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Improve event processing latency when gamepad/sensor is open 

By using the SDL_WaitEventTimeout_Device() path even when polling is required,
we can still achieve sub-millisecond latency for non-gamepad/sensor events when
a gamepad or sensor is in use by the application.
This commit is contained in:
Cameron Gutman 2024-03-18 20:16:04 -05:00
parent c17d2246fb
commit 43f0ae1e54
1 changed files with 36 additions and 35 deletions
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71
src/events/SDL_events.c
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@ -44,8 +44,11 @@
/* An arbitrary limit so we don't have unbounded growth */
#define SDL_MAX_QUEUED_EVENTS 65535
/* Determines how often we wake to call SDL_PumpEvents() in SDL_WaitEventTimeout_Device() */
#define PERIODIC_POLL_INTERVAL_MS 3000
/* Determines how often we pump events if joystick or sensor subsystems are active */
#define ENUMERATION_POLL_INTERVAL_MS 3000
/* Determines how often to pump events if joysticks or sensors are actively being read */
#define EVENT_POLL_INTERVAL_MS 1
typedef struct SDL_EventWatcher
{
@ -967,27 +970,41 @@ int SDL_PollEvent(SDL_Event *event)
return SDL_WaitEventTimeout(event, 0);
}
static SDL_bool SDL_events_need_periodic_poll(void)
static Sint16 SDL_events_get_polling_interval(void)
{
SDL_bool need_periodic_poll = SDL_FALSE;
Sint16 poll_interval = SDL_MAX_SINT16;
#ifndef SDL_JOYSTICK_DISABLED
need_periodic_poll =
SDL_WasInit(SDL_INIT_JOYSTICK) && SDL_update_joysticks;
if (SDL_WasInit(SDL_INIT_JOYSTICK) && SDL_update_joysticks) {
if (SDL_NumJoysticks() > 0) {
/* If we have joysticks open, we need to poll rapidly for events */
poll_interval = SDL_min(poll_interval, EVENT_POLL_INTERVAL_MS);
} else {
/* If not, just poll every few seconds to enumerate new joysticks */
poll_interval = SDL_min(poll_interval, ENUMERATION_POLL_INTERVAL_MS);
}
}
#endif
#ifndef SDL_SENSOR_DISABLED
need_periodic_poll = need_periodic_poll ||
(SDL_WasInit(SDL_INIT_SENSOR) && SDL_update_sensors);
if (SDL_WasInit(SDL_INIT_SENSOR) && SDL_update_sensors) {
if (SDL_NumSensors() > 0) {
/* If we have sensors open, we need to poll rapidly for events */
poll_interval = SDL_min(poll_interval, EVENT_POLL_INTERVAL_MS);
} else {
/* If not, just poll every few seconds to enumerate new sensors */
poll_interval = SDL_min(poll_interval, ENUMERATION_POLL_INTERVAL_MS);
}
}
#endif
return need_periodic_poll;
return poll_interval;
}
static int SDL_WaitEventTimeout_Device(_THIS, SDL_Window *wakeup_window, SDL_Event *event, Uint32 start, int timeout)
{
int loop_timeout = timeout;
SDL_bool need_periodic_poll = SDL_events_need_periodic_poll();
Sint16 poll_interval = SDL_events_get_polling_interval();
for (;;) {
/* Pump events on entry and each time we wake to ensure:
@ -1029,17 +1046,20 @@ static int SDL_WaitEventTimeout_Device(_THIS, SDL_Window *wakeup_window, SDL_Eve
}
loop_timeout = (int)((Uint32)timeout - elapsed);
}
if (need_periodic_poll) {
/* Adjust the timeout for any polling requirements we currently have. */
if (poll_interval != SDL_MAX_SINT16) {
if (loop_timeout >= 0) {
loop_timeout = SDL_min(loop_timeout, PERIODIC_POLL_INTERVAL_MS);
loop_timeout = SDL_min(loop_timeout, poll_interval);
} else {
loop_timeout = PERIODIC_POLL_INTERVAL_MS;
loop_timeout = poll_interval;
}
}
status = _this->WaitEventTimeout(_this, loop_timeout);
/* Set wakeup_window to NULL without holding the lock. */
_this->wakeup_window = NULL;
if (status == 0 && need_periodic_poll && loop_timeout == PERIODIC_POLL_INTERVAL_MS) {
if (status == 0 && poll_interval != SDL_MAX_SINT16 && loop_timeout == poll_interval) {
/* We may have woken up to poll. Try again */
continue;
} else if (status <= 0) {
@ -1052,25 +1072,6 @@ static int SDL_WaitEventTimeout_Device(_THIS, SDL_Window *wakeup_window, SDL_Eve
return 0;
}
static SDL_bool SDL_events_need_polling(void)
{
SDL_bool need_polling = SDL_FALSE;
#ifndef SDL_JOYSTICK_DISABLED
need_polling =
SDL_WasInit(SDL_INIT_JOYSTICK) &&
SDL_update_joysticks &&
(SDL_NumJoysticks() > 0);
#endif
#ifndef SDL_SENSOR_DISABLED
need_polling = need_polling ||
(SDL_WasInit(SDL_INIT_SENSOR) && SDL_update_sensors && (SDL_NumSensors() > 0));
#endif
return need_polling;
}
static SDL_Window *SDL_find_active_window(SDL_VideoDevice *_this)
{
SDL_Window *window;
@ -1143,7 +1144,7 @@ int SDL_WaitEventTimeout(SDL_Event *event, int timeout)
expiration = 0;
}
if (_this && _this->WaitEventTimeout && _this->SendWakeupEvent && !SDL_events_need_polling()) {
if (_this && _this->WaitEventTimeout && _this->SendWakeupEvent) {
/* Look if a shown window is available to send the wakeup event. */
wakeup_window = SDL_find_active_window(_this);
if (wakeup_window) {
@ -1167,7 +1168,7 @@ int SDL_WaitEventTimeout(SDL_Event *event, int timeout)
/* Timeout expired and no events */
return 0;
}
SDL_Delay(1);
SDL_Delay(EVENT_POLL_INTERVAL_MS);
break;
default:
/* Has events */