Specialized Listeners

The DTWAIN C++ interface has defined some specialized listeners for buffered memory transfers, and file transfers that use the Twain driver's internal file support.

DTwainBufferedListener

This specialized listener provides functions that save a buffered image data to a file.  The OnTransferReady( ), OnTransferStripDone( ), and OnTransferDone( ) functions are overridden in the DTwainBufferedTwainListener to save the acquired strips to a buffer, and when the acquisition is completed, write the strips to a file.

You can derive from these specialized listeners to provide your own listener functions.  However, you should call the base class listener function when your listener function is called:

class MyBufferedListener : public DTwainBufferedListener

{

  public:

        LRESULT OnTransferDone( DTwainSource& Source, LONG UserParam )

        {

           // your own processing

            // call base class function

            return DTwainBufferedListener::OnTransferDone( Source, UserParam );

        }

};

The only exception to this rule if if the listener event function allows specialized return values (such as OnPageContinue).