Fix high latency on present wait.

Author: squidbus

MoltenVK/MoltenVK/GPUObjects/MVKImage.mm

@@ -1629,8 +1629,9 @@ static void signalAndUntrack(const MVKSwapchainSignaler& signaler) {
 	// Ensure this image, the drawable, and the present fence are not destroyed while
 	// awaiting MTLCommandBuffer completion. We retain the drawable separately because
 	// a new drawable might be acquired by this image by then.
-	// Signal the fence from this callback, because the last one or two presentation
-	// completion callbacks can occasionally stall.
+	// Signal the fence and notify the swapchain that the present has completed
+	// from this callback, because the last one or two presentation completion
+	// callbacks can occasionally stall.
 	retain();
 	[mtlDrwbl retain];
 	auto* fence = presentInfo.fence;
@@ -1640,6 +1641,7 @@ static void signalAndUntrack(const MVKSwapchainSignaler& signaler) {
 		if (fence) { fence->release(); }
 		[mtlDrwbl release];
 		release();
+		if (_swapchain) { _swapchain->notifyPresentComplete(presentInfo); }
 	}];
 
 	signal(signaler.semaphore, signaler.semaphoreSignalToken, mtlCmdBuff);

MoltenVK/MoltenVK/GPUObjects/MVKSwapchain.h

@@ -123,6 +123,7 @@ class MVKSwapchain : public MVKVulkanAPIDeviceObject {
     void markFrameInterval();
 	void beginPresentation(const MVKImagePresentInfo& presentInfo);
 	void endPresentation(const MVKImagePresentInfo& presentInfo, uint64_t beginPresentTime, uint64_t actualPresentTime = 0);
+	void notifyPresentComplete(const MVKImagePresentInfo& presentInfo);
 	void forceUnpresentedImageCompletion();
 
 	MVKSurface* _surface = nullptr;

MoltenVK/MoltenVK/GPUObjects/MVKSwapchain.mm

@@ -277,7 +277,9 @@
 	_presentTimingHistory[_presentHistoryIndex].earliestPresentTime = actualPresentTime;
 	_presentTimingHistory[_presentHistoryIndex].presentMargin = actualPresentTime > beginPresentTime ? actualPresentTime - beginPresentTime : 0;
 	_presentHistoryIndex = (_presentHistoryIndex + 1) % kMaxPresentationHistory;
+}
 
+void MVKSwapchain::notifyPresentComplete(const MVKImagePresentInfo& presentInfo) {
 	if (presentInfo.presentId != 0) {
 		std::unique_lock pidLock(_currentPresentIdMutex);
 		_currentPresentId = std::max(_currentPresentId, presentInfo.presentId);