wl_signal(3)

NAME
wl_signal - A source of a type of observable event.

SYNOPSIS

#include <wayland-server-core.h>

  Public Member Functions
void wl_signal_emit_mutable (struct wl_signal *signal, void *data)

  Static Public Member Functions
static void wl_signal_init (struct wl_signal *signal)
static void wl_signal_add (struct wl_signal *signal, struct wl_listener *listener)
static struct wl_listener * wl_signal_get (struct wl_signal *signal, wl_notify_func_t notify)
static void wl_signal_emit (struct wl_signal *signal, void *data)

  Data Fields
struct wl_list listener_list

Detailed Description

A source of a type of observable event. Signals are recognized points where significant events can be observed. Compositors as well as the server can provide signals. Observers are wl_listener's that are added through wl_signal_add. Signals are emitted using wl_signal_emit, which will invoke all listeners until that listener is removed by wl_list_remove() (or whenever the signal is destroyed).

See also
    wl_listener for more information on using wl_signal

Member Function Documentation

  void wl_signal_add (struct wl_signal * signal, struct wl_listener * listener) [inline], [static]
Add the specified listener to this signal.

Parameters
    signal The signal that will emit events to the listener
    listener The listener to add

  void wl_signal_emit (struct wl_signal * signal, void * data) [inline], [static]
Emits this signal, notifying all registered listeners.

Parameters
    signal The signal object that will emit the signal
    data The data that will be emitted with the signal

  void wl_signal_emit_mutable (struct wl_signal * signal, void * data)
Emits this signal, notifying all registered listeners.

A safer version of wl_signal_emit() which can gracefully handle additions and deletions of any signal listener from within listener notification callbacks.

Listeners deleted during a signal emission and which have not already been notified at the time of deletion are not notified by that emission.

Listeners added (or readded) during signal emission are ignored by that emission.

Note that repurposing a listener without explicitly removing it and readding it is not supported and can lead to unexpected behavior.

Parameters
    signal The signal object that will emit the signal
    data The data that will be emitted with the signal

Since
    1.20.90

  struct wl_listener * wl_signal_get (struct wl_signal * signal, wl_notify_func_t notify) [inline], [static]
Gets the listener struct for the specified callback.

Parameters
    signal The signal that contains the specified listener
    notify The listener that is the target of this search

Returns
    the list item that corresponds to the specified listener, or NULL if none was found

  void wl_signal_init (struct wl_signal * signal) [inline], [static]
Initialize a new wl_signal for use.

Parameters
    signal The signal that will be initialized

Field Documentation

  struct wl_list wl_signal::listener_list

Author

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