Starting a TWAIN Session

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Before a TWAIN application can open a Source, it is necessary for the application to communicate with the TWAIN Source Manager (transition from TWAIN State 2 to State 3).  To do this, the DTWAIN_StartTwainSession function is called.

 

Normally, DTWAIN_StartTwainSession is automatically called by DTWAIN if a TWAIN session has not been started, and the application wants to select a Source. DTWAIN is smart enough to start the TWAIN session if one has not been started.

 

However, the application can call DTWAIN_StartTwainSession explicitly.  The application will need to start a TWAIN session explicitly if it needs to do any of the following:

 

Monitor and control the acquisition process by setting the notification window and capturing DTWAIN notifications and messages.
Use a different TWAIN_32.DLL (the TWAIN Data Source Manager) other than the default.