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/*
* Copyright (C) 2006 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#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.
*/
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 searching for an eventsink object that matches the targetID.
If one is found, it calls the sink's doEvent method, returning
either kHandled_EventResult or kNotHandled_EventResult. If no matching
eventsink is found, kSinkNotFound_EventResult is returned.
*/
static EventResult DoEvent(const SkEvent&, SkEventSinkID targetID);
/** 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;
};
#endif
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