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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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