Refactor compositor event handling path to be callback-based

content/renderer/input/input_handler_manager.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_RENDERER_INPUT_INPUT_HANDLER_MANAGER_H_
 #define CONTENT_RENDERER_INPUT_INPUT_HANDLER_MANAGER_H_
 
 #include "base/containers/scoped_ptr_hash_map.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "content/common/content_export.h"
 #include "content/common/input/input_event_ack_state.h"
 #include "content/renderer/render_view_impl.h"
+#include "ui/events/blink/input_handler_proxy.h"
 
 namespace base {
 class SingleThreadTaskRunner;
 }
 
 namespace cc {
 class InputHandler;
 struct InputHandlerScrollResult;
 }
 
@@ skipping 48 matching lines @@
       const cc::InputHandlerScrollResult& scroll_result);
 
   void NotifyInputEventHandledOnMainThread(int routing_id,
                                            blink::WebInputEvent::Type,
                                            InputEventAckState);
   void ProcessRafAlignedInputOnMainThread(int routing_id);
 
   // Callback only from the compositor's thread.
   void RemoveInputHandler(int routing_id);
 
+  using InputEventAckStateCallback =
+      base::Callback<void(InputEventAckState,
+                          ui::ScopedWebInputEvent,
+                          const ui::LatencyInfo&,
+                          std::unique_ptr<ui::DidOverscrollParams>)>;
   // Called from the compositor's thread.
-  virtual InputEventAckState HandleInputEvent(
-      int routing_id,
-      const blink::WebInputEvent* input_event,
-      ui::LatencyInfo* latency_info);
+  virtual void HandleInputEvent(int routing_id,
+                                ui::ScopedWebInputEvent input_event,
+                                const ui::LatencyInfo& latency_info,
+                                const InputEventAckStateCallback& callback);
 
   // Called from the compositor's thread.
   void DidOverscroll(int routing_id, const ui::DidOverscrollParams& params);

[chongz, 2016/08/30 17:58:03]

I cannot fully merge |DidOverscroll| and |DidHandleInputEvent| into a single
callback as other overscroll sources require the client interface.

A compromise solution is to rename |DidHandleInputEvent| =>
|DidHandleInputEventAndOverscroll|, such that:
  1. All InputEvent triggered overscroll will go into
|DidHandleInputEventAndOverscroll|
  2. Other sources of overscroll with go into |DidOverscroll|

Please see CL description for more detailed event path.

 
   // Called from the compositor's thread.
   void DidStartFlinging(int routing_id);
   void DidStopFlinging(int routing_id);
 
   // Called from the compositor's thread.
   void DidAnimateForInput();
 
   // Called from the compositor's thread.
   void NeedsMainFrame(int routing_id);
@@ skipping 13 matching lines @@
   void ObserveWheelEventAndResultOnCompositorThread(
       int routing_id,
       const blink::WebMouseWheelEvent& wheel_event,
       const cc::InputHandlerScrollResult& scroll_result);
 
   void ObserveGestureEventAndResultOnCompositorThread(
       int routing_id,
       const blink::WebGestureEvent& gesture_event,
       const cc::InputHandlerScrollResult& scroll_result);
 
+  using EventDisposition = ui::InputHandlerProxy::EventDisposition;
+  void DidHandleInputEventAndOverscroll(
+      const InputEventAckStateCallback& callback,
+      EventDisposition event_disposition,
+      ui::ScopedWebInputEvent input_event,
+      const ui::LatencyInfo& latency_info,
+      std::unique_ptr<ui::DidOverscrollParams> overscroll_params);
+
   typedef base::ScopedPtrHashMap<int,  // routing_id
                                  std::unique_ptr<InputHandlerWrapper>>
       InputHandlerMap;
   InputHandlerMap input_handlers_;
 
   const scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
   InputHandlerManagerClient* const client_;
   // May be null.
   SynchronousInputHandlerProxyClient* const synchronous_handler_proxy_client_;
   blink::scheduler::RendererScheduler* const renderer_scheduler_;  // Not owned.
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_INPUT_INPUT_HANDLER_MANAGER_H_