## gconf-listeners

gconf-listeners

## Synopsis

                        GConfListeners;
    void                (*GConfListenersCallback)           (GConfListeners *listeners,
                                                             const gchar *all_above_key,
                                                             guint cnxn_id,
                                                             gpointer listener_data,
                                                             gpointer user_data);
    GConfListeners*     gconf_listeners_new                 (void);
    void                gconf_listeners_free                (GConfListeners *listeners);
    guint               gconf_listeners_add                 (GConfListeners *listeners,
                                                             const gchar *listen_point,
                                                             gpointer listener_data,
                                                             GFreeFunc destroy_notify);
    void                gconf_listeners_remove              (GConfListeners *listeners,
                                                             guint cnxn_id);
    void                gconf_listeners_notify              (GConfListeners *listeners,
                                                             const gchar *all_above,
                                                             GConfListenersCallback callback,
                                                             gpointer user_data);
    guint               gconf_listeners_count               (GConfListeners *listeners);
    void                gconf_listeners_foreach             (GConfListeners *listeners,
                                                             GConfListenersForeach callback,
                                                             gpointer user_data);
    gboolean            gconf_listeners_get_data            (GConfListeners *listeners,
                                                             guint cnxn_id,
                                                             gpointer *listener_data_p,
                                                             const gchar **location_p);
    void                gconf_listeners_remove_if           (GConfListeners *listeners,
                                                             GConfListenersPredicate predicate,
                                                             gpointer user_data);

## Description

A GConfListeners object is used to store listeners who want notification of changes in a namespace section. It is a public API shared between gconfd and the GObject convenience wrapper.

## Details

### GConfListeners

    typedef struct _GConfListeners GConfListeners;

The GConfListeners structure contains nothing other than a dummy pointer. Internally the data about listeners is maintained through a listener table structure, LTable which contains data like the namespace, an array to hold the listeners, count of active listeners,value to be given to the next connection and the list of connection indices to be recycled. There is also a Listener structure maintaining data pertaining to listeners.

### GConfListenersCallback ()

    void                (*GConfListenersCallback)           (GConfListeners *listeners,
                                                             const gchar *all_above_key,
                                                             guint cnxn_id,
                                                             gpointer listener_data,
                                                             gpointer user_data);

This is the signature of a user function added with `gconf_listeners_notify()`. This function is called whenever the value of a key changes.

`listeners` : | a GConfListeners.
`all_above_key` : | the key that has changed.
`cnxn_id` : | the connection id got from `gconf_listeners_add()`.
`listener_data` : | the data field associated with each listener.
`user_data` : | the user data to be passed to the callback.

### gconf_listeners_new ()

    GConfListeners*     gconf_listeners_new                 (void);

Creates a new listener table and typecasts it to a GConfListeners.

Returns : | the newly allocated GConfListeners.

### gconf_listeners_free ()

    void                gconf_listeners_free                (GConfListeners *listeners);

Destroys the listener table.

`listeners` : | a GConfListeners.

### gconf_listeners_add ()

    guint               gconf_listeners_add                 (GConfListeners *listeners,
                                                             const gchar *listen_point,
                                                             gpointer listener_data,
                                                             GFreeFunc destroy_notify);

Creates a new Listener with the next available connection id and inserts it into the listener table. The newly created listener listens for changes below and including the `listen_point.Returns` the newly assigned connection id.

`listeners` : | a GConfListeners.
`listen_point` : | where to listen for changes.
`listener_data` : | data to pass to function.
`destroy_notify` : | pointer to the function to be called when the listener is destroyed.
Returns : | the newly assigned connection id, a guint value.

### gconf_listeners_remove ()

    void                gconf_listeners_remove              (GConfListeners *listeners,
                                                             guint cnxn_id);

Removes the listener from the listener table.

`listeners` : | a GConfListeners.
`cnxn_id` : | the connection id returned during `gconf_listeners_add()`.

### gconf_listeners_notify ()

    void                gconf_listeners_notify              (GConfListeners *listeners,
                                                             const gchar *all_above,
                                                             GConfListenersCallback callback,
                                                             gpointer user_data);

Notifies all the associated listeners that a key has changed.

`listeners` : | a GConfListeners.
`all_above` : | the key that has changed.
`callback` : | a GConfListenersCallback to be called.
`user_data` : | data to be passed to the callback.

### gconf_listeners_count ()

    guint               gconf_listeners_count               (GConfListeners *listeners);

Returns the number of alive listeners in the listener table.

`listeners` : | a GConfListeners
Returns : | the number of active listeners.

### gconf_listeners_foreach ()

    void                gconf_listeners_foreach             (GConfListeners *listeners,
                                                             GConfListenersForeach callback,
                                                             gpointer user_data);

Execute a function for each of the GConfListeners.

`listeners` : | a GConfListeners.
`callback` : | the function to be called.
`user_data` : | a gpointer.

### gconf_listeners_get_data ()

    gboolean            gconf_listeners_get_data            (GConfListeners *listeners,
                                                             guint cnxn_id,
                                                             gpointer *listener_data_p,
                                                             const gchar **location_p);

Obtains the data particular to a GConfListener.

`listeners` : | a GConfListeners.
`cnxn_id` : | the connection id, an integer.
`listener_data_p` : | the address for getting the listener data.
`location_p` : | a pointer to the address for getting the name.
Returns : | TRUE if the data could be obtained successfully, FALSE if an error occurs while retrieving the data.

### gconf_listeners_remove_if ()

    void                gconf_listeners_remove_if           (GConfListeners *listeners,
                                                             GConfListenersPredicate predicate,
                                                             gpointer user_data);

Remove the listener if a predicate is satisfied.

`listeners` : | a GConfListeners.
`predicate` : | the predicate checked for removal.
`user_data` : | a gpointer.