GSettingsBackend

typedef struct _GSettingsBackend GSettingsBackend;

An implementation of a settings storage repository.

struct GSettingsBackendClass

struct GSettingsBackendClass {
  GObjectClass parent_class;

  GVariant *    (*read)             (GSettingsBackend    *backend,
                                     const gchar         *key,
                                     const GVariantType  *expected_type,
                                     gboolean             default_value);

  gboolean      (*get_writable)     (GSettingsBackend    *backend,
                                     const gchar         *key);

  gboolean      (*write)            (GSettingsBackend    *backend,
                                     const gchar         *key,
                                     GVariant            *value,
                                     gpointer             origin_tag);
  gboolean      (*write_tree)       (GSettingsBackend    *backend,
                                     GTree               *tree,
                                     gpointer             origin_tag);
  void          (*reset)            (GSettingsBackend    *backend,
                                     const gchar         *key,
                                     gpointer             origin_tag);

  void          (*subscribe)        (GSettingsBackend    *backend,
                                     const gchar         *name);
  void          (*unsubscribe)      (GSettingsBackend    *backend,
                                     const gchar         *name);
  void          (*sync)             (GSettingsBackend    *backend);

  GPermission * (*get_permission)   (GSettingsBackend    *backend,
                                     const gchar         *path);

  gpointer padding[24];
};

G_SETTINGS_BACKEND_EXTENSION_POINT_NAME

#define G_SETTINGS_BACKEND_EXTENSION_POINT_NAME "gsettings-backend"

Extension point for GSettingsBackend functionality.

g_settings_backend_get_default ()

GSettingsBackend *  g_settings_backend_get_default      (void);

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.

Since 2.28

g_settings_backend_changed ()

void                g_settings_backend_changed          (GSettingsBackend *backend,
                                                         const gchar *key,
                                                         gpointer origin_tag);

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.

Since 2.26

g_settings_backend_path_changed ()

void                g_settings_backend_path_changed     (GSettingsBackend *backend,
                                                         const gchar *path,
                                                         gpointer origin_tag);

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.

Since 2.26

g_settings_backend_keys_changed ()

void                g_settings_backend_keys_changed     (GSettingsBackend *backend,
                                                         const gchar *path,
                                                         gchar const * const *items,
                                                         gpointer origin_tag);

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.

Since 2.26

g_settings_backend_path_writable_changed ()

void                g_settings_backend_path_writable_changed
                                                        (GSettingsBackend *backend,
                                                         const gchar *path);

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.

Since 2.26

g_settings_backend_writable_changed ()

void                g_settings_backend_writable_changed (GSettingsBackend *backend,
                                                         const gchar *key);

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.

Since 2.26

g_settings_backend_changed_tree ()

void                g_settings_backend_changed_tree     (GSettingsBackend *backend,
                                                         GTree *tree,
                                                         gpointer origin_tag);

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().

Since 2.26

g_settings_backend_flatten_tree ()

void                g_settings_backend_flatten_tree     (GTree *tree,
                                                         gchar **path,
                                                         const gchar ***keys,
                                                         GVariant ***values);

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.

Since 2.26

g_keyfile_settings_backend_new ()

GSettingsBackend *  g_keyfile_settings_backend_new      (const gchar *filename,
                                                         const gchar *root_path,
                                                         const gchar *root_group);

Creates a keyfile-backed GSettingsBackend.

The filename of the keyfile to use is given by filename.

All settings read to or written from the backend must fall under the path given in root_path (which must start and end with a slash and not contain two consecutive slashes). root_path may be "/".

If root_group is non-NULL then it specifies the name of the keyfile group used for keys that are written directly below root_path. For example, if root_path is "/apps/example/" and root_group is "toplevel", then settings the key "/apps/example/enabled" to a value of TRUE will cause the following to appear in the keyfile:

1
2

[toplevel]
enabled=true

If root_group is NULL then it is not permitted to store keys directly below the root_path.

For keys not stored directly below root_path (ie: in a sub-path), the name of the subpath (with the final slash stripped) is used as the name of the keyfile group. To continue the example, if "/apps/example/profiles/default/font-size" were set to 12 then the following would appear in the keyfile:

1
2

[profiles/default]
font-size=12

The backend will refuse writes (and return writability as being FALSE) for keys outside of root_path and, in the event that root_group is NULL, also for keys directly under root_path. Writes will also be refused if the backend detects that it has the inability to rewrite the keyfile (ie: the containing directory is not writable).

There is no checking done for your key namespace clashing with the syntax of the key file format. For example, if you have '[' or ']' characters in your path names or '=' in your key names you may be in trouble.

g_memory_settings_backend_new ()

GSettingsBackend *  g_memory_settings_backend_new       (void);

Creates a memory-backed GSettingsBackend.

This backend allows changes to settings, but does not write them to any backing storage, so the next time you run your application, the memory backend will start out with the default values again.

Since 2.28

g_null_settings_backend_new ()

GSettingsBackend *  g_null_settings_backend_new         (void);

Creates a readonly GSettingsBackend.

This backend does not allow changes to settings, so all settings will always have their default values.

Since 2.28