gesture_event_queue.h | Explore in Territory

// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_INPUT_GESTURE_EVENT_QUEUE_H_
#define COMPONENTS_INPUT_GESTURE_EVENT_QUEUE_H_

#include <stddef.h>

#include "base/containers/circular_deque.h"
#include "base/memory/raw_ptr.h"
#include "base/time/time.h"
#include "base/timer/timer.h"
#include "components/input/event_with_latency_info.h"
#include "components/input/fling_controller.h"
#include "base/component_export.h"
#include "third_party/blink/public/common/input/web_input_event.h"
#include "third_party/blink/public/mojom/input/input_event_result.mojom-shared.h"

namespace content {
class MockRenderWidgetHost;
}  // namespace content

namespace input {
class GestureEventQueueTest;

// Interface with which the GestureEventQueue can forward gesture events, and
// dispatch gesture event responses.
class COMPONENT_EXPORT(INPUT) GestureEventQueueClient { … };

// Despite its name, this class isn't so much one queue as it is a collection
// of queues and filters. This class applies logic to determine if an event
// should be queued, filtered altogether, or sent immediately; it tracks sent
// events and ACKs them to the clilent in the order they were dispatched. This
// class applies a series of filters and queues for various scenarios:
// 1. The sequence is filtered for bounces. A bounce is when the finger lifts
//    from the screen briefly during an in-progress scroll. If this happens,
//    non-GestureScrollUpdate events are queued until the de-bounce interval
//    passes or another GestureScrollUpdate event occurs.
// 2. Unnecessary GestureFlingCancel events are filtered by fling controller.
//    These are GestureFlingCancels that have no corresponding GestureFlingStart
//    in the queue. GestureFlingStarts are also filtered and translated to
//    scroll gestures by the fling controller.
// 3. Taps immediately after a GestureFlingCancel (caused by the same tap) are
//    filtered by fling controller.
// 4. Gesture events are queued while we're waiting to determine the allowed
//    touch actions.
// Sent events are kept in a queue until a response from the renderer is
// received for that event. The client is notified of ACKs in the order the
// events were sent, not ACK'd. This means an ACK'd event that was sent after
// an event still awaiting an ACK won't notify the client until the earlier
// event is ACK'd.
class COMPONENT_EXPORT(INPUT) GestureEventQueue { … };

}  // namespace input

#endif  // COMPONENTS_INPUT_GESTURE_EVENT_QUEUE_H_
chromium/components/input/gesture_event_queue.h
