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// Copyright 2014-2023 The Khronos Group Inc.
//
// SPDX-License-Identifier: CC-BY-4.0
include::{generated}/meta/{refprefix}VK_KHR_win32_surface.adoc[]
=== Other Extension Metadata
*Last Modified Date*::
2017-04-24
*IP Status*::
No known IP claims.
*Contributors*::
- Patrick Doane, Blizzard
- Faith Ekstrand, Intel
- Ian Elliott, LunarG
- Courtney Goeltzenleuchter, LunarG
- Jesse Hall, Google
- James Jones, NVIDIA
- Antoine Labour, Google
- Jon Leech, Khronos
- David Mao, AMD
- Norbert Nopper, Freescale
- Alon Or-bach, Samsung
- Daniel Rakos, AMD
- Graham Sellers, AMD
- Ray Smith, ARM
- Jeff Vigil, Qualcomm
- Chia-I Wu, LunarG
=== Description
The `VK_KHR_win32_surface` extension is an instance extension.
It provides a mechanism to create a slink:VkSurfaceKHR object (defined by
the `apiext:VK_KHR_surface` extension) that refers to a Win32 code:HWND, as
well as a query to determine support for rendering to the windows desktop.
include::{generated}/interfaces/VK_KHR_win32_surface.adoc[]
=== Issues
1) Does Win32 need a way to query for compatibility between a particular
physical device and a specific screen? Compatibility between a physical
device and a window generally only depends on what screen the window is on.
However, there is not an obvious way to identify a screen without already
having a window on the screen.
*RESOLVED*: No.
While it may be useful, there is not a clear way to do this on Win32.
However, a method was added to query support for presenting to the windows
desktop as a whole.
2) If a native window object (code:HWND) is used by one graphics API, and
then is later used by a different graphics API (one of which is Vulkan), can
these uses interfere with each other?
*RESOLVED*: Yes.
Uses of a window object by multiple graphics APIs results in undefined:
behavior.
Such behavior may succeed when using one Vulkan implementation but fail when
using a different Vulkan implementation.
Potential failures include:
* Creating then destroying a flip presentation model DXGI swapchain on a
window object can prevent flink:vkCreateSwapchainKHR from succeeding on
the same window object.
* Creating then destroying a slink:VkSwapchainKHR on a window object can
prevent creation of a bitblt model DXGI swapchain on the same window
object.
* Creating then destroying a slink:VkSwapchainKHR on a window object can
effectively code:SetPixelFormat to a different format than the format
chosen by an OpenGL application.
* Creating then destroying a slink:VkSwapchainKHR on a window object on
one slink:VkPhysicalDevice can prevent flink:vkCreateSwapchainKHR from
succeeding on the same window object, but on a different
slink:VkPhysicalDevice that is associated with a different Vulkan ICD.
In all cases the problem can be worked around by creating a new window
object.
Technical details include:
* Creating a DXGI swapchain over a window object can alter the object for
the remainder of its lifetime.
The alteration persists even after the DXGI swapchain has been
destroyed.
This alteration can make it impossible for a conformant Vulkan
implementation to create a slink:VkSwapchainKHR over the same window
object.
Mention of this alteration can be found in the remarks section of the
MSDN documentation for code:DXGI_SWAP_EFFECT.
* Calling GDI's code:SetPixelFormat (needed by OpenGL's WGL layer) on a
window object alters the object for the remainder of its lifetime.
The MSDN documentation for code:SetPixelFormat explains that a window
object's pixel format can be set only one time.
* Creating a slink:VkSwapchainKHR over a window object can alter the
object for its remaining lifetime.
Either of the above alterations may occur as a side effect of
flink:vkCreateSwapchainKHR.
=== Version History
* Revision 1, 2015-09-23 (Jesse Hall)
** Initial draft, based on the previous contents of VK_EXT_KHR_swapchain
(later renamed VK_EXT_KHR_surface).
* Revision 2, 2015-10-02 (James Jones)
** Added presentation support query for win32 desktops.
* Revision 3, 2015-10-26 (Ian Elliott)
** Renamed from VK_EXT_KHR_win32_surface to VK_KHR_win32_surface.
* Revision 4, 2015-11-03 (Daniel Rakos)
** Added allocation callbacks to vkCreateWin32SurfaceKHR.
* Revision 5, 2015-11-28 (Daniel Rakos)
** Updated the surface create function to take a pCreateInfo structure.
* Revision 6, 2017-04-24 (Jeff Juliano)
** Add issue 2 addressing reuse of a native window object in a different
Graphics API, or by a different Vulkan ICD.
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