SettingsBackend#
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 callschanged()
.Added in version 2.26.
- Parameters:
tree – a
Tree
containing the changesorigin_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
andvalues
usingfree()
. You should not attempt to free or unref the contents ofkeys
orvalues
.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 theGSETTINGS_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 initems
must form a valid key name whenpath
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 initems
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 casechanged()
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 keysorigin_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
Virtual Methods#
- class SettingsBackend
-
- do_read(key: str, expected_type: VariantType, default_value: bool) Variant #
The type of the None singleton.
- Parameters:
key
expected_type
default_value
- do_read_user_value(key: str, expected_type: VariantType) Variant #
The type of the None singleton.
- Parameters:
key
expected_type
- do_reset(key: str, origin_tag: None) None #
The type of the None singleton.
- Parameters:
key
origin_tag