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Improve event processing latency when gamepad/sensor is open

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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 22:52:08 -05:00 • committed by Sam Lantinga
parent 1eb7b79986
commit d3a785e521
1 changed files with 32 additions and 29 deletions
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61
src/events/SDL_events.c
View file

@ -45,8 +45,11 @@
/* 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_NS (3 * SDL_NS_PER_SECOND)
/* Determines how often we pump events if joystick or sensor subsystems are active */
#define ENUMERATION_POLL_INTERVAL_NS (3 * SDL_NS_PER_SECOND)
/* Determines how often to pump events if joysticks or sensors are actively being read */
#define EVENT_POLL_INTERVAL_NS SDL_MS_TO_NS(1)
/* Make sure the type in the SDL_Event aligns properly across the union */
SDL_COMPILE_TIME_ASSERT(SDL_Event_type, sizeof(Uint32) == sizeof(SDL_EventType));
@ -1013,21 +1016,36 @@ SDL_bool SDL_PollEvent(SDL_Event *event)
return SDL_WaitEventTimeoutNS(event, 0);
}
static SDL_bool SDL_events_need_periodic_poll(void)
static Sint64 SDL_events_get_polling_interval(void)
{
SDL_bool need_periodic_poll = SDL_FALSE;
Sint64 poll_intervalNS = SDL_MAX_SINT64;
#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_JoysticksOpened()) {
/* If we have joysticks open, we need to poll rapidly for events */
poll_intervalNS = SDL_min(poll_intervalNS, EVENT_POLL_INTERVAL_NS);
} else {
/* If not, just poll every few seconds to enumerate new joysticks */
poll_intervalNS = SDL_min(poll_intervalNS, ENUMERATION_POLL_INTERVAL_NS);
}
}
#endif
return need_periodic_poll;
#ifndef SDL_SENSOR_DISABLED
if (SDL_WasInit(SDL_INIT_SENSOR) && SDL_update_sensors && SDL_SensorsOpened()) {
/* If we have sensors open, we need to poll rapidly for events */
poll_intervalNS = SDL_min(poll_intervalNS, EVENT_POLL_INTERVAL_NS);
}
#endif
return poll_intervalNS;
}
static int SDL_WaitEventTimeout_Device(SDL_VideoDevice *_this, SDL_Window *wakeup_window, SDL_Event *event, Uint64 start, Sint64 timeoutNS)
{
Sint64 loop_timeoutNS = timeoutNS;
SDL_bool need_periodic_poll = SDL_events_need_periodic_poll();
Sint64 poll_intervalNS = SDL_events_get_polling_interval();
for (;;) {
int status;
@ -1069,17 +1087,18 @@ static int SDL_WaitEventTimeout_Device(SDL_VideoDevice *_this, SDL_Window *wakeu
}
loop_timeoutNS = (timeoutNS - elapsed);
}
if (need_periodic_poll) {
/* Adjust the timeout for any polling requirements we currently have. */
if (poll_intervalNS != SDL_MAX_SINT64) {
if (loop_timeoutNS >= 0) {
loop_timeoutNS = SDL_min(loop_timeoutNS, PERIODIC_POLL_INTERVAL_NS);
loop_timeoutNS = SDL_min(loop_timeoutNS, poll_intervalNS);
} else {
loop_timeoutNS = PERIODIC_POLL_INTERVAL_NS;
loop_timeoutNS = poll_intervalNS;
}
}
status = _this->WaitEventTimeout(_this, loop_timeoutNS);
/* Set wakeup_window to NULL without holding the lock. */
_this->wakeup_window = NULL;
if (status == 0 && need_periodic_poll && loop_timeoutNS == PERIODIC_POLL_INTERVAL_NS) {
if (status == 0 && poll_intervalNS != SDL_MAX_SINT64 && loop_timeoutNS == poll_intervalNS) {
/* We may have woken up to poll. Try again */
continue;
} else if (status <= 0) {
@ -1092,22 +1111,6 @@ static int SDL_WaitEventTimeout_Device(SDL_VideoDevice *_this, SDL_Window *wakeu
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_JoysticksOpened();
#endif
#ifndef SDL_SENSOR_DISABLED
need_polling = need_polling ||
(SDL_WasInit(SDL_INIT_SENSOR) && SDL_update_sensors && SDL_SensorsOpened());
#endif
return need_polling;
}
static SDL_Window *SDL_find_active_window(SDL_VideoDevice *_this)
{
SDL_Window *window;
@ -1192,7 +1195,7 @@ SDL_bool SDL_WaitEventTimeoutNS(SDL_Event *event, Sint64 timeoutNS)
/* We should have completely handled timeoutNS == 0 above */
SDL_assert(timeoutNS != 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) {
@ -1216,7 +1219,7 @@ SDL_bool SDL_WaitEventTimeoutNS(SDL_Event *event, Sint64 timeoutNS)
return SDL_TRUE;
}
Uint64 delay = SDL_MS_TO_NS(1);
Uint64 delay = EVENT_POLL_INTERVAL_NS;
if (timeoutNS > 0) {
Uint64 now = SDL_GetTicksNS();
if (now >= expiration) {