144 lines
4.9 KiB
Plaintext
144 lines
4.9 KiB
Plaintext
// Copyright (c) 2014-2017 Khronos Group. This work is licensed under a
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// Creative Commons Attribution 4.0 International License; see
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// http://creativecommons.org/licenses/by/4.0/
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include::meta/VK_KHR_display_swapchain.txt[]
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*Last Modified Date*::
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2017-03-13
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*IP Status*::
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No known IP claims.
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*Contributors*::
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- James Jones, NVIDIA
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- Jeff Vigil, Qualcomm
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- Jesse Hall, Google
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This extension provides an API to create a swapchain directly on a device's
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display without any underlying window system.
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=== New Object Types
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None
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=== New Enum Constants
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* Extending elink:VkStructureType:
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** ename:VK_STRUCTURE_TYPE_DISPLAY_PRESENT_INFO_KHR
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* Extending elink:VkResult:
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** ename:VK_ERROR_INCOMPATIBLE_DISPLAY_KHR
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=== New Enums
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None
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=== New Structures
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* slink:VkDisplayPresentInfoKHR
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=== New Functions
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* flink:vkCreateSharedSwapchainsKHR
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=== Issues
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1) Should swapchains sharing images each hold a reference to the images, or
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should it be up to the application to destroy the swapchains and images in
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an order that avoids the need for reference counting?
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*RESOLVED*: Take a reference.
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The lifetime of presentable images is already complex enough.
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2) Should the pname:srcRect/pname:dstRect parameters be specified as part of
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the present command, or at swapchain creation time?
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*RESOLVED*: As part of the presentation command.
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This allows moving and scaling the image on the screen without the need to
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respecify the mode or create a new swapchain and presentable images.
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3) Should pname:srcRect/pname:dstRect be specified as rects, or separate
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offset/extent values?
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*RESOLVED*: As rects.
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Specifying them separately might make it easier for hardware to expose
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support for one but not the other, but in such cases applications must just
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take care to obey the reported capabilities and not use non-zero offsets or
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extents that require scaling, as appropriate.
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4) How can applications create multiple swapchains that use the same images?
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*RESOLVED*: By calling flink:vkCreateSharedSwapchainsKHR.
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An earlier resolution used flink:vkCreateSwapchainKHR, chaining multiple
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slink:VkSwapchainCreateInfoKHR structures through pname:pNext.
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In order to allow each swapchain to also allow other extension structs, a
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level of indirection was used: slink:VkSwapchainCreateInfoKHR::pname:pNext
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pointed to a different structure, which had both an pname:sType/pname:pNext
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for additional extensions, and also had a pointer to the next
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slink:VkSwapchainCreateInfoKHR structure.
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The number of swapchains to be created could only be found by walking this
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linked list of alternating structures, and the pname:pSwapchains out
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parameter was reinterpreted to be an array of slink:VkSwapchainKHR handles.
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Another option considered was a method to specify a "`shared`" swapchain
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when creating a new swapchain, such that groups of swapchains using the same
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images could be built up one at a time.
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This was deemed unusable because drivers need to know all of the displays an
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image will be used on when determining which internal formats and layouts to
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use for that image.
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=== Examples
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[NOTE]
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.Note
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====
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The example code for the +VK_KHR_display+ and +VK_KHR_display_swapchain+
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extensions was removed from the appendix after revision 1.0.43.
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The display swapchain creation example code was ported to the cube demo that
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is shipped with the official Khronos SDK, and is being kept up-to-date in
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that location (see:
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https://github.com/KhronosGroup/Vulkan-LoaderAndValidationLayers/blob/master/demos/cube.c).
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====
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=== Version History
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* Revision 1, 2015-07-29 (James Jones)
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- Initial draft
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* Revision 2, 2015-08-21 (Ian Elliott)
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- Renamed this extension and all of its enumerations, types, functions,
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etc.
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This makes it compliant with the proposed standard for Vulkan
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extensions.
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- Switched from "revision" to "version", including use of the
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VK_MAKE_VERSION macro in the header file.
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* Revision 3, 2015-09-01 (James Jones)
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- Restore single-field revision number.
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* Revision 4, 2015-09-08 (James Jones)
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- Allow creating multiple swap chains that share the same images using a
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single call to vkCreateSwapChainKHR().
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* Revision 5, 2015-09-10 (Alon Or-bach)
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- Removed underscores from SWAP_CHAIN in two enums.
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* Revision 6, 2015-10-02 (James Jones)
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- Added support for smart panels/buffered displays.
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* Revision 7, 2015-10-26 (Ian Elliott)
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- Renamed from VK_EXT_KHR_display_swapchain to VK_KHR_display_swapchain.
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* Revision 8, 2015-11-03 (Daniel Rakos)
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- Updated sample code based on the changes to VK_KHR_swapchain.
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* Revision 9, 2015-11-10 (Jesse Hall)
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- Replaced VkDisplaySwapchainCreateInfoKHR with
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vkCreateSharedSwapchainsKHR, changing resolution of issue #4.
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* Revision 10, 2017-03-13 (James Jones)
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- Closed all remaining issues.
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The specification and implementations have been shipping with the
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proposed resolutions for some time now.
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- Removed the sample code and noted it has been integrated into the
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official Vulkan SDK cube demo.
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