e2d37c2a07
Also removes a reference to GrBackendTextureDesc in a comment and updates markdown docs. Docs-Preview: https://skia.org/?cl=24861 Bug: skia: Change-Id: Ic6490d5ef46953450e6dee69271397bb2b94d0d6 Reviewed-on: https://skia-review.googlesource.com/24861 Commit-Queue: Brian Salomon <bsalomon@google.com> Reviewed-by: Robert Phillips <robertphillips@google.com>
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Vulkan
Skis has a Vulkan implementation of its GPU backend. The Vulkan backend can be built alongside the OpenGL backend. The client can select between the OpenGL and Vulkan implementation at runtime. The Vulkan backend has reached feature parity with the OpenGL backend. At this time we find that many Vulkan drivers have bugs that Skia triggers for which we have no workaround. We are reporting bugs to vendors as we find them.
Windows and Linux
To build the Vulkan backend, set skia_vulkan_sdk to the path to your Vulkan SDK in args.gn.
This defaults to the environment variable VULKAN_SDK.
Android
The Vulkan backend can run on any device with Vulkan drivers, including all Android N+ devices.
To build the Vulkan backend, set ndk_api = 24 in args.gn to target Android N.
Using the Vulkan Backend
To create a GrContext that is backed by Vulkan the client creates a Vulkan device and queue, initializes a GrVkBackendContext to describe the context, and then calls GrContext::Create:
sk_sp<GrVkBackendContext> vkContext = new GrVkBackendContext;
vkBackendContext.fInstance = vkInstance;
vkBackendContext.fPhysicalDevice = vkPhysDevice;
...
vkBackendContext.fInterface.reset(GrVkCreateInterface(instance, vkPhysDevice, extensionFlags);
...
sk_sp<GrContext> context = GrContext::Create(kVulkan_GrBackend, (GrBackendContext) vkBackendContext);
When using the Vulkan backend, GrVkImageInfo is used to construct GrBackendTexture and GrBackendRenderTarget objects that in turn are used to create SkSurface and SkImage objects that refer to VkImages created by the Skia client.
The GrBackendObject returned by SkImage::getTextureHandle(), SkSurface::getTextureHandle(), and SkSurface::getRenderTargetHandle() should be interpreted as a GrVkImageInfo*. This allows a client to get the backing VkImage of a SkImage or SkSurface.
GrVkImageInfo specifies a VkImage and associated state (tiling, layout, format, etc). After getting a GrVkImageInfo* via getTextureHandle() or getRenderTargetHandle(), the client should check the fImageLayout field to know what layout Skia left the VkImage in before using the VkImage. If the client changes the layout of the VkImage, GrVkImageInfo::updateImageLayout(VkImageLayout layout) should be called before resuming Skia rendering.
The client is responsible for any synchronization or barriers needed before Skia performs I/O on a VkImage imported into Skia via GrVkImageInfo. Skia will assume it can start issuing commands referencing the VkImage without the need for additional synchronization.