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/*
* Copyright 2006 The Android Open Source Project
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkEventSink_DEFINED
#define SkEventSink_DEFINED
#include "SkRefCnt.h"
#include "SkEvent.h"
struct SkTagList;
/** \class SkEventSink
SkEventSink is the base class for all objects that receive SkEvents.
*/
class SkEventSink : public SkRefCnt {
public:
SkEventSink();
virtual ~SkEventSink();
/**
* Returns this eventsink's unique ID. Use this to post SkEvents to
* this eventsink.
*/
SkEventSinkID getSinkID() const { return fID; }
/**
* Call this to pass an event to this object for processing. Returns true if the
* event was handled.
*/
bool doEvent(const SkEvent&);
/** Returns true if the sink (or one of its subclasses) understands the event as a query.
If so, the sink may modify the event to communicate its "answer".
*/
bool doQuery(SkEvent* query);
/**
* Add sinkID to the list of listeners, to receive events from calls to sendToListeners()
* and postToListeners(). If sinkID already exists in the listener list, no change is made.
*/
void addListenerID(SkEventSinkID sinkID);
/**
* Copy listeners from one event sink to another, typically from parent to child.
* @param from the event sink to copy the listeners from
*/
void copyListeners(const SkEventSink& from);
/**
* Remove sinkID from the list of listeners. If sinkID does not appear in the list,
* no change is made.
*/
void removeListenerID(SkEventSinkID);
/**
* Returns true if there are 1 or more listeners attached to this eventsink
*/
bool hasListeners() const;
/**
* Posts a copy of evt to each of the eventsinks in the lisener list.
* This ignores the targetID and target proc in evt.
*/
void postToListeners(const SkEvent& evt, SkMSec delay = 0);
enum EventResult {
kHandled_EventResult, //!< the eventsink returned true from its doEvent method
kNotHandled_EventResult, //!< the eventsink returned false from its doEvent method
kSinkNotFound_EventResult //!< no matching eventsink was found for the event's getSink().
};
/**
* DoEvent handles dispatching the event to its target ID or proc.
*/
static EventResult DoEvent(const SkEvent&);
/**
* Returns the matching eventsink, or null if not found
*/
static SkEventSink* FindSink(SkEventSinkID);
protected:
/** Override this to handle events in your subclass. Be sure to call the inherited version
for events that you don't handle.
*/
virtual bool onEvent(const SkEvent&);
virtual bool onQuery(SkEvent*);
SkTagList* findTagList(U8CPU tag) const;
void addTagList(SkTagList*);
void removeTagList(U8CPU tag);
private:
SkEventSinkID fID;
SkTagList* fTagHead;
// for our private link-list
SkEventSink* fNextSink;
typedef SkRefCnt INHERITED;
};
#endif
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