[Android] Perform eager gesture recognition on MotionEvents

content/browser/renderer_host/input/gesture_event_packet.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_BROWSER_RENDERER_HOST_INPUT_GESTURE_EVENT_PACKET_H_
+#define CONTENT_BROWSER_RENDERER_HOST_INPUT_GESTURE_EVENT_PACKET_H_
+
+#include "content/common/content_export.h"
+#include "third_party/WebKit/public/web/WebInputEvent.h"
+
+namespace content {
+
+// Acts as a transport container for gestures created by a particular event, be
+// that synthetic or otherwise.
+class CONTENT_EXPORT GestureEventPacket {
+ public:
+  enum GestureSource {
+    TOUCH_BEGIN,   // The start of a new gesture sequence.
+    TOUCH,         // Continuation of an existing gesture sequence.
+    TOUCH_TIMEOUT, // Timeout from an existing gesture sequence.
+    SYNTHETIC,     // Non-touch-derived gesture sequence.
+    GESTURE_SOURCE_DEFAULT = TOUCH
+  };
+
+  GestureEventPacket();
+  explicit GestureEventPacket(GestureSource source);
+  ~GestureEventPacket();
+
+  void Push(const blink::WebGestureEvent& gesture);
+
+  const blink::WebGestureEvent& gesture(size_t i) const { return gestures_[i]; }
+  size_t gesture_count() const { return gesture_count_; }
+  GestureSource gesture_source() const { return gesture_source_; }
+
+  // Utility methods for creating a packet from a particular event.
+  static GestureEventPacket FromTouch(const blink::WebTouchEvent& event);
+  static GestureEventPacket FromGesture(GestureSource source,
+                                        const blink::WebGestureEvent& event);
+
+private:
+  enum { kMaxGesturesPerTouch = 5 };

[tdresser, 2014/01/23 16:32:43]

Using an enum for a single constant isn't very common (~64 occurrences, compared
to ~8000 for const int). I'd prefer a const int, unless there's a specific
reason you've used an enum here.

[jdduke (slow), 2014/01/23 22:52:34]

I think the enum might be a bit more clear here as it's used for the member
array length.

+  blink::WebGestureEvent gestures_[kMaxGesturesPerTouch];
+  size_t gesture_count_;
+  GestureSource gesture_source_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_GESTURE_EVENT_PACKET_H_