content/browser/renderer_host/input/gesture_event_filter.cc - platform/external/chromium_org - Git at Google

 // 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.

 #include "content/browser/renderer_host/input/gesture_event_filter.h"

 #include "base/command_line.h"
 #include "base/strings/string_number_conversions.h"
 #include "content/browser/renderer_host/input/input_router.h"
 #include "content/browser/renderer_host/input/touchpad_tap_suppression_controller.h"
 #include "content/browser/renderer_host/input/touchscreen_tap_suppression_controller.h"
 #include "content/public/common/content_switches.h"

 using WebKit::WebGestureEvent;
 using WebKit::WebInputEvent;

 namespace content {
 namespace {

 // Default debouncing interval duration: if a scroll is in progress, non-scroll
 // events during this interval are deferred to either its end or discarded on
 // receipt of another GestureScrollUpdate.
 static const int kDebouncingIntervalTimeMs = 30;

 }  // namespace

 GestureEventFilter::GestureEventFilter(
     GestureEventFilterClient* client,
     TouchpadTapSuppressionControllerClient* touchpad_client)
      : client_(client),
        fling_in_progress_(false),
        scrolling_in_progress_(false),
        ignore_next_ack_(false),
        combined_scroll_pinch_(gfx::Transform()),
        touchpad_tap_suppression_controller_(
            new TouchpadTapSuppressionController(touchpad_client)),
        touchscreen_tap_suppression_controller_(
            new TouchscreenTapSuppressionController(this)),
        debounce_interval_time_ms_(kDebouncingIntervalTimeMs) {
   DCHECK(client);
   DCHECK(touchpad_tap_suppression_controller_);
 }

 GestureEventFilter::~GestureEventFilter() { }

 bool GestureEventFilter::ShouldDiscardFlingCancelEvent(
     const GestureEventWithLatencyInfo& gesture_event) const {
   if (coalesced_gesture_events_.empty() && fling_in_progress_)
     return false;
   GestureEventQueue::const_reverse_iterator it =
       coalesced_gesture_events_.rbegin();
   while (it != coalesced_gesture_events_.rend()) {
     if (it->event.type == WebInputEvent::GestureFlingStart)
       return false;
     if (it->event.type == WebInputEvent::GestureFlingCancel)
       return true;
     it++;
   }
   return true;
 }

 bool GestureEventFilter::ShouldForwardForBounceReduction(
     const GestureEventWithLatencyInfo& gesture_event) {
   if (debounce_interval_time_ms_ ==  0)
     return true;
   switch (gesture_event.event.type) {
     case WebInputEvent::GestureScrollUpdate:
       if (!scrolling_in_progress_) {
         debounce_deferring_timer_.Start(
             FROM_HERE,
             base::TimeDelta::FromMilliseconds(debounce_interval_time_ms_),
             this,
             &GestureEventFilter::SendScrollEndingEventsNow);
       } else {
         // Extend the bounce interval.
         debounce_deferring_timer_.Reset();
       }
       scrolling_in_progress_ = true;
       debouncing_deferral_queue_.clear();
       return true;
     case WebInputEvent::GesturePinchBegin:
     case WebInputEvent::GesturePinchEnd:
     case WebInputEvent::GesturePinchUpdate:
       // TODO(rjkroege): Debounce pinch (http://crbug.com/147647)
       return true;
     default:
       if (scrolling_in_progress_) {
         debouncing_deferral_queue_.push_back(gesture_event);
         return false;
       }
       return true;
   }

   NOTREACHED();
   return false;
 }

 // NOTE: The filters are applied successively. This simplifies the change.
 bool GestureEventFilter::ShouldForward(
     const GestureEventWithLatencyInfo& gesture_event) {
   return ShouldForwardForZeroVelocityFlingStart(gesture_event) &&
       ShouldForwardForBounceReduction(gesture_event) &&
       ShouldForwardForGFCFiltering(gesture_event) &&
       ShouldForwardForTapSuppression(gesture_event) &&
       ShouldForwardForCoalescing(gesture_event);
 }

 bool GestureEventFilter::ShouldForwardForZeroVelocityFlingStart(
     const GestureEventWithLatencyInfo& gesture_event) const {
   return gesture_event.event.type != WebInputEvent::GestureFlingStart ||
       gesture_event.event.sourceDevice != WebGestureEvent::Touchpad ||
       gesture_event.event.data.flingStart.velocityX != 0 ||
       gesture_event.event.data.flingStart.velocityY != 0;
 }

 bool GestureEventFilter::ShouldForwardForGFCFiltering(
     const GestureEventWithLatencyInfo& gesture_event) const {
   return gesture_event.event.type != WebInputEvent::GestureFlingCancel ||
       !ShouldDiscardFlingCancelEvent(gesture_event);
 }

 bool GestureEventFilter::ShouldForwardForTapSuppression(
     const GestureEventWithLatencyInfo& gesture_event) {
   switch (gesture_event.event.type) {
     case WebInputEvent::GestureFlingCancel:
       if (gesture_event.event.sourceDevice == WebGestureEvent::Touchscreen)
         touchscreen_tap_suppression_controller_->GestureFlingCancel();
       else
         touchpad_tap_suppression_controller_->GestureFlingCancel();
       return true;
     case WebInputEvent::GestureTapDown:
       return !touchscreen_tap_suppression_controller_->
           ShouldDeferGestureTapDown(gesture_event);
     case WebInputEvent::GestureTapCancel:
       return !touchscreen_tap_suppression_controller_->
           ShouldSuppressGestureTapCancel();
     case WebInputEvent::GestureTap:
     case WebInputEvent::GestureTapUnconfirmed:
       return !touchscreen_tap_suppression_controller_->
           ShouldSuppressGestureTap();
     default:
       return true;
   }
   NOTREACHED();
   return false;
 }

 bool GestureEventFilter::ShouldForwardForCoalescing(
     const GestureEventWithLatencyInfo& gesture_event) {
   switch (gesture_event.event.type) {
     case WebInputEvent::GestureFlingCancel:
       fling_in_progress_ = false;
       break;
     case WebInputEvent::GestureFlingStart:
       fling_in_progress_ = true;
       break;
     case WebInputEvent::GesturePinchUpdate:
     case WebInputEvent::GestureScrollUpdate:
       MergeOrInsertScrollAndPinchEvent(gesture_event);
       return ShouldHandleEventNow();
     default:
       break;
   }
   EnqueueEvent(gesture_event);

   // Ensure that if the added event ignores its ack, it is fired and
   // removed from |coalesced_gesture_events_|.
   SendEventsIgnoringAck();
   return ShouldHandleEventNow();
 }

 void GestureEventFilter::ProcessGestureAck(InputEventAckState ack_result,
                                            WebInputEvent::Type type,
                                            const ui::LatencyInfo& latency) {
   if (ShouldIgnoreAckForGestureType(type))
     return;

   if (coalesced_gesture_events_.empty()) {
     DLOG(ERROR) << "Received unexpected ACK for event type " << type;
     return;
   }

   // Ack'ing an event may enqueue additional gesture events.  By ack'ing the
   // event before the forwarding of queued events below, such additional events
   // can be coalesced with existing queued events prior to dispatch.
   GestureEventWithLatencyInfo event_with_latency =
       coalesced_gesture_events_.front();
   DCHECK_EQ(event_with_latency.event.type, type);
   event_with_latency.latency.AddNewLatencyFrom(latency);
   client_->OnGestureEventAck(event_with_latency, ack_result);

   const bool processed = (INPUT_EVENT_ACK_STATE_CONSUMED == ack_result);
   if (type == WebInputEvent::GestureFlingCancel) {
     if (event_with_latency.event.sourceDevice == WebGestureEvent::Touchscreen)
       touchscreen_tap_suppression_controller_->GestureFlingCancelAck(processed);
     else
       touchpad_tap_suppression_controller_->GestureFlingCancelAck(processed);
   }
   coalesced_gesture_events_.pop_front();

   // If the event which was just ACKed was blocking events ignoring ack, fire
   // those events now.
   SendEventsIgnoringAck();

   if (ignore_next_ack_) {
     ignore_next_ack_ = false;
     return;
   }

   if (coalesced_gesture_events_.empty())
     return;

   const GestureEventWithLatencyInfo& first_gesture_event =
       coalesced_gesture_events_.front();

   // TODO(yusufo): Introduce GesturePanScroll so that these can be combined
   // into one gesture and kept inside the queue that way.
   // Check for the coupled GesturePinchUpdate before sending either event,
   // handling the case where the first GestureScrollUpdate ack is synchronous.
   GestureEventWithLatencyInfo second_gesture_event;
   if (first_gesture_event.event.type == WebInputEvent::GestureScrollUpdate &&
       coalesced_gesture_events_.size() > 1 &&
       coalesced_gesture_events_[1].event.type ==
           WebInputEvent::GesturePinchUpdate) {
     second_gesture_event = coalesced_gesture_events_[1];
     ignore_next_ack_ = true;
   }

   client_->SendGestureEventImmediately(first_gesture_event);
   if (second_gesture_event.event.type != WebInputEvent::Undefined)
     client_->SendGestureEventImmediately(second_gesture_event);
 }

 TouchpadTapSuppressionController*
     GestureEventFilter::GetTouchpadTapSuppressionController() {
   return touchpad_tap_suppression_controller_.get();
 }

 bool GestureEventFilter::HasQueuedGestureEvents() const {
   return !coalesced_gesture_events_.empty();
 }

 void GestureEventFilter::FlingHasBeenHalted() {
   fling_in_progress_ = false;
 }

 bool GestureEventFilter::ShouldHandleEventNow() const {
   return coalesced_gesture_events_.size() == 1;
 }

 void GestureEventFilter::ForwardGestureEvent(
     const GestureEventWithLatencyInfo& gesture_event) {
   if (ShouldForwardForCoalescing(gesture_event))
     client_->SendGestureEventImmediately(gesture_event);
 }

 void GestureEventFilter::SendScrollEndingEventsNow() {
   scrolling_in_progress_ = false;
   GestureEventQueue debouncing_deferral_queue;
   debouncing_deferral_queue.swap(debouncing_deferral_queue_);
   for (GestureEventQueue::const_iterator it = debouncing_deferral_queue.begin();
        it != debouncing_deferral_queue.end(); it++) {
     if (ShouldForwardForGFCFiltering(*it) &&
         ShouldForwardForTapSuppression(*it) &&
         ShouldForwardForCoalescing(*it)) {
       client_->SendGestureEventImmediately(*it);
     }
   }
 }

 void GestureEventFilter::MergeOrInsertScrollAndPinchEvent(
     const GestureEventWithLatencyInfo& gesture_event) {
   if (coalesced_gesture_events_.size() <= 1) {
     EnqueueEvent(gesture_event);
     return;
   }
   GestureEventWithLatencyInfo* last_event = &coalesced_gesture_events_.back();
   if (last_event->CanCoalesceWith(gesture_event)) {
     last_event->CoalesceWith(gesture_event);
     if (!combined_scroll_pinch_.IsIdentity()) {
       combined_scroll_pinch_.ConcatTransform(
           GetTransformForEvent(gesture_event));
     }
     return;
   }
   if (coalesced_gesture_events_.size() == 2 ||
       (coalesced_gesture_events_.size() == 3 && ignore_next_ack_) ||
       !ShouldTryMerging(gesture_event, *last_event)) {
     EnqueueEvent(gesture_event);
     return;
   }
   GestureEventWithLatencyInfo scroll_event;
   GestureEventWithLatencyInfo pinch_event;
   scroll_event.event.modifiers |= gesture_event.event.modifiers;
   scroll_event.event.timeStampSeconds = gesture_event.event.timeStampSeconds;
   scroll_event.latency = gesture_event.latency;
   scroll_event.latency.MergeWith(last_event->latency);
   pinch_event = scroll_event;
   scroll_event.event.type = WebInputEvent::GestureScrollUpdate;
   pinch_event.event.type = WebInputEvent::GesturePinchUpdate;
   pinch_event.event.x = gesture_event.event.type ==
       WebInputEvent::GesturePinchUpdate ?
           gesture_event.event.x : last_event->event.x;
   pinch_event.event.y = gesture_event.event.type ==
       WebInputEvent::GesturePinchUpdate ?
           gesture_event.event.y : last_event->event.y;

   combined_scroll_pinch_.ConcatTransform(GetTransformForEvent(gesture_event));
   GestureEventWithLatencyInfo* second_last_event = &coalesced_gesture_events_
       [coalesced_gesture_events_.size() - 2];
   if (ShouldTryMerging(gesture_event, *second_last_event)) {
     scroll_event.latency.MergeWith(second_last_event->latency);
     pinch_event.latency.MergeWith(second_last_event->latency);
     coalesced_gesture_events_.pop_back();
   } else {
     DCHECK(combined_scroll_pinch_ == GetTransformForEvent(gesture_event));
     combined_scroll_pinch_.
         PreconcatTransform(GetTransformForEvent(*last_event));
   }
   coalesced_gesture_events_.pop_back();
   float combined_scale =
       SkMScalarToFloat(combined_scroll_pinch_.matrix().get(0, 0));
   float combined_scroll_pinch_x =
       SkMScalarToFloat(combined_scroll_pinch_.matrix().get(0, 3));
   float combined_scroll_pinch_y =
       SkMScalarToFloat(combined_scroll_pinch_.matrix().get(1, 3));
   scroll_event.event.data.scrollUpdate.deltaX =
       (combined_scroll_pinch_x + pinch_event.event.x) / combined_scale -
       pinch_event.event.x;
   scroll_event.event.data.scrollUpdate.deltaY =
       (combined_scroll_pinch_y + pinch_event.event.y) / combined_scale -
       pinch_event.event.y;
   coalesced_gesture_events_.push_back(scroll_event);
   pinch_event.event.data.pinchUpdate.scale = combined_scale;
   coalesced_gesture_events_.push_back(pinch_event);
 }

 bool GestureEventFilter::ShouldTryMerging(
     const GestureEventWithLatencyInfo& new_event,
     const GestureEventWithLatencyInfo& event_in_queue) const {
   DLOG_IF(WARNING,
           new_event.event.timeStampSeconds <
           event_in_queue.event.timeStampSeconds)
           << "Event time not monotonic?\n";
   return (event_in_queue.event.type == WebInputEvent::GestureScrollUpdate ||
       event_in_queue.event.type == WebInputEvent::GesturePinchUpdate) &&
       event_in_queue.event.modifiers == new_event.event.modifiers;
 }

 gfx::Transform GestureEventFilter::GetTransformForEvent(
     const GestureEventWithLatencyInfo& gesture_event) const {
   gfx::Transform gesture_transform = gfx::Transform();
   if (gesture_event.event.type == WebInputEvent::GestureScrollUpdate) {
     gesture_transform.Translate(gesture_event.event.data.scrollUpdate.deltaX,
                                 gesture_event.event.data.scrollUpdate.deltaY);
   } else if (gesture_event.event.type == WebInputEvent::GesturePinchUpdate) {
     float scale = gesture_event.event.data.pinchUpdate.scale;
     gesture_transform.Translate(-gesture_event.event.x, -gesture_event.event.y);
     gesture_transform.Scale(scale,scale);
     gesture_transform.Translate(gesture_event.event.x, gesture_event.event.y);
   }
   return gesture_transform;
 }

 void GestureEventFilter::SendEventsIgnoringAck() {
   GestureEventWithLatencyInfo gesture_event;
   while (!coalesced_gesture_events_.empty()) {
     gesture_event = coalesced_gesture_events_.front();
     if (!GestureEventFilter::ShouldIgnoreAckForGestureType(
             gesture_event.event.type)) {
       return;
     }
     coalesced_gesture_events_.pop_front();
     client_->SendGestureEventImmediately(gesture_event);
   }
 }

 bool GestureEventFilter::ShouldIgnoreAckForGestureType(
     WebInputEvent::Type type) {
   return type == WebInputEvent::GestureTapDown ||
       type == WebInputEvent::GestureShowPress ||
       type == WebInputEvent::GestureTapCancel;
 }

 void GestureEventFilter::EnqueueEvent(
     const GestureEventWithLatencyInfo& gesture_event) {
   coalesced_gesture_events_.push_back(gesture_event);
   // Scroll and pinch events contributing to |combined_scroll_pinch_| will be
   // manually added to the queue in |MergeOrInsertScrollAndPinchEvent()|.
   combined_scroll_pinch_ = gfx::Transform();
 }

 }  // namespace content
	// 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.

	#include "content/browser/renderer_host/input/gesture_event_filter.h"

	#include "base/command_line.h"
	#include "base/strings/string_number_conversions.h"
	#include "content/browser/renderer_host/input/input_router.h"
	#include "content/browser/renderer_host/input/touchpad_tap_suppression_controller.h"
	#include "content/browser/renderer_host/input/touchscreen_tap_suppression_controller.h"
	#include "content/public/common/content_switches.h"

	using WebKit::WebGestureEvent;
	using WebKit::WebInputEvent;

	namespace content {
	namespace {

	// Default debouncing interval duration: if a scroll is in progress, non-scroll
	// events during this interval are deferred to either its end or discarded on
	// receipt of another GestureScrollUpdate.
	static const int kDebouncingIntervalTimeMs = 30;

	} // namespace

	GestureEventFilter::GestureEventFilter(
	GestureEventFilterClient* client,
	TouchpadTapSuppressionControllerClient* touchpad_client)
	: client_(client),
	fling_in_progress_(false),
	scrolling_in_progress_(false),
	ignore_next_ack_(false),
	combined_scroll_pinch_(gfx::Transform()),
	touchpad_tap_suppression_controller_(
	new TouchpadTapSuppressionController(touchpad_client)),
	touchscreen_tap_suppression_controller_(
	new TouchscreenTapSuppressionController(this)),
	debounce_interval_time_ms_(kDebouncingIntervalTimeMs) {
	DCHECK(client);
	DCHECK(touchpad_tap_suppression_controller_);
	}

	GestureEventFilter::~GestureEventFilter() { }

	bool GestureEventFilter::ShouldDiscardFlingCancelEvent(
	const GestureEventWithLatencyInfo& gesture_event) const {
	if (coalesced_gesture_events_.empty() && fling_in_progress_)
	return false;
	GestureEventQueue::const_reverse_iterator it =
	coalesced_gesture_events_.rbegin();
	while (it != coalesced_gesture_events_.rend()) {
	if (it->event.type == WebInputEvent::GestureFlingStart)
	return false;
	if (it->event.type == WebInputEvent::GestureFlingCancel)
	return true;
	it++;
	}
	return true;
	}

	bool GestureEventFilter::ShouldForwardForBounceReduction(
	const GestureEventWithLatencyInfo& gesture_event) {
	if (debounce_interval_time_ms_ == 0)
	return true;
	switch (gesture_event.event.type) {
	case WebInputEvent::GestureScrollUpdate:
	if (!scrolling_in_progress_) {
	debounce_deferring_timer_.Start(
	FROM_HERE,
	base::TimeDelta::FromMilliseconds(debounce_interval_time_ms_),
	this,
	&GestureEventFilter::SendScrollEndingEventsNow);
	} else {
	// Extend the bounce interval.
	debounce_deferring_timer_.Reset();
	}
	scrolling_in_progress_ = true;
	debouncing_deferral_queue_.clear();
	return true;
	case WebInputEvent::GesturePinchBegin:
	case WebInputEvent::GesturePinchEnd:
	case WebInputEvent::GesturePinchUpdate:
	// TODO(rjkroege): Debounce pinch (http://crbug.com/147647)
	return true;
	default:
	if (scrolling_in_progress_) {
	debouncing_deferral_queue_.push_back(gesture_event);
	return false;
	}
	return true;
	}

	NOTREACHED();
	return false;
	}

	// NOTE: The filters are applied successively. This simplifies the change.
	bool GestureEventFilter::ShouldForward(
	const GestureEventWithLatencyInfo& gesture_event) {
	return ShouldForwardForZeroVelocityFlingStart(gesture_event) &&
	ShouldForwardForBounceReduction(gesture_event) &&
	ShouldForwardForGFCFiltering(gesture_event) &&
	ShouldForwardForTapSuppression(gesture_event) &&
	ShouldForwardForCoalescing(gesture_event);
	}

	bool GestureEventFilter::ShouldForwardForZeroVelocityFlingStart(
	const GestureEventWithLatencyInfo& gesture_event) const {
	return gesture_event.event.type != WebInputEvent::GestureFlingStart \|\|
	gesture_event.event.sourceDevice != WebGestureEvent::Touchpad \|\|
	gesture_event.event.data.flingStart.velocityX != 0 \|\|
	gesture_event.event.data.flingStart.velocityY != 0;
	}

	bool GestureEventFilter::ShouldForwardForGFCFiltering(
	const GestureEventWithLatencyInfo& gesture_event) const {
	return gesture_event.event.type != WebInputEvent::GestureFlingCancel \|\|
	!ShouldDiscardFlingCancelEvent(gesture_event);
	}

	bool GestureEventFilter::ShouldForwardForTapSuppression(
	const GestureEventWithLatencyInfo& gesture_event) {
	switch (gesture_event.event.type) {
	case WebInputEvent::GestureFlingCancel:
	if (gesture_event.event.sourceDevice == WebGestureEvent::Touchscreen)
	touchscreen_tap_suppression_controller_->GestureFlingCancel();
	else
	touchpad_tap_suppression_controller_->GestureFlingCancel();
	return true;
	case WebInputEvent::GestureTapDown:
	return !touchscreen_tap_suppression_controller_->
	ShouldDeferGestureTapDown(gesture_event);
	case WebInputEvent::GestureTapCancel:
	return !touchscreen_tap_suppression_controller_->
	ShouldSuppressGestureTapCancel();
	case WebInputEvent::GestureTap:
	case WebInputEvent::GestureTapUnconfirmed:
	return !touchscreen_tap_suppression_controller_->
	ShouldSuppressGestureTap();
	default:
	return true;
	}
	NOTREACHED();
	return false;
	}

	bool GestureEventFilter::ShouldForwardForCoalescing(
	const GestureEventWithLatencyInfo& gesture_event) {
	switch (gesture_event.event.type) {
	case WebInputEvent::GestureFlingCancel:
	fling_in_progress_ = false;
	break;
	case WebInputEvent::GestureFlingStart:
	fling_in_progress_ = true;
	break;
	case WebInputEvent::GesturePinchUpdate:
	case WebInputEvent::GestureScrollUpdate:
	MergeOrInsertScrollAndPinchEvent(gesture_event);
	return ShouldHandleEventNow();
	default:
	break;
	}
	EnqueueEvent(gesture_event);

	// Ensure that if the added event ignores its ack, it is fired and
	// removed from \|coalesced_gesture_events_\|.
	SendEventsIgnoringAck();
	return ShouldHandleEventNow();
	}

	void GestureEventFilter::ProcessGestureAck(InputEventAckState ack_result,
	WebInputEvent::Type type,
	const ui::LatencyInfo& latency) {
	if (ShouldIgnoreAckForGestureType(type))
	return;

	if (coalesced_gesture_events_.empty()) {
	DLOG(ERROR) << "Received unexpected ACK for event type " << type;
	return;
	}

	// Ack'ing an event may enqueue additional gesture events. By ack'ing the
	// event before the forwarding of queued events below, such additional events
	// can be coalesced with existing queued events prior to dispatch.
	GestureEventWithLatencyInfo event_with_latency =
	coalesced_gesture_events_.front();
	DCHECK_EQ(event_with_latency.event.type, type);
	event_with_latency.latency.AddNewLatencyFrom(latency);
	client_->OnGestureEventAck(event_with_latency, ack_result);

	const bool processed = (INPUT_EVENT_ACK_STATE_CONSUMED == ack_result);
	if (type == WebInputEvent::GestureFlingCancel) {
	if (event_with_latency.event.sourceDevice == WebGestureEvent::Touchscreen)
	touchscreen_tap_suppression_controller_->GestureFlingCancelAck(processed);
	else
	touchpad_tap_suppression_controller_->GestureFlingCancelAck(processed);
	}
	coalesced_gesture_events_.pop_front();

	// If the event which was just ACKed was blocking events ignoring ack, fire
	// those events now.
	SendEventsIgnoringAck();

	if (ignore_next_ack_) {
	ignore_next_ack_ = false;
	return;
	}

	if (coalesced_gesture_events_.empty())
	return;

	const GestureEventWithLatencyInfo& first_gesture_event =
	coalesced_gesture_events_.front();

	// TODO(yusufo): Introduce GesturePanScroll so that these can be combined
	// into one gesture and kept inside the queue that way.
	// Check for the coupled GesturePinchUpdate before sending either event,
	// handling the case where the first GestureScrollUpdate ack is synchronous.
	GestureEventWithLatencyInfo second_gesture_event;
	if (first_gesture_event.event.type == WebInputEvent::GestureScrollUpdate &&
	coalesced_gesture_events_.size() > 1 &&
	coalesced_gesture_events_[1].event.type ==
	WebInputEvent::GesturePinchUpdate) {
	second_gesture_event = coalesced_gesture_events_[1];
	ignore_next_ack_ = true;
	}

	client_->SendGestureEventImmediately(first_gesture_event);
	if (second_gesture_event.event.type != WebInputEvent::Undefined)
	client_->SendGestureEventImmediately(second_gesture_event);
	}

	TouchpadTapSuppressionController*
	GestureEventFilter::GetTouchpadTapSuppressionController() {
	return touchpad_tap_suppression_controller_.get();
	}

	bool GestureEventFilter::HasQueuedGestureEvents() const {
	return !coalesced_gesture_events_.empty();
	}

	void GestureEventFilter::FlingHasBeenHalted() {
	fling_in_progress_ = false;
	}

	bool GestureEventFilter::ShouldHandleEventNow() const {
	return coalesced_gesture_events_.size() == 1;
	}

	void GestureEventFilter::ForwardGestureEvent(
	const GestureEventWithLatencyInfo& gesture_event) {
	if (ShouldForwardForCoalescing(gesture_event))
	client_->SendGestureEventImmediately(gesture_event);
	}

	void GestureEventFilter::SendScrollEndingEventsNow() {
	scrolling_in_progress_ = false;
	GestureEventQueue debouncing_deferral_queue;
	debouncing_deferral_queue.swap(debouncing_deferral_queue_);
	for (GestureEventQueue::const_iterator it = debouncing_deferral_queue.begin();
	it != debouncing_deferral_queue.end(); it++) {
	if (ShouldForwardForGFCFiltering(*it) &&
	ShouldForwardForTapSuppression(*it) &&
	ShouldForwardForCoalescing(*it)) {
	client_->SendGestureEventImmediately(*it);
	}
	}
	}

	void GestureEventFilter::MergeOrInsertScrollAndPinchEvent(
	const GestureEventWithLatencyInfo& gesture_event) {
	if (coalesced_gesture_events_.size() <= 1) {
	EnqueueEvent(gesture_event);
	return;
	}
	GestureEventWithLatencyInfo* last_event = &coalesced_gesture_events_.back();
	if (last_event->CanCoalesceWith(gesture_event)) {
	last_event->CoalesceWith(gesture_event);
	if (!combined_scroll_pinch_.IsIdentity()) {
	combined_scroll_pinch_.ConcatTransform(
	GetTransformForEvent(gesture_event));
	}
	return;
	}
	if (coalesced_gesture_events_.size() == 2 \|\|
	(coalesced_gesture_events_.size() == 3 && ignore_next_ack_) \|\|
	!ShouldTryMerging(gesture_event, *last_event)) {
	EnqueueEvent(gesture_event);
	return;
	}
	GestureEventWithLatencyInfo scroll_event;
	GestureEventWithLatencyInfo pinch_event;
	scroll_event.event.modifiers \|= gesture_event.event.modifiers;
	scroll_event.event.timeStampSeconds = gesture_event.event.timeStampSeconds;
	scroll_event.latency = gesture_event.latency;
	scroll_event.latency.MergeWith(last_event->latency);
	pinch_event = scroll_event;
	scroll_event.event.type = WebInputEvent::GestureScrollUpdate;
	pinch_event.event.type = WebInputEvent::GesturePinchUpdate;
	pinch_event.event.x = gesture_event.event.type ==
	WebInputEvent::GesturePinchUpdate ?
	gesture_event.event.x : last_event->event.x;
	pinch_event.event.y = gesture_event.event.type ==
	WebInputEvent::GesturePinchUpdate ?
	gesture_event.event.y : last_event->event.y;

	combined_scroll_pinch_.ConcatTransform(GetTransformForEvent(gesture_event));
	GestureEventWithLatencyInfo* second_last_event = &coalesced_gesture_events_
	[coalesced_gesture_events_.size() - 2];
	if (ShouldTryMerging(gesture_event, *second_last_event)) {
	scroll_event.latency.MergeWith(second_last_event->latency);
	pinch_event.latency.MergeWith(second_last_event->latency);
	coalesced_gesture_events_.pop_back();
	} else {
	DCHECK(combined_scroll_pinch_ == GetTransformForEvent(gesture_event));
	combined_scroll_pinch_.
	PreconcatTransform(GetTransformForEvent(*last_event));
	}
	coalesced_gesture_events_.pop_back();
	float combined_scale =
	SkMScalarToFloat(combined_scroll_pinch_.matrix().get(0, 0));
	float combined_scroll_pinch_x =
	SkMScalarToFloat(combined_scroll_pinch_.matrix().get(0, 3));
	float combined_scroll_pinch_y =
	SkMScalarToFloat(combined_scroll_pinch_.matrix().get(1, 3));
	scroll_event.event.data.scrollUpdate.deltaX =
	(combined_scroll_pinch_x + pinch_event.event.x) / combined_scale -
	pinch_event.event.x;
	scroll_event.event.data.scrollUpdate.deltaY =
	(combined_scroll_pinch_y + pinch_event.event.y) / combined_scale -
	pinch_event.event.y;
	coalesced_gesture_events_.push_back(scroll_event);
	pinch_event.event.data.pinchUpdate.scale = combined_scale;
	coalesced_gesture_events_.push_back(pinch_event);
	}

	bool GestureEventFilter::ShouldTryMerging(
	const GestureEventWithLatencyInfo& new_event,
	const GestureEventWithLatencyInfo& event_in_queue) const {
	DLOG_IF(WARNING,
	new_event.event.timeStampSeconds <
	event_in_queue.event.timeStampSeconds)
	<< "Event time not monotonic?\n";
	return (event_in_queue.event.type == WebInputEvent::GestureScrollUpdate \|\|
	event_in_queue.event.type == WebInputEvent::GesturePinchUpdate) &&
	event_in_queue.event.modifiers == new_event.event.modifiers;
	}

	gfx::Transform GestureEventFilter::GetTransformForEvent(
	const GestureEventWithLatencyInfo& gesture_event) const {
	gfx::Transform gesture_transform = gfx::Transform();
	if (gesture_event.event.type == WebInputEvent::GestureScrollUpdate) {
	gesture_transform.Translate(gesture_event.event.data.scrollUpdate.deltaX,
	gesture_event.event.data.scrollUpdate.deltaY);
	} else if (gesture_event.event.type == WebInputEvent::GesturePinchUpdate) {
	float scale = gesture_event.event.data.pinchUpdate.scale;
	gesture_transform.Translate(-gesture_event.event.x, -gesture_event.event.y);
	gesture_transform.Scale(scale,scale);
	gesture_transform.Translate(gesture_event.event.x, gesture_event.event.y);
	}
	return gesture_transform;
	}

	void GestureEventFilter::SendEventsIgnoringAck() {
	GestureEventWithLatencyInfo gesture_event;
	while (!coalesced_gesture_events_.empty()) {
	gesture_event = coalesced_gesture_events_.front();
	if (!GestureEventFilter::ShouldIgnoreAckForGestureType(
	gesture_event.event.type)) {
	return;
	}
	coalesced_gesture_events_.pop_front();
	client_->SendGestureEventImmediately(gesture_event);
	}
	}

	bool GestureEventFilter::ShouldIgnoreAckForGestureType(
	WebInputEvent::Type type) {
	return type == WebInputEvent::GestureTapDown \|\|
	type == WebInputEvent::GestureShowPress \|\|
	type == WebInputEvent::GestureTapCancel;
	}

	void GestureEventFilter::EnqueueEvent(
	const GestureEventWithLatencyInfo& gesture_event) {
	coalesced_gesture_events_.push_back(gesture_event);
	// Scroll and pinch events contributing to \|combined_scroll_pinch_\| will be
	// manually added to the queue in \|MergeOrInsertScrollAndPinchEvent()\|.
	combined_scroll_pinch_ = gfx::Transform();
	}

	} // namespace content