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, this should return NULL. 24 virtual EventTarget* FindTargetForEvent(EventTarget* root, 25 Event* event); 26 27 // Same as FindTargetForEvent(), but used for positional events. The location 28 // etc. of |event| are in |root|'s coordinate system. When finding the target 29 // for the event, the targeter can mutate the |event| (e.g. change the 30 // coordinate to be in the returned target's coordinate system) so that it can 31 // be dispatched to the target without any farther modification. 32 virtual EventTarget* FindTargetForLocatedEvent(EventTarget* root, 33 LocatedEvent* event); 34 35 // Returns true if |target| or one of its descendants can be a target of 36 // |event|. This requires that |target| and its descendants are not 37 // prohibited from accepting the event, and that the event is within an 38 // actionable region of the target's bounds. Note that the location etc. of 39 // |event| is in |target|'s parent's coordinate system. 40 // TODO(tdanderson|sadrul): This function should be made non-virtual and 41 // non-public. 42 virtual bool SubtreeShouldBeExploredForEvent(EventTarget* target, 43 const LocatedEvent& event); 44 45 // Returns the next best target for |event| as compared to |previous_target|. 46 // Also mutates |event| so that it can be dispatched to the returned target 47 // (e.g., by changing |event|'s location to be in the returned target's 48 // coordinate space). 49 virtual EventTarget* FindNextBestTarget(EventTarget* previous_target, 50 Event* event); 51 52 protected: 53 // Returns false if neither |target| nor any of its descendants are allowed 54 // to accept |event| for reasons unrelated to the event's location or the 55 // target's bounds. For example, overrides of this function may consider 56 // attributes such as the visibility or enabledness of |target|. Note that 57 // the location etc. of |event| is in |target|'s parent's coordinate system. 58 virtual bool SubtreeCanAcceptEvent(EventTarget* target, 59 const LocatedEvent& event) const; 60 61 // Returns whether the location of the event is in an actionable region of the 62 // target. Note that the location etc. of |event| is in the |target|'s 63 // parent's coordinate system. 64 virtual bool EventLocationInsideBounds(EventTarget* target, 65 const LocatedEvent& event) const; 66 }; 67 68 } // namespace ui 69 70 #endif // UI_EVENTS_EVENT_TARGETER_H_ 71