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// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_SCHEDULER_MAIN_THREAD_USE_CASE_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_SCHEDULER_MAIN_THREAD_USE_CASE_H_
#include "third_party/blink/renderer/platform/platform_export.h"
#include "third_party/perfetto/include/perfetto/tracing/string_helpers.h"
namespace blink::scheduler {
// `UseCase` encapsulates several high-level states that are use to apply
// different scheduling policies, e.g. compositor task queue priority, RAIL
// mode, and task deferral.
enum class UseCase {
// No active use case detected.
kNone,
// A page is loading, first contentful paint has not been detected, and a
// user gesture has not yet been detected.
kEarlyLoading,
// A page is loading, first contentful paint has been detected, and a user
// gesture has not yet been detected.
kLoading,
// A gesture has recently started and we are about to run main thread touch
// listeners to find out the actual gesture type. To minimize touch latency,
// only input handling work should run in this state.
//
// Note: this `UseCase` only occurs when touchstart event handlers are on the
// critical path, i.e. they are non-passive.
kTouchstart,
// A continuous gesture (e.g., scroll, pinch) which is being driven by the
// compositor thread.
kCompositorGesture,
// A continuous gesture (e.g., scroll, pinch) which is being driven by the
// compositor thread but also observed by the main thread. An example is
// synchronized scrolling where a scroll listener on the main thread changes
// page layout based on the current scroll position.
kSynchronizedGesture,
// A continuous gesture (e.g., scroll) which is being handled by the main
// thread.
kMainThreadGesture,
// An unspecified touch gesture which is being handled by the main thread.
// Note that since we don't have a full view of the use case, we should be
// careful to prioritize all work equally.
//
// TODO(crbug.com/40589651): Try to remove this `UseCase`.
kMainThreadCustomInputHandling,
// A discrete input (e.g. keypress, click), was detected and we're waiting for
// the subsequent paint.
kDiscreteInputResponse,
kMaxValue = kDiscreteInputResponse
};
PLATFORM_EXPORT perfetto::StaticString UseCaseToString(UseCase);
} // namespace blink::scheduler
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_SCHEDULER_MAIN_THREAD_USE_CASE_H_
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