Struct gio::SettingsSchema

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pub struct SettingsSchema { /* private fields */ }
Expand description

The SettingsSchemaSource 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.

SettingsSchemaSource 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:

⚠️ The following code is in c ⚠️

typedef struct
{
   …
   GSettingsSchemaSource *schema_source;
   …
} Plugin;

Plugin *
initialise_plugin (const gchar *dir)
{
  Plugin *plugin;

  …

  plugin->schema_source =
    g_settings_schema_source_new_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:

⚠️ The following code is in c ⚠️

{
  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.

Implementations§

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impl SettingsSchema

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pub fn as_ptr(&self) -> *mut GSettingsSchema

Return the inner pointer to the underlying C value.

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pub unsafe fn from_glib_ptr_borrow<'a>( ptr: *const *const GSettingsSchema ) -> &'a Self

Borrows the underlying C value.

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impl SettingsSchema

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pub fn id(&self) -> GString

Get the ID of @self.

§Returns

the ID

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pub fn key(&self, name: &str) -> SettingsSchemaKey

Gets the key named @name from @self.

It is a programmer error to request a key that does not exist. See g_settings_schema_list_keys().

§name

the name of a key

§Returns

the #GSettingsSchemaKey for @name

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pub fn path(&self) -> Option<GString>

Gets the path associated with @self, or None.

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 therefore describe multiple sets of keys at different locations. For relocatable schemas, this function will return None.

§Returns

the path of the schema, or None

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pub fn has_key(&self, name: &str) -> bool

Checks if @self has a key named @name.

§name

the name of a key

§Returns

true if such a key exists

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pub fn list_children(&self) -> Vec<GString>

Gets the list of children in @self.

You should free the return value with g_strfreev() when you are done with it.

§Returns

a list of the children on @settings, in no defined order

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pub fn list_keys(&self) -> Vec<GString>

Introspects the list of keys on @self.

You should probably not be calling this function from “normal” code (since you should already know what keys are in your schema). This function is intended for introspection reasons.

§Returns

a list of the keys on @self, in no defined order

Trait Implementations§

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impl Clone for SettingsSchema

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fn clone(&self) -> Self

Returns a copy of the value. Read more
1.0.0 · source§

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for SettingsSchema

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl From<SettingsSchema> for Value

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fn from(s: SettingsSchema) -> Self

Converts to this type from the input type.
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impl HasParamSpec for SettingsSchema

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type ParamSpec = ParamSpecBoxed

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type SetValue = SettingsSchema

Preferred value to be used as setter for the associated ParamSpec.
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type BuilderFn = fn(_: &str) -> ParamSpecBoxedBuilder<'_, SettingsSchema>

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fn param_spec_builder() -> Self::BuilderFn

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impl Hash for SettingsSchema

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fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher. Read more
1.3.0 · source§

fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher. Read more
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impl Ord for SettingsSchema

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fn cmp(&self, other: &SettingsSchema) -> Ordering

This method returns an Ordering between self and other. Read more
1.21.0 · source§

fn max(self, other: Self) -> Self
where Self: Sized,

Compares and returns the maximum of two values. Read more
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fn min(self, other: Self) -> Self
where Self: Sized,

Compares and returns the minimum of two values. Read more
1.50.0 · source§

fn clamp(self, min: Self, max: Self) -> Self
where Self: Sized + PartialOrd,

Restrict a value to a certain interval. Read more
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impl PartialEq for SettingsSchema

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fn eq(&self, other: &SettingsSchema) -> bool

This method tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl PartialOrd for SettingsSchema

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fn partial_cmp(&self, other: &SettingsSchema) -> Option<Ordering>

This method returns an ordering between self and other values if one exists. Read more
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fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator. Read more
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fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more
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fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator. Read more
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fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more
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impl StaticType for SettingsSchema

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fn static_type() -> Type

Returns the type identifier of Self.
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impl Eq for SettingsSchema

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impl StructuralPartialEq for SettingsSchema

Auto Trait Implementations§

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where T: 'static + ?Sized,

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impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GSList> for T

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impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *mut GSList> for T

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impl<T> FromGlibPtrArrayContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GSList> for T

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