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// Copyright 2016 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_MOUSE_WHEEL_EVENT_QUEUE_H_
#define CONTENT_BROWSER_RENDERER_HOST_INPUT_MOUSE_WHEEL_EVENT_QUEUE_H_
#include <memory>
#include "base/containers/circular_deque.h"
#include "base/time/time.h"
#include "content/browser/renderer_host/event_with_latency_info.h"
#include "content/common/content_export.h"
#include "content/public/common/input_event_ack_source.h"
#include "content/public/common/input_event_ack_state.h"
#include "third_party/blink/public/platform/web_input_event.h"
namespace content {
class QueuedWebMouseWheelEvent;
// Interface with which MouseWheelEventQueue can forward mouse wheel events,
// and dispatch mouse wheel event responses.
class CONTENT_EXPORT MouseWheelEventQueueClient {
public:
virtual ~MouseWheelEventQueueClient() {}
virtual void SendMouseWheelEventImmediately(
const MouseWheelEventWithLatencyInfo& event) = 0;
virtual void ForwardGestureEventWithLatencyInfo(
const blink::WebGestureEvent& event,
const ui::LatencyInfo& latency_info) = 0;
virtual void OnMouseWheelEventAck(const MouseWheelEventWithLatencyInfo& event,
InputEventAckSource ack_source,
InputEventAckState ack_result) = 0;
virtual bool IsWheelScrollInProgress() = 0;
};
// A queue for throttling and coalescing mouse wheel events.
class CONTENT_EXPORT MouseWheelEventQueue {
public:
// The |client| must outlive the MouseWheelEventQueue.
// |IsWheelScrollInProgress| indicates whether mouse wheel events should
// generate Scroll[Begin|Update|End] on unhandled acknowledge events.
MouseWheelEventQueue(MouseWheelEventQueueClient* client);
~MouseWheelEventQueue();
// Adds an event to the queue. The event may be coalesced with previously
// queued events (e.g. consecutive mouse-wheel events can be coalesced into a
// single mouse-wheel event). The event may also be immediately forwarded to
// the renderer (e.g. when there are no other queued mouse-wheel event).
void QueueEvent(const MouseWheelEventWithLatencyInfo& event);
// Notifies the queue that a mouse wheel event has been processed by the
// renderer.
void ProcessMouseWheelAck(InputEventAckSource ack_source,
InputEventAckState ack_result,
const ui::LatencyInfo& latency_info);
// When GestureScrollBegin is received, and it is a different source
// than mouse wheels terminate the current GestureScroll if there is one.
// When Gesture{ScrollEnd,FlingStart} is received, resume generating
// gestures.
void OnGestureScrollEvent(const GestureEventWithLatencyInfo& gesture_event);
bool has_pending() const WARN_UNUSED_RESULT {
return !wheel_queue_.empty() || event_sent_for_gesture_ack_;
}
size_t queued_size() const { return wheel_queue_.size(); }
bool event_in_flight() const {
return event_sent_for_gesture_ack_ != nullptr;
}
private:
void TryForwardNextEventToRenderer();
void SendScrollEnd(blink::WebGestureEvent update_event, bool synthetic);
void SendScrollBegin(const blink::WebGestureEvent& gesture_update,
bool synthetic);
void RecordLatchingUmaMetric(bool latched);
// True if gesture scroll events can be generated for the wheel event sent for
// ack.
bool CanGenerateGestureScroll(InputEventAckState ack_result) const;
MouseWheelEventQueueClient* client_;
base::circular_deque<std::unique_ptr<QueuedWebMouseWheelEvent>> wheel_queue_;
std::unique_ptr<QueuedWebMouseWheelEvent> event_sent_for_gesture_ack_;
// True if the ack for the first wheel event in a scroll sequence is not
// consumed. This lets us to send the rest of the wheel events in the sequence
// as non-blocking.
bool send_wheel_events_async_;
blink::WebGestureDevice scrolling_device_;
DISALLOW_COPY_AND_ASSIGN(MouseWheelEventQueue);
};
} // namespace content
#endif // CONTENT_BROWSER_RENDERER_HOST_INPUT_MOUSE_WHEEL_EVENT_QUEUE_H_
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