这只是一个注册表的添加删除用的。不知道为什么要多加入两个基类
/* Copyright (C) 2002-2005 RealVNC Ltd.  All Rights Reserved.
*
* This is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This software 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this software; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
* USA.
*/

// -=- RegConfig.h

// Class which monitors the registry and reads in the registry settings
// whenever they change, or are added or removed.

#ifndef __RFB_WIN32_REG_CONFIG_H__
#define __RFB_WIN32_REG_CONFIG_H__

#include <rfb/Threading.h>
#include <rfb/Configuration.h>
#include <rfb_win32/Registry.h>
#include <rfb_win32/EventManager.h>
#include <rfb_win32/Handle.h>

namespace rfb {

  namespace win32 {

    class RegConfig : EventHandler {
    public:
      RegConfig(EventManager* em);
      ~RegConfig();

      // Specify the registry key to read Configuration items from
      bool setKey(const HKEY rootkey, const TCHAR* keyname);

      // Support for a callback, run in the RegConfig host thread whenever
      // the registry configuration changes
      // 这里说是回调，不明白他是怎么回调的。回调的哪个函数。
      class Callback {
      public:
        virtual ~Callback() {}
        virtual void regConfigChanged() = 0;
      };
      void setCallback(Callback* cb) { callback = cb; }

      // Read entries from the specified key into the Configuration
      static void loadRegistryConfig(RegKey& key);
    protected:
      // EventHandler interface and trigger event
      virtual void processEvent(HANDLE event);

      EventManager* eventMgr;
      Handle event;
      Callback* callback;
      RegKey key;
    };

    class RegConfigThread : Thread {
    public:
      RegConfigThread();
      ~RegConfigThread();

      // Start the thread, reading from the specified key
      bool start(const HKEY rootkey, const TCHAR* keyname);
    protected:
      void run();
      Thread* join();
      EventManager eventMgr;
      RegConfig config;
    };

  };

};

#endif // __RFB_WIN32_REG_CONFIG_H__

***************************************************8
下面是EventHandler,EventManager两个类。
/* Copyright (C) 2002-2005 RealVNC Ltd.  All Rights Reserved.
*
* This is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This software 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this software; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
* USA.
*/

// -=- EventManager.h

// Win32 event manager.  Caller supplies event & handler pairs and
// then uses getMessage() in place of ::GetMessage() in the main
// loop.  EventManager calls the event handler whenever the event
// is set.
// Ownership of events remains with the caller.
// It is the responsibility of handlers to reset events.

#ifndef __RFB_WIN32_EVENT_MGR_H__
#define __RFB_WIN32_EVENT_MGR_H__

#include <rfb_win32/Win32Util.h>

namespace rfb {
  namespace win32 {

    class EventHandler {
    public:
      virtual ~EventHandler() {}
      virtual void processEvent(HANDLE event) = 0;
    };

    class EventManager {
    public:
      EventManager();
      virtual ~EventManager();

      // Add a Win32 event & handler for it
      //   NB: The handler must call ResetEvent on the event.
      //   NB: The caller retains ownership of the event.
          //  添加一个事件
      virtual bool addEvent(HANDLE event, EventHandler* ecb);

      // Remove a Win32 event
      virtual void removeEvent(HANDLE event);

      // getMessage
      //   Waits for a message to become available on the thread's message queue,
      //   and returns it.  If any registered events become set while waiting then
      //   their handlers are called before returning.
      //   Returns zero if the message is WM_QUIT, -1 in case of error, >0 otherwise.
      virtual BOOL getMessage(MSG* msg, HWND hwnd, UINT minMsg, UINT maxMsg);

    protected:
      // checkTimeouts
      //   Derived classes should override this to perform any extra processing,
      //   returning the maximum number of milliseconds after which the callback
      //   should be called again.
      virtual int checkTimeouts();

      HANDLE events[MAXIMUM_WAIT_OBJECTS];
      EventHandler* handlers[MAXIMUM_WAIT_OBJECTS-1];
      int eventCount;
    };

  };
};

#endif

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