1 2 /* 3 * Copyright 2006 The Android Open Source Project 4 * 5 * Use of this source code is governed by a BSD-style license that can be 6 * found in the LICENSE file. 7 */ 8 9 10 #ifndef SkEventSink_DEFINED 11 #define SkEventSink_DEFINED 12 13 #include "SkRefCnt.h" 14 #include "SkEvent.h" 15 16 struct SkTagList; 17 18 /** \class SkEventSink 19 20 SkEventSink is the base class for all objects that receive SkEvents. 21 */ 22 class SkEventSink : public SkRefCnt { 23 public: 24 SkEventSink(); 25 virtual ~SkEventSink(); 26 27 /** 28 * Returns this eventsink's unique ID. Use this to post SkEvents to 29 * this eventsink. 30 */ getSinkID()31 SkEventSinkID getSinkID() const { return fID; } 32 33 /** 34 * Call this to pass an event to this object for processing. Returns true if the 35 * event was handled. 36 */ 37 bool doEvent(const SkEvent&); 38 39 /** Returns true if the sink (or one of its subclasses) understands the event as a query. 40 If so, the sink may modify the event to communicate its "answer". 41 */ 42 bool doQuery(SkEvent* query); 43 44 /** 45 * Add sinkID to the list of listeners, to receive events from calls to sendToListeners() 46 * and postToListeners(). If sinkID already exists in the listener list, no change is made. 47 */ 48 void addListenerID(SkEventSinkID sinkID); 49 50 /** 51 * Copy listeners from one event sink to another, typically from parent to child. 52 * @param from the event sink to copy the listeners from 53 */ 54 void copyListeners(const SkEventSink& from); 55 56 /** 57 * Remove sinkID from the list of listeners. If sinkID does not appear in the list, 58 * no change is made. 59 */ 60 void removeListenerID(SkEventSinkID); 61 62 /** 63 * Returns true if there are 1 or more listeners attached to this eventsink 64 */ 65 bool hasListeners() const; 66 67 /** 68 * Posts a copy of evt to each of the eventsinks in the lisener list. 69 * This ignores the targetID and target proc in evt. 70 */ 71 void postToListeners(const SkEvent& evt, SkMSec delay = 0); 72 73 enum EventResult { 74 kHandled_EventResult, //!< the eventsink returned true from its doEvent method 75 kNotHandled_EventResult, //!< the eventsink returned false from its doEvent method 76 kSinkNotFound_EventResult //!< no matching eventsink was found for the event's getSink(). 77 }; 78 79 /** 80 * DoEvent handles dispatching the event to its target ID or proc. 81 */ 82 static EventResult DoEvent(const SkEvent&); 83 84 /** 85 * Returns the matching eventsink, or null if not found 86 */ 87 static SkEventSink* FindSink(SkEventSinkID); 88 89 protected: 90 /** Override this to handle events in your subclass. Be sure to call the inherited version 91 for events that you don't handle. 92 */ 93 virtual bool onEvent(const SkEvent&); 94 virtual bool onQuery(SkEvent*); 95 96 SkTagList* findTagList(U8CPU tag) const; 97 void addTagList(SkTagList*); 98 void removeTagList(U8CPU tag); 99 100 private: 101 SkEventSinkID fID; 102 SkTagList* fTagHead; 103 104 // for our private link-list 105 SkEventSink* fNextSink; 106 }; 107 108 #endif 109 110