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Fixed event pump starvation if the application frequently pushes its own events

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This commit is contained in:
Sam Lantinga 2022-01-06 11:27:44 -08:00
parent e0c5399119
commit 31f8c3ef44
1 changed files with 44 additions and 21 deletions
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63
src/events/SDL_events.c
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@ -59,6 +59,7 @@ static SDL_EventWatcher *SDL_event_watchers = NULL;
static int SDL_event_watchers_count = 0;
static SDL_bool SDL_event_watchers_dispatching = SDL_FALSE;
static SDL_bool SDL_event_watchers_removed = SDL_FALSE;
static SDL_atomic_t SDL_sentinel_pending;
typedef struct {
Uint32 bits[8];
@ -479,6 +480,7 @@ SDL_StopEventLoop(void)
SDL_EventQ.free = NULL;
SDL_EventQ.wmmsg_used = NULL;
SDL_EventQ.wmmsg_free = NULL;
SDL_AtomicSet(&SDL_sentinel_pending, 0);
/* Clear disabled event state */
for (i = 0; i < SDL_arraysize(SDL_disabled_events); ++i) {
@ -574,7 +576,9 @@ SDL_AddEvent(SDL_Event * event)
}
entry->event = *event;
if (event->type == SDL_SYSWMEVENT) {
if (event->type == SDL_POLLSENTINEL) {
SDL_AtomicAdd(&SDL_sentinel_pending, 1);
} else if (event->type == SDL_SYSWMEVENT) {
entry->msg = *event->syswm.msg;
entry->event.syswm.msg = &entry->msg;
}
@ -620,6 +624,10 @@ SDL_CutEvent(SDL_EventEntry *entry)
SDL_EventQ.tail = entry->prev;
}
if (entry->event.type == SDL_POLLSENTINEL) {
SDL_AtomicAdd(&SDL_sentinel_pending, -1);
}
entry->next = SDL_EventQ.free;
SDL_EventQ.free = entry;
SDL_assert(SDL_AtomicGet(&SDL_EventQ.count) > 0);
@ -648,9 +656,9 @@ SDL_SendWakeupEvent()
}
/* Lock the event queue, take a peep at it, and unlock it */
int
SDL_PeepEvents(SDL_Event * events, int numevents, SDL_eventaction action,
Uint32 minType, Uint32 maxType)
static int
SDL_PeepEventsInternal(SDL_Event * events, int numevents, SDL_eventaction action,
Uint32 minType, Uint32 maxType, SDL_bool include_sentinel)
{
int i, used;
@ -713,10 +721,12 @@ SDL_PeepEvents(SDL_Event * events, int numevents, SDL_eventaction action,
SDL_CutEvent(entry);
}
}
if (type != SDL_POLLSENTINEL || include_sentinel) {
++used;
}
}
}
}
if (SDL_EventQ.lock) {
SDL_UnlockMutex(SDL_EventQ.lock);
}
@ -730,6 +740,12 @@ SDL_PeepEvents(SDL_Event * events, int numevents, SDL_eventaction action,
return (used);
}
int
SDL_PeepEvents(SDL_Event * events, int numevents, SDL_eventaction action,
Uint32 minType, Uint32 maxType)
{
return SDL_PeepEventsInternal(events, numevents, action, minType, maxType, SDL_FALSE);
}
SDL_bool
SDL_HasEvent(Uint32 type)
@ -815,6 +831,14 @@ SDL_PumpEvents(void)
#endif
SDL_SendPendingSignalEvents(); /* in case we had a signal handler fire, etc. */
if (SDL_GetEventState(SDL_POLLSENTINEL) == SDL_ENABLE) {
SDL_Event sentinel;
SDL_zero(sentinel);
sentinel.type = SDL_POLLSENTINEL;
SDL_PushEvent(&sentinel);
}
}
/* Public functions */
@ -952,17 +976,27 @@ SDL_WaitEventTimeout(SDL_Event * event, int timeout)
SDL_Window *wakeup_window;
Uint32 start = 0;
Uint32 expiration = 0;
SDL_bool include_sentinel = (timeout == 0) ? SDL_TRUE : SDL_FALSE;
/* If there isn't a poll sentinel event pending, pump events and add one */
if (SDL_AtomicGet(&SDL_sentinel_pending) == 0) {
SDL_PumpEvents();
}
/* First check for existing events */
switch (SDL_PeepEvents(event, 1, SDL_GETEVENT, SDL_FIRSTEVENT, SDL_LASTEVENT)) {
switch (SDL_PeepEventsInternal(event, 1, SDL_GETEVENT, SDL_FIRSTEVENT, SDL_LASTEVENT, include_sentinel)) {
case -1:
return 0;
case 0:
if (timeout == 0) {
/* No events available, and no timeout */
return 0;
}
break;
default:
/* Check whether we have reached the end of the poll cycle, and no more events are left */
if (timeout == 0 && event && event->type == SDL_POLLSENTINEL) {
return (SDL_PeepEvents(event, 1, SDL_GETEVENT, SDL_FIRSTEVENT, SDL_LASTEVENT) == 1);
if (event && event->type == SDL_POLLSENTINEL) {
/* Reached the end of a poll cycle, and no timeout */
return 0;
}
/* Has existing events */
return 1;
@ -973,7 +1007,7 @@ SDL_WaitEventTimeout(SDL_Event * event, int timeout)
expiration = start + timeout;
}
if (timeout != 0 && _this && _this->WaitEventTimeout && _this->SendWakeupEvent && !SDL_events_need_polling()) {
if (_this && _this->WaitEventTimeout && _this->SendWakeupEvent && !SDL_events_need_polling()) {
/* Look if a shown window is available to send the wakeup event. */
wakeup_window = SDL_find_active_window(_this);
if (wakeup_window) {
@ -993,10 +1027,6 @@ SDL_WaitEventTimeout(SDL_Event * event, int timeout)
case -1:
return 0;
case 0:
if (timeout == 0) {
/* Polling and no events, just return */
return 0;
}
if (timeout > 0 && SDL_TICKS_PASSED(SDL_GetTicks(), expiration)) {
/* Timeout expired and no events */
return 0;
@ -1004,13 +1034,6 @@ SDL_WaitEventTimeout(SDL_Event * event, int timeout)
SDL_Delay(1);
break;
default:
if (timeout == 0 && SDL_GetEventState(SDL_POLLSENTINEL) == SDL_ENABLE) {
/* We are at the start of a poll cycle with at least one new event.
Add a sentinel event to mark the end of the cycle. */
SDL_Event sentinel;
sentinel.type = SDL_POLLSENTINEL;
SDL_PushEvent(&sentinel);
}
/* Has events */
return 1;
}