Vulkan-Docs/doc/specs/vulkan/appendices/VK_KHR_display_swapchain.txt
Jon Leech 0cc6bba634 Change log for September 15, 2017 Vulkan 1.0.61 spec update:
* Bump API patch number and header version number to 61 for this update.

Github Issues:

  * Provide alternate length attributes (altlen=) in the XML schema, for
    those using length attributes to generate code instead of documentation
    (public issue 555).
  * Fix erroneous references to `latex:` being used for asciidoc math
    markup, rather than `latexmath:` (public pull request 556).
  * Add author ID to XML for Kazan software renderer (public pull request
    557).

Internal Issues:

  * Add the <<fundamentals-abi,Application Binary Interface>> section
    describing platform ABI requirements and recommendations, add examples
    of function and function pointer declarations to the
    <<boilerplate-platform-specific-calling-conventions, Platform-Specific
    Calling Conventions>> section, and remove related language that existed
    elsewhere in the specification (internal issue 64).
  * Describe where to document valid usage interactions of chained
    structures in the style guide, and fix one case now appearing in
    slink:VkBufferCreateInfo instead of the child
    slink:VkDedicatedAllocationBufferCreateInfoNV structure (internal issue
    715).
  * Add example to the style guide of describing enumerated types which are
    empty when the spec is built without relevant extensions enabled, and
    apply it to existing examples for
    elink:VkDescriptorSetLayoutCreateFlagBits and
    elink:VkSubpassDescriptionFlagBits (internal issue 864).
  * Add a note to the <<fundamentals-validusage-enums, Valid Usage for
    Enumerated Types>> section that the special values suffixed with
    etext:_BEGIN_RANGE, etext:_END_RANGE, etext:_RANGE_SIZE and
    etext:_MAX_ENUM are not part of the API and should: not be used by
    applications (internal issue 872).
  * Added note to flink:vkCmdUpdateBuffers explaining the performance
    penalty for copies done in this way, and why the upper copy limit is
    what it is (internal issue 952).
  * Update `VK_KHX_device_group` to split some functionality into the new
    `VK_KHR_bind_memory2` extension, and rename that functionality (internal
    issue 969).
  * Remove *Status* fields from extension appendices, since they are by
    definition published and complete by the time they reach the public
    github repository (internal issue 973).

Other Issues:

  * Update Data Format specification dependency to version 1.2 and change
    references to DF sections accordingly.
  * Update XML to make the pname:pAllocator parameter of
    flink:vkRegisterDeviceEventEXT and flink:vkRegisterDisplayEventEXT in
    the `VK_EXT_display_control` extension as optional.

New Extensions:

  * `VK_KHR_bind_memory2`
  * `VK_KHR_image_format_list`
  * `VK_KHR_maintenance2`
  * `VK_KHR_sampler_ycbcr_conversion`
2017-09-14 22:41:33 -07:00

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