A passthrough GSettings backend (with broken change signalling)

passthrough-backend.c

#define G_SETTINGS_ENABLE_BACKEND
#include <gio/gio.h>
#include <gio/gsettingsbackend.h>

typedef GSettingsBackendClass PassthroughSettingsBackendClass;
typedef struct _PassthroughSettingsBackend PassthroughSettingsBackend;

struct _PassthroughSettingsBackend
{
    GSettingsBackend backend;

    GSettingsBackend *real;
};

static GType passthrough_settings_backend_get_type (void);
G_DEFINE_TYPE(PassthroughSettingsBackend, passthrough_settings_backend, G_TYPE_SETTINGS_BACKEND)

static GVariant *
passthrough_settings_backend_read (GSettingsBackend   *backend,
                                   const gchar        *key,
                                   const GVariantType *expected_type,
                                   gboolean            default_value)
{
    PassthroughSettingsBackend *b = (PassthroughSettingsBackend *)backend;

    g_message ("passthrough_settings_backend_read(%s)", key);
    return G_SETTINGS_BACKEND_GET_CLASS (b->real)->read (b->real, key, expected_type, default_value);
}

static GVariant *
passthrough_settings_backend_read_user_value (GSettingsBackend   *backend,
                                              const gchar        *key,
                                              const GVariantType *expected_type)
{
    PassthroughSettingsBackend *b = (PassthroughSettingsBackend *)backend;

    g_message ("passthrough_settings_backend_read_user_value(%s)", key);
    return G_SETTINGS_BACKEND_GET_CLASS (b->real)->read_user_value (b->real, key, expected_type);
}

static gboolean
passthrough_settings_backend_write (GSettingsBackend *backend,
                                    const gchar      *key,
                                    GVariant         *value,
                                    gpointer          origin_tag)
{
    PassthroughSettingsBackend *b = (PassthroughSettingsBackend *)backend;

    return G_SETTINGS_BACKEND_GET_CLASS (b->real)->write (b->real, key, value, origin_tag);
}

static gboolean
passthrough_settings_backend_write_tree (GSettingsBackend *backend,
                                         GTree            *tree,
                                         gpointer          origin_tag)
{
    PassthroughSettingsBackend *b = (PassthroughSettingsBackend *)backend;

    return G_SETTINGS_BACKEND_GET_CLASS (b->real)->write_tree (b->real, tree, origin_tag);
}

static void
passthrough_settings_backend_reset (GSettingsBackend *backend,
                                    const gchar      *key,
                                    gpointer          origin_tag)
{
    PassthroughSettingsBackend *b = (PassthroughSettingsBackend *)backend;

    G_SETTINGS_BACKEND_GET_CLASS (b->real)->reset (b->real, key, origin_tag);
}

static gboolean
passthrough_settings_backend_get_writable (GSettingsBackend *backend,
                                           const gchar      *name)
{
    PassthroughSettingsBackend *b = (PassthroughSettingsBackend *)backend;

    return G_SETTINGS_BACKEND_GET_CLASS (b->real)->get_writable (b->real, name);
}

static void
passthrough_settings_backend_subscribe (GSettingsBackend *backend,
                                        const gchar      *name)
{
    PassthroughSettingsBackend *b = (PassthroughSettingsBackend *)backend;

    G_SETTINGS_BACKEND_GET_CLASS (b->real)->subscribe (b->real, name);
}

static void
passthrough_settings_backend_unsubscribe (GSettingsBackend *backend,
                                          const gchar      *name)
{
    PassthroughSettingsBackend *b = (PassthroughSettingsBackend *)backend;

    G_SETTINGS_BACKEND_GET_CLASS (b->real)->unsubscribe (b->real, name);
}

static void
passthrough_settings_backend_sync (GSettingsBackend *backend)
{
    PassthroughSettingsBackend *b = (PassthroughSettingsBackend *)backend;

    G_SETTINGS_BACKEND_GET_CLASS (b->real)->sync (b->real);
}

static void
passthrough_settings_backend_init (PassthroughSettingsBackend *backend)
{
    GIOExtensionPoint *ep;
    GIOExtension *e;

    g_message("passthrough_settings_backend_init");
    ep = g_io_extension_point_lookup (G_SETTINGS_BACKEND_EXTENSION_POINT_NAME);
    e = g_io_extension_point_get_extension_by_name (ep, "dconf");

    backend->real = g_object_new (g_io_extension_get_type (e), NULL);
}

static void
passthrough_settings_backend_finalize (GObject *object)
{
    PassthroughSettingsBackend *backend = (PassthroughSettingsBackend *)object;

    g_clear_object (&backend->real);
    G_OBJECT_CLASS (passthrough_settings_backend_parent_class)->finalize (object);
}

static void
passthrough_settings_backend_class_init (GSettingsBackendClass *class)
{
    GObjectClass *object_class = G_OBJECT_CLASS (class);

    object_class->finalize = passthrough_settings_backend_finalize;

    class->read = passthrough_settings_backend_read;
    class->read_user_value = passthrough_settings_backend_read_user_value;
    class->write = passthrough_settings_backend_write;
    class->write_tree = passthrough_settings_backend_write_tree;
    class->reset = passthrough_settings_backend_reset;
    class->get_writable = passthrough_settings_backend_get_writable;
    class->subscribe = passthrough_settings_backend_subscribe;
    class->unsubscribe = passthrough_settings_backend_unsubscribe;
    class->sync = passthrough_settings_backend_sync;
}

void
g_io_module_load (GIOModule *module)
{
  g_type_module_use (G_TYPE_MODULE (module));
  g_io_extension_point_implement (G_SETTINGS_BACKEND_EXTENSION_POINT_NAME,
                                  passthrough_settings_backend_get_type (),
                                  "passthrough", 10);
}

void
g_io_module_unload (GIOModule *module)
{
  g_assert_not_reached ();
}

gchar **
g_io_module_query (void)
{
  return g_strsplit (G_SETTINGS_BACKEND_EXTENSION_POINT_NAME, "!", 0);
}