vlc_events.h 5.45 KB
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/*****************************************************************************
 * events.h: events definitions
 * Interface used to send events.
 *****************************************************************************
 * Copyright (C) 2007 the VideoLAN team
 * $Id$
 *
 * Authors: Pierre d'Herbemont
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
 *****************************************************************************/

#ifndef VLC_EVENTS_H
# define VLC_EVENTS_H

#include <vlc_arrays.h>
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#include <vlc_meta.h>
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/**
 * \file
 * This file is the interface definition for events
 * (implementation in src/misc/events.c)
 */

/*****************************************************************************
 * Documentation
 *****************************************************************************/
/*
 **** Background
 *
 * This implements a way to send and receive event for an object (which can be
 * a simple C struct or less).
 * 
 * This is in direct concurrency with the Variable based Callback
 * (see src/misc/variables.c).
 *
 * It has the following advantages over Variable based Callback:
 * - No need to implement the whole VLC_COMMON_MEMBERS in the object,
 * thus it reduce it size. This is especially true for input_item_t which
 * doesn't have VLC_COMMON_MEMBERS. This is the first reason of existence of
 * this implementation.
 * - Libvlc can easily be based upon that.
 * - Existing event are clearly declared (in include/vlc_events.h)
 *
 *
 **** Example usage
 *
 * (vlc_cool_object_t doesn't need to have the VLC_COMMON_MEMBERS.)
 *
 * struct vlc_cool_object_t 
 * {
 *        ...
 *        vlc_event_manager_t p_event_manager;
 *        ...
 * }
 *
 * vlc_my_cool_object_new()
 * {
 *        ...
 *        vlc_event_manager_Create( &p_self->p_event_manager, p_this );
 *        vlc_event_manager_register_event_type(p_self->p_event_manager,
 *                vlc_MyCoolObjectDidSomething, p_e)
 *        ...
 * }
 *
 * vlc_my_cool_object_release()
 * {
 *         ...
 *         vlc_event_manager_release( p_self->p_event_manager );
 *         ...
 * }
 *
 * vlc_my_cool_object_do_something()
 * {
 *        ...
 *        vlc_event_t event;
 *        event.type = vlc_MyCoolObjectDidSomething;
 *        event.u.my_cool_object_did_something.what_it_did = kSomething;
 *        vlc_event_send( p_self->p_event_manager, &event );
 * }
 * */
 
  /*****************************************************************************
 * Event Type
 *****************************************************************************/

/* Private structure defined in misc/events.c */
struct vlc_event_listeners_group_t;

/* Event manager type */
typedef struct vlc_event_manager_t
{
    void * p_obj;
    DECL_ARRAY(struct vlc_event_listeners_group_t *) listeners_groups;
} vlc_event_manager_t;

/* List of event */
typedef enum vlc_event_type_t {
    vlc_InputItemMetaChanged
} vlc_event_type_t;

/* Event definition */
typedef struct vlc_event_t
{
    vlc_event_type_t type;
    void * p_obj; /* Sender object, automatically filled by event_Send() */
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    union vlc_event_type_specific
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    {
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        struct vlc_input_item_meta_changed
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        {
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            vlc_meta_type_t meta_type;
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        } input_item_meta_changed;
    } u;
} vlc_event_t;

/* Event callback type */
typedef void ( *vlc_event_callback_t )( const vlc_event_t *, void * );

 /*****************************************************************************
 * Event manager
 *****************************************************************************/

/*
 * p_obj points to the object that owns the event manager, and from
 * which events are sent
 */
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VLC_EXPORT(int, vlc_event_manager_init, ( vlc_event_manager_t * p_em,
                                          void * p_obj ));
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/*
 * Destroy
 */
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VLC_EXPORT(void, vlc_event_manager_fini, ( vlc_event_manager_t * p_em ));
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/*
 * Tells a specific event manager that it will handle event_type object
 */
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VLC_EXPORT(int, vlc_event_manager_register_event_type,
                ( vlc_event_manager_t * p_em, vlc_event_type_t event_type ));
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/*
 * Send an event to the listener attached to this p_em.
 */
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VLC_EXPORT(void, vlc_event_send, ( vlc_event_manager_t * p_em,
                                   vlc_event_t * p_event ));
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/*
 * Add a callback for an event.
 */
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VLC_EXPORT(int, vlc_event_attach, ( vlc_event_manager_t * p_event_manager,
                                    vlc_event_type_t event_type,
                                    vlc_event_callback_t pf_callback,
                                    void *p_user_data ));
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/*
 * Remove a callback for an event.
 */
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VLC_EXPORT(int, vlc_event_detach, ( vlc_event_manager_t *p_event_manager,
                                    vlc_event_type_t event_type,
                                    vlc_event_callback_t pf_callback,
                                     void *p_user_data ));
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#endif /* VLC_EVENTS_H */