Fix small memory issues with MVKPresentableSwapchainImage.

- Fix Metal validation error caused by CAMetalDrawable released before
  MTLCommandBuffer is finished using it.
- When presenting, MVKPresentableSwapchainImage retains in-flight
  CAMetalDrawable until MTLCommandBuffer completion.

- Fix memory leak of MVKFences and MVKSemaphores when a
  swapchain image is acquired more than it is presented.
- Force MVKPresentableSwapchainImage to untrack any tracked fences or
  semaphores when it is destroyed.

- Update MoltenVK version to 1.2.2.

Docs/Whats_New.md

@@ -13,6 +13,18 @@ Copyright (c) 2015-2022 [The Brenwill Workshop Ltd.](http://www.brenwill.com)
 
 
 
+MoltenVK 1.2.2
+--------------
+
+Released TBD
+
+- Fix Metal validation error caused by `CAMetalDrawable` released before 
+  `MTLCommandBuffer` is finished using it.
+- Fix memory leak of `MVKFences` and `MVKSemaphores` when 
+  a swapchain image is acquired more than it is presented.
+
+
+
 MoltenVK 1.2.1
 --------------
 

MoltenVK/MoltenVK/API/vk_mvk_moltenvk.h

@@ -51,7 +51,7 @@ typedef unsigned long MTLArgumentBuffersTier;
  */
 #define MVK_VERSION_MAJOR   1
 #define MVK_VERSION_MINOR   2
-#define MVK_VERSION_PATCH   1
+#define MVK_VERSION_PATCH   2
 
 #define MVK_MAKE_VERSION(major, minor, patch)    (((major) * 10000) + ((minor) * 100) + (patch))
 #define MVK_VERSION     MVK_MAKE_VERSION(MVK_VERSION_MAJOR, MVK_VERSION_MINOR, MVK_VERSION_PATCH)

MoltenVK/MoltenVK/GPUObjects/MVKImage.h

@@ -473,6 +473,7 @@ protected:
 	void signalPresentationSemaphore(const MVKSwapchainSignaler& signaler, id<MTLCommandBuffer> mtlCmdBuff);
 	static void markAsTracked(const MVKSwapchainSignaler& signaler);
 	static void unmarkAsTracked(const MVKSwapchainSignaler& signaler);
+	void untrackAllSignalers();
 	void renderWatermark(id<MTLCommandBuffer> mtlCmdBuff);
 
 	id<CAMetalDrawable> _mtlDrawable;

MoltenVK/MoltenVK/GPUObjects/MVKImage.mm

@@ -1287,6 +1287,18 @@ void MVKPresentableSwapchainImage::unmarkAsTracked(const MVKSwapchainSignaler& s
 	if (signaler.fence) { signaler.fence->release(); }
 }
 
+// Untrack any signalers that are still tracking, releasing the fences and semaphores.
+void MVKPresentableSwapchainImage::untrackAllSignalers() {
+	lock_guard<mutex> lock(_availabilityLock);
+
+	if ( !_availability.isAvailable ) {
+		unmarkAsTracked(_preSignaler);
+		for (auto& sig : _availabilitySignalers) {
+			unmarkAsTracked(sig);
+		}
+	}
+}
+
 
 #pragma mark Metal
 
@@ -1345,9 +1357,12 @@ void MVKPresentableSwapchainImage::presentCAMetalDrawable(id<MTLCommandBuffer> m
 		_availabilitySignalers.erase(sigIter);
 	}
 
-	// Ensure this image is not destroyed while awaiting MTLCommandBuffer completion
+	// Ensure this image and the drawable are not destroyed while awaiting MTLCommandBuffer completion.
+	// We retain the drawable separately because new drawable might be acquired by this image by then.
 	retain();
+	[mtlDrwbl retain];
 	[mtlCmdBuff addCompletedHandler: ^(id<MTLCommandBuffer> mcb) {
+		[mtlDrwbl release];
 		makeAvailable(signaler);
 		release();
 	}];
@@ -1405,8 +1420,11 @@ MVKPresentableSwapchainImage::MVKPresentableSwapchainImage(MVKDevice* device,
 	_preSignaler = MVKSwapchainSignaler{nullptr, nullptr, 0};
 }
 
+// Unsignaled signalers will exist if this image is acquired more than it is presented.
+// Ensure they are untracked so the fences and semaphores will be released.
 MVKPresentableSwapchainImage::~MVKPresentableSwapchainImage() {
 	releaseMetalDrawable();
+	untrackAllSignalers();
 }