Notification Callback

Any print component or listening application that is interested in receiving notifications must provide objects that expose the IPrintAsyncNotifyCallback interface. The interface inherits from IUnknown so that the clients of the spooler notification mechanism can implement either a COM or a C++ object.

A listening application must provide a pointer to an IPrintAsyncNotifyCallback interface when it registers to receive notifications. The notification sender must provide a pointer to an IPrintAsyncNotifyCallback interface if it is interested in a response and it creates a bidirectional channel.


#define INTERFACE IPrintAsyncNotifyCallback
DECLARE_INTERFACE_(IPrintAsyncNotifyCallback, IUnknown)
{
    STDMETHOD(QueryInterface)(
        THIS_
        REFIID riid,
        void** ppvObj
        ) PURE;
 
    STDMETHOD_(ULONG, AddRef)(
        THIS
        ) PURE;
 
    STDMETHOD_(ULONG, Release)(
        THIS
        ) PURE;
 
    STDMETHOD(OnEventNotify)(
         THIS_
 IN IPrintAsyncNotifyChannel*,
         IN IPrintAsyncNotifyDataObject*
         ) PURE;
 
 STDMETHOD(ChannelClosed)(
         THIS_
         IN IPrintAsyncNotifyChannel*,
         IN IPrintAsyncNotifyDataObject*
         ) PURE;
};

When a notification is sent from one end of the channel, the spooler service calls the IPrintAsyncNotifyCallback::OnEventNotify method at the other end of the channel to deliver the notification.

When the notification channel is closed at one end, the spooler service calls the IPrintAsyncNotifyCallback::ChannelClosed method at the other end to announce that the channel is closed. The reason for closing the channel is delivered as a notification.

If either the server or the listening application dies, the spooler rundown code detects this condition and the "still alive" end of the channel that is still alive is notified by a IPrintAsyncNotifyCallback::ChannelClosed call, in which a NOTIFICATION_RELEASE message is delivered.

 

 

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