1 2--- 3title: "Vulkan" 4linkTitle: "Vulkan" 5 6--- 7 8 9Skia has a Vulkan implementation of its GPU backend. The Vulkan backend can be 10built alongside the OpenGL backend. The client can select between the OpenGL 11and Vulkan implementation at runtime. The Vulkan backend has reached feature 12parity with the OpenGL backend. At this time we find that many Vulkan drivers 13have bugs that Skia triggers for which we have no workaround. We are reporting 14bugs to vendors as we find them. 15 16Windows and Linux 17----------------- 18To build the Vulkan backend, set `skia_use_vulkan=true` in `args.gn`. 19 20Android 21------- 22The Vulkan backend can run on any device with Vulkan drivers, including all Android N+ devices. 23To build the Vulkan backend, set `ndk_api = 24` in `args.gn` to target Android N. 24 25Using the Vulkan Backend 26------------------------ 27 28To 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: 29 30<!--?prettify lang=c++?--> 31 sk_sp<GrVkBackendContext> vkContext = new GrVkBackendContext; 32 vkBackendContext.fInstance = vkInstance; 33 vkBackendContext.fPhysicalDevice = vkPhysDevice; 34 ... 35 vkBackendContext.fInterface.reset(GrVkCreateInterface(instance, vkPhysDevice, extensionFlags); 36 ... 37 38 sk_sp<GrContext> context = GrContext::MakeVulkan(vkBackendContext); 39 40When using the Vulkan backend, GrVkImageInfo is used to construct GrBackendTexture 41and GrBackendRenderTarget objects that in turn are used to create SkSurface and SkImage 42objects that refer to VkImages created by the Skia client. 43 44The GrBackendObject returned by SkImage::getTextureHandle(), 45SkSurface::getTextureHandle(), and SkSurface::getRenderTargetHandle() should be 46interpreted as a GrVkImageInfo*. This allows a client to get the backing VkImage 47of a SkImage or SkSurface. 48 49GrVkImageInfo specifies a VkImage and associated state (tiling, layout, format, etc). 50After getting a GrVkImageInfo* via getTextureHandle() or 51getRenderTargetHandle(), the client should check the fImageLayout field to know 52what layout Skia left the VkImage in before using the VkImage. If the client 53changes the layout of the VkImage, 54GrVkImageInfo::updateImageLayout(VkImageLayout layout) should be called before 55resuming Skia rendering. 56 57The client is responsible for any synchronization or barriers needed before 58Skia performs I/O on a VkImage imported into Skia via GrVkImageInfo. Skia will 59assume it can start issuing commands referencing the VkImage without the need 60for additional synchronization. 61 62