## GConf Core Interfaces

GConf Core Interfaces — Basic functions to initialize GConf and get/set values

##

# Synopsis

    gboolean    gconf_init                      (int argc,
                                                 char **argv,
                                                 GError **err);
    void        gconf_preinit                   (gpointer app,
                                                 gpointer mod_info);
    void        gconf_postinit                  (gpointer app,
                                                 gpointer mod_info);
    gboolean    gconf_is_initialized            (void);
    void        (*GConfNotifyFunc)              (GConfEngine *conf,
                                                 guint cnxn_id,
                                                 GConfEntry *entry,
                                                 gpointer user_data);
    guint       gconf_engine_notify_add         (GConfEngine *conf,
                                                 const gchar *namespace_section,
                                                 GConfNotifyFunc func,
                                                 gpointer user_data,
                                                 GError **err);
    void        gconf_engine_notify_remove      (GConfEngine *conf,
                                                 guint cnxn);
    GConfValue* gconf_engine_get                (GConfEngine *conf,
                                                 const gchar *key,
                                                 GError **err);
    GConfValue* gconf_engine_get_with_locale    (GConfEngine *conf,
                                                 const gchar *key,
                                                 const gchar *locale,
                                                 GError **err);
    GConfValue* gconf_engine_get_without_default
                                                (GConfEngine *conf,
                                                 const gchar *key,
                                                 GError **err);
    GConfEntry* gconf_engine_get_entry          (GConfEngine *conf,
                                                 const gchar *key,
                                                 const gchar *locale,
                                                 gboolean use_schema_default,
                                                 GError **err);
    GConfValue* gconf_engine_get_default_from_schema
                                                (GConfEngine *conf,
                                                 const gchar *key,
                                                 GError **err);
    gboolean    gconf_engine_set                (GConfEngine *conf,
                                                 const gchar *key,
                                                 const GConfValue *value,
                                                 GError **err);
    gboolean    gconf_engine_unset              (GConfEngine *conf,
                                                 const gchar *key,
                                                 GError **err);
    gboolean    gconf_engine_associate_schema   (GConfEngine *conf,
                                                 const gchar *key,
                                                 const gchar *schema_key,
                                                 GError **err);
    GSList*     gconf_engine_all_entries        (GConfEngine *conf,
                                                 const gchar *dir,
                                                 GError **err);
    GSList*     gconf_engine_all_dirs           (GConfEngine *conf,
                                                 const gchar *dir,
                                                 GError **err);
    void        gconf_engine_suggest_sync       (GConfEngine *conf,
                                                 GError **err);
    gboolean    gconf_engine_dir_exists         (GConfEngine *conf,
                                                 const gchar *dir,
                                                 GError **err);
    gboolean    gconf_valid_key                 (const gchar *key,
                                                 gchar **why_invalid);
    gboolean    gconf_key_is_below              (const gchar *above,
                                                 const gchar *below);
    gdouble     gconf_engine_get_float          (GConfEngine *conf,
                                                 const gchar *key,
                                                 GError **err);
    gint        gconf_engine_get_int            (GConfEngine *conf,
                                                 const gchar *key,
                                                 GError **err);
    gchar*      gconf_engine_get_string         (GConfEngine *conf,
                                                 const gchar *key,
                                                 GError **err);
    gboolean    gconf_engine_get_bool           (GConfEngine *conf,
                                                 const gchar *key,
                                                 GError **err);
    GConfSchema* gconf_engine_get_schema        (GConfEngine *conf,
                                                 const gchar *key,
                                                 GError **err);
    GSList*     gconf_engine_get_list           (GConfEngine *conf,
                                                 const gchar *key,
                                                 GConfValueType list_type,
                                                 GError **err);
    gboolean    gconf_engine_get_pair           (GConfEngine *conf,
                                                 const gchar *key,
                                                 GConfValueType car_type,
                                                 GConfValueType cdr_type,
                                                 gpointer car_retloc,
                                                 gpointer cdr_retloc,
                                                 GError **err);
    gboolean    gconf_engine_set_float          (GConfEngine *conf,
                                                 const gchar *key,
                                                 gdouble val,
                                                 GError **err);
    gboolean    gconf_engine_set_int            (GConfEngine *conf,
                                                 const gchar *key,
                                                 gint val,
                                                 GError **err);
    gboolean    gconf_engine_set_string         (GConfEngine *conf,
                                                 const gchar *key,
                                                 const gchar *val,
                                                 GError **err);
    gboolean    gconf_engine_set_bool           (GConfEngine *conf,
                                                 const gchar *key,
                                                 gboolean val,
                                                 GError **err);
    gboolean    gconf_engine_set_schema         (GConfEngine *conf,
                                                 const gchar *key,
                                                 const GConfSchema *val,
                                                 GError **err);
    gboolean    gconf_engine_set_list           (GConfEngine *conf,
                                                 const gchar *key,
                                                 GConfValueType list_type,
                                                 GSList *list,
                                                 GError **err);
    gboolean    gconf_engine_set_pair           (GConfEngine *conf,
                                                 const gchar *key,
                                                 GConfValueType car_type,
                                                 GConfValueType cdr_type,
                                                 gconstpointer address_of_car,
                                                 gconstpointer address_of_cdr,
                                                 GError **err);
    struct      GConfEnumStringPair;
    gboolean    gconf_string_to_enum            (GConfEnumStringPair lookup_table[],
                                                 const gchar *str,
                                                 gint *enum_value_retloc);
    const gchar* gconf_enum_to_string           (GConfEnumStringPair lookup_table[],
                                                 gint enum_value);

## Description

These functions initialize GConf, and communicate with the gconfd server via a GConfEngine object. You can install a notification request on the server, get values, set values, list directories, and associate schema names with keys.

Most of this interface is replicated in the GtkObject wrapper (GConfClient object); an alternative to the value-setting functions is the GConfChangeSet interface.

## Details

### gconf_init ()

    gboolean    gconf_init                      (int argc,
                                                 char **argv,
                                                 GError **err);

### Warning

`gconf_init` is deprecated and should not be used in newly-written code.

Initializes the GConf library. Creates a connection to a CORBA ORB, and initializes OAF (the object activation framework) if it isn't already initialized.

`argc` : |
`argv` : |
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | TRUE on success, FALSE otherwise.

### gconf_preinit ()

    void        gconf_preinit                   (gpointer app,
                                                 gpointer mod_info);

### Warning

`gconf_preinit` is deprecated and should not be used in newly-written code.

`app` : |
`mod_info` : |

### gconf_postinit ()

    void        gconf_postinit                  (gpointer app,
                                                 gpointer mod_info);

### Warning

`gconf_postinit` is deprecated and should not be used in newly-written code.

`app` : |
`mod_info` : |

### gconf_is_initialized ()

    gboolean    gconf_is_initialized            (void);

### Warning

`gconf_is_initialized` is deprecated and should not be used in newly-written code.

Asks whether the library has been initialized.

Returns : | TRUE if the library has been initialized.

### GConfNotifyFunc ()

    void        (*GConfNotifyFunc)              (GConfEngine *conf,
                                                 guint cnxn_id,
                                                 GConfEntry *entry,
                                                 gpointer user_data);

A callback function invoked when a key's value changes. The `cnxn_id` parameter will be the connection ID returned from `gconf_engine_notify_add()`. `key` will be the full path of the changed key, `value` will be the new value if the key is set. If the key is unset, `value` will be the default value if one exists, or NULL otherwise. `is_default` indicates whether a value is a default setting or a user setting. If `value` is NULL, `is_default` will be TRUE. `user_data` is the data passed to `gconf_engine_notify_add()`.

`conf` : | the GConfEngine passed to `gconf_engine_notify_add()`.
`cnxn_id` : | the ID returned from `gconf_engine_notify_add()`.
`entry` : |
`user_data` : | the user data passed to `gconf_engine_notify_add()`.

### gconf_engine_notify_add ()

    guint       gconf_engine_notify_add         (GConfEngine *conf,
                                                 const gchar *namespace_section,
                                                 GConfNotifyFunc func,
                                                 gpointer user_data,
                                                 GError **err);

Registers a notification request with the gconfd server. The server will notify the client when any key at or below `namespace_section` is set or unset. Try to watch the smallest possible part of the namespace; otherwise you will slow down the server and your application with unnecessary notifications. Note that you should prefer `gconf_client_notify_add()` if you're using the GtkObject wrapper library, because `gconf_client_notify_add()` does not require a client-server conversation for every callback. `gconf_engine_notify_add()` requests a different server notification for every callback. The function returns an ID you can use to remove the notification request; 0 is an invalid ID, and is returned if an error occurs.

`conf` : | a GConfEngine to monitor for changes.
`namespace_section` : | the directory or key to watch; you will be notified of changes at or below this point.
`func` : | the callback to invoke when a notification is received from the server.
`user_data` : | the data to pass to the callback.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | an ID for the notification request, or 0 on error.

### gconf_engine_notify_remove ()

    void        gconf_engine_notify_remove      (GConfEngine *conf,
                                                 guint cnxn);

Removes a notification request.

`conf` : | the GConfEngine you were monitoring for changes.
`cnxn` : | The ID returned by `gconf_engine_notify_add()`.

### gconf_engine_get ()

    GConfValue* gconf_engine_get                (GConfEngine *conf,
                                                 const gchar *key,
                                                 GError **err);

Returns the GConfValue stored at `key`, or NULL if no value is set. You must call `gconf_value_free()` to free the returned value. If you know the expected type of the value, you probably want to use the type-specific convenience wrappers (`gconf_engine_get_int()`, etc.) because they will do the type-checking for you and return the appropriate type. Automatically returns the default value for a key, if the key is unset and a default exists.

`conf` : | a GConfEngine to get the value from.
`key` : | the key to get.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | newly-allocated GConfValue, or NULL if unset and no default exists.

### gconf_engine_get_with_locale ()

    GConfValue* gconf_engine_get_with_locale    (GConfEngine *conf,
                                                 const gchar *key,
                                                 const gchar *locale,
                                                 GError **err);

Requests the value appropriate for a particular locale. Right now, only values of type `GCONF_VALUE_SCHEMA` are localized; the locale is meaningless for other value types. Also, `gconf_engine_get()` automatically requests the value in the user's current locale. So this function is only useful if you want a schema for some locale other than the user's current locale. Except for the additional argument, this function is identical to `gconf_engine_get()` in all respects.

`conf` : | a GConfEngine to get the value from.
`key` : | the key to get.
`locale` : | preferred locale (as in the locale-related environment variables).
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | newly-allocated GConfValue, or NULL if unset.

### gconf_engine_get_without_default ()

    GConfValue* gconf_engine_get_without_default
                                                (GConfEngine *conf,
                                                 const gchar *key,
                                                 GError **err);

Identical to `gconf_engine_get()`, except that it will return NULL in place of the default value if the key is unset. Note that `gconf_engine_get()` can also return NULL if no default exists or an error occurs.

`conf` : | a GConfEngine to get the value from.
`key` : | the key to get.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | newly-allocated GConfValue, or NULL if unset.

### gconf_engine_get_entry ()

    GConfEntry* gconf_engine_get_entry          (GConfEngine *conf,
                                                 const gchar *key,
                                                 const gchar *locale,
                                                 gboolean use_schema_default,
                                                 GError **err);

Obtain the full GConfEntry for a value.

`conf` : |
`key` : |
`locale` : |
`use_schema_default` : |
`err` : |
Returns : |

### gconf_engine_get_default_from_schema ()

    GConfValue* gconf_engine_get_default_from_schema
                                                (GConfEngine *conf,
                                                 const gchar *key,
                                                 GError **err);

Returns the default value stored in the key's schema, if the key has a schema associated and the schema exists and the schema contains a default value. Note that `gconf_engine_get()`, `gconf_engine_get_string()`, and so on already return the default value if no other value is found, so normally you do not need this function. This function is just for convenience; you could also get the GConfMetaInfo for the key, read the schema name from there, then look up the schema by name and extract the default value.

`conf` : | a GConfEngine to get the value from.
`key` : | the key to get the default value for.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | newly-allocated GConfValue, or NULL if unset.

### gconf_engine_set ()

    gboolean    gconf_engine_set                (GConfEngine *conf,
                                                 const gchar *key,
                                                 const GConfValue *value,
                                                 GError **err);

Sets the value of `key` to `value`. Does not modify the passed-in GConfValue, you must free it yourself. You may prefer a type-specific convenience wrapper, such as `gconf_engine_set_int()`.

An error of note is `GCONF_OVERRIDDEN`, indicating that the system administrator has "forced" a value for this key. If no writable configuration sources exist, it is not an error, but GConf will just forget all your values; this allows users to have a configuration-free setup without a constant barrage of error messages.

`conf` : | a GConfEngine to set the value in.
`key` : | the key to set.
`value` : | the new value of `key`.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | TRUE on success, FALSE on error.

### gconf_engine_unset ()

    gboolean    gconf_engine_unset              (GConfEngine *conf,
                                                 const gchar *key,
                                                 GError **err);

Unsets the value of `key`; if `key` is already unset, has no effect. An error of note is `GCONF_OVERRIDDEN`, indicating that the system administrator has "forced" a value for this key.

`conf` : | a GConfEngine to affect.
`key` : | the key to unset.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | TRUE on success, FALSE on error.

### gconf_engine_associate_schema ()

    gboolean    gconf_engine_associate_schema   (GConfEngine *conf,
                                                 const gchar *key,
                                                 const gchar *schema_key,
                                                 GError **err);

Directs GConf to find the schema for `key` at location `schema_key`. That is, the value stored at `schema_key` should have type GCONF_VALUE_SCHEMA, and be descriptive of `key`. Normally you don't call this function from C code; you can ship a special file with your application and ask gconftool to install schema associations into the database during "make install."

`conf` : | a GConfEngine to affect.
`key` : | the key to associate the schema with.
`schema_key` : | the key where the schema will be stored.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | TRUE on success, FALSE on error.

### gconf_engine_all_entries ()

    GSList*     gconf_engine_all_entries        (GConfEngine *conf,
                                                 const gchar *dir,
                                                 GError **err);

Lists the key-value pairs in `dir`. Does not list subdirectories; for that use `gconf_engine_all_dirs()`. The returned list contains GConfEntry objects. A GConfEntry contains an absolute key and a value. The list is not recursive, it contains only the immediate children of `dir`. To free the returned list, `gconf_entry_free()` each list element, then `g_slist_free()` the list itself.

`conf` : | a GConfEngine.
`dir` : | Directory to list.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | List of GConfEntry.

### gconf_engine_all_dirs ()

    GSList*     gconf_engine_all_dirs           (GConfEngine *conf,
                                                 const gchar *dir,
                                                 GError **err);

Lists the subdirectories in `dir`. The returned list contains allocated strings. Each string is the absolute path of a subdirectory. You should `g_free()` each string in the list, then `g_slist_free()` the list itself.

`conf` : | a GConfEngine.
`dir` : | Directory to get subdirectories from.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | List of allocated subdirectory names.

### gconf_engine_suggest_sync ()

    void        gconf_engine_suggest_sync       (GConfEngine *conf,
                                                 GError **err);

Suggests to gconfd that you've just finished a block of changes, and it would be an optimal time to sync to permanent storage. This is only a suggestion; and gconfd will eventually sync even if you don't call `gconf_engine_suggest_sync()`. This function is just a "hint" provided to gconfd to maximize efficiency and minimize data loss.

`conf` : | the GConfEngine to suggest syncing to.
`err` : | the return location for an allocated GError, or NULL to ignore errors.

### gconf_engine_dir_exists ()

    gboolean    gconf_engine_dir_exists         (GConfEngine *conf,
                                                 const gchar *dir,
                                                 GError **err);

Queries whether the directory `dir` exists in the GConf database. Returns TRUE or FALSE.

`conf` : | a GConfEngine.
`dir` : | Directory to check for.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | TRUE or FALSE.

### gconf_valid_key ()

    gboolean    gconf_valid_key                 (const gchar *key,
                                                 gchar **why_invalid);

Asks whether a key is syntactically correct, that is, it ensures that the key consists of slash-separated strings and contains only legal characters. Normally you shouldn't need to call this function; the GConf functions all check this for you and return an error if the key is invalid. However, it may be useful to validate input to an entry field or the like. If you pass a non-NULL address as the `why_invalid` argument, an allocated string is returned explaining why the key is invalid, if it is. If the key is valid the `why_invalid` argument is unused.

`key` : | key to check.
`why_invalid` : | return location for an explanation of the problem, if any. `g_free()` the returned string.
Returns : | TRUE if the key is valid, or FALSE if not.

### gconf_key_is_below ()

    gboolean    gconf_key_is_below              (const gchar *above,
                                                 const gchar *below);

Asks whether the key `below` would be found below the key `above`, were they both to exist in the database. For example, /foo is always found below / and above /foo/bar. This probably isn't useful but GConf uses it internally so here it is if you need it.

`above` : | the key on the "left hand side" of the predicate.
`below` : | the key on the "right hand side."
Returns : | TRUE or FALSE.

### gconf_engine_get_float ()

    gdouble     gconf_engine_get_float          (GConfEngine *conf,
                                                 const gchar *key,
                                                 GError **err);

Requests the floating point number (`GCONF_VALUE_FLOAT`) stored at `key`. Automatically performs type-checking, so if a non-float is stored at `key`, an error is returned. On error, or if `key` is unset, 0.0 is returned.

`conf` : | a GConfEngine.
`key` : | key you want the value of.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | the value of `key`, or 0.0 if no value is obtained.

### gconf_engine_get_int ()

    gint        gconf_engine_get_int            (GConfEngine *conf,
                                                 const gchar *key,
                                                 GError **err);

Requests the integer (`GCONF_VALUE_INT`) stored at `key`. Automatically performs type-checking, so if a non-integer is stored at `key`, an error is returned. On error, or if `key` is unset, 0 is returned.

`conf` : | a GConfEngine.
`key` : | key you want the value of.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | the value of `key`, or 0 if no value is obtained.

### gconf_engine_get_string ()

    gchar*      gconf_engine_get_string         (GConfEngine *conf,
                                                 const gchar *key,
                                                 GError **err);

Requests the string (`GCONF_VALUE_STRING`) stored at `key`. Automatically performs type-checking, so if a non-string is stored at `key`, an error is returned. On error, or if `key` is unset, NULL is returned.

`conf` : | a GConfEngine.
`key` : | key you want the value of.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | allocated string (value of `key`), or NULL if no value is obtained.

### gconf_engine_get_bool ()

    gboolean    gconf_engine_get_bool           (GConfEngine *conf,
                                                 const gchar *key,
                                                 GError **err);

Requests the boolean value (`GCONF_VALUE_BOOL`) stored at `key`. Automatically performs type-checking, so if a non-bool is stored at `key`, an error is returned. On error, or if `key` is unset, FALSE is returned.

`conf` : | a GConfEngine.
`key` : | key you want the value of.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | the value of `key`, or FALSE if no value is obtained.

### gconf_engine_get_schema ()

    GConfSchema* gconf_engine_get_schema        (GConfEngine *conf,
                                                 const gchar *key,
                                                 GError **err);

Requests the schema (`GCONF_VALUE_SCHEMA`) stored at `key`. Automatically performs type-checking, so if a non-schema is stored at `key`, an error is returned. If no value is set or an error occurs, NULL is returned.

`conf` : | a GConfEngine.
`key` : | key you want the value of.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | the value of `key` as an allocated GConfSchema, or NULL if no value was obtained.

### gconf_engine_get_list ()

    GSList*     gconf_engine_get_list           (GConfEngine *conf,
                                                 const gchar *key,
                                                 GConfValueType list_type,
                                                 GError **err);

Requests the list (`GCONF_VALUE_LIST`) stored at `key`. Automatically performs type-checking, so if a non-list is stored at `key`, or the list does not contain elements of type `list_type`, an error is returned. If no value is set or an error occurs, NULL is returned. Note that NULL is also the empty list, so if you need to distinguish the empty list from an unset value, you must use `gconf_engine_get()` to obtain a raw GConfValue.

Remember that GConf lists can only store primitive types: `GCONF_VALUE_FLOAT`, `GCONF_VALUE_INT`, `GCONF_VALUE_BOOL`, `GCONF_VALUE_STRING`, `GCONF_VALUE_SCHEMA`. Also remember that lists must be uniform, you may not mix types in the same list.

The type of the list elements depends on `list_type`. A GConfValue with type `GCONF_VALUE_LIST` normally stores a list of more GConfValue objects. `gconf_engine_get_list()` automatically converts to primitive C types. Thus, the list->data fields in the returned list contain:

`GCONF_VALUE_INT` | The integer itself, converted with `GINT_TO_POINTER()`
`GCONF_VALUE_BOOL` | The bool itself, converted with `GINT_TO_POINTER()`
`GCONF_VALUE_FLOAT` | A pointer to gdouble, which should be freed with `g_free()`
`GCONF_VALUE_STRING` | A pointer to gchar, which should be freed with `g_free()`
`GCONF_VALUE_SCHEMA` | A pointer to GConfSchema, which should be freed with `gconf_schema_free()`

In the `GCONF_VALUE_FLOAT` and `GCONF_VALUE_STRING` cases, you must `g_free()` each list element. In the `GCONF_VALUE_SCHEMA` case you must `gconf_schema_free()` each element. In all cases you must free the list itself with `g_slist_free()`.

`conf` : | a GConfEngine.
`key` : | key you want the value of.
`list_type` : | type of each list element.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | an allocated list, with elements as described above.

### gconf_engine_get_pair ()

    gboolean    gconf_engine_get_pair           (GConfEngine *conf,
                                                 const gchar *key,
                                                 GConfValueType car_type,
                                                 GConfValueType cdr_type,
                                                 gpointer car_retloc,
                                                 gpointer cdr_retloc,
                                                 GError **err);

Requests the pair (`GCONF_VALUE_PAIR`) stored at `key`. Automatically performs type-checking, so if a non-pair is stored at `key`, or the pair does not have the right `car_type` and `cdr_type`, an error is returned. Remember that the car of a pair is its first value, and the cdr is its second value, in the Lisp tradition.

Remember that GConf pairs can only store primitive types: `GCONF_VALUE_FLOAT`, `GCONF_VALUE_INT`, `GCONF_VALUE_BOOL`, `GCONF_VALUE_STRING`, `GCONF_VALUE_SCHEMA`.

`gconf_engine_get_pair()` stores the two fields of the pair in the locations pointed to by `car_retloc` and `cdr_retloc`. The type of these pointers depends on the corresponding `car_type` and `cdr_type`:

`GCONF_VALUE_INT` | pointer to gint
`GCONF_VALUE_BOOL` | pointer to gboolean
`GCONF_VALUE_FLOAT` | pointer to gdouble
`GCONF_VALUE_STRING` | pointer to gchar*
`GCONF_VALUE_SCHEMA` | pointer to GConfSchema*

In the `GCONF_VALUE_STRING` case, you must `g_free()` the string(s) stored in the return location(s). In the `GCONF_VALUE_SCHEMA` case you must `gconf_schema_free()` the returned schema. If there's an error or the value is unset, `car_retloc` and `cdr_retloc` are left unchanged.

`gconf_engine_get_pair()` returns TRUE on success.

An example of `gconf_engine_get_pair()` in action:

    gdouble car = 10.0;
    gchar* cdr  = NULL;
    GError* error = NULL;

    if (!gconf_engine_get_pair(conf, "/foo",
                        GCONF_VALUE_FLOAT,
                        GCONF_VALUE_STRING,
                        &car, &cdr, &error))
      {
        /* Note: car/cdr should be untouched, because an error occurred */
        g_assert(error != NULL);
        fprintf(stderr, "Error: s\n", error->message);
        g_error_free(error);
        error = NULL;
      }
    else
      {
        /* Note: car/cdr may be untouched even though there was no error,
           if no value was set for "/foo"
         */
        printf("Found pair (g,s)\n", car, cdr);
        if (cdr != NULL)
          g_free(cdr);
      }

`conf` : | a GConfEngine.
`key` : | key you want the value of.
`car_type` : | desired type of the pair's first field (car).
`cdr_type` : | desired type of the pair's second field (cdr).
`car_retloc` : | address of a return location for the car.
`cdr_retloc` : | address of a return location for the cdr.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | TRUE on success, FALSE on error.

### gconf_engine_set_float ()

    gboolean    gconf_engine_set_float          (GConfEngine *conf,
                                                 const gchar *key,
                                                 gdouble val,
                                                 GError **err);

Change the value of `key` to `val`. Automatically creates the `key` if it didn't exist before (ie it was unset or it only had a default value). If the key already exists but doesn't store a float (GCONF_VALUE_FLOAT), `gconf_engine_set_float()` will fail.

`conf` : | a GConfEngine.
`key` : | key you want to set the value of.
`val` : | new value of `key`.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | TRUE on success, FALSE on error.

### gconf_engine_set_int ()

    gboolean    gconf_engine_set_int            (GConfEngine *conf,
                                                 const gchar *key,
                                                 gint val,
                                                 GError **err);

Change the value of `key` to `val`. Automatically creates the `key` if it didn't exist before (ie it was unset or it only had a default value). If the key already exists but doesn't store an integer (GCONF_VALUE_INT), `gconf_engine_set_int()` will fail.

`conf` : | a GConfEngine.
`key` : | key you want to set the value of.
`val` : | new value of `key`.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | TRUE on success, FALSE on error.

### gconf_engine_set_string ()

    gboolean    gconf_engine_set_string         (GConfEngine *conf,
                                                 const gchar *key,
                                                 const gchar *val,
                                                 GError **err);

Change the value of `key` to `val`. Automatically creates the `key` if it didn't exist before (ie it was unset or it only had a default value). If the key already exists but doesn't store a string (GCONF_VALUE_STRING), `gconf_engine_set_string()` will fail.

`conf` : | a GConfEngine.
`key` : | key you want to set the value of.
`val` : | new value of `key`.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | TRUE on success, FALSE on error.

### gconf_engine_set_bool ()

    gboolean    gconf_engine_set_bool           (GConfEngine *conf,
                                                 const gchar *key,
                                                 gboolean val,
                                                 GError **err);

Change the value of `key` to `val`. Automatically creates the `key` if it didn't exist before (ie it was unset or it only had a default value). If the key already exists but but doesn't store a boolean (GCONF_VALUE_BOOL), `gconf_engine_set_bool()` will fail.

`conf` : | a GConfEngine.
`key` : | key you want to set the value of.
`val` : | new value of `key`.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | TRUE on success, FALSE on error.

### gconf_engine_set_schema ()

    gboolean    gconf_engine_set_schema         (GConfEngine *conf,
                                                 const gchar *key,
                                                 const GConfSchema *val,
                                                 GError **err);

Change the value of `key` to `val`. Automatically creates the `key` if it didn't exist before (ie it was unset or it only had a default value). If the key already exists but doesn't store a schema value (GCONF_VALUE_SCHEMA), `gconf_engine_set_schema()` will fail.

`conf` : | a GConfEngine.
`key` : | key you want to set the value of.
`val` : | new value of `key`.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | TRUE on success, FALSE on error.

### gconf_engine_set_list ()

    gboolean    gconf_engine_set_list           (GConfEngine *conf,
                                                 const gchar *key,
                                                 GConfValueType list_type,
                                                 GSList *list,
                                                 GError **err);

`conf` : | a GConfEngine.
`key` : | key you want to set the value of.
`list_type` : | type of each list element.
`list` : | new value of `key`.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | TRUE on success, FALSE on error.

### gconf_engine_set_pair ()

    gboolean    gconf_engine_set_pair           (GConfEngine *conf,
                                                 const gchar *key,
                                                 GConfValueType car_type,
                                                 GConfValueType cdr_type,
                                                 gconstpointer address_of_car,
                                                 gconstpointer address_of_cdr,
                                                 GError **err);

`conf` : | a GConfEngine.
`key` : | key you want to set the value of.
`car_type` : | type of the pair's first field (car).
`cdr_type` : | type of the pair's second field (cdr).
`address_of_car` : | address of the car.
`address_of_cdr` : | address of the cdr.
`err` : | the return location for an allocated GError, or NULL to ignore errors.
Returns : | TRUE on success, FALSE on error.

### struct GConfEnumStringPair

    struct GConfEnumStringPair {

      gint enum_value;
      const gchar* str;
    };

### gconf_string_to_enum ()

    gboolean    gconf_string_to_enum            (GConfEnumStringPair lookup_table[],
                                                 const gchar *str,
                                                 gint *enum_value_retloc);

It's best to store enumeration values as strings rather than integers. This is robust against changes in the enumeration, and also human-readable. This function makes it more convenient to store enums as strings.

The first argument is a lookup table, typically declared statically as follows:

    static GConfEnumStringPair foo_enum_lookup_table[] = {
      { FOO_BLAH, "Blah" },
      { FOO_BAR,  "Bar"  },
      { 0, NULL }
    };

Note that the last element of the table is `{ 0, NULL }`. Typically the strings you use should be semi-human-readable, for GTK+ and GNOME stripping off the library prefix and converting to StudlyCaps is the recommended convention.

The function returns TRUE if a match for the string is found, and if a match is found the enum value is placed in `enum_value_retloc`.

`lookup_table` : | a lookup table mapping enum values to strings.
`str` : | the string to convert to an enum value.
`enum_value_retloc` : | the address of an enum variable.
Returns : | TRUE if a match was found.

### gconf_enum_to_string ()

    const gchar* gconf_enum_to_string           (GConfEnumStringPair lookup_table[],
                                                 gint enum_value);

See `gconf_string_to_enum()` for background information on this function.

`lookup_table` : | a lookup table mapping enum values to strings.
`enum_value` : | the enumeration value to convert to a string.
Returns : | a pointer to the proper string in the lookup table, or NULL if no match was found.