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// Copyright 2014 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 <stdint.h>
#include <queue>
#include "base/macros.h"
#include "ui/events/event_constants.h"
#include "ui/events/gesture_detection/bitset_32.h"
#include "ui/events/gesture_detection/gesture_detection_export.h"
#include "ui/events/gesture_detection/gesture_event_data_packet.h"
namespace ui {
// Interface with which the |TouchDispositionGestureFilter| forwards gestures
// for a given touch event.
class GESTURE_DETECTION_EXPORT TouchDispositionGestureFilterClient {
virtual void ForwardGestureEvent(const GestureEventData&) = 0;
// Given a stream of touch-derived gesture packets, produces a refined gesture
// sequence based on the ack dispositions of the generating touch events.
class GESTURE_DETECTION_EXPORT TouchDispositionGestureFilter {
explicit TouchDispositionGestureFilter(
TouchDispositionGestureFilterClient* client);
// To be called upon production of touch-derived gestures by the platform,
// *prior* to the generating touch being forward to the renderer. In
// particular, |packet| contains [0, n] gestures that correspond to a given
// touch event. It is imperative that a single packet is received for
// *each* touch event, even those that did not produce a gesture.
enum PacketResult {
SUCCESS, // Packet successfully queued.
INVALID_PACKET_ORDER, // Packets were received in the wrong order, i.e.,
// TOUCH_BEGIN should always precede other packets.
INVALID_PACKET_TYPE, // Packet had an invalid type.
PacketResult OnGesturePacket(const GestureEventDataPacket& packet);
// OnTouchEventAck must be called upon receipt of every touch event ack.
void OnTouchEventAck(uint32_t unique_touch_event_id, bool event_consumed);
// Whether there are any active gesture sequences still queued in the filter.
bool IsEmpty() const;
// A single GestureSequence corresponds to all gestures created
// between the first finger down and the last finger up, including gestures
// generated by timeouts from a statinoary finger.
typedef std::queue<GestureEventDataPacket> GestureSequence;
// Utility class for maintaining the touch and gesture handling state for the
// current gesture sequence.
class GestureHandlingState {
// To be called on each touch event ack.
void OnTouchEventAck(bool event_consumed, bool is_touch_start_event);
// Returns true iff the gesture should be dropped.
bool Filter(EventType type);
// Whether an event of |type| has been filtered from the current sequence.
bool HasFilteredGestureType(EventType type) const;
// True iff the sequence has had any touch down event consumed.
bool start_touch_consumed_;
// True iff the most recently ack'ed touch event was consumed.
bool current_touch_consumed_;
// Indicates whether the previous gesture of a given type was dropped.
BitSet32 last_gesture_of_type_dropped_;
// Indicates whether *any* previous gesture of a given type was dropped.
BitSet32 any_gesture_of_type_dropped_;
void FilterAndSendPacket(const GestureEventDataPacket& packet);
void SendGesture(const GestureEventData& gesture,
const GestureEventDataPacket& packet);
void CancelTapIfNecessary(const GestureEventDataPacket& packet);
void CancelFlingIfNecessary(const GestureEventDataPacket& packet);
void EndScrollIfNecessary(const GestureEventDataPacket& packet);
void PopGestureSequence();
void SendAckedEvents();
GestureSequence& Head();
GestureSequence& Tail();
TouchDispositionGestureFilterClient* client_;
std::queue<GestureSequence> sequences_;
GestureHandlingState state_;
// Bookkeeping for inserting synthetic Gesture{Tap,Fling}Cancel events
// when necessary, e.g., GestureTapCancel when scrolling begins, or
// GestureFlingCancel when a user taps following a GestureFlingStart.
int ending_event_motion_event_id_;
MotionEvent::ToolType ending_event_primary_tool_type_;
bool needs_tap_ending_event_;
bool needs_show_press_event_;
bool needs_fling_ending_event_;
bool needs_scroll_ending_event_;
} // namespace ui