MoltenVK/MoltenVK/GPUObjects/MVKSwapchain.mm - external/github.com/KhronosGroup/MoltenVK - Git at Google

 /*
  * MVKSwapchain.mm
  *
  * Copyright (c) 2015-2020 The Brenwill Workshop Ltd. (http://www.brenwill.com)
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include "MVKSurface.h"
 #include "MVKSwapchain.h"
 #include "MVKImage.h"
 #include "MVKQueue.h"
 #include "MVKFoundation.h"
 #include "MVKOSExtensions.h"
 #include "MVKWatermark.h"
 #include "MVKWatermarkTextureContent.h"
 #include "MVKWatermarkShaderSource.h"
 #include "mvk_datatypes.hpp"
 #include "MVKLogging.h"
 #import "CAMetalLayer+MoltenVK.h"
 #import "MVKBlockObserver.h"

 #include <libkern/OSByteOrder.h>

 using namespace std;


 #pragma mark -
 #pragma mark MVKSwapchain

 void MVKSwapchain::propogateDebugName() {
 	if (_debugName) {
 		size_t imgCnt = _presentableImages.size();
 		for (size_t imgIdx = 0; imgIdx < imgCnt; imgIdx++) {
 			NSString* nsName = [[NSString alloc] initWithFormat: @"%@(%lu)", _debugName, imgIdx];	// temp retain
 			_presentableImages[imgIdx]->setDebugName(nsName.UTF8String);
 			[nsName release];																		// release temp string
 		}
 	}
 }

 VkResult MVKSwapchain::getImages(uint32_t* pCount, VkImage* pSwapchainImages) {

 	// Get the number of surface images
 	uint32_t imgCnt = getImageCount();

 	// If images aren't actually being requested yet, simply update the returned count
 	if ( !pSwapchainImages ) {
 		*pCount = imgCnt;
 		return VK_SUCCESS;
 	}

 	// Determine how many images we'll return, and return that number
 	VkResult result = (*pCount >= imgCnt) ? VK_SUCCESS : VK_INCOMPLETE;
 	*pCount = min(*pCount, imgCnt);

 	// Now populate the images
 	for (uint32_t imgIdx = 0; imgIdx < *pCount; imgIdx++) {
 		pSwapchainImages[imgIdx] = (VkImage)_presentableImages[imgIdx];
 	}

 	return result;
 }

 VkResult MVKSwapchain::acquireNextImageKHR(uint64_t timeout,
 										   VkSemaphore semaphore,
 										   VkFence fence,
 										   uint32_t deviceMask,
 										   uint32_t* pImageIndex) {

 	if ( getIsSurfaceLost() ) { return VK_ERROR_SURFACE_LOST_KHR; }

 	// Find the image that has the shortest wait by finding the smallest availability measure.
 	MVKPresentableSwapchainImage* minWaitImage = nullptr;
 	MVKSwapchainImageAvailability minAvailability = { kMVKUndefinedLargeUInt64, false };
 	uint32_t imgCnt = getImageCount();
 	for (uint32_t imgIdx = 0; imgIdx < imgCnt; imgIdx++) {
 		auto* img = getPresentableImage(imgIdx);
 		auto imgAvail = img->getAvailability();
 		if (imgAvail < minAvailability) {
 			minAvailability = imgAvail;
 			minWaitImage = img;
 		}
 	}

 	// Return the index of the image with the shortest wait,
 	// and signal the semaphore and fence when it's available
 	*pImageIndex = minWaitImage->_swapchainIndex;
 	minWaitImage->acquireAndSignalWhenAvailable((MVKSemaphore*)semaphore, (MVKFence*)fence);

 	return getHasSurfaceSizeChanged() ? VK_ERROR_OUT_OF_DATE_KHR : VK_SUCCESS;
 }

 bool MVKSwapchain::getHasSurfaceSizeChanged() {
 	return !CGSizeEqualToSize(_mtlLayer.naturalDrawableSizeMVK, _mtlLayerOrigDrawSize);
 }

 uint64_t MVKSwapchain::getNextAcquisitionID() { return ++_currentAcquisitionID; }

 // Releases any surfaces that are not currently being displayed,
 // so they can be used by a different swapchain.
 void MVKSwapchain::releaseUndisplayedSurfaces() {}


 #pragma mark Rendering

 // Called automatically when a swapchain image is about to be presented to the surface by the queue.
 // Activities include marking the frame interval and rendering the watermark if needed.
 void MVKSwapchain::willPresentSurface(id<MTLTexture> mtlTexture, id<MTLCommandBuffer> mtlCmdBuff) {
     markFrameInterval();
     renderWatermark(mtlTexture, mtlCmdBuff);
 }

 // If the product has not been fully licensed, renders the watermark image to the surface.
 void MVKSwapchain::renderWatermark(id<MTLTexture> mtlTexture, id<MTLCommandBuffer> mtlCmdBuff) {
     if (_device->_pMVKConfig->displayWatermark) {
         if ( !_licenseWatermark ) {
             _licenseWatermark = new MVKWatermarkRandom(getMTLDevice(),
                                                        __watermarkTextureContent,
                                                        __watermarkTextureWidth,
                                                        __watermarkTextureHeight,
                                                        __watermarkTextureFormat,
                                                        getPixelFormats()->getMTLPixelFormatBytesPerRow(__watermarkTextureFormat, __watermarkTextureWidth),
                                                        __watermarkShaderSource);
         }
         _licenseWatermark->render(mtlTexture, mtlCmdBuff, _performanceStatistics.lastFrameInterval / 1000.0);
     } else {
         if (_licenseWatermark) {
             _licenseWatermark->destroy();
             _licenseWatermark = nullptr;
         }
     }
 }

 // Calculates and remembers the time interval between frames.
 void MVKSwapchain::markFrameInterval() {
     if ( !(_device->_pMVKConfig->performanceTracking || _licenseWatermark) ) { return; }

     uint64_t prevFrameTime = _lastFrameTime;
     _lastFrameTime = mvkGetTimestamp();
     _performanceStatistics.lastFrameInterval = mvkGetElapsedMilliseconds(prevFrameTime, _lastFrameTime);

     // Low pass filter.
     // y[i] := α * x[i] + (1-α) * y[i-1]  OR
     // y[i] := y[i-1] + α * (x[i] - y[i-1])
     _performanceStatistics.averageFrameInterval += _averageFrameIntervalFilterAlpha * (_performanceStatistics.lastFrameInterval - _performanceStatistics.averageFrameInterval);
     _performanceStatistics.averageFramesPerSecond = 1000.0 / _performanceStatistics.averageFrameInterval;

 // Uncomment for per-frame logging.
 //	MVKLogDebug("Frame interval: %.2f ms. Avg frame interval: %.2f ms. Frame number: %d.",
 //				_performanceStatistics.lastFrameInterval,
 //				_performanceStatistics.averageFrameInterval,
 //				_currentPerfLogFrameCount + 1);

     uint32_t perfLogCntLimit = _device->_pMVKConfig->performanceLoggingFrameCount;
     if ((perfLogCntLimit > 0) && (++_currentPerfLogFrameCount >= perfLogCntLimit)) {
 		_currentPerfLogFrameCount = 0;
 		MVKLogInfo("Frame interval: %.2f ms. Avg frame interval: %.2f ms. Avg FPS: %.2f. Reporting every: %d frames. Elapsed time: %.3f seconds.",
 				   _performanceStatistics.lastFrameInterval,
 				   _performanceStatistics.averageFrameInterval,
 				   _performanceStatistics.averageFramesPerSecond,
 				   perfLogCntLimit,
 				   mvkGetElapsedMilliseconds() / 1000.0);
 	}
 }

 #if MVK_MACOS
 struct CIE1931XY {
 	uint16_t x;
 	uint16_t y;
 } __attribute__((packed));

 // According to D.3.28:
 //   "[x and y] specify the normalized x and y chromaticity coordinates, respectively...
 //    in normalized increments of 0.00002."
 static inline uint16_t FloatToCIE1931Unorm(float x) { return OSSwapHostToBigInt16((uint16_t)(x * 100000 / 2)); }
 static inline CIE1931XY VkXYColorEXTToCIE1931XY(VkXYColorEXT xy) {
 	return { FloatToCIE1931Unorm(xy.x), FloatToCIE1931Unorm(xy.y) };
 }
 #endif

 void MVKSwapchain::setHDRMetadataEXT(const VkHdrMetadataEXT& metadata) {
 #if MVK_MACOS
 	// We were given metadata as floats, but CA wants it as specified in H.265.
 	// More specifically, it wants "Mastering display colour volume" (D.2.28) and
 	// "Content light level information" (D.2.35) SEI messages, with big-endian
 	// integers. We have to convert.
 	struct ColorVolumeSEI {
 		CIE1931XY display_primaries[3];  // Green, blue, red
 		CIE1931XY white_point;
 		uint32_t max_display_mastering_luminance;
 		uint32_t min_display_mastering_luminance;
 	} __attribute__((packed));
 	struct LightLevelSEI {
 		uint16_t max_content_light_level;
 		uint16_t max_pic_average_light_level;
 	} __attribute__((packed));
 	ColorVolumeSEI colorVol;
 	LightLevelSEI lightLevel;
 	// According to D.3.28:
 	//   "For describing mastering displays that use red, green, and blue colour
 	//    primaries, it is suggested that index value c equal to 0 should correspond
 	//    to the green primary, c equal to 1 should correspond to the blue primary
 	//    and c equal to 2 should correspond to the red colour primary."
 	colorVol.display_primaries[0] = VkXYColorEXTToCIE1931XY(metadata.displayPrimaryGreen);
 	colorVol.display_primaries[1] = VkXYColorEXTToCIE1931XY(metadata.displayPrimaryBlue);
 	colorVol.display_primaries[2] = VkXYColorEXTToCIE1931XY(metadata.displayPrimaryRed);
 	colorVol.white_point = VkXYColorEXTToCIE1931XY(metadata.whitePoint);
 	// Later in D.3.28:
 	//   "max_display_mastering_luminance and min_display_mastering_luminance specify
 	//    the nominal maximum and minimum display luminance, respectively, of the mastering
 	//    display in units of 0.0001 candelas [sic] per square metre."
 	// N.B. 1 nit = 1 cd/m^2
 	colorVol.max_display_mastering_luminance = OSSwapHostToBigInt32((uint32_t)(metadata.maxLuminance * 10000));
 	colorVol.min_display_mastering_luminance = OSSwapHostToBigInt32((uint32_t)(metadata.minLuminance * 10000));
 	lightLevel.max_content_light_level = OSSwapHostToBigInt16((uint16_t)metadata.maxContentLightLevel);
 	lightLevel.max_pic_average_light_level = OSSwapHostToBigInt16((uint16_t)metadata.maxFrameAverageLightLevel);
 	NSData* colorVolData = [NSData dataWithBytes: &colorVol length: sizeof(colorVol)];
 	NSData* lightLevelData = [NSData dataWithBytes: &lightLevel length: sizeof(lightLevel)];
 	CAEDRMetadata* caMetadata = [CAEDRMetadata HDR10MetadataWithDisplayInfo: colorVolData
 																contentInfo: lightLevelData
 														 opticalOutputScale: 1];
 	_mtlLayer.EDRMetadata = caMetadata;
 	[caMetadata release];
 	[colorVolData release];
 	[lightLevelData release];
 	_mtlLayer.wantsExtendedDynamicRangeContent = YES;
 #endif
 }


 #pragma mark Construction

 MVKSwapchain::MVKSwapchain(MVKDevice* device,
 						   const VkSwapchainCreateInfoKHR* pCreateInfo) : MVKVulkanAPIDeviceObject(device), _surfaceLost(false) {
 	_currentAcquisitionID = 0;
 	_layerObserver = nil;

 	// If applicable, release any surfaces (not currently being displayed) from the old swapchain.
 	MVKSwapchain* oldSwapchain = (MVKSwapchain*)pCreateInfo->oldSwapchain;
 	if (oldSwapchain) { oldSwapchain->releaseUndisplayedSurfaces(); }

 	uint32_t imgCnt = mvkClamp(pCreateInfo->minImageCount,
 							   _device->_pMetalFeatures->minSwapchainImageCount,
 							   _device->_pMetalFeatures->maxSwapchainImageCount);
 	initCAMetalLayer(pCreateInfo, imgCnt);
     initSurfaceImages(pCreateInfo, imgCnt);		// After initCAMetalLayer()
     initFrameIntervalTracking();

     _licenseWatermark = NULL;
 }

 // Initializes the CAMetalLayer underlying the surface of this swapchain.
 void MVKSwapchain::initCAMetalLayer(const VkSwapchainCreateInfoKHR* pCreateInfo, uint32_t imgCnt) {

 	MVKSurface* mvkSrfc = (MVKSurface*)pCreateInfo->surface;
 	if ( !mvkSrfc->getCAMetalLayer() ) {
 		setConfigurationResult(mvkSrfc->getConfigurationResult());
 		_surfaceLost = true;
 		return;
 	}

 	_mtlLayer = mvkSrfc->getCAMetalLayer();
 	_mtlLayer.device = getMTLDevice();
 	_mtlLayer.pixelFormat = getPixelFormats()->getMTLPixelFormatFromVkFormat(pCreateInfo->imageFormat);
 	_mtlLayer.maximumDrawableCountMVK = imgCnt;
 	_mtlLayer.displaySyncEnabledMVK = (pCreateInfo->presentMode != VK_PRESENT_MODE_IMMEDIATE_KHR);
 	_mtlLayer.magnificationFilter = _device->_pMVKConfig->swapchainMagFilterUseNearest ? kCAFilterNearest : kCAFilterLinear;
 	_mtlLayer.framebufferOnly = !mvkIsAnyFlagEnabled(pCreateInfo->imageUsage, (VK_IMAGE_USAGE_TRANSFER_SRC_BIT |
 																			   VK_IMAGE_USAGE_TRANSFER_DST_BIT |
 																			   VK_IMAGE_USAGE_SAMPLED_BIT |
 																			   VK_IMAGE_USAGE_STORAGE_BIT));
 	if (pCreateInfo->compositeAlpha != VK_COMPOSITE_ALPHA_INHERIT_BIT_KHR) {
 		_mtlLayer.opaque = pCreateInfo->compositeAlpha == VK_COMPOSITE_ALPHA_OPAQUE_BIT_KHR;
 	}

 	switch (pCreateInfo->imageColorSpace) {
 		case VK_COLOR_SPACE_SRGB_NONLINEAR_KHR:
 			_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceSRGB);
 			break;
 		case VK_COLOR_SPACE_DISPLAY_P3_NONLINEAR_EXT:
 			_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceDisplayP3);
 			_mtlLayer.wantsExtendedDynamicRangeContentMVK = YES;
 			break;
 		case VK_COLOR_SPACE_EXTENDED_SRGB_LINEAR_EXT:
 			_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceExtendedLinearSRGB);
 			_mtlLayer.wantsExtendedDynamicRangeContentMVK = YES;
 			break;
 		case VK_COLOR_SPACE_EXTENDED_SRGB_NONLINEAR_EXT:
 			_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceExtendedSRGB);
 			_mtlLayer.wantsExtendedDynamicRangeContentMVK = YES;
 			break;
 		case VK_COLOR_SPACE_DISPLAY_P3_LINEAR_EXT:
 			_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceExtendedLinearDisplayP3);
 			_mtlLayer.wantsExtendedDynamicRangeContentMVK = YES;
 			break;
 		case VK_COLOR_SPACE_DCI_P3_NONLINEAR_EXT:
 			_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceDCIP3);
 			_mtlLayer.wantsExtendedDynamicRangeContentMVK = YES;
 			break;
 		case VK_COLOR_SPACE_BT709_NONLINEAR_EXT:
 			_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceITUR_709);
 			break;
 		case VK_COLOR_SPACE_BT2020_LINEAR_EXT:
 			_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceExtendedLinearITUR_2020);
 			_mtlLayer.wantsExtendedDynamicRangeContentMVK = YES;
 			break;
 		case VK_COLOR_SPACE_HDR10_ST2084_EXT:
 			_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceITUR_2020_PQ_EOTF);
 			_mtlLayer.wantsExtendedDynamicRangeContentMVK = YES;
 			break;
 		case VK_COLOR_SPACE_HDR10_HLG_EXT:
 			_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceITUR_2020_HLG);
 			_mtlLayer.wantsExtendedDynamicRangeContentMVK = YES;
 			break;
 		case VK_COLOR_SPACE_ADOBERGB_NONLINEAR_EXT:
 			_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceAdobeRGB1998);
 			break;
 		case VK_COLOR_SPACE_PASS_THROUGH_EXT:
 		default:
 			// Nothing - the default is not to do color matching.
 			break;
 	}
 	_mtlLayerOrigDrawSize = _mtlLayer.updatedDrawableSizeMVK;

 	// TODO: set additional CAMetalLayer properties before extracting drawables:
 	//	- presentsWithTransaction
 	//	- drawsAsynchronously

 	if ( [_mtlLayer.delegate isKindOfClass: [PLATFORM_VIEW_CLASS class]] ) {
 		// Sometimes, the owning view can replace its CAMetalLayer. In that case, the client
 		// needs to recreate the swapchain, or no content will be displayed.
 		_layerObserver = [MVKBlockObserver observerWithBlock: ^(NSString* path, id, NSDictionary*, void*) {
 			if ( ![path isEqualToString: @"layer"] ) { return; }
 			this->_surfaceLost = true;
 			[this->_layerObserver release];
 			this->_layerObserver = nil;
 		} forObject: _mtlLayer.delegate atKeyPath: @"layer"];
 	}
 }

 // Initializes the array of images used for the surface of this swapchain.
 // The CAMetalLayer should already be initialized when this is called.
 void MVKSwapchain::initSurfaceImages(const VkSwapchainCreateInfoKHR* pCreateInfo, uint32_t imgCnt) {

     if ( getIsSurfaceLost() ) {
         return;
     }

     VkExtent2D imgExtent = mvkVkExtent2DFromCGSize(_mtlLayerOrigDrawSize);

     VkImageCreateInfo imgInfo = {
         .sType = VK_STRUCTURE_TYPE_IMAGE_CREATE_INFO,
         .pNext = VK_NULL_HANDLE,
         .imageType = VK_IMAGE_TYPE_2D,
         .format = getPixelFormats()->getVkFormatFromMTLPixelFormat(_mtlLayer.pixelFormat),
         .extent = { imgExtent.width, imgExtent.height, 1 },
         .mipLevels = 1,
         .arrayLayers = 1,
         .samples = VK_SAMPLE_COUNT_1_BIT,
         .tiling = VK_IMAGE_TILING_OPTIMAL,
         .usage = pCreateInfo->imageUsage,
         .flags = 0,
     };

 	if (mvkAreAllFlagsEnabled(pCreateInfo->flags, VK_SWAPCHAIN_CREATE_MUTABLE_FORMAT_BIT_KHR)) {
 		mvkEnableFlags(imgInfo.flags, VK_IMAGE_CREATE_MUTABLE_FORMAT_BIT | VK_IMAGE_CREATE_EXTENDED_USAGE_BIT);
 	}
 	if (mvkAreAllFlagsEnabled(pCreateInfo->flags, VK_SWAPCHAIN_CREATE_SPLIT_INSTANCE_BIND_REGIONS_BIT_KHR)) {
 		// We don't really support this, but set the flag anyway.
 		mvkEnableFlags(imgInfo.flags, VK_IMAGE_CREATE_SPLIT_INSTANCE_BIND_REGIONS_BIT);
 	}

 	for (uint32_t imgIdx = 0; imgIdx < imgCnt; imgIdx++) {
 		_presentableImages.push_back(_device->createPresentableSwapchainImage(&imgInfo, this, imgIdx, NULL));
 	}

     MVKLogInfo("Created %d swapchain images with initial size (%d, %d).", imgCnt, imgExtent.width, imgExtent.height);
 }

 // Initialize frame interval tracking, including start time and filtering parameters.
 void MVKSwapchain::initFrameIntervalTracking() {
     _performanceStatistics.lastFrameInterval = 0;
     _performanceStatistics.averageFrameInterval = 0;
     _performanceStatistics.averageFramesPerSecond = 0;
     _currentPerfLogFrameCount = 0;

 	_lastFrameTime = mvkGetTimestamp();

     // Establish the alpha parameter of a low-pass filter for averaging frame intervals.
     double RC_over_dt = 10.0;
     _averageFrameIntervalFilterAlpha = 1.0 / (1.0 + RC_over_dt);
 }

 MVKSwapchain::~MVKSwapchain() {
 	for (auto& img : _presentableImages) { _device->destroyPresentableSwapchainImage(img, NULL); }

     if (_licenseWatermark) { _licenseWatermark->destroy(); }
     [this->_layerObserver release];
 }
	/*
	* MVKSwapchain.mm
	*
	* Copyright (c) 2015-2020 The Brenwill Workshop Ltd. (http://www.brenwill.com)
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include "MVKSurface.h"
	#include "MVKSwapchain.h"
	#include "MVKImage.h"
	#include "MVKQueue.h"
	#include "MVKFoundation.h"
	#include "MVKOSExtensions.h"
	#include "MVKWatermark.h"
	#include "MVKWatermarkTextureContent.h"
	#include "MVKWatermarkShaderSource.h"
	#include "mvk_datatypes.hpp"
	#include "MVKLogging.h"
	#import "CAMetalLayer+MoltenVK.h"
	#import "MVKBlockObserver.h"

	#include <libkern/OSByteOrder.h>

	using namespace std;


	#pragma mark -
	#pragma mark MVKSwapchain

	void MVKSwapchain::propogateDebugName() {
	if (_debugName) {
	size_t imgCnt = _presentableImages.size();
	for (size_t imgIdx = 0; imgIdx < imgCnt; imgIdx++) {
	NSString* nsName = [[NSString alloc] initWithFormat: @"%@(%lu)", _debugName, imgIdx]; // temp retain
	_presentableImages[imgIdx]->setDebugName(nsName.UTF8String);
	[nsName release]; // release temp string
	}
	}
	}

	VkResult MVKSwapchain::getImages(uint32_t* pCount, VkImage* pSwapchainImages) {

	// Get the number of surface images
	uint32_t imgCnt = getImageCount();

	// If images aren't actually being requested yet, simply update the returned count
	if ( !pSwapchainImages ) {
	*pCount = imgCnt;
	return VK_SUCCESS;
	}

	// Determine how many images we'll return, and return that number
	VkResult result = (*pCount >= imgCnt) ? VK_SUCCESS : VK_INCOMPLETE;
	pCount = min(pCount, imgCnt);

	// Now populate the images
	for (uint32_t imgIdx = 0; imgIdx < *pCount; imgIdx++) {
	pSwapchainImages[imgIdx] = (VkImage)_presentableImages[imgIdx];
	}

	return result;
	}

	VkResult MVKSwapchain::acquireNextImageKHR(uint64_t timeout,
	VkSemaphore semaphore,
	VkFence fence,
	uint32_t deviceMask,
	uint32_t* pImageIndex) {

	if ( getIsSurfaceLost() ) { return VK_ERROR_SURFACE_LOST_KHR; }

	// Find the image that has the shortest wait by finding the smallest availability measure.
	MVKPresentableSwapchainImage* minWaitImage = nullptr;
	MVKSwapchainImageAvailability minAvailability = { kMVKUndefinedLargeUInt64, false };
	uint32_t imgCnt = getImageCount();
	for (uint32_t imgIdx = 0; imgIdx < imgCnt; imgIdx++) {
	auto* img = getPresentableImage(imgIdx);
	auto imgAvail = img->getAvailability();
	if (imgAvail < minAvailability) {
	minAvailability = imgAvail;
	minWaitImage = img;
	}
	}

	// Return the index of the image with the shortest wait,
	// and signal the semaphore and fence when it's available
	*pImageIndex = minWaitImage->_swapchainIndex;
	minWaitImage->acquireAndSignalWhenAvailable((MVKSemaphore)semaphore, (MVKFence)fence);

	return getHasSurfaceSizeChanged() ? VK_ERROR_OUT_OF_DATE_KHR : VK_SUCCESS;
	}

	bool MVKSwapchain::getHasSurfaceSizeChanged() {
	return !CGSizeEqualToSize(_mtlLayer.naturalDrawableSizeMVK, _mtlLayerOrigDrawSize);
	}

	uint64_t MVKSwapchain::getNextAcquisitionID() { return ++_currentAcquisitionID; }

	// Releases any surfaces that are not currently being displayed,
	// so they can be used by a different swapchain.
	void MVKSwapchain::releaseUndisplayedSurfaces() {}


	#pragma mark Rendering

	// Called automatically when a swapchain image is about to be presented to the surface by the queue.
	// Activities include marking the frame interval and rendering the watermark if needed.
	void MVKSwapchain::willPresentSurface(id<MTLTexture> mtlTexture, id<MTLCommandBuffer> mtlCmdBuff) {
	markFrameInterval();
	renderWatermark(mtlTexture, mtlCmdBuff);
	}

	// If the product has not been fully licensed, renders the watermark image to the surface.
	void MVKSwapchain::renderWatermark(id<MTLTexture> mtlTexture, id<MTLCommandBuffer> mtlCmdBuff) {
	if (_device->_pMVKConfig->displayWatermark) {
	if ( !_licenseWatermark ) {
	_licenseWatermark = new MVKWatermarkRandom(getMTLDevice(),
	__watermarkTextureContent,
	__watermarkTextureWidth,
	__watermarkTextureHeight,
	__watermarkTextureFormat,
	getPixelFormats()->getMTLPixelFormatBytesPerRow(__watermarkTextureFormat, __watermarkTextureWidth),
	__watermarkShaderSource);
	}
	_licenseWatermark->render(mtlTexture, mtlCmdBuff, _performanceStatistics.lastFrameInterval / 1000.0);
	} else {
	if (_licenseWatermark) {
	_licenseWatermark->destroy();
	_licenseWatermark = nullptr;
	}
	}
	}

	// Calculates and remembers the time interval between frames.
	void MVKSwapchain::markFrameInterval() {
	if ( !(_device->_pMVKConfig->performanceTracking \|\| _licenseWatermark) ) { return; }

	uint64_t prevFrameTime = _lastFrameTime;
	_lastFrameTime = mvkGetTimestamp();
	_performanceStatistics.lastFrameInterval = mvkGetElapsedMilliseconds(prevFrameTime, _lastFrameTime);

	// Low pass filter.
	// y[i] := α * x[i] + (1-α) * y[i-1] OR
	// y[i] := y[i-1] + α * (x[i] - y[i-1])
	_performanceStatistics.averageFrameInterval += _averageFrameIntervalFilterAlpha * (_performanceStatistics.lastFrameInterval - _performanceStatistics.averageFrameInterval);
	_performanceStatistics.averageFramesPerSecond = 1000.0 / _performanceStatistics.averageFrameInterval;

	// Uncomment for per-frame logging.
	// MVKLogDebug("Frame interval: %.2f ms. Avg frame interval: %.2f ms. Frame number: %d.",
	// _performanceStatistics.lastFrameInterval,
	// _performanceStatistics.averageFrameInterval,
	// _currentPerfLogFrameCount + 1);

	uint32_t perfLogCntLimit = _device->_pMVKConfig->performanceLoggingFrameCount;
	if ((perfLogCntLimit > 0) && (++_currentPerfLogFrameCount >= perfLogCntLimit)) {
	_currentPerfLogFrameCount = 0;
	MVKLogInfo("Frame interval: %.2f ms. Avg frame interval: %.2f ms. Avg FPS: %.2f. Reporting every: %d frames. Elapsed time: %.3f seconds.",
	_performanceStatistics.lastFrameInterval,
	_performanceStatistics.averageFrameInterval,
	_performanceStatistics.averageFramesPerSecond,
	perfLogCntLimit,
	mvkGetElapsedMilliseconds() / 1000.0);
	}
	}

	#if MVK_MACOS
	struct CIE1931XY {
	uint16_t x;
	uint16_t y;
	} __attribute__((packed));

	// According to D.3.28:
	// "[x and y] specify the normalized x and y chromaticity coordinates, respectively...
	// in normalized increments of 0.00002."
	static inline uint16_t FloatToCIE1931Unorm(float x) { return OSSwapHostToBigInt16((uint16_t)(x * 100000 / 2)); }
	static inline CIE1931XY VkXYColorEXTToCIE1931XY(VkXYColorEXT xy) {
	return { FloatToCIE1931Unorm(xy.x), FloatToCIE1931Unorm(xy.y) };
	}
	#endif

	void MVKSwapchain::setHDRMetadataEXT(const VkHdrMetadataEXT& metadata) {
	#if MVK_MACOS
	// We were given metadata as floats, but CA wants it as specified in H.265.
	// More specifically, it wants "Mastering display colour volume" (D.2.28) and
	// "Content light level information" (D.2.35) SEI messages, with big-endian
	// integers. We have to convert.
	struct ColorVolumeSEI {
	CIE1931XY display_primaries[3]; // Green, blue, red
	CIE1931XY white_point;
	uint32_t max_display_mastering_luminance;
	uint32_t min_display_mastering_luminance;
	} __attribute__((packed));
	struct LightLevelSEI {
	uint16_t max_content_light_level;
	uint16_t max_pic_average_light_level;
	} __attribute__((packed));
	ColorVolumeSEI colorVol;
	LightLevelSEI lightLevel;
	// According to D.3.28:
	// "For describing mastering displays that use red, green, and blue colour
	// primaries, it is suggested that index value c equal to 0 should correspond
	// to the green primary, c equal to 1 should correspond to the blue primary
	// and c equal to 2 should correspond to the red colour primary."
	colorVol.display_primaries[0] = VkXYColorEXTToCIE1931XY(metadata.displayPrimaryGreen);
	colorVol.display_primaries[1] = VkXYColorEXTToCIE1931XY(metadata.displayPrimaryBlue);
	colorVol.display_primaries[2] = VkXYColorEXTToCIE1931XY(metadata.displayPrimaryRed);
	colorVol.white_point = VkXYColorEXTToCIE1931XY(metadata.whitePoint);
	// Later in D.3.28:
	// "max_display_mastering_luminance and min_display_mastering_luminance specify
	// the nominal maximum and minimum display luminance, respectively, of the mastering
	// display in units of 0.0001 candelas [sic] per square metre."
	// N.B. 1 nit = 1 cd/m^2
	colorVol.max_display_mastering_luminance = OSSwapHostToBigInt32((uint32_t)(metadata.maxLuminance * 10000));
	colorVol.min_display_mastering_luminance = OSSwapHostToBigInt32((uint32_t)(metadata.minLuminance * 10000));
	lightLevel.max_content_light_level = OSSwapHostToBigInt16((uint16_t)metadata.maxContentLightLevel);
	lightLevel.max_pic_average_light_level = OSSwapHostToBigInt16((uint16_t)metadata.maxFrameAverageLightLevel);
	NSData* colorVolData = [NSData dataWithBytes: &colorVol length: sizeof(colorVol)];
	NSData* lightLevelData = [NSData dataWithBytes: &lightLevel length: sizeof(lightLevel)];
	CAEDRMetadata* caMetadata = [CAEDRMetadata HDR10MetadataWithDisplayInfo: colorVolData
	contentInfo: lightLevelData
	opticalOutputScale: 1];
	_mtlLayer.EDRMetadata = caMetadata;
	[caMetadata release];
	[colorVolData release];
	[lightLevelData release];
	_mtlLayer.wantsExtendedDynamicRangeContent = YES;
	#endif
	}


	#pragma mark Construction

	MVKSwapchain::MVKSwapchain(MVKDevice* device,
	const VkSwapchainCreateInfoKHR* pCreateInfo) : MVKVulkanAPIDeviceObject(device), _surfaceLost(false) {
	_currentAcquisitionID = 0;
	_layerObserver = nil;

	// If applicable, release any surfaces (not currently being displayed) from the old swapchain.
	MVKSwapchain* oldSwapchain = (MVKSwapchain*)pCreateInfo->oldSwapchain;
	if (oldSwapchain) { oldSwapchain->releaseUndisplayedSurfaces(); }

	uint32_t imgCnt = mvkClamp(pCreateInfo->minImageCount,
	_device->_pMetalFeatures->minSwapchainImageCount,
	_device->_pMetalFeatures->maxSwapchainImageCount);
	initCAMetalLayer(pCreateInfo, imgCnt);
	initSurfaceImages(pCreateInfo, imgCnt); // After initCAMetalLayer()
	initFrameIntervalTracking();

	_licenseWatermark = NULL;
	}

	// Initializes the CAMetalLayer underlying the surface of this swapchain.
	void MVKSwapchain::initCAMetalLayer(const VkSwapchainCreateInfoKHR* pCreateInfo, uint32_t imgCnt) {

	MVKSurface* mvkSrfc = (MVKSurface*)pCreateInfo->surface;
	if ( !mvkSrfc->getCAMetalLayer() ) {
	setConfigurationResult(mvkSrfc->getConfigurationResult());
	_surfaceLost = true;
	return;
	}

	_mtlLayer = mvkSrfc->getCAMetalLayer();
	_mtlLayer.device = getMTLDevice();
	_mtlLayer.pixelFormat = getPixelFormats()->getMTLPixelFormatFromVkFormat(pCreateInfo->imageFormat);
	_mtlLayer.maximumDrawableCountMVK = imgCnt;
	_mtlLayer.displaySyncEnabledMVK = (pCreateInfo->presentMode != VK_PRESENT_MODE_IMMEDIATE_KHR);
	_mtlLayer.magnificationFilter = _device->_pMVKConfig->swapchainMagFilterUseNearest ? kCAFilterNearest : kCAFilterLinear;
	_mtlLayer.framebufferOnly = !mvkIsAnyFlagEnabled(pCreateInfo->imageUsage, (VK_IMAGE_USAGE_TRANSFER_SRC_BIT \|
	VK_IMAGE_USAGE_TRANSFER_DST_BIT \|
	VK_IMAGE_USAGE_SAMPLED_BIT \|
	VK_IMAGE_USAGE_STORAGE_BIT));
	if (pCreateInfo->compositeAlpha != VK_COMPOSITE_ALPHA_INHERIT_BIT_KHR) {
	_mtlLayer.opaque = pCreateInfo->compositeAlpha == VK_COMPOSITE_ALPHA_OPAQUE_BIT_KHR;
	}

	switch (pCreateInfo->imageColorSpace) {
	case VK_COLOR_SPACE_SRGB_NONLINEAR_KHR:
	_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceSRGB);
	break;
	case VK_COLOR_SPACE_DISPLAY_P3_NONLINEAR_EXT:
	_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceDisplayP3);
	_mtlLayer.wantsExtendedDynamicRangeContentMVK = YES;
	break;
	case VK_COLOR_SPACE_EXTENDED_SRGB_LINEAR_EXT:
	_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceExtendedLinearSRGB);
	_mtlLayer.wantsExtendedDynamicRangeContentMVK = YES;
	break;
	case VK_COLOR_SPACE_EXTENDED_SRGB_NONLINEAR_EXT:
	_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceExtendedSRGB);
	_mtlLayer.wantsExtendedDynamicRangeContentMVK = YES;
	break;
	case VK_COLOR_SPACE_DISPLAY_P3_LINEAR_EXT:
	_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceExtendedLinearDisplayP3);
	_mtlLayer.wantsExtendedDynamicRangeContentMVK = YES;
	break;
	case VK_COLOR_SPACE_DCI_P3_NONLINEAR_EXT:
	_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceDCIP3);
	_mtlLayer.wantsExtendedDynamicRangeContentMVK = YES;
	break;
	case VK_COLOR_SPACE_BT709_NONLINEAR_EXT:
	_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceITUR_709);
	break;
	case VK_COLOR_SPACE_BT2020_LINEAR_EXT:
	_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceExtendedLinearITUR_2020);
	_mtlLayer.wantsExtendedDynamicRangeContentMVK = YES;
	break;
	case VK_COLOR_SPACE_HDR10_ST2084_EXT:
	_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceITUR_2020_PQ_EOTF);
	_mtlLayer.wantsExtendedDynamicRangeContentMVK = YES;
	break;
	case VK_COLOR_SPACE_HDR10_HLG_EXT:
	_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceITUR_2020_HLG);
	_mtlLayer.wantsExtendedDynamicRangeContentMVK = YES;
	break;
	case VK_COLOR_SPACE_ADOBERGB_NONLINEAR_EXT:
	_mtlLayer.colorspace = CGColorSpaceCreateWithName(kCGColorSpaceAdobeRGB1998);
	break;
	case VK_COLOR_SPACE_PASS_THROUGH_EXT:
	default:
	// Nothing - the default is not to do color matching.
	break;
	}
	_mtlLayerOrigDrawSize = _mtlLayer.updatedDrawableSizeMVK;

	// TODO: set additional CAMetalLayer properties before extracting drawables:
	// - presentsWithTransaction
	// - drawsAsynchronously

	if ( [_mtlLayer.delegate isKindOfClass: [PLATFORM_VIEW_CLASS class]] ) {
	// Sometimes, the owning view can replace its CAMetalLayer. In that case, the client
	// needs to recreate the swapchain, or no content will be displayed.
	_layerObserver = [MVKBlockObserver observerWithBlock: ^(NSString* path, id, NSDictionary, void) {
	if ( ![path isEqualToString: @"layer"] ) { return; }
	this->_surfaceLost = true;
	[this->_layerObserver release];
	this->_layerObserver = nil;
	} forObject: _mtlLayer.delegate atKeyPath: @"layer"];
	}
	}

	// Initializes the array of images used for the surface of this swapchain.
	// The CAMetalLayer should already be initialized when this is called.
	void MVKSwapchain::initSurfaceImages(const VkSwapchainCreateInfoKHR* pCreateInfo, uint32_t imgCnt) {

	if ( getIsSurfaceLost() ) {
	return;
	}

	VkExtent2D imgExtent = mvkVkExtent2DFromCGSize(_mtlLayerOrigDrawSize);

	VkImageCreateInfo imgInfo = {
	.sType = VK_STRUCTURE_TYPE_IMAGE_CREATE_INFO,
	.pNext = VK_NULL_HANDLE,
	.imageType = VK_IMAGE_TYPE_2D,
	.format = getPixelFormats()->getVkFormatFromMTLPixelFormat(_mtlLayer.pixelFormat),
	.extent = { imgExtent.width, imgExtent.height, 1 },
	.mipLevels = 1,
	.arrayLayers = 1,
	.samples = VK_SAMPLE_COUNT_1_BIT,
	.tiling = VK_IMAGE_TILING_OPTIMAL,
	.usage = pCreateInfo->imageUsage,
	.flags = 0,
	};

	if (mvkAreAllFlagsEnabled(pCreateInfo->flags, VK_SWAPCHAIN_CREATE_MUTABLE_FORMAT_BIT_KHR)) {
	mvkEnableFlags(imgInfo.flags, VK_IMAGE_CREATE_MUTABLE_FORMAT_BIT \| VK_IMAGE_CREATE_EXTENDED_USAGE_BIT);
	}
	if (mvkAreAllFlagsEnabled(pCreateInfo->flags, VK_SWAPCHAIN_CREATE_SPLIT_INSTANCE_BIND_REGIONS_BIT_KHR)) {
	// We don't really support this, but set the flag anyway.
	mvkEnableFlags(imgInfo.flags, VK_IMAGE_CREATE_SPLIT_INSTANCE_BIND_REGIONS_BIT);
	}

	for (uint32_t imgIdx = 0; imgIdx < imgCnt; imgIdx++) {
	_presentableImages.push_back(_device->createPresentableSwapchainImage(&imgInfo, this, imgIdx, NULL));
	}

	MVKLogInfo("Created %d swapchain images with initial size (%d, %d).", imgCnt, imgExtent.width, imgExtent.height);
	}

	// Initialize frame interval tracking, including start time and filtering parameters.
	void MVKSwapchain::initFrameIntervalTracking() {
	_performanceStatistics.lastFrameInterval = 0;
	_performanceStatistics.averageFrameInterval = 0;
	_performanceStatistics.averageFramesPerSecond = 0;
	_currentPerfLogFrameCount = 0;

	_lastFrameTime = mvkGetTimestamp();

	// Establish the alpha parameter of a low-pass filter for averaging frame intervals.
	double RC_over_dt = 10.0;
	_averageFrameIntervalFilterAlpha = 1.0 / (1.0 + RC_over_dt);
	}

	MVKSwapchain::~MVKSwapchain() {
	for (auto& img : _presentableImages) { _device->destroyPresentableSwapchainImage(img, NULL); }

	if (_licenseWatermark) { _licenseWatermark->destroy(); }
	[this->_layerObserver release];
	}