1 // Copyright (c) 2013 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef UI_EVENTS_EVENT_TARGETER_H_ 6 #define UI_EVENTS_EVENT_TARGETER_H_ 7 8 #include "base/compiler_specific.h" 9 #include "ui/events/event.h" 10 #include "ui/events/events_export.h" 11 12 namespace ui { 13 14 class Event; 15 class EventTarget; 16 class LocatedEvent; 17 18 class EVENTS_EXPORT EventTargeter { 19 public: 20 virtual ~EventTargeter(); 21 22 // Returns the target |event| should be dispatched to. If there is no such 23 // target, return NULL. If |event| is a located event, the location of |event| 24 // is in the coordinate space of |root|. Furthermore, the targeter can mutate 25 // the event (e.g., by changing the location of the event to be in the 26 // returned target's coordinate space) so that it can be dispatched to the 27 // target without any further modification. 28 virtual EventTarget* FindTargetForEvent(EventTarget* root, 29 Event* event); 30 31 // Same as FindTargetForEvent(), but used for positional events. The location 32 // etc. of |event| are in |root|'s coordinate system. When finding the target 33 // for the event, the targeter can mutate the |event| (e.g. change the 34 // coordinate to be in the returned target's coordinate system) so that it can 35 // be dispatched to the target without any further modification. 36 // TODO(tdanderson|sadrul): This should not be in the public API of 37 // EventTargeter. 38 virtual EventTarget* FindTargetForLocatedEvent(EventTarget* root, 39 LocatedEvent* event); 40 41 // Returns true if |target| or one of its descendants can be a target of 42 // |event|. This requires that |target| and its descendants are not 43 // prohibited from accepting the event, and that the event is within an 44 // actionable region of the target's bounds. Note that the location etc. of 45 // |event| is in |target|'s parent's coordinate system. 46 // TODO(tdanderson|sadrul): This function should be made non-virtual and 47 // non-public. 48 virtual bool SubtreeShouldBeExploredForEvent(EventTarget* target, 49 const LocatedEvent& event); 50 51 // Returns the next best target for |event| as compared to |previous_target|. 52 // |event| is in the local coordinate space of |previous_target|. 53 // Also mutates |event| so that it can be dispatched to the returned target 54 // (e.g., by changing |event|'s location to be in the returned target's 55 // coordinate space). 56 virtual EventTarget* FindNextBestTarget(EventTarget* previous_target, 57 Event* event); 58 59 protected: 60 // Returns false if neither |target| nor any of its descendants are allowed 61 // to accept |event| for reasons unrelated to the event's location or the 62 // target's bounds. For example, overrides of this function may consider 63 // attributes such as the visibility or enabledness of |target|. Note that 64 // the location etc. of |event| is in |target|'s parent's coordinate system. 65 virtual bool SubtreeCanAcceptEvent(EventTarget* target, 66 const LocatedEvent& event) const; 67 68 // Returns whether the location of the event is in an actionable region of the 69 // target. Note that the location etc. of |event| is in the |target|'s 70 // parent's coordinate system. 71 virtual bool EventLocationInsideBounds(EventTarget* target, 72 const LocatedEvent& event) const; 73 }; 74 75 } // namespace ui 76 77 #endif // UI_EVENTS_EVENT_TARGETER_H_ 78
