SettingsBackend

class SettingsBackend(**properties: Any)

Superclasses: Object

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 Settings, 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 Tree. These trees always have strings as keys and Variant as values.

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.

Methods

class SettingsBackend
changed(key: str, origin_tag: None) → None

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.

Added in version 2.26.

Parameters:

  • key – the name of the key

  • origin_tag – the origin tag

changed_tree(tree: Tree, origin_tag: None) → None

This call is a convenience wrapper. It gets the list of changes from tree, computes the longest common prefix and calls changed().

Added in version 2.26.

Parameters:

  • tree – a Tree containing the changes

  • origin_tag – the origin tag

flatten_tree(tree: Tree) → tuple[str, list[str], list[Variant]]

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 free(). You should not attempt to free or unref the contents of keys or values.

Added in version 2.26.

Parameters:

tree – a Tree containing the changes

get_default() → SettingsBackend

Returns the default SettingsBackend. 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.

Added in version 2.28.

keys_changed(path: str, items: Sequence[str], origin_tag: None) → None

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 changed(). These two calls can be used interchangeably if exactly one item has changed (although in that case 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.

Added in version 2.26.

Parameters:

  • path – the path containing the changes

  • items – the None-terminated list of changed keys

  • origin_tag – the origin tag

path_changed(path: str, origin_tag: None) → None

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 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.

Added in version 2.26.

Parameters:

  • path – the path containing the changes

  • origin_tag – the origin tag

path_writable_changed(path: str) → None

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.

Added in version 2.26.

Parameters:

path – the name of the path

writable_changed(key: str) → None

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.

Added in version 2.26.

Parameters:

key – the name of the key

Virtual Methods

class SettingsBackend
do_get_writable(key: str) → bool
Parameters:

key

do_read(key: str, expected_type: VariantType, default_value: bool) → Variant
Parameters:

  • key

  • expected_type

  • default_value

do_read_user_value(key: str, expected_type: VariantType) → Variant
Parameters:

  • key

  • expected_type

do_reset(key: str, origin_tag: None) → None
Parameters:

  • key

  • origin_tag

do_subscribe(name: str) → None
Parameters:

name

do_sync() → None
do_unsubscribe(name: str) → None
Parameters:

name

do_write(key: str, value: Variant, origin_tag: None) → bool
Parameters:

  • key

  • value

  • origin_tag

do_write_tree(tree: Tree, origin_tag: None) → bool
Parameters:

  • tree

  • origin_tag

Fields

class SettingsBackend
parent_instance
priv