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Make sure we only dispatch events on the main thread when using application callbacks

main
Sam Lantinga 2023-11-04 11:06:42 -07:00
parent 274da8561c
commit 4481754359
1 changed files with 51 additions and 30 deletions
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81
src/main/SDL_main_callbacks.c
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@ -27,11 +27,57 @@ static SDL_AppIterate_func SDL_main_iteration_callback;
static SDL_AppQuit_func SDL_main_quit_callback;
static SDL_AtomicInt apprc; // use an atomic, since events might land from any thread and we don't want to wrap this all in a mutex. A CAS makes sure we only move from zero once.
static int SDLCALL EventWatcher(void *userdata, SDL_Event *event)
// Return true if this event needs to be processed before returning from the event watcher
static SDL_bool ShouldDispatchImmediately(SDL_Event *event)
{
if (SDL_AtomicGet(&apprc) == 0) { // if already quitting, don't send the event to the app.
switch (event->type) {
case SDL_EVENT_TERMINATING:
case SDL_EVENT_LOW_MEMORY:
case SDL_EVENT_WILL_ENTER_BACKGROUND:
case SDL_EVENT_DID_ENTER_BACKGROUND:
case SDL_EVENT_WILL_ENTER_FOREGROUND:
case SDL_EVENT_DID_ENTER_FOREGROUND:
return SDL_TRUE;
default:
return SDL_FALSE;
}
}
static void SDL_DispatchMainCallbackEvent(SDL_Event *event)
{
if (SDL_AtomicGet(&apprc) == 0) { // if already quitting, don't send the event to the app.
SDL_AtomicCAS(&apprc, 0, SDL_main_event_callback(event));
}
SDL_CleanupEvent(event);
}
static void SDL_DispatchMainCallbackEvents()
{
SDL_Event events[16];
for (;;) {
int count = SDL_PeepEvents(events, SDL_arraysize(events), SDL_GETEVENT, SDL_EVENT_FIRST, SDL_EVENT_LAST);
if (count <= 0) {
break;
}
for (int i = 0; i < count; ++i) {
SDL_Event *event = &events[i];
if (!ShouldDispatchImmediately(event)) {
SDL_DispatchMainCallbackEvent(event);
}
}
}
}
static int SDLCALL SDL_MainCallbackEventWatcher(void *userdata, SDL_Event *event)
{
if (ShouldDispatchImmediately(event)) {
// Make sure any currently queued events are processed then dispatch this before continuing
SDL_DispatchMainCallbackEvents();
SDL_DispatchMainCallbackEvent(event);
} else {
// We'll process this event later from the main event queue
}
return 0;
}
@ -50,34 +96,10 @@ int SDL_InitMainCallbacks(int argc, char* argv[], SDL_AppInit_func appinit, SDL_
return -1;
}
// drain any initial events that might have arrived before we added a watcher.
SDL_Event event;
SDL_Event *pending_events = NULL;
int total_pending_events = 0;
while (SDL_PollEvent(&event)) {
void *ptr = SDL_realloc(pending_events, sizeof (SDL_Event) * (total_pending_events + 1));
if (!ptr) {
SDL_OutOfMemory();
SDL_free(pending_events);
SDL_AtomicSet(&apprc, -1);
return -1;
}
pending_events = (SDL_Event *) ptr;
SDL_copyp(&pending_events[total_pending_events], &event);
total_pending_events++;
}
if (SDL_AddEventWatch(EventWatcher, NULL) == -1) {
SDL_free(pending_events);
if (SDL_AddEventWatch(SDL_MainCallbackEventWatcher, NULL) < 0) {
SDL_AtomicSet(&apprc, -1);
return -1;
}
for (int i = 0; i < total_pending_events; i++) {
SDL_PushEvent(&pending_events[i]);
}
SDL_free(pending_events);
}
return SDL_AtomicGet(&apprc);
@ -85,9 +107,8 @@ int SDL_InitMainCallbacks(int argc, char* argv[], SDL_AppInit_func appinit, SDL_
int SDL_IterateMainCallbacks(void)
{
// Just pump events and empty the queue, EventWatcher sends the events to the app.
SDL_PumpEvents();
SDL_FlushEvents(SDL_EVENT_FIRST, SDL_EVENT_LAST);
SDL_DispatchMainCallbackEvents();
int rc = SDL_main_iteration_callback();
if (!SDL_AtomicCAS(&apprc, 0, rc)) {
@ -99,7 +120,7 @@ int SDL_IterateMainCallbacks(void)
void SDL_QuitMainCallbacks(void)
{
SDL_DelEventWatch(EventWatcher, NULL);
SDL_DelEventWatch(SDL_MainCallbackEventWatcher, NULL);
SDL_main_quit_callback();
// for symmetry, you should explicitly Quit what you Init, but we might come through here uninitialized and SDL_Quit() will clear everything anyhow.