Class SettingsSchema

java.lang.Object
org.javagi.base.ProxyInstance
org.gnome.gio.SettingsSchema
All Implemented Interfaces:
Proxy
@Generated("org.javagi.JavaGI") public class SettingsSchema extends ProxyInstance

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:

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:

{
  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.

Since:
2.32

  • Constructor Details

    • SettingsSchema

      public SettingsSchema(MemorySegment address)
      Create a SettingsSchema proxy instance for the provided memory address.
      Parameters:
      address - the memory address of the native object

  • Method Details

    • getType

      public static @Nullable Type getType()
      Get the GType of the SettingsSchema class.
      Returns:
      the GType

    • getMemoryLayout

      public static MemoryLayout getMemoryLayout()
      The memory layout of the native struct.
      Returns:
      the memory layout

    • getId

      public String getId()
      Get the ID of schema.
      Returns:
      the ID

    • getKey

      public SettingsSchemaKey getKey(String name)

      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().

      Parameters:
      name - the name of a key
      Returns:
      the GSettingsSchemaKey for name
      Since:
      2.40

    • getPath

      public @Nullable String getPath()

      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 therefore describe multiple sets of keys at different locations. For relocatable schemas, this function will return null.

      Returns:
      the path of the schema, or null
      Since:
      2.32

    • hasKey

      public boolean hasKey(String name)
      Checks if this SettingsSchema has a key named name.
      Parameters:
      name - the name of a key
      Returns:
      true if such a key exists
      Since:
      2.40

    • listChildren

      public String[] listChildren()

      Gets the list of children in schema.

      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
      Since:
      2.44

    • listKeys

      public String[] listKeys()

      Introspects the list of keys on schema.

      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 schema, in no defined order
      Since:
      2.46

    • ref

      public SettingsSchema ref()
      Increase the reference count of schema, returning a new reference.
      Returns:
      a new reference to this SettingsSchema
      Since:
      2.32

    • unref

      public void unref()
      Decrease the reference count of schema, possibly freeing it.
      Since:
      2.32