class Gio::SettingsSchema

Gio::SettingsSchema
Reference
Object

Overview

The Gio::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.

Gio::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:

WARNING ⚠️ 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:

WARNING ⚠️ 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.

Defined in:

lib/gi-crystal/src/auto/gio-2.0/settings_schema.cr

Constructors

.new(pointer : Pointer(Void), transfer : GICrystal::Transfer)

Class Method Summary

.g_type : UInt64
Returns the type id (GType) registered in GLib type system.

Instance Method Summary

#finalize
#has_key(name : String) : Bool
#id : String
#key(name : String) : Gio::SettingsSchemaKey
#list_children : Enumerable(String)
#list_keys : Enumerable(String)
#path : String | Nil
#ref : Gio::SettingsSchema
#to_unsafe : Pointer(Void)
#unref : Nil

Constructor Detail

def self.new(pointer : Pointer(Void), transfer : GICrystal::Transfer) #

Class Method Detail

def self.g_type : UInt64 #

Returns the type id (GType) registered in GLib type system.

Instance Method Detail

def finalize #

def has_key(name : String) : Bool #

def id : String #

def key(name : String) : Gio::SettingsSchemaKey #

def list_children : Enumerable(String) #

def list_keys : Enumerable(String) #

def path : String | Nil #

def ref : Gio::SettingsSchema #

def to_unsafe : Pointer(Void) #

def unref : Nil #

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