// Copyright 2014-2021 The Khronos Group, Inc.
//
// SPDX-License-Identifier: CC-BY-4.0

include::{generated}/meta/{refprefix}VK_KHR_surface.txt[]

=== Other Extension Metadata

*Last Modified Date*::
    2016-08-25
*IP Status*::
    No known IP claims.
*Contributors*::
  - Patrick Doane, Blizzard
  - Ian Elliott, LunarG
  - Jesse Hall, Google
  - 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

=== Description

The `VK_KHR_surface` extension is an instance extension.
It introduces slink:VkSurfaceKHR objects, which abstract native platform
surface or window objects for use with Vulkan.
It also provides a way to determine whether a queue family in a physical
device supports presenting to particular surface.

Separate extensions for each platform provide the mechanisms for creating
slink:VkSurfaceKHR objects, but once created they may be used in this and
other platform-independent extensions, in particular the
`<<VK_KHR_swapchain>>` extension.

include::{generated}/interfaces/VK_KHR_surface.txt[]

=== Examples

[NOTE]
.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).
====

=== Issues

1) Should this extension include a method to query whether a physical device
supports presenting to a specific window or native surface on a given
platform?

*RESOLVED*: Yes.
Without this, applications would need to create a device instance to
determine whether a particular window can be presented to.
Knowing that a device supports presentation to a platform in general is not
sufficient, as a single machine might support multiple seats, or instances
of the platform that each use different underlying physical devices.
Additionally, on some platforms, such as the X Window System, different
drivers and devices might be used for different windows depending on which
section of the desktop they exist on.

2) Should the flink:vkGetPhysicalDeviceSurfaceCapabilitiesKHR,
flink:vkGetPhysicalDeviceSurfaceFormatsKHR, and
flink:vkGetPhysicalDeviceSurfacePresentModesKHR functions be in this
extension and operate on physical devices, rather than being in
`<<VK_KHR_swapchain>>` (i.e. device extension) and being dependent on
slink:VkDevice?

*RESOLVED*: Yes.
While it might be useful to depend on sname:VkDevice (and therefore on
enabled extensions and features) for the queries, Vulkan was released only
with the slink:VkPhysicalDevice versions.
Many cases can be resolved by a Valid Usage statement, and/or by a separate
pname:pNext chain version of the query struct specific to a given extension
or parameters, via extensible versions of the queries:
flink:vkGetPhysicalDeviceSurfaceCapabilities2KHR,
flink:vkGetPhysicalDeviceSurfaceFormats2KHR.
and flink:vkGetPhysicalDeviceSurfacePresentModes2EXT,


3) Should Vulkan support Xlib or XCB as the API for accessing the X Window
System platform?

*RESOLVED*: Both.
XCB is a more modern and efficient API, but Xlib usage is deeply ingrained
in many applications and likely will remain in use for the foreseeable
future.
Not all drivers necessarily need to support both, but including both as
options in the core specification will probably encourage support, which
should in turn ease adoption of the Vulkan API in older codebases.
Additionally, the performance improvements possible with XCB likely will not
have a measurable impact on the performance of Vulkan presentation and other
minimal window system interactions defined here.

4) Should the GBM platform be included in the list of platform enums?

*RESOLVED*: Deferred, and will be addressed with a platform-specific
extension to be written in the future.

=== 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)
    - Created initial Description section.
    - Removed query for whether a platform requires the use of a queue for
      presentation, since it was decided that presentation will always be
      modeled as being part of the queue.
    - Fixed typos and other minor mistakes.

  * Revision 3, 2015-05-26 (Ian Elliott)
    - Improved the Description section.

  * Revision 4, 2015-05-27 (James Jones)
    - Fixed compilation errors in example code.

  * Revision 5, 2015-06-01 (James Jones)
    - Added issues 1 and 2 and made related spec updates.

  * Revision 6, 2015-06-01 (James Jones)
    - Merged the platform type mappings table previously removed from
      VK_KHR_swapchain with the platform description table in this spec.
    - Added issues 3 and 4 documenting choices made when building the
      initial list of native platforms supported.

  * Revision 7, 2015-06-11 (Ian Elliott)
    - Updated table 1 per input from the KHR TSG.
    - Updated issue 4 (GBM) per discussion with Daniel Stone.
      He will create a platform-specific extension sometime in the future.

  * Revision 8, 2015-06-17 (James Jones)
    - Updated enum-extending values using new convention.
    - Fixed the value of VK_SURFACE_PLATFORM_INFO_TYPE_SUPPORTED_KHR.

  * Revision 9, 2015-06-17 (James Jones)
    - Rebased on Vulkan API version 126.

  * Revision 10, 2015-06-18 (James Jones)
    - Marked issues 2 and 3 resolved.

  * Revision 11, 2015-06-23 (Ian Elliott)
    - Examples now show use of function pointers for extension functions.
    - Eliminated extraneous whitespace.

  * Revision 12, 2015-07-07 (Daniel Rakos)
    - Added error section describing when each error is expected to be
      reported.
    - Replaced the term "`queue node index`" with "`queue family index`" in
      the spec as that is the agreed term to be used in the latest version
      of the core header and spec.
    - Replaced bool32_t with VkBool32.

  * Revision 13, 2015-08-06 (Daniel Rakos)
    - Updated spec against latest core API header version.

  * Revision 14, 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.
    - Did miscellaneous cleanup, etc.

  * Revision 15, 2015-08-20 (Ian Elliott--porting a 2015-07-29 change from
    James Jones)
    - Moved the surface transform enums here from VK_WSI_swapchain so they
      could be reused by VK_WSI_display.

  * Revision 16, 2015-09-01 (James Jones)
    - Restore single-field revision number.

  * Revision 17, 2015-09-01 (James Jones)
    - Fix example code compilation errors.

  * Revision 18, 2015-09-26 (Jesse Hall)
    - Replaced VkSurfaceDescriptionKHR with the VkSurfaceKHR object, which
      is created via layered extensions.
      Added VkDestroySurfaceKHR.

  * Revision 19, 2015-09-28 (Jesse Hall)
    - Renamed from VK_EXT_KHR_swapchain to VK_EXT_KHR_surface.

  * Revision 20, 2015-09-30 (Jeff Vigil)
    - Add error result VK_ERROR_SURFACE_LOST_KHR.

  * Revision 21, 2015-10-15 (Daniel Rakos)
    - Updated the resolution of issue #2 and include the surface capability
      queries in this extension.
    - Renamed SurfaceProperties to SurfaceCapabilities as it better reflects
      that the values returned are the capabilities of the surface on a
      particular device.
    - Other minor cleanup and consistency changes.

  * Revision 22, 2015-10-26 (Ian Elliott)
    - Renamed from VK_EXT_KHR_surface to VK_KHR_surface.

  * Revision 23, 2015-11-03 (Daniel Rakos)
    - Added allocation callbacks to vkDestroySurfaceKHR.

  * Revision 24, 2015-11-10 (Jesse Hall)
    - Removed VkSurfaceTransformKHR.
      Use VkSurfaceTransformFlagBitsKHR instead.
    - Rename VkSurfaceCapabilitiesKHR member maxImageArraySize to
      maxImageArrayLayers.

  * Revision 25, 2016-01-14 (James Jones)
    - Moved VK_ERROR_NATIVE_WINDOW_IN_USE_KHR from the
      VK_KHR_android_surface to the VK_KHR_surface extension.

  * 2016-08-23 (Ian Elliott)
    - Update the example code, to not have so many characters per line, and
      to split out a new example to show how to obtain function pointers.

  * 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.
