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// Copyright (c) 2013 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_TARGETER_H_
#define UI_EVENTS_EVENT_TARGETER_H_
#include "base/compiler_specific.h"
#include "ui/events/event.h"
#include "ui/events/events_export.h"
namespace ui {
class Event;
class EventTarget;
class LocatedEvent;
class EVENTS_EXPORT EventTargeter {
public:
virtual ~EventTargeter();
// Returns the target |event| should be dispatched to. If there is no such
// target, return NULL. If |event| is a located event, the location of |event|
// is in the coordinate space of |root|. Furthermore, the targeter can mutate
// the event (e.g., by changing the location of the event to be in the
// returned target's coordinate space) so that it can be dispatched to the
// target without any further modification.
virtual EventTarget* FindTargetForEvent(EventTarget* root,
Event* event);
// Same as FindTargetForEvent(), but used for positional events. The location
// etc. of |event| are in |root|'s coordinate system. When finding the target
// for the event, the targeter can mutate the |event| (e.g. change the
// coordinate to be in the returned target's coordinate system) so that it can
// be dispatched to the target without any further modification.
// TODO(tdanderson|sadrul): This should not be in the public API of
// EventTargeter.
virtual EventTarget* FindTargetForLocatedEvent(EventTarget* root,
LocatedEvent* event);
// Returns true if |target| or one of its descendants can be a target of
// |event|. This requires that |target| and its descendants are not
// prohibited from accepting the event, and that the event is within an
// actionable region of the target's bounds. Note that the location etc. of
// |event| is in |target|'s parent's coordinate system.
// TODO(tdanderson|sadrul): This function should be made non-virtual and
// non-public.
virtual bool SubtreeShouldBeExploredForEvent(EventTarget* target,
const LocatedEvent& event);
// Returns the next best target for |event| as compared to |previous_target|.
// |event| is in the local coordinate space of |previous_target|.
// Also mutates |event| so that it can be dispatched to the returned target
// (e.g., by changing |event|'s location to be in the returned target's
// coordinate space).
virtual EventTarget* FindNextBestTarget(EventTarget* previous_target,
Event* event);
protected:
// Returns false if neither |target| nor any of its descendants are allowed
// to accept |event| for reasons unrelated to the event's location or the
// target's bounds. For example, overrides of this function may consider
// attributes such as the visibility or enabledness of |target|. Note that
// the location etc. of |event| is in |target|'s parent's coordinate system.
virtual bool SubtreeCanAcceptEvent(EventTarget* target,
const LocatedEvent& event) const;
// Returns whether the location of the event is in an actionable region of the
// target. Note that the location etc. of |event| is in the |target|'s
// parent's coordinate system.
virtual bool EventLocationInsideBounds(EventTarget* target,
const LocatedEvent& event) const;
};
} // namespace ui
#endif // UI_EVENTS_EVENT_TARGETER_H_
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