WIP Add getCoalescedEvents API using vector of WebInputEvents

third_party/WebKit/public/platform/CoalescedWebInputEvent.h

+/*
+ * Copyright (C) 2009 Google Inc. All rights reserved.

[dtapuska, 2016/11/21 18:21:18]

wrong copy right use the simplified one for chromium.

+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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+ */
+
+#ifndef CoalescedWebInputEvent_h

[dglazkov, 2016/12/06 03:46:47]

Nit: WebCoalescedInputEvent <-- "Web" is the prefix, signifying this is part of
the Web* API.

+#define CoalescedWebInputEvent_h
+
+#include "WebInputEvent.h"
+
+#include <memory>
+
+namespace blink {
+
+// This class is representing a polymorphic WebInputEvent structure with its
+// coalesced events. The event could be any events defined in WebInputEvent.h.
+class CoalescedWebInputEvent {

[jbroman, 2016/11/22 15:27:37]

nit: I'd actually prefer the words in the other order (WebCoalescedInputEvent),
so that "Web" remains a prefix of classes in public/ (there are a couple
exceptions); not sure how public/OWNERS feel.

+ public:
+  struct WebInputEventDeleter {
+    WebInputEventDeleter();
+    void operator()(blink::WebInputEvent* web_event) const;

[jbroman, 2016/11/22 15:27:37]

Hmm. I thought WebInputEvent (and its derived classes) was specifically designed
to be trivially copyable/destructible, in which case this deleter doesn't
actually wind up doing anything interesting. Is that so, or not?

[Navid Zolghadr, 2016/11/22 15:38:04]

I believe their destructor is not virtual intentionally. So they default
destructor would not delete the child object property if the pointer is
referring to the parent class. So we had to implement a delete operator. This
very same logic also exists in ui/events/blink/web_input_event_traits.cc which
if we agree that I can move it here and use it outside of Blink I'm going to
remove.

[jbroman, 2016/11/22 16:02:39]

OK. Strictly speaking this is the most correct thing to do, though I think we
were already relying elsewhere on it being legal to destroy these objects
without calling their destructor. (I'm not familiar enough with how
WebInputEvent is used to be confident of that, though.)

+  };
+
+  using ScopedWebInputEvent =
+      std::unique_ptr<WebInputEvent, WebInputEventDeleter>;
+
+  CoalescedWebInputEvent(ScopedWebInputEvent);
+  CoalescedWebInputEvent(const WebInputEvent&);
+  CoalescedWebInputEvent(const WebInputEvent&,
+                         const std::vector<const WebInputEvent*>&);
+
+  WebInputEvent* eventPointer();

[dtapuska, 2016/11/21 18:21:18]

should we have a const ptr version as well? How often do we pass the raw
WebInputEvent ptr around. Isn't it mostly const?

+  const WebInputEvent& event() const;
+  void addCoalescedEvent(const blink::WebInputEvent&);
+  size_t coalescedEventSize();

[dtapuska, 2016/11/21 18:21:18]

const?

+  WebInputEvent* coalescedEvent(int index);
+  const std::vector<WebInputEvent*>& getCoalescedEventsPointers();

[dtapuska, 2016/11/21 18:21:18]

is this const function?

+
+ private:
+  ScopedWebInputEvent mEvent;

[dtapuska, 2016/11/21 18:21:18]

These are a weird format for member definition.

+  std::vector<ScopedWebInputEvent> mCoalescedEvents;

[jbroman, 2016/11/22 15:27:37]

Blink style: m_event, m_coalescedEvents

std::vector is still discouraged in public/. Prefer WebVector.

[Navid Zolghadr, 2016/11/22 15:38:04]

Alright. I didn't know about WebVector. So can I use WebVector all the way in
the Blink as well or should I convert it to Vector as soon as possible?
Going back to your other point if we were to carry over a vector around instead
of this new type I believe two things will changed (similar to patchset 1).
First is that the deletion logic doesn't need to be in Blink and can live were
they are right now in ui/events/blink/web_input_event_traits.cc. Also I need to
change all those parameters in all the function along the way to include
WebVector. Is that okay?

[jbroman, 2016/11/22 16:02:39]

WebVector is legal throughout Blink if you're dealing with an object coming from
the Blink API. WTF::Vector is preferred inside Blink's core generally.

+};
+
+typedef std::unique_ptr<CoalescedWebInputEvent> ScopedCoalescedWebInputEvent;
+
+}  // namespace blink
+
+#endif