SCI32: Improve performance when flushing events during video playback

Calling through EventManager::getSciEvent to flush events is
pretty inefficient and created stalls that lead to dropped
frames during the chapter 7 chase in Phantasmagoria 1.

If necessary, performance could be improved further by extending
Common::EventManager to expose SDL_FlushEvents, but this seems to
finish in 0-1ms so should be OK for now.

Refs Trac#9974, Trac#9975.

3 files changed, 12 insertions, 13 deletions

diff --git a/engines/sci/event.cpp b/engines/sci/event.cpp
index 873b6bb48a..b1be46aded 100644
--- a/engines/sci/event.cpp
+++ b/engines/sci/event.cpp
@@ -408,6 +408,13 @@ SciEvent EventManager::getSciEvent(uint32 mask) {
 	return event;
 }
 
+void EventManager::flushEvents() {
+	Common::EventManager *em = g_system->getEventManager();
+	Common::Event event;
+	while (em->pollEvent(event));
+	_events.clear();
+}
+
 #ifdef ENABLE_SCI32
 void EventManager::setHotRectanglesActive(const bool active) {
 	_hotRectanglesActive = active;
diff --git a/engines/sci/event.h b/engines/sci/event.h
index b06d2ae429..614a5a64e7 100644
--- a/engines/sci/event.h
+++ b/engines/sci/event.h
@@ -138,6 +138,7 @@ public:
 
 	void updateScreen();
 	SciEvent getSciEvent(uint32 mask);
+	void flushEvents();
 
 private:
 	SciEvent getScummVMEvent();
diff --git a/engines/sci/graphics/video32.cpp b/engines/sci/graphics/video32.cpp
index 22be48c0f8..e0f83c6e82 100644
--- a/engines/sci/graphics/video32.cpp
+++ b/engines/sci/graphics/video32.cpp
@@ -56,18 +56,6 @@ namespace Graphics { struct Surface; }
 
 namespace Sci {
 
-static void flushEvents(EventManager *eventMan) {
-	// Flushing all the keyboard and mouse events out of the event manager
-	// keeps events queued from before the start of playback from accidentally
-	// activating a video stop flag
-	for (;;) {
-		const SciEvent event = eventMan->getSciEvent(SCI_EVENT_ANY & ~SCI_EVENT_QUIT);
-		if (event.type == SCI_EVENT_NONE) {
-			break;
-		}
-	}
-}
-
 bool VideoPlayer::open(const Common::String &fileName) {
 	if (!_decoder->loadFile(fileName)) {
 		warning("Failed to load %s", fileName.c_str());
@@ -129,7 +117,10 @@ bool VideoPlayer::endHQVideo() {
 }
 
 VideoPlayer::EventFlags VideoPlayer::playUntilEvent(const EventFlags flags, const uint32 maxSleepMs) {
-	flushEvents(_eventMan);
+	// Flushing all the keyboard and mouse events out of the event manager
+	// keeps events queued from before the start of playback from accidentally
+	// activating a video stop flag
+	_eventMan->flushEvents();
 	_decoder->start();
 
 	EventFlags stopFlag = kEventFlagNone;