src/events/SDL_events.c

/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2004 Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library 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
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the Free
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    Sam Lantinga
    slouken@libsdl.org
*/

#ifdef SAVE_RCSID
static char rcsid =
 "@(#) $Id$";
#endif

/* General event handling code for SDL */

#include <stdio.h>
#include <string.h>

#include "SDL.h"
#include "SDL_thread.h"
#include "SDL_mutex.h"
#include "SDL_events.h"
#include "SDL_events_c.h"
#include "SDL_timer_c.h"
#ifndef DISABLE_JOYSTICK
#include "SDL_joystick_c.h"
#endif
#ifndef ENABLE_X11
#define DISABLE_X11
#endif
#include "SDL_syswm.h"
#include "SDL_sysevents.h"

/* Public data -- the event filter */
SDL_EventFilter SDL_EventOK = NULL;
Uint8 SDL_ProcessEvents[SDL_NUMEVENTS];
static Uint32 SDL_eventstate = 0;

/* Private data -- event queue */
#define MAXEVENTS	128
static struct {
	SDL_mutex *lock;
	int active;
	int head;
	int tail;
	SDL_Event event[MAXEVENTS];
	int wmmsg_next;
	struct SDL_SysWMmsg wmmsg[MAXEVENTS];
} SDL_EventQ;

/* Private data -- event locking structure */
static struct {
	SDL_mutex *lock;
	int safe;
} SDL_EventLock;

/* Thread functions */
static SDL_Thread *SDL_EventThread = NULL;	/* Thread handle */
static Uint32 event_thread;			/* The event thread id */

void SDL_Lock_EventThread(void)
{
	if ( SDL_EventThread && (SDL_ThreadID() != event_thread) ) {
		/* Grab lock and spin until we're sure event thread stopped */
		SDL_mutexP(SDL_EventLock.lock);
		while ( ! SDL_EventLock.safe ) {
			SDL_Delay(1);
		}
	}
}
void SDL_Unlock_EventThread(void)
{
	if ( SDL_EventThread && (SDL_ThreadID() != event_thread) ) {
		SDL_mutexV(SDL_EventLock.lock);
	}
}

static int SDL_GobbleEvents(void *unused)
{
	event_thread = SDL_ThreadID();
	while ( SDL_EventQ.active ) {
		SDL_VideoDevice *video = current_video;
		SDL_VideoDevice *this  = current_video;

		/* Get events from the video subsystem */
		if ( video ) {
			video->PumpEvents(this);
		}

		/* Queue pending key-repeat events */
		SDL_CheckKeyRepeat();

#ifndef DISABLE_JOYSTICK
		/* Check for joystick state change */
		if ( SDL_numjoysticks && (SDL_eventstate & SDL_JOYEVENTMASK) ) {
			SDL_JoystickUpdate();
		}
#endif

		/* Give up the CPU for the rest of our timeslice */
		SDL_EventLock.safe = 1;
		if ( SDL_timer_running ) {
			SDL_ThreadedTimerCheck();
		}
		SDL_Delay(1);

		/* Check for event locking.
		   On the P of the lock mutex, if the lock is held, this thread
		   will wait until the lock is released before continuing.  The
		   safe flag will be set, meaning that the other thread can go
		   about it's business.  The safe flag is reset before the V,
		   so as soon as the mutex is free, other threads can see that
		   it's not safe to interfere with the event thread.
		 */
		SDL_mutexP(SDL_EventLock.lock);
		SDL_EventLock.safe = 0;
		SDL_mutexV(SDL_EventLock.lock);
	}
	SDL_SetTimerThreaded(0);
	event_thread = 0;
	return(0);
}

static int SDL_StartEventThread(Uint32 flags)
{
	/* Reset everything to zero */
	SDL_EventThread = NULL;
	memset(&SDL_EventLock, 0, sizeof(SDL_EventLock));

	/* Create the lock and set ourselves active */
#ifndef DISABLE_THREADS
	SDL_EventQ.lock = SDL_CreateMutex();
	if ( SDL_EventQ.lock == NULL ) {
#ifdef macintosh /* On MacOS 7/8, you can't multithread, so no lock needed */
		;
#else
		return(-1);
#endif
	}
#endif /* !DISABLE_THREADS */
	SDL_EventQ.active = 1;

	if ( (flags&SDL_INIT_EVENTTHREAD) == SDL_INIT_EVENTTHREAD ) {
		SDL_EventLock.lock = SDL_CreateMutex();
		if ( SDL_EventLock.lock == NULL ) {
			return(-1);
		}
		SDL_EventLock.safe = 0;

		/* The event thread will handle timers too */
		SDL_SetTimerThreaded(2);
		SDL_EventThread = SDL_CreateThread(SDL_GobbleEvents, NULL);
		if ( SDL_EventThread == NULL ) {
			return(-1);
		}
	} else {
		event_thread = 0;
	}
	return(0);
}

static void SDL_StopEventThread(void)
{
	SDL_EventQ.active = 0;
	if ( SDL_EventThread ) {
		SDL_WaitThread(SDL_EventThread, NULL);
		SDL_EventThread = NULL;
		SDL_DestroyMutex(SDL_EventLock.lock);
	}
	SDL_DestroyMutex(SDL_EventQ.lock);
}

Uint32 SDL_EventThreadID(void)
{
	return(event_thread);
}

/* Public functions */

void SDL_StopEventLoop(void)
{
	/* Halt the event thread, if running */
	SDL_StopEventThread();

	/* Shutdown event handlers */
	SDL_AppActiveQuit();
	SDL_KeyboardQuit();
	SDL_MouseQuit();
	SDL_QuitQuit();

	/* Clean out EventQ */
	SDL_EventQ.head = 0;
	SDL_EventQ.tail = 0;
	SDL_EventQ.wmmsg_next = 0;
}

/* This function (and associated calls) may be called more than once */
int SDL_StartEventLoop(Uint32 flags)
{
	int retcode;

	/* Clean out the event queue */
	SDL_EventThread = NULL;
	SDL_EventQ.lock = NULL;
	SDL_StopEventLoop();

	/* No filter to start with, process most event types */
	SDL_EventOK = NULL;
	memset(SDL_ProcessEvents,SDL_ENABLE,sizeof(SDL_ProcessEvents));
	SDL_eventstate = ~0;
	/* It's not save to call SDL_EventState() yet */
	SDL_eventstate &= ~(0x00000001 << SDL_SYSWMEVENT);
	SDL_ProcessEvents[SDL_SYSWMEVENT] = SDL_IGNORE;

	/* Initialize event handlers */
	retcode = 0;
	retcode += SDL_AppActiveInit();
	retcode += SDL_KeyboardInit();
	retcode += SDL_MouseInit();
	retcode += SDL_QuitInit();
	if ( retcode < 0 ) {
		/* We don't expect them to fail, but... */
		return(-1);
	}

	/* Create the lock and event thread */
	if ( SDL_StartEventThread(flags) < 0 ) {
		SDL_StopEventLoop();
		return(-1);
	}
	return(0);
}


/* Add an event to the event queue -- called with the queue locked */
static int SDL_AddEvent(SDL_Event *event)
{
	int tail, added;

	tail = (SDL_EventQ.tail+1)%MAXEVENTS;
	if ( tail == SDL_EventQ.head ) {
		/* Overflow, drop event */
		added = 0;
	} else {
		SDL_EventQ.event[SDL_EventQ.tail] = *event;
		if (event->type == SDL_SYSWMEVENT) {
			/* Note that it's possible to lose an event */
			int next = SDL_EventQ.wmmsg_next;
			SDL_EventQ.wmmsg[next] = *event->syswm.msg;
		        SDL_EventQ.event[SDL_EventQ.tail].syswm.msg =
						&SDL_EventQ.wmmsg[next];
			SDL_EventQ.wmmsg_next = (next+1)%MAXEVENTS;
		}
		SDL_EventQ.tail = tail;
		added = 1;
	}
	return(added);
}

/* Cut an event, and return the next valid spot, or the tail */
/*                           -- called with the queue locked */
static int SDL_CutEvent(int spot)
{
	if ( spot == SDL_EventQ.head ) {
		SDL_EventQ.head = (SDL_EventQ.head+1)%MAXEVENTS;
		return(SDL_EventQ.head);
	} else
	if ( (spot+1)%MAXEVENTS == SDL_EventQ.tail ) {
		SDL_EventQ.tail = spot;
		return(SDL_EventQ.tail);
	} else
	/* We cut the middle -- shift everything over */
	{
		int here, next;

		/* This can probably be optimized with memcpy() -- careful! */
		if ( --SDL_EventQ.tail < 0 ) {
			SDL_EventQ.tail = MAXEVENTS-1;
		}
		for ( here=spot; here != SDL_EventQ.tail; here = next ) {
			next = (here+1)%MAXEVENTS;
			SDL_EventQ.event[here] = SDL_EventQ.event[next];
		}
		return(spot);
	}
	/* NOTREACHED */
}

/* Lock the event queue, take a peep at it, and unlock it */
int SDL_PeepEvents(SDL_Event *events, int numevents, SDL_eventaction action,
								Uint32 mask)
{
	int i, used;

	/* Don't look after we've quit */
	if ( ! SDL_EventQ.active ) {
		return(-1);
	}
	/* Lock the event queue */
	used = 0;
	if ( SDL_mutexP(SDL_EventQ.lock) == 0 ) {
		if ( action == SDL_ADDEVENT ) {
			for ( i=0; i<numevents; ++i ) {
				used += SDL_AddEvent(&events[i]);
			}
		} else {
			SDL_Event tmpevent;
			int spot;

			/* If 'events' is NULL, just see if they exist */
			if ( events == NULL ) {
				action = SDL_PEEKEVENT;
				numevents = 1;
				events = &tmpevent;
			}
			spot = SDL_EventQ.head;
			while ((used < numevents)&&(spot != SDL_EventQ.tail)) {
				if ( mask & SDL_EVENTMASK(SDL_EventQ.event[spot].type) ) {
					events[used++] = SDL_EventQ.event[spot];
					if ( action == SDL_GETEVENT ) {
						spot = SDL_CutEvent(spot);
					} else {
						spot = (spot+1)%MAXEVENTS;
					}
				} else {
					spot = (spot+1)%MAXEVENTS;
				}
			}
		}
		SDL_mutexV(SDL_EventQ.lock);
	} else {
		SDL_SetError("Couldn't lock event queue");
		used = -1;
	}
	return(used);
}

/* Run the system dependent event loops */
void SDL_PumpEvents(void)
{
	if ( !SDL_EventThread ) {
		SDL_VideoDevice *video = current_video;
		SDL_VideoDevice *this  = current_video;

		/* Get events from the video subsystem */
		if ( video ) {
			video->PumpEvents(this);
		}

		/* Queue pending key-repeat events */
		SDL_CheckKeyRepeat();

#ifndef DISABLE_JOYSTICK
		/* Check for joystick state change */
		if ( SDL_numjoysticks && (SDL_eventstate & SDL_JOYEVENTMASK) ) {
			SDL_JoystickUpdate();
		}
#endif
	}
}

/* Public functions */

int SDL_PollEvent (SDL_Event *event)
{
	SDL_PumpEvents();

	/* We can't return -1, just return 0 (no event) on error */
	if ( SDL_PeepEvents(event, 1, SDL_GETEVENT, SDL_ALLEVENTS) <= 0 )
		return 0;
	return 1;
}

int SDL_WaitEvent (SDL_Event *event)
{
	while ( 1 ) {
		SDL_PumpEvents();
		switch(SDL_PeepEvents(event, 1, SDL_GETEVENT, SDL_ALLEVENTS)) {
		    case -1: return 0;
		    case 1: return 1;
		    case 0: SDL_Delay(10);
		}
	}
}

int SDL_PushEvent(SDL_Event *event)
{
	if ( SDL_PeepEvents(event, 1, SDL_ADDEVENT, 0) <= 0 )
		return -1;
	return 0;
}

void SDL_SetEventFilter (SDL_EventFilter filter)
{
	SDL_Event bitbucket;

	/* Set filter and discard pending events */
	SDL_EventOK = filter;
	while ( SDL_PollEvent(&bitbucket) > 0 )
		;
}

SDL_EventFilter SDL_GetEventFilter(void)
{
	return(SDL_EventOK);
}

Uint8 SDL_EventState (Uint8 type, int state)
{
	SDL_Event bitbucket;
	Uint8 current_state;

	/* If SDL_ALLEVENTS was specified... */
	if ( type == 0xFF ) {
		current_state = SDL_IGNORE;
		for ( type=0; type<SDL_NUMEVENTS; ++type ) {
			if ( SDL_ProcessEvents[type] != SDL_IGNORE ) {
				current_state = SDL_ENABLE;
			}
			SDL_ProcessEvents[type] = state;
			if ( state == SDL_ENABLE ) {
				SDL_eventstate |= (0x00000001 << (type));
			} else {
				SDL_eventstate &= ~(0x00000001 << (type));
			}
		}
		while ( SDL_PollEvent(&bitbucket) > 0 )
			;
		return(current_state);
	}

	/* Just set the state for one event type */
	current_state = SDL_ProcessEvents[type];
	switch (state) {
		case SDL_IGNORE:
		case SDL_ENABLE:
			/* Set state and discard pending events */
			SDL_ProcessEvents[type] = state;
			if ( state == SDL_ENABLE ) {
				SDL_eventstate |= (0x00000001 << (type));
			} else {
				SDL_eventstate &= ~(0x00000001 << (type));
			}
			while ( SDL_PollEvent(&bitbucket) > 0 )
				;
			break;
		default:
			/* Querying state? */
			break;
	}
	return(current_state);
}

/* This is a generic event handler.
 */
int SDL_PrivateSysWMEvent(SDL_SysWMmsg *message)
{
	int posted;

	posted = 0;
	if ( SDL_ProcessEvents[SDL_SYSWMEVENT] == SDL_ENABLE ) {
		SDL_Event event;
		memset(&event, 0, sizeof(event));
		event.type = SDL_SYSWMEVENT;
		event.syswm.msg = message;
		if ( (SDL_EventOK == NULL) || (*SDL_EventOK)(&event) ) {
			posted = 1;
			SDL_PushEvent(&event);
		}
	}
	/* Update internal event state */
	return(posted);
}