Add InputEvent and EventPacket types for batched input delivery

content/common/input/input_event.h

+// Copyright (c) 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_COMMON_INPUT_INPUT_EVENT_H_
+#define CONTENT_COMMON_INPUT_INPUT_EVENT_H_
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "content/common/content_export.h"
+
+namespace content {
+
+// An id'ed event that carries a specific input payload.
+class CONTENT_EXPORT InputEvent {
+ public:
+  // Input data carried by the InputEvent.
+  class Payload {
+   public:
+    enum Type {
+      IPC_MESSAGE,
+      WEB_INPUT_EVENT,
+    };
+    virtual ~Payload() {}
+    virtual Type GetType() const = 0;
+  };
+
+  // |id| should be non-zero and |payload| should be non-NULL.

[palmer, 2013/09/03 23:12:47]

But the implementation doesn't enforce this. If it really matters, you should
enforce it and have defined semantics for what happens if the caller doesn't
meet the interface requirements.

[jdduke (slow), 2013/09/04 17:53:24]

Well, it's enforced via DCHECK, though I suppose it's not really necessary as
the user could create an invalid event via the empty constructor (necessary for
serialization...)

[palmer, 2013/09/05 01:20:15]

Yeah, DCHECK is not really enforcement. But on a closer look, I think you can
get by here by referring to the |valid| function in the comment. Something like,
"A valid InputEvent has a non-zero |id| and a non-NULL |payload|."

(True enforcement happens at run-time in the browser process.)

[jdduke (slow), 2013/09/05 19:31:48]

Done.

+  static scoped_ptr<InputEvent> Create(int64 id, scoped_ptr<Payload> payload);
+
+  template <typename PayloadType>
+  static scoped_ptr<InputEvent> Create(int64 id,
+                                       scoped_ptr<PayloadType> payload) {
+    return Create(id, payload.template PassAs<Payload>());
+  }
+
+  InputEvent();
+  virtual ~InputEvent();
+
+  // Used for deserialization.
+  void Initialize(int64 id, scoped_ptr<Payload> payload);
+
+  int64 id() const { return id_; }
+  const Payload* payload() const { return payload_.get(); }
+  bool valid() const { return id() && payload(); }
+
+ protected:
+  InputEvent(int64 id, scoped_ptr<Payload> payload);
+
+ private:
+  int64 id_;
+  scoped_ptr<Payload> payload_;
+
+  DISALLOW_COPY_AND_ASSIGN(InputEvent);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_COMMON_INPUT_INPUT_EVENT_H_