phoenix-firestorm/indra/llcommon/llevent.h

/**
 * @file llevent.h
 * @author Tom Yedwab
 * @brief LLEvent and LLEventListener base classes.
 *
 * $LicenseInfo:firstyear=2001&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2010, Linden Research, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License only.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */

#ifndef LL_EVENT_H
#define LL_EVENT_H

#include "llsd.h"
#include "llrefcount.h"
#include "llpointer.h"

namespace LLOldEvents
{

class LLEventListener;
class LLEvent;
class LLEventDispatcher;
class LLObservable;

// Abstract event. All events derive from LLEvent
class LL_COMMON_API LLEvent : public LLThreadSafeRefCount
{
protected:
    virtual ~LLEvent();

public:
    LLEvent(LLObservable* source, const std::string& desc = "") : mSource(source), mDesc(desc) { }

    LLObservable* getSource() { return mSource; }
    virtual LLSD        getValue() { return LLSD(); }
    // Determines whether this particular listener
    //   should be notified of this event.
    // If this function returns true, handleEvent is
    //   called on the listener with this event as the
    //   argument.
    // Defaults to handling all events. Override this
    //   if associated with an Observable with many different listeners
    virtual bool accept(LLEventListener* listener);

    // return a string describing the event
    virtual const std::string& desc();

private:
    LLObservable* mSource;
    std::string mDesc;
};

// Abstract listener. All listeners derive from LLEventListener
class LL_COMMON_API LLEventListener : public LLThreadSafeRefCount
{
protected:
    virtual ~LLEventListener();

public:

    // Processes the event.
    // TODO: Make the return value less ambiguous?
    virtual bool handleEvent(LLPointer<LLEvent> event, const LLSD& userdata) = 0;

    // Called when an dispatcher starts/stops listening
    virtual bool handleAttach(LLEventDispatcher *dispatcher) = 0;
    virtual bool handleDetach(LLEventDispatcher *dispatcher) = 0;
};

// A listener which tracks references to it and cleans up when it's deallocated
class LL_COMMON_API LLSimpleListener : public LLEventListener
{
public:
    void clearDispatchers();
    virtual bool handleAttach(LLEventDispatcher *dispatcher);
    virtual bool handleDetach(LLEventDispatcher *dispatcher);

protected:
    ~LLSimpleListener();
    std::vector<LLEventDispatcher *> mDispatchers;
};

class LLObservable; // defined below

// A structure which stores a Listener and its metadata
struct LLListenerEntry
{
    LLEventListener* listener;
    LLSD filter;
    LLSD userdata;
};

// Base class for a dispatcher - an object which listens
// to events being fired and relays them to their
// appropriate destinations.
class LL_COMMON_API LLEventDispatcher : public LLThreadSafeRefCount
{
protected:
    virtual ~LLEventDispatcher();

public:
    // The default constructor creates a default simple dispatcher implementation.
    // The simple implementation has an array of listeners and fires every event to
    // all of them.
    LLEventDispatcher();

    // This dispatcher is being attached to an observable object.
    // If we return false, the attach fails.
    bool engage(LLObservable* observable);

    // This dispatcher is being detached from an observable object.
    void disengage(LLObservable* observable);

    // Adds a listener to this dispatcher, with a given user data
    // that will be passed to the listener when an event is fired.
    // Duplicate pointers are removed on addtion.
    void addListener(LLEventListener *listener, LLSD filter, const LLSD& userdata);

    // Removes a listener from this dispatcher
    void removeListener(LLEventListener *listener);

    // Gets a list of interested listeners
    std::vector<LLListenerEntry> getListeners() const;

    // Handle an event that has just been fired by communicating it
    // to listeners, passing it across a network, etc.
    bool fireEvent(LLPointer<LLEvent> event, LLSD filter);

public:
    class Impl;
private:
    Impl* impl;
};

// Interface for observable data (data that fires events)
// In order for this class to work properly, it needs
// an instance of an LLEventDispatcher to route events to their
// listeners.
class LL_COMMON_API LLObservable
{
public:
    // Initialize with the default Dispatcher
    LLObservable();
    virtual ~LLObservable();

    // Replaces the existing dispatcher pointer to the new one,
    // informing the dispatcher of the change.
    virtual bool setDispatcher(LLPointer<LLEventDispatcher> dispatcher);

    // Returns the current dispatcher pointer.
    virtual LLEventDispatcher* getDispatcher();

    void addListener(LLEventListener *listener, LLSD filter = "", const LLSD& userdata = "")
    {
        if (mDispatcher.notNull()) mDispatcher->addListener(listener, filter, userdata);
    }
    void removeListener(LLEventListener *listener)
    {
        if (mDispatcher.notNull()) mDispatcher->removeListener(listener);
    }
    // Notifies the dispatcher of an event being fired.
    void fireEvent(LLPointer<LLEvent> event, LLSD filter = LLSD());

protected:
    LLPointer<LLEventDispatcher> mDispatcher;
};

class LLValueChangedEvent : public LLEvent
{
public:
    LLValueChangedEvent(LLObservable* source, LLSD value) : LLEvent(source, "value_changed"), mValue(value) { }
    LLSD getValue() { return mValue; }
    LLSD mValue;
};

} // LLOldEvents

#endif // LL_EVENT_H