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/*
* Copyright 2022 Google LLC
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef skgpu_graphite_DawnBackendContext_DEFINED
#define skgpu_graphite_DawnBackendContext_DEFINED
#include "include/core/SkTypes.h"
#include "webgpu/webgpu_cpp.h" // NO_G3_REWRITE
#include <memory>
namespace skgpu::graphite {
class Context;
struct ContextOptions;
/**
* WebGPU needs to allow the main thread loop to run to detect GPU progress. Dawn native has a
* function wgpu::Instance::ProcessEvents, not (currently) present in WebGPU, that can be used to
* detect GPU progress.
*
* When compiling using Emscripten/WASM the -s ASYNCIFY option can be used to yield. E.g.:
*
* EM_ASYNC_JS(void, asyncSleep, (), {
* await new Promise((resolve, _) = > {
* setTimeout(resolve, 0);
* })
* });
*
* WebGPUTickFunction(wgpu::Device&) { asyncSleep(); }
*
* If no DawnTickFunction is provided then the graphite::Context will be "non-yielding". This
* implies the following restrictions on the Context:
*
* 1) SyncToCpu::kYes is disallowed as a parameter to Context::submit.
* 2) The client must guarantee that GPU work has completed before destroying Context as Context
* cannot await the work completion in its destructor. Context reports whether it is awaiting
* GPU work completion via Context::hasUnfinishedGpuWork().
*
* Using a non-yielding Context makes it possible to build and run Graphite/Dawn on WebGPU without
* -s ASYNCIFY.
*/
using DawnTickFunction = void(const wgpu::Instance& device);
#if !defined(__EMSCRIPTEN__)
SK_API inline void DawnNativeProcessEventsFunction(const wgpu::Instance& instance) {
instance.ProcessEvents();
}
#endif
// The DawnBackendContext contains all of the base Dawn objects needed by the graphite Dawn
// backend. The client will create this object and pass it into the Context::MakeDawn factory call
// when setting up Skia.
struct SK_API DawnBackendContext {
wgpu::Instance fInstance;
wgpu::Device fDevice;
wgpu::Queue fQueue;
// See comment on DawnTickFunction.
DawnTickFunction* fTick =
#if defined(__EMSCRIPTEN__)
nullptr;
#else
DawnNativeProcessEventsFunction;
#endif
};
namespace ContextFactory {
SK_API std::unique_ptr<Context> MakeDawn(const DawnBackendContext&, const ContextOptions&);
} // namespace ContextFactory
} // namespace skgpu::graphite
#endif // skgpu_graphite_DawnBackendContext_DEFINED
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