65 lines
2.5 KiB
Plaintext
65 lines
2.5 KiB
Plaintext
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// Copyright (c) 2017-2019 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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[[headless,headless]]
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=== Presenting to headless surfaces
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Vulkan rendering can be presented to a headless surface, where the
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presentation operation is a no-op producing no externally-visible result.
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[NOTE]
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.Note
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====
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Because there is no real presentation target, the headless presentation
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engine may be extended to impose an arbitrary or customisable set of
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restrictions and features.
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This makes it a useful portable test target for applications targeting a
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wide range of presentation engines where the actual target presentation
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engines might be scarce, unavailable or otherwise undesirable or
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inconvenient to use for general Vulkan application development.
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The usual surface query mechanisms must be used to determine the actual
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restrictions and features of the implementation.
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====
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[open,refpage='vkCreateHeadlessSurfaceEXT',desc='Create a headless slink:VkSurfaceKHR object',type='protos']
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--
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To create a headless sname:VkSurfaceKHR object, call:
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include::{generated}/api/protos/vkCreateHeadlessSurfaceEXT.txt[]
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* pname:instance is the instance to associate the surface with.
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* pname:pCreateInfo is a pointer to an instance of the
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slink:VkHeadlessSurfaceCreateInfoEXT structure containing parameters
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affecting the creation of the surface object.
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* pname:pAllocator is the allocator used for host memory allocated for the
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surface object when there is no more specific allocator available (see
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<<memory-allocation,Memory Allocation>>).
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* pname:pSurface points to a sname:VkSurfaceKHR handle in which the
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created surface object is returned.
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include::{generated}/validity/protos/vkCreateHeadlessSurfaceEXT.txt[]
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--
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[open,refpage='VkHeadlessSurfaceCreateInfoEXT',desc='Structure specifying parameters of a newly created headless surface object',type='structs']
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--
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The sname:VkHeadlessSurfaceCreateInfoEXT structure is defined as:
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include::{generated}/api/structs/VkHeadlessSurfaceCreateInfoEXT.txt[]
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* pname:sType is the type of this structure.
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* pname:pNext is `NULL` or a pointer to an extension-specific structure.
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* pname:flags is reserved for future use.
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include::{generated}/validity/structs/VkHeadlessSurfaceCreateInfoEXT.txt[]
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--
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For headless surfaces, pname:currentExtent is undefined [eq]#(0xFFFFFFFF,
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0xFFFFFFFF)#.
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Whatever the application sets a swapchain's pname:imageExtent to will be the
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size of the surface, after the first image is presented.
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