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GIO Reference Manual | ![]() |
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Top | Description | Object Hierarchy | Properties |
#include <gio/gsettingsbackend.h> GSettingsBackend; GSettingsBackendClass; #define G_SETTINGS_BACKEND_EXTENSION_POINT_NAME void g_settings_backend_changed (GSettingsBackend *backend
,const gchar *key
,gpointer origin_tag
); void g_settings_backend_path_changed (GSettingsBackend *backend
,const gchar *path
,gpointer origin_tag
); void g_settings_backend_keys_changed (GSettingsBackend *backend
,const gchar *path
,gchar const * const *items
,gpointer origin_tag
); void g_settings_backend_path_writable_changed (GSettingsBackend *backend
,const gchar *path
); void g_settings_backend_writable_changed (GSettingsBackend *backend
,const gchar *key
); void g_settings_backend_changed_tree (GSettingsBackend *backend
,GTree *tree
,gpointer origin_tag
); void g_settings_backend_setup (const gchar *context
,GSettingsBackend *backend
); void g_settings_backend_setup_keyfile (const gchar *context
,const gchar *filename
);
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
typedef struct _GSettingsBackend GSettingsBackend;
An implementation of a settings storage repository.
typedef struct { GObjectClass parent_class; gboolean (*supports_context) (const gchar *context); GVariant * (*read) (GSettingsBackend *backend, const gchar *key, const GVariantType *expected_type); gboolean (*write) (GSettingsBackend *backend, const gchar *key, GVariant *value, gpointer origin_tag); gboolean (*write_keys) (GSettingsBackend *backend, GTree *tree, gpointer origin_tag); void (*reset) (GSettingsBackend *backend, const gchar *key, gpointer origin_tag); void (*reset_path) (GSettingsBackend *backend, const gchar *path, gpointer origin_tag); gboolean (*get_writable) (GSettingsBackend *backend, const gchar *key); void (*subscribe) (GSettingsBackend *backend, const gchar *name); void (*unsubscribe) (GSettingsBackend *backend, const gchar *name); } GSettingsBackendClass;
#define G_SETTINGS_BACKEND_EXTENSION_POINT_NAME "gsettings-backend"
Extension point for GSettingsBackend functionality.
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 occuring 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.
|
a GSettingsBackend implementation |
|
the name of the key |
|
the origin tag |
Since 2.26
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.
|
a GSettingsBackend implementation |
|
the path containing the changes |
|
the origin tag |
Since 2.26
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.
|
a GSettingsBackend implementation |
|
the path containing the changes |
|
the NULL -terminated list of changed keys
|
|
the origin tag |
Since 2.26
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.
|
a GSettingsBackend implementation |
|
the name of the path |
Since 2.26
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.
|
a GSettingsBackend implementation |
|
the name of the key |
Since 2.26
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()
.
|
a GSettingsBackend implementation |
|
a GTree containing the changes |
|
the origin tag |
Since 2.26
void g_settings_backend_setup (const gchar *context
,GSettingsBackend *backend
);
Sets up backend
for use with GSettings.
If you create a GSettings with its context property set to context
then it will use the backend given to this function. See
g_settings_new_with_context()
.
The backend must be set up before any settings objects are created for the named context.
It is not possible to specify a backend for the default context.
This function takes a reference on backend
and never releases it.
|
a context string (not NULL or "")
|
|
a GSettingsBackend |
Since 2.26
void g_settings_backend_setup_keyfile (const gchar *context
,const gchar *filename
);
Sets up a keyfile for use with GSettings.
If you create a GSettings with its context property set to context
then the settings will be stored in the keyfile at filename
. See
g_settings_new_with_context()
.
The keyfile must be setup before any settings objects are created for the named context.
It is not possible to specify a keyfile for the default context.
If the path leading up to filename
does not exist, it will be
recursively created with user-only permissions. If the keyfile is
not writable, any GSettings objects created using context
will
return FALSE
for any calls to g_settings_is_writable()
and any
attempts to write will fail.
|
a context string (not NULL or "")
|
|
a filename |
Since 2.26
"context"
property"context" gchar* : Read / Write / Construct Only
The "context" property gives a hint to the backend as to what storage to use. It is up to the implementation to make use of this information.
E.g. DConf supports "user", "system", "defaults" and "login" contexts.
If your backend supports different contexts, you should also
provide an implementation of the supports_context()
class
function in GSettingsBackendClass.
Default value: ""