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## Extension and Version Dependencies

• Requires Vulkan 1.0

• Requires VK_KHR_surface

## Contact

2017-10-06

IP Status

No known IP claims.

Interactions and External Dependencies
• Interacts with Vulkan 1.1

Contributors
• Patrick Doane, Blizzard

• Ian Elliott, LunarG

• Mathias Heyer, NVIDIA

• James Jones, NVIDIA

• David Mao, AMD

• Norbert Nopper, Freescale

• Alon Or-bach, Samsung

• Daniel Rakos, AMD

• Graham Sellers, AMD

• Jeff Vigil, Qualcomm

• Chia-I Wu, LunarG

• Jason Ekstrand, Intel

• Matthaeus G. Chajdas, AMD

• Ray Smith, ARM

## Description

The VK_KHR_swapchain extension is the device-level companion to the VK_KHR_surface extension. It introduces VkSwapchainKHR objects, which provide the ability to present rendering results to a surface.

## New Structures

If Version 1.1 is supported:

## New Enums

If Version 1.1 is supported:

## New Enum Constants

• VK_KHR_SWAPCHAIN_EXTENSION_NAME

• VK_KHR_SWAPCHAIN_SPEC_VERSION

• Extending VkImageLayout:

• VK_IMAGE_LAYOUT_PRESENT_SRC_KHR

• Extending VkObjectType:

• VK_OBJECT_TYPE_SWAPCHAIN_KHR

• Extending VkResult:

• VK_ERROR_OUT_OF_DATE_KHR

• VK_SUBOPTIMAL_KHR

• Extending VkStructureType:

• VK_STRUCTURE_TYPE_PRESENT_INFO_KHR

• VK_STRUCTURE_TYPE_SWAPCHAIN_CREATE_INFO_KHR

If Version 1.1 is supported:

• Extending VkStructureType:

• VK_STRUCTURE_TYPE_ACQUIRE_NEXT_IMAGE_INFO_KHR

• VK_STRUCTURE_TYPE_BIND_IMAGE_MEMORY_SWAPCHAIN_INFO_KHR

• VK_STRUCTURE_TYPE_DEVICE_GROUP_PRESENT_CAPABILITIES_KHR

• VK_STRUCTURE_TYPE_DEVICE_GROUP_PRESENT_INFO_KHR

• VK_STRUCTURE_TYPE_DEVICE_GROUP_SWAPCHAIN_CREATE_INFO_KHR

• VK_STRUCTURE_TYPE_IMAGE_SWAPCHAIN_CREATE_INFO_KHR

• Extending VkSwapchainCreateFlagBitsKHR:

• VK_SWAPCHAIN_CREATE_PROTECTED_BIT_KHR

• VK_SWAPCHAIN_CREATE_SPLIT_INSTANCE_BIND_REGIONS_BIT_KHR

## Issues

1) Does this extension allow the application to specify the memory backing of the presentable images?

RESOLVED: No. Unlike standard images, the implementation will allocate the memory backing of the presentable image.

2) What operations are allowed on presentable images?

RESOLVED: This is determined by the image usage flags specified when creating the presentable image’s swapchain.

3) Does this extension support MSAA presentable images?

RESOLVED: No. Presentable images are always single-sampled. Multi-sampled rendering must use regular images. To present the rendering results the application must manually resolve the multi- sampled image to a single-sampled presentable image prior to presentation.

4) Does this extension support stereo/multi-view presentable images?

RESOLVED: Yes. The number of views associated with a presentable image is determined by the imageArrayLayers specified when creating a swapchain. All presentable images in a given swapchain use the same array size.

5) Are the layers of stereo presentable images half-sized?

RESOLVED: No. The image extents always match those requested by the application.

6) Do the “present” and “acquire next image” commands operate on a queue? If not, do they need to include explicit semaphore objects to interlock them with queue operations?

RESOLVED: The present command operates on a queue. The image ownership operation it represents happens in order with other operations on the queue, so no explicit semaphore object is required to synchronize its actions.

Applications may want to acquire the next image in separate threads from those in which they manage their queue, or in multiple threads. To make such usage easier, the acquire next image command takes a semaphore to signal as a method of explicit synchronization. The application must later queue a wait for this semaphore before queuing execution of any commands using the image.

7) Does vkAcquireNextImageKHR block if no images are available?

RESOLVED: The command takes a timeout parameter. Special values for the timeout are 0, which makes the call a non-blocking operation, and UINT64_MAX, which blocks indefinitely. Values in between will block for up to the specified time. The call will return when an image becomes available or an error occurs. It may, but is not required to, return before the specified timeout expires if the swapchain becomes out of date.

8) Can multiple presents be queued using one vkQueuePresentKHR call?

RESOLVED: Yes. VkPresentInfoKHR contains a list of swapchains and corresponding image indices that will be presented. When supported, all presentations queued with a single vkQueuePresentKHR call will be applied atomically as one operation. The same swapchain must not appear in the list more than once. Later extensions may provide applications stronger guarantees of atomicity for such present operations, and/or allow them to query whether atomic presentation of a particular group of swapchains is possible.

9) How do the presentation and acquire next image functions notify the application the targeted surface has changed?

RESOLVED: Two new result codes are introduced for this purpose:

• VK_SUBOPTIMAL_KHR - Presentation will still succeed, subject to the window resize behavior, but the swapchain is no longer configured optimally for the surface it targets. Applications should query updated surface information and recreate their swapchain at the next convenient opportunity.

• VK_ERROR_OUT_OF_DATE_KHR - Failure. The swapchain is no longer compatible with the surface it targets. The application must query updated surface information and recreate the swapchain before presentation will succeed.

These can be returned by both vkAcquireNextImageKHR and vkQueuePresentKHR.

10) Does the vkAcquireNextImageKHR command return a semaphore to the application via an output parameter, or accept a semaphore to signal from the application as an object handle parameter?

RESOLVED: Accept a semaphore to signal as an object handle. This avoids the need to specify whether the application must destroy the semaphore or whether it is owned by the swapchain, and if the latter, what its lifetime is and whether it can be reused for other operations once it is received from vkAcquireNextImageKHR.

11) What types of swapchain queuing behavior should be exposed? Options include swap interval specification, mailbox/most recent vs. FIFO queue management, targeting specific vertical blank intervals or absolute times for a given present operation, and probably others. For some of these, whether they are specified at swapchain creation time or as per-present parameters needs to be decided as well.

RESOLVED: The base swapchain extension will expose 3 possible behaviors (of which, FIFO will always be supported):

• Immediate present: Does not wait for vertical blanking period to update the current image, likely resulting in visible tearing. No internal queue is used. Present requests are applied immediately.

• Mailbox queue: Waits for the next vertical blanking period to update the current image. No tearing should be observed. An internal single-entry queue is used to hold pending presentation requests. If the queue is full when a new presentation request is received, the new request replaces the existing entry, and any images associated with the prior entry become available for reuse by the application.

• FIFO queue: Waits for the next vertical blanking period to update the current image. No tearing should be observed. An internal queue containing numSwapchainImages - 1 entries is used to hold pending presentation requests. New requests are appended to the end of the queue, and one request is removed from the beginning of the queue and processed during each vertical blanking period in which the queue is non-empty

Not all surfaces will support all of these modes, so the modes supported will be returned using a surface information query. All surfaces must support the FIFO queue mode. Applications must choose one of these modes up front when creating a swapchain. Switching modes can be accomplished by recreating the swapchain.

12) Can VK_PRESENT_MODE_MAILBOX_KHR provide non-blocking guarantees for vkAcquireNextImageKHR? If so, what is the proper criteria?

RESOLVED: Yes. The difficulty is not immediately obvious here. Naively, if at least 3 images are requested, mailbox mode should always have an image available for the application if the application does not own any images when the call to vkAcquireNextImageKHR was made. However, some presentation engines may have more than one “current” image, and would still need to block in some cases. The right requirement appears to be that if the application allocates the surface’s minimum number of images + 1 then it is guaranteed non-blocking behavior when it does not currently own any images.

13) Is there a way to create and initialize a new swapchain for a surface that has generated a VK_SUBOPTIMAL_KHR return code while still using the old swapchain?

RESOLVED: Not as part of this specification. This could be useful to allow the application to create an “optimal” replacement swapchain and rebuild all its command buffers using it in a background thread at a low priority while continuing to use the “suboptimal” swapchain in the main thread. It could probably use the same “atomic replace” semantics proposed for recreating direct-to-device swapchains without incurring a mode switch. However, after discussion, it was determined some platforms probably could not support concurrent swapchains for the same surface though, so this will be left out of the base KHR extensions. A future extension could add this for platforms where it is supported.

14) Should there be a special value for VkSurfaceCapabilitiesKHR::maxImageCount to indicate there are no practical limits on the number of images in a swapchain?

RESOLVED: Yes. There will often be cases where there is no practical limit to the number of images in a swapchain other than the amount of available resources (i.e., memory) in the system. Trying to derive a hard limit from things like memory size is prone to failure. It is better in such cases to leave it to applications to figure such soft limits out via trial/failure iterations.

15) Should there be a special value for VkSurfaceCapabilitiesKHR::currentExtent to indicate the size of the platform surface is undefined?

RESOLVED: Yes. On some platforms (Wayland, for example), the surface size is defined by the images presented to it rather than the other way around.

16) Should there be a special value for VkSurfaceCapabilitiesKHR::maxImageExtent to indicate there is no practical limit on the surface size?

RESOLVED: No. It seems unlikely such a system would exist. 0 could be used to indicate the platform places no limits on the extents beyond those imposed by Vulkan for normal images, but this query could just as easily return those same limits, so a special “unlimited” value does not seem useful for this field.

17) How should surface rotation and mirroring be exposed to applications? How do they specify rotation and mirroring transforms applied prior to presentation?

RESOLVED: Applications can query both the supported and current transforms of a surface. Both are specified relative to the device’s “natural” display rotation and direction. The supported transforms indicate which orientations the presentation engine accepts images in. For example, a presentation engine that does not support transforming surfaces as part of presentation, and which is presenting to a surface that is displayed with a 90-degree rotation, would return only one supported transform bit: VK_SURFACE_TRANSFORM_ROTATE_90_BIT_KHR. Applications must transform their rendering by the transform they specify when creating the swapchain in preTransform field.

18) Can surfaces ever not support VK_MIRROR_NONE? Can they support vertical and horizontal mirroring simultaneously? Relatedly, should VK_MIRROR_NONE[_BIT] be zero, or bit one, and should applications be allowed to specify multiple pre and current mirror transform bits, or exactly one?

RESOLVED: Since some platforms may not support presenting with a transform other than the native window’s current transform, and prerotation/mirroring are specified relative to the device’s natural rotation and direction, rather than relative to the surface’s current rotation and direction, it is necessary to express lack of support for no mirroring. To allow this, the MIRROR_NONE enum must occupy a bit in the flags. Since MIRROR_NONE must be a bit in the bitmask rather than a bitmask with no values set, allowing more than one bit to be set in the bitmask would make it possible to describe undefined transforms such as VK_MIRROR_NONE_BIT | VK_MIRROR_HORIZONTAL_BIT, or a transform that includes both “no mirroring” and “horizontal mirroring” simultaneously. Therefore, it is desirable to allow specifying all supported mirroring transforms using only one bit. The question then becomes, should there be a VK_MIRROR_HORIZONTAL_AND_VERTICAL_BIT to represent a simultaneous horizontal and vertical mirror transform? However, such a transform is equivalent to a 180 degree rotation, so presentation engines and applications that wish to support or use such a transform can express it through rotation instead. Therefore, 3 exclusive bits are sufficient to express all needed mirroring transforms.

19) Should support for sRGB be required?

RESOLVED: In the advent of UHD and HDR display devices, proper color space information is vital to the display pipeline represented by the swapchain. The app can discover the supported format/color-space pairs and select a pair most suited to its rendering needs. Currently only the sRGB color space is supported, future extensions may provide support for more color spaces. See issues 23 and 24.

20) Is there a mechanism to modify or replace an existing swapchain with one targeting the same surface?

RESOLVED: Yes. This is described above in the text.

21) Should there be a way to set prerotation and mirroring using native APIs when presenting using a Vulkan swapchain?

RESOLVED: Yes. The transforms that can be expressed in this extension are a subset of those possible on native platforms. If a platform exposes a method to specify the transform of presented images for a given surface using native methods and exposes more transforms or other properties for surfaces than Vulkan supports, it might be impossible, difficult, or inconvenient to set some of those properties using Vulkan KHR extensions and some using the native interfaces. To avoid overwriting properties set using native commands when presenting using a Vulkan swapchain, the application can set the pretransform to “inherit”, in which case the current native properties will be used, or if none are available, a platform-specific default will be used. Platforms that do not specify a reasonable default or do not provide native mechanisms to specify such transforms should not include the inherit bits in the supportedTransforms bitmask they return in VkSurfaceCapabilitiesKHR.

22) Should the content of presentable images be clipped by objects obscuring their target surface?

RESOLVED: Applications can choose which behavior they prefer. Allowing the content to be clipped could enable more efficient presentation methods on some platforms, but some applications might rely on the content of presentable images to perform techniques such as partial updates or motion blurs.

23) What is the purpose of specifying a VkColorSpaceKHR along with VkFormat when creating a swapchain?

RESOLVED: While Vulkan itself is color space agnostic (e.g. even the meaning of R, G, B and A can be freely defined by the rendering application), the swapchain eventually will have to present the images on a display device with specific color reproduction characteristics. If any color space transformations are necessary before an image can be displayed, the color space of the presented image must be known to the swapchain. A swapchain will only support a restricted set of color format and -space pairs. This set can be discovered via vkGetPhysicalDeviceSurfaceFormatsKHR. As it can be expected that most display devices support the sRGB color space, at least one format/color-space pair has to be exposed, where the color space is VK_COLOR_SPACE_SRGB_NONLINEAR_KHR.

24) How are sRGB formats and the sRGB color space related?

RESOLVED: While Vulkan exposes a number of SRGB texture formats, using such formats does not guarantee working in a specific color space. It merely means that the hardware can directly support applying the non-linear transfer functions defined by the sRGB standard color space when reading from or writing to images of those formats. Still, it is unlikely that a swapchain will expose a *_SRGB format along with any color space other than VK_COLOR_SPACE_SRGB_NONLINEAR_KHR.

On the other hand, non-*_SRGB formats will be very likely exposed in pair with a SRGB color space. This means, the hardware will not apply any transfer function when reading from or writing to such images, yet they will still be presented on a device with sRGB display characteristics. In this case the application is responsible for applying the transfer function, for instance by using shader math.

25) How are the lifetimes of surfaces and swapchains targeting them related?

RESOLVED: A surface must outlive any swapchains targeting it. A VkSurfaceKHR owns the binding of the native window to the Vulkan driver.

26) How can the client control the way the alpha component of swapchain images is treated by the presentation engine during compositing?

RESOLVED: We should add new enum values to allow the client to negotiate with the presentation engine on how to treat image alpha values during the compositing process. Since not all platforms can practically control this through the Vulkan driver, a value of VK_COMPOSITE_ALPHA_INHERIT_BIT_KHR is provided like for surface transforms.

27) Is vkCreateSwapchainKHR the right function to return VK_ERROR_NATIVE_WINDOW_IN_USE_KHR, or should the various platform-specific VkSurfaceKHR factory functions catch this error earlier?

RESOLVED: For most platforms, the VkSurfaceKHR structure is a simple container holding the data that identifies a native window or other object representing a surface on a particular platform. For the surface factory functions to return this error, they would likely need to register a reference on the native objects with the native display server somehow, and ensure no other such references exist. Surfaces were not intended to be that heavyweight.

Swapchains are intended to be the objects that directly manipulate native windows and communicate with the native presentation mechanisms. Swapchains will already need to communicate with the native display server to negotiate allocation and/or presentation of presentable images for a native surface. Therefore, it makes more sense for swapchain creation to be the point at which native object exclusivity is enforced. Platforms may choose to enforce further restrictions on the number of VkSurfaceKHR objects that may be created for the same native window if such a requirement makes sense on a particular platform, but a global requirement is only sensible at the swapchain level.

## Examples

 Note The example code for the VK_KHR_surface and VK_KHR_swapchain extensions was removed from the appendix after revision 1.0.29. This WSI example code was ported to the cube demo that is shipped with the official Khronos SDK, and is being kept up-to-date in that location (see: https://github.com/KhronosGroup/Vulkan-Tools/blob/master/cube/cube.c).

## Version History

• Revision 1, 2015-05-20 (James Jones)

• Initial draft, based on LunarG KHR spec, other KHR specs, patches attached to bugs.

• Revision 2, 2015-05-22 (Ian Elliott)

• Made many agreed-upon changes from 2015-05-21 KHR TSG meeting. This includes using only a queue for presentation, and having an explicit function to acquire the next image.

• Fixed typos and other minor mistakes.

• Revision 3, 2015-05-26 (Ian Elliott)

• Improved the Description section.

• Added or resolved issues that were found in improving the Description. For example, pSurfaceDescription is used consistently, instead of sometimes using pSurface.

• Revision 4, 2015-05-27 (James Jones)

• Fixed some grammatical errors and typos

• Filled in the description of imageUseFlags when creating a swapchain.

• Added a description of swapInterval.

• Replaced the paragraph describing the order of operations on a queue for image ownership and presentation.

• Revision 5, 2015-05-27 (James Jones)

• Imported relevant issues from the (abandoned) vk_wsi_persistent_swapchain_images extension.

• Added issues 6 and 7, regarding behavior of the acquire next image and present commands with respect to queues.

• Updated spec language and examples to align with proposed resolutions to issues 6 and 7.

• Revision 6, 2015-05-27 (James Jones)

• Added issue 8, regarding atomic presentation of multiple swapchains

• Updated spec language and examples to align with proposed resolution to issue 8.

• Revision 7, 2015-05-27 (James Jones)

• Fixed compilation errors in example code, and made related spec fixes.

• Revision 8, 2015-05-27 (James Jones)

• Added issue 9, and the related VK_SUBOPTIMAL_KHR result code.

• Renamed VK_OUT_OF_DATE_KHR to VK_ERROR_OUT_OF_DATE_KHR.

• Revision 9, 2015-05-27 (James Jones)

• Added inline proposed resolutions (marked with [JRJ]) to some XXX questions/issues. These should be moved to the issues section in a subsequent update if the proposals are adopted.

• Revision 10, 2015-05-28 (James Jones)

• Converted vkAcquireNextImageKHR back to a non-queue operation that uses a VkSemaphore object for explicit synchronization.

• Added issue 10 to determine whether vkAcquireNextImageKHR generates or returns semaphores, or whether it operates on a semaphore provided by the application.

• Revision 11, 2015-05-28 (James Jones)

• Marked issues 6, 7, and 8 resolved.

• Renamed VkSurfaceCapabilityPropertiesKHR to VkSurfacePropertiesKHR to better convey the mutable nature of the information it contains.

• Revision 12, 2015-05-28 (James Jones)

• Added issue 11 with a proposed resolution, and the related issue 12.

• Updated various sections of the spec to match the proposed resolution to issue 11.

• Revision 13, 2015-06-01 (James Jones)

• Moved some structures to VK_EXT_KHR_swap_chain to resolve the specification’s issues 1 and 2.

• Revision 14, 2015-06-01 (James Jones)

• Added code for example 4 demonstrating how an application might make use of the two different present and acquire next image KHR result codes.

• Revision 15, 2015-06-01 (James Jones)

• Added issues 14 - 16 and related spec language.

• Fixed some spelling errors.

• Added language describing the meaningful return values for vkAcquireNextImageKHR and vkQueuePresentKHR.

• Revision 16, 2015-06-02 (James Jones)

• Added issues 17 and 18, as well as related spec language.

• Removed some erroneous text added by mistake in the last update.

• Revision 17, 2015-06-15 (Ian Elliott)

• Changed special value from “-1” to “0” so that the data types can be unsigned.

• Revision 18, 2015-06-15 (Ian Elliott)

• Clarified the values of VkSurfacePropertiesKHR::minImageCount and the timeout parameter of the vkAcquireNextImageKHR function.

• Revision 19, 2015-06-17 (James Jones)

• Misc. cleanup. Removed resolved inline issues and fixed typos.

• Fixed clarification of VkSurfacePropertiesKHR::minImageCount made in version 18.

• Added a brief “Image Ownership” definition to the list of terms used in the spec.

• Revision 20, 2015-06-17 (James Jones)

• Updated enum-extending values using new convention.

• Revision 21, 2015-06-17 (James Jones)

• Added language describing how to use VK_IMAGE_LAYOUT_PRESENT_SOURCE_KHR.

• Cleaned up an XXX comment regarding the description of which queues vkQueuePresentKHR can be used on.

• Revision 22, 2015-06-17 (James Jones)

• Rebased on Vulkan API version 126.

• Revision 23, 2015-06-18 (James Jones)

• Updated language for issue 12 to read as a proposed resolution.

• Marked issues 11, 12, 13, 16, and 17 resolved.

• Temporarily added links to the relevant bugs under the remaining unresolved issues.

• Added issues 19 and 20 as well as proposed resolutions.

• Revision 24, 2015-06-19 (Ian Elliott)

• Changed special value for VkSurfacePropertiesKHR::currentExtent back to “-1” from “0”. This value will never need to be unsigned, and “0” is actually a legal value.

• Revision 25, 2015-06-23 (Ian Elliott)

• Examples now show use of function pointers for extension functions.

• Eliminated extraneous whitespace.

• Revision 26, 2015-06-25 (Ian Elliott)

• Resolved Issues 9 & 10 per KHR TSG meeting.

• Revision 27, 2015-06-25 (James Jones)

• Added oldSwapchain member to VkSwapchainCreateInfoKHR.

• Revision 28, 2015-06-25 (James Jones)

• Added the “inherit” bits to the rotation and mirroring flags and the associated issue 21.

• Revision 29, 2015-06-25 (James Jones)

• Added the “clipped” flag to VkSwapchainCreateInfoKHR, and the associated issue 22.

• Specified that presenting an image does not modify it.

• Revision 30, 2015-06-25 (James Jones)

• Added language to the spec that clarifies the behavior of vkCreateSwapchainKHR() when the oldSwapchain field of VkSwapchainCreateInfoKHR is not NULL.

• Revision 31, 2015-06-26 (Ian Elliott)

• Example of new VkSwapchainCreateInfoKHR members, “oldSwapchain” and “clipped”.

• Example of using VkSurfacePropertiesKHR::{min|max}ImageCount to set VkSwapchainCreateInfoKHR::minImageCount.

• Rename vkGetSurfaceInfoKHR()'s 4th parameter to “pDataSize”, for consistency with other functions.

• Add macro with C-string name of extension (just to header file).

• Revision 32, 2015-06-26 (James Jones)

• Minor adjustments to the language describing the behavior of “oldSwapchain”

• Fixed the version date on my previous two updates.

• Revision 33, 2015-06-26 (Jesse Hall)

• Add usage flags to VkSwapchainCreateInfoKHR

• Revision 34, 2015-06-26 (Ian Elliott)

• Rename vkQueuePresentKHR()'s 2nd parameter to “pPresentInfo”, for consistency with other functions.

• Revision 35, 2015-06-26 (Jason Ekstrand)

• Merged the VkRotationFlagBitsKHR and VkMirrorFlagBitsKHR enums into a single VkSurfaceTransformFlagBitsKHR enum.

• Revision 36, 2015-06-26 (Jason Ekstrand)

• Added a VkSurfaceTransformKHR enum that is not a bitmask. Each value in VkSurfaceTransformKHR corresponds directly to one of the bits in VkSurfaceTransformFlagBitsKHR so transforming from one to the other is easy. Having a separate enum means that currentTransform and preTransform are now unambiguous by definition.

• Revision 37, 2015-06-29 (Ian Elliott)

• Corrected one of the signatures of vkAcquireNextImageKHR, which had the last two parameters switched from what it is elsewhere in the specification and header files.

• Revision 38, 2015-06-30 (Ian Elliott)

• Corrected a typo in description of the vkGetSwapchainInfoKHR() function.

• Corrected a typo in header file comment for VkPresentInfoKHR::sType.

• Revision 39, 2015-07-07 (Daniel Rakos)

• Added error section describing when each error is expected to be reported.

• Replaced bool32_t with VkBool32.

• Revision 40, 2015-07-10 (Ian Elliott)

• Updated to work with version 138 of the vulkan.h header. This includes declaring the VkSwapchainKHR type using the new VK_DEFINE_NONDISP_HANDLE macro, and no longer extending VkObjectType (which was eliminated).

• Revision 41 2015-07-09 (Mathias Heyer)

• Revision 42, 2015-07-10 (Daniel Rakos)

• Updated query mechanism to reflect the convention changes done in the core spec.

• Removed “queue” from the name of VK_STRUCTURE_TYPE_QUEUE_PRESENT_INFO_KHR to be consistent with the established naming convention.

• Removed reference to the no longer existing VkObjectType enum.

• Revision 43, 2015-07-17 (Daniel Rakos)

• Added support for concurrent sharing of swapchain images across queue families.

• Updated sample code based on recent changes

• Revision 44, 2015-07-27 (Ian Elliott)

• Noted that support for VK_PRESENT_MODE_FIFO_KHR is required. That is ICDs may optionally support IMMEDIATE and MAILBOX, but must support FIFO.

• Revision 45, 2015-08-07 (Ian Elliott)

• Corrected a typo in spec file (type and variable name had wrong case for the imageColorSpace member of the VkSwapchainCreateInfoKHR struct).

• Corrected a typo in header file (last parameter in PFN_vkGetSurfacePropertiesKHR was missing “KHR” at the end of type: VkSurfacePropertiesKHR).

• Revision 46, 2015-08-20 (Ian Elliott)

• Renamed this extension and all of its enumerations, types, functions, etc. This makes it compliant with the proposed standard for Vulkan extensions.

• Switched from “revision” to “version”, including use of the VK_MAKE_VERSION macro in the header file.

• Made improvements to several descriptions.

• Changed the status of several issues from PROPOSED to RESOLVED, leaving no unresolved issues.

• Resolved several TODOs, did miscellaneous cleanup, etc.

• Revision 47, 2015-08-20 (Ian Elliott—​porting a 2015-07-29 change from James Jones)

• Moved the surface transform enums to VK_WSI_swapchain so they could be reused by VK_WSI_display.

• Revision 48, 2015-09-01 (James Jones)

• Various minor cleanups.

• Revision 49, 2015-09-01 (James Jones)

• Restore single-field revision number.

• Revision 50, 2015-09-01 (James Jones)

• Update Example #4 to include code that illustrates how to use the oldSwapchain field.

• Revision 51, 2015-09-01 (James Jones)

• Fix example code compilation errors.

• Revision 52, 2015-09-08 (Matthaeus G. Chajdas)

• Corrected a typo.

• Revision 53, 2015-09-10 (Alon Or-bach)

• Removed underscore from SWAP_CHAIN left in VK_STRUCTURE_TYPE_SWAPCHAIN_CREATE_INFO_KHR.

• Revision 54, 2015-09-11 (Jesse Hall)

• Described the execution and memory coherence requirements for image transitions to and from VK_IMAGE_LAYOUT_PRESENT_SOURCE_KHR.

• Revision 55, 2015-09-11 (Ray Smith)

• Added errors for destroying and binding memory to presentable images

• Revision 56, 2015-09-18 (James Jones)

• Added fence argument to vkAcquireNextImageKHR

• Added example of how to meter a host thread based on presentation rate.

• Revision 57, 2015-09-26 (Jesse Hall)

• Replace VkSurfaceDescriptionKHR with VkSurfaceKHR.

• Added issue 25 with agreed resolution.

• Revision 58, 2015-09-28 (Jesse Hall)

• Renamed from VK_EXT_KHR_device_swapchain to VK_EXT_KHR_swapchain.

• Revision 59, 2015-09-29 (Ian Elliott)

• Changed vkDestroySwapchainKHR() to return void.

• Revision 60, 2015-10-01 (Jeff Vigil)

• Revision 61, 2015-10-05 (Jason Ekstrand)

• Added the VkCompositeAlpha enum and corresponding structure fields.

• Revision 62, 2015-10-12 (Daniel Rakos)

• Revision 63, 2015-10-15 (Daniel Rakos)

• Moved surface capability queries to VK_EXT_KHR_surface.

• Revision 64, 2015-10-26 (Ian Elliott)

• Renamed from VK_EXT_KHR_swapchain to VK_KHR_swapchain.

• Revision 65, 2015-10-28 (Ian Elliott)

• Added optional pResult member to VkPresentInfoKHR, so that per-swapchain results can be obtained from vkQueuePresentKHR().

• Revision 66, 2015-11-03 (Daniel Rakos)

• Added allocation callbacks to create and destroy functions.

• Updated resource transition language.

• Updated sample code.

• Revision 67, 2015-11-10 (Jesse Hall)

• Modify naming and member ordering to match API style conventions, and so the VkSwapchainCreateInfoKHR image property members mirror corresponding VkImageCreateInfo members but with an 'image' prefix.

• Make VkPresentInfoKHR::pResults non-const; it is an output array parameter.

• Make pPresentInfo parameter to vkQueuePresentKHR const.

• Revision 68, 2016-04-05 (Ian Elliott)

• Moved the “validity” include for vkAcquireNextImage to be in its proper place, after the prototype and list of parameters.

• Clarified language about presentable images, including how they are acquired, when applications can and cannot use them, etc. As part of this, removed language about “ownership” of presentable images, and replaced it with more-consistent language about presentable images being “acquired” by the application.

• 2016-08-23 (Ian Elliott)

• Update the example code, to use the final API command names, to not have so many characters per line, and to split out a new example to show how to obtain function pointers. This code is more similar to the LunarG “cube” demo program.

• 2016-08-25 (Ian Elliott)

• A note was added at the beginning of the example code, stating that it will be removed from future versions of the appendix.

• Revision 69, 2017-09-07 (Tobias Hector)

• Added interactions with Vulkan 1.1

• Revision 70, 2017-10-06 (Ian Elliott)

• Corrected interactions with Vulkan 1.1