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62 lines
2.5 KiB
62 lines
2.5 KiB
7 months ago
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---
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title: "Vulkan"
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linkTitle: "Vulkan"
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---
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Skia has a Vulkan implementation of its GPU backend. The Vulkan backend can be
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built alongside the OpenGL backend. The client can select between the OpenGL
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and Vulkan implementation at runtime. The Vulkan backend has reached feature
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parity with the OpenGL backend. At this time we find that many Vulkan drivers
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have bugs that Skia triggers for which we have no workaround. We are reporting
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bugs to vendors as we find them.
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Windows and Linux
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-----------------
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To build the Vulkan backend, set `skia_use_vulkan=true` in `args.gn`.
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Android
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-------
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The Vulkan backend can run on any device with Vulkan drivers, including all Android N+ devices.
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To build the Vulkan backend, set `ndk_api = 24` in `args.gn` to target Android N.
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Using the Vulkan Backend
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------------------------
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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::MakeVulkan:
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<!--?prettify lang=c++?-->
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sk_sp<GrVkBackendContext> vkContext = new GrVkBackendContext;
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vkBackendContext.fInstance = vkInstance;
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vkBackendContext.fPhysicalDevice = vkPhysDevice;
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...
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vkBackendContext.fInterface.reset(GrVkCreateInterface(instance, vkPhysDevice, extensionFlags);
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...
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sk_sp<GrContext> context = GrContext::MakeVulkan(vkBackendContext);
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When using the Vulkan backend, GrVkImageInfo is used to construct GrBackendTexture
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and GrBackendRenderTarget objects that in turn are used to create SkSurface and SkImage
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objects that refer to VkImages created by the Skia client.
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The GrBackendObject returned by SkImage::getTextureHandle(),
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SkSurface::getTextureHandle(), and SkSurface::getRenderTargetHandle() should be
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interpreted as a GrVkImageInfo*. This allows a client to get the backing VkImage
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of a SkImage or SkSurface.
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GrVkImageInfo specifies a VkImage and associated state (tiling, layout, format, etc).
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After getting a GrVkImageInfo* via getTextureHandle() or
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getRenderTargetHandle(), the client should check the fImageLayout field to know
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what layout Skia left the VkImage in before using the VkImage. If the client
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changes the layout of the VkImage,
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GrVkImageInfo::updateImageLayout(VkImageLayout layout) should be called before
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resuming Skia rendering.
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The client is responsible for any synchronization or barriers needed before
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Skia performs I/O on a VkImage imported into Skia via GrVkImageInfo. Skia will
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assume it can start issuing commands referencing the VkImage without the need
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for additional synchronization.
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