and thus the partial string list would have been freed upon g_object_set_qdata_full().

    Parameters

    • quark: number

      A #GQuark, naming the user data pointer

    Returns object

  • thawNotify(): void
  • Reverts the effect of a previous call to g_object_freeze_notify(). The freeze count is decreased on object and when it reaches zero, queued "notify" signals are emitted.

    Duplicate notifications for each property are squashed so that at most one #GObject::notify signal is emitted for each property, in the reverse order in which they have been queued.

    It is an error to call this function when the freeze count is zero.

    Returns void

  • unref(): void
  • Decreases the reference count of object. When its reference count drops to 0, the object is finalized (i.e. its memory is freed).

    If the pointer to the #GObject may be reused in future (for example, if it is an instance variable of another object), it is recommended to clear the pointer to %NULL rather than retain a dangling pointer to a potentially invalid #GObject instance. Use g_clear_object() for this.

    Returns void

  • watchClosure(closure: TClosure<any, any>): void
  • This function essentially limits the life time of the closure to the life time of the object. That is, when the object is finalized, the closure is invalidated by calling g_closure_invalidate() on it, in order to prevent invocations of the closure with a finalized (nonexisting) object. Also, g_object_ref() and g_object_unref() are added as marshal guards to the closure, to ensure that an extra reference count is held on object during invocation of the closure. Usually, this function will be called on closures that use this object as closure data.

    Parameters

    • closure: TClosure<any, any>

      #GClosure to watch

    Returns void

  • writableChanged(key: string): void
  • Signals that the writability of a single key has possibly changed.

    Since GSettings performs no locking operations for itself, this call will always be made in response to external events.

    Parameters

    • key: string

      the name of the key

    Returns void

  • compatControl(what: number, data: object): number
  • Calculate the longest common prefix of all keys in a tree and write out an array of the key names relative to that prefix and, optionally, the value to store at each of those keys.

    You must free the value returned in path, keys and values using g_free(). You should not attempt to free or unref the contents of keys or values.

    Parameters

    • tree: GLib.Tree

      a #GTree containing the changes

    Returns [string, string[], GLib.Variant[]]

  • Returns the default #GSettingsBackend. It is possible to override the default by setting the GSETTINGS_BACKEND environment variable to the name of a settings backend.

    The user gets a reference to the backend.

    Returns SettingsBackend

  • Find the #GParamSpec with the given name for an interface. Generally, the interface vtable passed in as g_iface will be the default vtable from g_type_default_interface_ref(), or, if you know the interface has already been loaded, g_type_default_interface_peek().

    Parameters

    • gIface: TypeInterface

      any interface vtable for the interface, or the default vtable for the interface

    • propertyName: string

      name of a property to look up.

    Returns ParamSpec

  • Add a property to an interface; this is only useful for interfaces that are added to GObject-derived types. Adding a property to an interface forces all objects classes with that interface to have a compatible property. The compatible property could be a newly created #GParamSpec, but normally g_object_class_override_property() will be used so that the object class only needs to provide an implementation and inherits the property description, default value, bounds, and so forth from the interface property.

    This function is meant to be called from the interface's default vtable initialization function (the class_init member of #GTypeInfo.) It must not be called after after class_init has been called for any object types implementing this interface.

    If pspec is a floating reference, it will be consumed.

    Parameters

    • gIface: TypeInterface

      any interface vtable for the interface, or the default vtable for the interface.

    • pspec: ParamSpec

      the #GParamSpec for the new property

    Returns void

  • Lists the properties of an interface.Generally, the interface vtable passed in as g_iface will be the default vtable from g_type_default_interface_ref(), or, if you know the interface has already been loaded, g_type_default_interface_peek().

    Parameters

    • gIface: TypeInterface

      any interface vtable for the interface, or the default vtable for the interface

    Returns ParamSpec[]

  • Creates a new instance of a #GObject subtype and sets its properties.

    Construction parameters (see %G_PARAM_CONSTRUCT, %G_PARAM_CONSTRUCT_ONLY) which are not explicitly specified are set to their default values.

    Parameters

    • objectType: GType<unknown>

      the type id of the #GObject subtype to instantiate

    • parameters: GObject.Parameter[]

      an array of #GParameter

    Returns GObject.Object

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