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GIO Reference Manual | ![]() |
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Top | Description | Object Hierarchy |
GSettingsSchema, GSettingsSchemaSourceGSettingsSchema, GSettingsSchemaSource — Introspecting and controlling the loading of GSettings schemas |
GSettingsSchemaSource; #define G_TYPE_SETTINGS_SCHEMA_SOURCE GSettingsSchemaSource * g_settings_schema_source_get_default (void
); GSettingsSchemaSource * g_settings_schema_source_ref (GSettingsSchemaSource *source
); void g_settings_schema_source_unref (GSettingsSchemaSource *source
); GSettingsSchemaSource * g_settings_schema_source_new_from_directory (const gchar *directory
,GSettingsSchemaSource *parent
,gboolean trusted
,GError **error
); void g_settings_schema_source_list_schemas (GSettingsSchemaSource *source
,gboolean recursive
,gchar ***non_relocatable
,gchar ***relocatable
); GSettingsSchema * g_settings_schema_source_lookup (GSettingsSchemaSource *source
,const gchar *schema_id
,gboolean recursive
); GSettingsSchema; #define G_TYPE_SETTINGS_SCHEMA GSettingsSchema * g_settings_schema_ref (GSettingsSchema *schema
); void g_settings_schema_unref (GSettingsSchema *schema
); const gchar * g_settings_schema_get_id (GSettingsSchema *schema
); const gchar * g_settings_schema_get_path (GSettingsSchema *schema
); GSettingsSchemaKey; gboolean g_settings_schema_has_key (GSettingsSchema *schema
,const gchar *key
); GSettingsSchemaKey * g_settings_schema_get_key (GSettingsSchema *schema
,const gchar *key
); GSettingsSchemaKey * g_settings_schema_key_ref (GSettingsSchemaKey *key
); void g_settings_schema_key_unref (GSettingsSchemaKey *key
); const GVariantType * g_settings_schema_key_get_value_type (GSettingsSchemaKey *key
); GVariant * g_settings_schema_key_get_default_value (GSettingsSchemaKey *key
); GVariant * g_settings_schema_key_get_range (GSettingsSchemaKey *key
); gboolean g_settings_schema_key_range_check (GSettingsSchemaKey *key
,GVariant *value
); const gchar * g_settings_schema_key_get_summary (GSettingsSchemaKey *key
); const gchar * g_settings_schema_key_get_description (GSettingsSchemaKey *key
);
The GSettingsSchemaSource and GSettingsSchema APIs provide a mechanism for advanced control over the loading of schemas and a mechanism for introspecting their content.
Plugin loading systems that wish to provide plugins a way to access settings face the problem of how to make the schemas for these settings visible to GSettings. Typically, a plugin will want to ship the schema along with itself and it won't be installed into the standard system directories for schemas.
GSettingsSchemaSource provides a mechanism for dealing with this by allowing the creation of a new 'schema source' from which schemas can be acquired. This schema source can then become part of the metadata associated with the plugin and queried whenever the plugin requires access to some settings.
Consider the following example:
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typedef struct { ... GSettingsSchemaSource *schema_source; ... } Plugin; Plugin * initialise_plugin (const gchar *dir) { Plugin *plugin; ... plugin->schema_source = g_settings_new_schema_source_from_directory (dir, g_settings_schema_source_get_default (), FALSE, NULL); ... return plugin; } ... GSettings * plugin_get_settings (Plugin *plugin, const gchar *schema_id) { GSettingsSchema *schema; if (schema_id == NULL) schema_id = plugin->identifier; schema = g_settings_schema_source_lookup (plugin->schema_source, schema_id, FALSE); if (schema == NULL) { ... disable the plugin or abort, etc ... } return g_settings_new_full (schema, NULL, NULL); } |
The code above shows how hooks should be added to the code that initialises (or enables) the plugin to create the schema source and how an API can be added to the plugin system to provide a convenient way for the plugin to access its settings, using the schemas that it ships.
From the standpoint of the plugin, it would need to ensure that it ships a gschemas.compiled file as part of itself, and then simply do the following:
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{ GSettings *settings; gint some_value; settings = plugin_get_settings (self, NULL); some_value = g_settings_get_int (settings, "some-value"); ... } |
It's also possible that the plugin system expects the schema source files (ie: .gschema.xml files) instead of a gschemas.compiled file. In that case, the plugin loading system must compile the schemas for itself before attempting to create the settings source.
typedef struct _GSettingsSchemaSource GSettingsSchemaSource;
This is an opaque structure type. You may not access it directly.
Since 2.32
#define G_TYPE_SETTINGS_SCHEMA_SOURCE (g_settings_schema_source_get_type ())
A boxed GType corresponding to GSettingsSchemaSource.
Since 2.32
GSettingsSchemaSource * g_settings_schema_source_get_default
(void
);
Gets the default system schema source.
This function is not required for normal uses of GSettings but it may be useful to authors of plugin management systems or to those who want to introspect the content of schemas.
If no schemas are installed, NULL
will be returned.
The returned source may actually consist of multiple schema sources
from different directories, depending on which directories were given
in XDG_DATA_DIRS
and
GSETTINGS_SCHEMA_DIR
. For this reason, all lookups
performed against the default source should probably be done
recursively.
Returns : |
the default schema source. [transfer none] |
Since 2.32
GSettingsSchemaSource * g_settings_schema_source_ref (GSettingsSchemaSource *source
);
Increase the reference count of source
, returning a new reference.
|
a GSettingsSchemaSource |
Returns : |
a new reference to source
|
Since 2.32
void g_settings_schema_source_unref (GSettingsSchemaSource *source
);
Decrease the reference count of source
, possibly freeing it.
|
a GSettingsSchemaSource |
Since 2.32
GSettingsSchemaSource * g_settings_schema_source_new_from_directory (const gchar *directory
,GSettingsSchemaSource *parent
,gboolean trusted
,GError **error
);
Attempts to create a new schema source corresponding to the contents of the given directory.
This function is not required for normal uses of GSettings but it may be useful to authors of plugin management systems.
The directory should contain a file called
gschemas.compiled
as produced by
glib-compile-schemas.
If trusted
is TRUE
then gschemas.compiled
is
trusted not to be corrupted. This assumption has a performance
advantage, but can result in crashes or inconsistent behaviour in the
case of a corrupted file. Generally, you should set trusted
to
TRUE
for files installed by the system and to FALSE
for files in
the home directory.
If parent
is non-NULL
then there are two effects.
First, if g_settings_schema_source_lookup()
is called with the
recursive
flag set to TRUE
and the schema can not be found in the
source, the lookup will recurse to the parent.
Second, any references to other schemas specified within this
source (ie: child
or extends
)
references may be resolved from the parent
.
For this second reason, except in very unusual situations, the
parent
should probably be given as the default schema source, as
returned by g_settings_schema_source_get_default()
.
|
the filename of a directory |
|
a GSettingsSchemaSource, or NULL . [allow-none]
|
|
TRUE , if the directory is trusted |
|
a pointer to a GError pointer set to NULL , or NULL
|
Since 2.32
void g_settings_schema_source_list_schemas (GSettingsSchemaSource *source
,gboolean recursive
,gchar ***non_relocatable
,gchar ***relocatable
);
Lists the schemas in a given source.
If recursive
is TRUE
then include parent sources. If FALSE
then
only include the schemas from one source (ie: one directory). You
probably want TRUE
.
Non-relocatable schemas are those for which you can call
g_settings_new()
. Relocatable schemas are those for which you must
use g_settings_new_with_path()
.
Do not call this function from normal programs. This is designed for use by database editors, commandline tools, etc.
|
a GSettingsSchemaSource |
|
if we should recurse |
|
the list of non-relocatable schemas. [out][transfer full] |
|
the list of relocatable schemas. [out][transfer full] |
Since 2.40
GSettingsSchema * g_settings_schema_source_lookup (GSettingsSchemaSource *source
,const gchar *schema_id
,gboolean recursive
);
Looks up a schema with the identifier schema_id
in source
.
This function is not required for normal uses of GSettings but it may be useful to authors of plugin management systems or to those who want to introspect the content of schemas.
If the schema isn't found directly in source
and recursive
is TRUE
then the parent sources will also be checked.
If the schema isn't found, NULL
is returned.
|
a GSettingsSchemaSource |
|
a schema ID |
|
TRUE if the lookup should be recursive |
Returns : |
a new GSettingsSchema. [transfer full] |
Since 2.32
typedef struct _GSettingsSchema GSettingsSchema;
This is an opaque structure type. You may not access it directly.
Since 2.32
#define G_TYPE_SETTINGS_SCHEMA (g_settings_schema_get_type ())
A boxed GType corresponding to GSettingsSchema.
Since 2.32
GSettingsSchema * g_settings_schema_ref (GSettingsSchema *schema
);
Increase the reference count of schema
, returning a new reference.
|
a GSettingsSchema |
Returns : |
a new reference to schema
|
Since 2.32
void g_settings_schema_unref (GSettingsSchema *schema
);
Decrease the reference count of schema
, possibly freeing it.
|
a GSettingsSchema |
Since 2.32
const gchar * g_settings_schema_get_id (GSettingsSchema *schema
);
Get the ID of schema
.
|
a GSettingsSchema |
Returns : |
the ID. [transfer none] |
const gchar * g_settings_schema_get_path (GSettingsSchema *schema
);
Gets the path associated with schema
, or NULL
.
Schemas may be single-instance or relocatable. Single-instance schemas correspond to exactly one set of keys in the backend database: those located at the path returned by this function.
Relocatable schemas can be referenced by other schemas and can
threfore describe multiple sets of keys at different locations. For
relocatable schemas, this function will return NULL
.
|
a GSettingsSchema |
Returns : |
the path of the schema, or NULL . [transfer none]
|
Since 2.32
gboolean g_settings_schema_has_key (GSettingsSchema *schema
,const gchar *key
);
Checks if schema
has a key named name
.
|
a GSettingsSchema |
|
the name of a key |
Returns : |
TRUE if such a key exists |
Since 2.40
GSettingsSchemaKey * g_settings_schema_get_key (GSettingsSchema *schema
,const gchar *key
);
Gets the key named name
from schema
.
It is a programmer error to request a key that does not exist. See
g_settings_schema_list_keys()
.
|
a GSettingsSchema |
|
the name of a key |
Returns : |
the GSettingsSchemaKey for name . [transfer full]
|
Since 2.40
GSettingsSchemaKey * g_settings_schema_key_ref (GSettingsSchemaKey *key
);
Increase the reference count of key
, returning a new reference.
|
a GSettingsSchemaKey |
Returns : |
a new reference to key
|
Since 2.40
void g_settings_schema_key_unref (GSettingsSchemaKey *key
);
Decrease the reference count of key
, possibly freeing it.
|
a GSettingsSchemaKey |
Since 2.40
const GVariantType * g_settings_schema_key_get_value_type
(GSettingsSchemaKey *key
);
Gets the GVariantType of key
.
|
a GSettingsSchemaKey |
Returns : |
the type of key . [transfer none]
|
Since 2.40
GVariant * g_settings_schema_key_get_default_value
(GSettingsSchemaKey *key
);
Gets the default value for key
.
Note that this is the default value according to the schema. System administrator defaults and lockdown are not visible via this API.
|
a GSettingsSchemaKey |
Returns : |
the default value for the key. [transfer full] |
Since 2.40
GVariant * g_settings_schema_key_get_range (GSettingsSchemaKey *key
);
Queries the range of a key.
This function will return a GVariant that fully describes the range
of values that are valid for key
.
The type of GVariant returned is (sv)
. The
string describes the type of range restriction in effect. The type
and meaning of the value contained in the variant depends on the
string.
If the string is 'type'
then the variant contains
an empty array. The element type of that empty array is the expected
type of value and all values of that type are valid.
If the string is 'enum'
then the variant contains
an array enumerating the possible values. Each item in the array is
a possible valid value and no other values are valid.
If the string is 'flags'
then the variant contains
an array. Each item in the array is a value that may appear zero or
one times in an array to be used as the value for this key. For
example, if the variant contained the array ['x',
'y']
then the valid values for the key would be
[]
, ['x']
,
['y']
, ['x', 'y']
and
['y', 'x']
.
Finally, if the string is 'range'
then the variant
contains a pair of like-typed values -- the minimum and maximum
permissible values for this key.
This information should not be used by normal programs. It is considered to be a hint for introspection purposes. Normal programs should already know what is permitted by their own schema. The format may change in any way in the future -- but particularly, new forms may be added to the possibilities described above.
You should free the returned value with g_variant_unref()
when it is
no longer needed.
|
a GSettingsSchemaKey |
Returns : |
a GVariant describing the range. [transfer full] |
Since 2.40
gboolean g_settings_schema_key_range_check (GSettingsSchemaKey *key
,GVariant *value
);
Checks if the given value
is of the correct type and within the
permitted range for key
.
It is a programmer error if value
is not of the correct type -- you
must check for this first.
|
a GSettingsSchemaKey |
|
the value to check |
Returns : |
TRUE if value is valid for key
|
Since 2.40
const gchar * g_settings_schema_key_get_summary (GSettingsSchemaKey *key
);
Gets the summary for key
.
If no summary has been provided in the schema for key
, returns
NULL
.
The summary is a short description of the purpose of the key; usually one short sentence. Summaries can be translated and the value returned from this function is is the current locale.
This function is slow. The summary and description information for the schemas is not stored in the compiled schema database so this function has to parse all of the source XML files in the schema directory.
|
a GSettingsSchemaKey |
Returns : |
the summary for key , or NULL
|
Since 2.34
const gchar * g_settings_schema_key_get_description
(GSettingsSchemaKey *key
);
Gets the description for key
.
If no description has been provided in the schema for key
, returns
NULL
.
The description can be one sentence to several paragraphs in length. Paragraphs are delimited with a double newline. Descriptions can be translated and the value returned from this function is is the current locale.
This function is slow. The summary and description information for the schemas is not stored in the compiled schema database so this function has to parse all of the source XML files in the schema directory.
|
a GSettingsSchemaKey |
Returns : |
the description for key , or NULL
|
Since 2.34