Refactoring: Extract gesture event filtering into helper class.

content/browser/renderer_host/gesture_event_filter.cc

Index: content/browser/renderer_host/gesture_event_filter.cc
diff --git a/content/browser/renderer_host/gesture_event_filter.cc b/content/browser/renderer_host/gesture_event_filter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..cf99f45e2414649584611a36ae9f672f511f30e6
--- /dev/null
+++ b/content/browser/renderer_host/gesture_event_filter.cc
@@ -0,0 +1,111 @@
+// Copyright (c) 2012 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.
+
+#include "content/browser/renderer_host/gesture_event_filter.h"
+
+#include "content/browser/renderer_host/render_widget_host_impl.h"
+#include "content/browser/renderer_host/tap_suppression_controller.h"
+
+namespace content {
+namespace {
+// Returns |true| if two gesture events should be coalesced.
+bool ShouldCoalesceGestureEvents(const WebKit::WebGestureEvent& last_event,
+                                 const WebKit::WebGestureEvent& new_event) {
+  return new_event.type == WebInputEvent::GestureScrollUpdate &&
+      last_event.type == new_event.type &&
+      last_event.modifiers == new_event.modifiers;
+}
+} // namespace
+
+GestureEventFilter::GestureEventFilter(RenderWidgetHostImpl* rwhv)
+     : render_widget_host_(rwhv),
+       fling_in_progress_(false),
+       gesture_event_pending_(false),
+       tap_suppression_controller_(new TapSuppressionController(rwhv)) {
+}
+
+GestureEventFilter::~GestureEventFilter() { }
+
+bool GestureEventFilter::ShouldDiscardFlingCancelEvent(
+    const WebKit::WebGestureEvent& gesture_event) {
+  DCHECK(gesture_event.type == WebInputEvent::GestureFlingCancel);
+  if (coalesced_gesture_events_.empty() && fling_in_progress_)
+    return false;
+  GestureEventQueue::reverse_iterator it =
+      coalesced_gesture_events_.rbegin();
+  while (it != coalesced_gesture_events_.rend()) {
+    if (it->type == WebInputEvent::GestureFlingStart)
+      return false;
+    if (it->type == WebInputEvent::GestureFlingCancel)
+      return true;
+    it++;
+  }
+  return true;
+}
+
+bool GestureEventFilter::ShouldForward(const WebGestureEvent& gesture_event) {
+  if (gesture_event.type == WebInputEvent::GestureFlingCancel) {
+    if (ShouldDiscardFlingCancelEvent(gesture_event))
+      return false;
+    fling_in_progress_ = false;
+  }
+
+  if (gesture_event_pending_) {
+    if (coalesced_gesture_events_.empty() ||
+        !ShouldCoalesceGestureEvents(coalesced_gesture_events_.back(),
+                                     gesture_event)) {
+     coalesced_gesture_events_.push_back(gesture_event);
+    } else {
+      WebGestureEvent* last_gesture_event =
+          &coalesced_gesture_events_.back();
+      last_gesture_event->deltaX += gesture_event.deltaX;
+      last_gesture_event->deltaY += gesture_event.deltaY;
+      DCHECK_GE(gesture_event.timeStampSeconds,
+                last_gesture_event->timeStampSeconds);
+      last_gesture_event->timeStampSeconds = gesture_event.timeStampSeconds;
+    }
+    return false;
+  }
+  gesture_event_pending_ = true;
+
+  if (gesture_event.type == WebInputEvent::GestureFlingCancel) {
+    tap_suppression_controller_->GestureFlingCancel(
+        gesture_event.timeStampSeconds);
+  } else if (gesture_event.type == WebInputEvent::GestureFlingStart) {
+    fling_in_progress_ = true;
+  }
+
+  return true;
+}
+
+void GestureEventFilter::Reset() {
+  fling_in_progress_ = false;
+  coalesced_gesture_events_.clear();
+  gesture_event_pending_ = false;
+}
+
+void GestureEventFilter::ProcessGestureAck(bool processed, int type) {
+  if (type == WebInputEvent::GestureFlingCancel)
+    tap_suppression_controller_->GestureFlingCancelAck(processed);
+
+  gesture_event_pending_ = false;
+
+  // Now send the next (coalesced) gesture event.
+  if (!coalesced_gesture_events_.empty()) {
+    WebGestureEvent next_gesture_event =
+        coalesced_gesture_events_.front();
+    coalesced_gesture_events_.pop_front();
+    render_widget_host_->ForwardGestureEvent(next_gesture_event);
+  }
+}
+
+TapSuppressionController*  GestureEventFilter::GetTapSuppressionController() {
+  return tap_suppression_controller_.get();
+}
+
+void GestureEventFilter::FlingHasBeenHalted() {
+  fling_in_progress_ = false;
+}
+
+} // namespace content