| // 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_ |