Don't queue application events that need to be handled immediately

This makes it more clear that these events can't be handled in the normal event loop. It also makes pause and resume transparent to applications that don't handle them, which is a nice side effect.

src/events/SDL_events.c

@@ -1452,19 +1452,15 @@ SDL_bool SDL_WaitEventTimeoutNS(SDL_Event *event, Sint64 timeoutNS)
     }
 }
 
-int SDL_PushEvent(SDL_Event *event)
+static SDL_bool SDL_CallEventWatchers(SDL_Event *event)
 {
-    if (!event->common.timestamp) {
-        event->common.timestamp = SDL_GetTicksNS();
-    }
-
     if ((SDL_EventOK.callback || SDL_event_watchers_count > 0) &&
         (event->common.type != SDL_EVENT_POLL_SENTINEL)) {
         SDL_LockMutex(SDL_event_watchers_lock);
         {
             if (SDL_EventOK.callback && !SDL_EventOK.callback(SDL_EventOK.userdata, event)) {
                 SDL_UnlockMutex(SDL_event_watchers_lock);
-                return 0;
+                return SDL_FALSE;
             }
 
             if (SDL_event_watchers_count > 0) {
@@ -1495,6 +1491,19 @@ int SDL_PushEvent(SDL_Event *event)
         SDL_UnlockMutex(SDL_event_watchers_lock);
     }
 
+    return SDL_TRUE;
+}
+
+int SDL_PushEvent(SDL_Event *event)
+{
+    if (!event->common.timestamp) {
+        event->common.timestamp = SDL_GetTicksNS();
+    }
+
+    if (!SDL_CallEventWatchers(event)) {
+        return 0;
+    }
+
     if (SDL_PeepEvents(event, 1, SDL_ADDEVENT, 0, 0) <= 0) {
         return -1;
     }
@@ -1707,7 +1716,21 @@ int SDL_SendAppEvent(SDL_EventType eventType)
         SDL_Event event;
         event.type = eventType;
         event.common.timestamp = 0;
-        posted = (SDL_PushEvent(&event) > 0);
+
+        switch (eventType) {
+        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:
+            // We won't actually queue this event, it needs to be handled in this call stack by an event watcher
+            posted = SDL_CallEventWatchers(&event);
+            break;
+        default:
+            posted = (SDL_PushEvent(&event) > 0);
+            break;
+        }
     }
     return posted;
 }