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// Copyright 2018 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 UI_EVENTS_EVENT_OBSERVER_H_
#define UI_EVENTS_EVENT_OBSERVER_H_
#include "ui/events/events_export.h"
namespace ui {
class Event;
// EventObservers are notified of events but are unable to modify the events or
// mark them as handled before they are dispatched to EventHandlers.
//
// Window service clients may use this interface for observation of events that
// target the window manager or other clients. Clients should limit the types
// and duration of observation, as there is a system-wide perf/battery penalty,
// especially for frequently occurring events, like mouse moves. Events with
// targets outside of the client's scope will have a null target.
class EVENTS_EXPORT EventObserver {
public:
// Called for all events matching the requested event types.
// The root location of located events is always in screen coordinates.
virtual void OnEvent(const Event& event) = 0;
protected:
virtual ~EventObserver() {}
};
} // namespace ui
#endif // UI_EVENTS_EVENT_OBSERVER_H_
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