chromium/third_party/blink/renderer/platform/widget/input/frame_widget_input_handler_impl.h

// Copyright 2017 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_WIDGET_INPUT_FRAME_WIDGET_INPUT_HANDLER_IMPL_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_WIDGET_INPUT_FRAME_WIDGET_INPUT_HANDLER_IMPL_H_

#include "third_party/blink/public/mojom/input/input_handler.mojom-blink.h"
#include "third_party/blink/public/mojom/input/stylus_writing_gesture.mojom-blink.h"
#include "third_party/blink/renderer/platform/platform_export.h"

namespace blink {
class MainThreadEventQueue;
class WidgetBase;

// This class provides an implementation of FrameWidgetInputHandler mojo
// interface. When a compositor thread is being used in the renderer the mojo
// channel is bound on the compositor thread. Method calls, and events received
// on the compositor thread are then placed in the MainThreadEventQueue for the
// associated WidgetBase. This is done as to ensure that input related
// messages and events that are handled on the compositor thread aren't
// executed before other input events that need to be processed on the
// main thread. ie. Since some messages flow to the compositor thread
// all input needs to flow there so the ordering of events is kept in sequence.
//
// eg. (B = Browser, CT = Compositor Thread, MT = Main Thread)
//   B sends MouseEvent
//   B sends Copy message
//   CT receives MouseEvent (CT might do something with the MouseEvent)
//   CT places MouseEvent in MainThreadEventQueue
//   CT receives Copy message (CT has no use for the Copy message)
//   CT places Copy message in MainThreadEventQueue
//   MT receives MouseEvent
//   MT receives Copy message
//
// When a compositor thread isn't used the mojo channel is just bound
// on the main thread and messages are handled right away.
class PLATFORM_EXPORT FrameWidgetInputHandlerImpl
    : public mojom::blink::FrameWidgetInputHandler { … };

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_WIDGET_INPUT_FRAME_WIDGET_INPUT_HANDLER_IMPL_H_