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─────PWB Extensions─────────────────────────────────────────────────────────
 
  Syntax:  void pascal EXPORT DeRegisterEvent( EVT far *Event );
           void pascal EXPORT RegisterEvent  ( EVT far *Event );
 
  See:     ◄PWB Softcr Switch►
 
     The RegisterEvent and DeRegisterEvent functions allow your
     extension to install an event handler. An event handler is a
     function that PWB calls when a certain event occurs. For user
     extensions, only the newline event is supported.
 
     For the newline event, PWB calls your handler after you execute the
     Newline or Emacsnewl functions and the Softcr switch is set to Yes.
     Your handler then specifies the new position for the cursor.
 
     The event structure that you register gives the address of the
     event handler, and specifies the type of event. A newline event is
     defined in your extension as follows:
 
         EVT EvtNewline = { 0, Handler, 0, EVT_NEWLINE, 0 };
 
     The event structure has the definition:
 
         struct eventType {                  // Event definition struct
             struct eventType far *pEVTNext; //   Next handler in list
             flagType (pascal EXPORT *func)
                             (EVTargs far *);//   Handler
             EVTargs far *pEVTargs;          //   Pointer to arg
             unsigned    evtType;            //   Type
             PFILE       focus;              //   File at event time
             };
         typedef struct eventType EVT;
 
     You specify only the handler function and the event type in the
     structure. The other members are used by PWB and should be empty
     (zero).
 
     Your event function must have the prototype:
 
         flagType pascal EXPORT Handler( EVTargs far *EventArg );
 
     When the event occurs, PWB calls your event handler with a pointer
     to an event argument structure. Your handler returns TRUE if it
     handles the event. Otherwise your handler returns FALSE to pass the
     event to other event handlers.
 
     The event argument is defined in EXT.H as follows:
 
         struct newlinevent {      // Newline event argument
             PFILE     pFile;      // pFile at time of event
             char far *lpszSuffix; // file suffix
             LINE      line;       // current line of pFile
             COL       newcol;     // returns x-position on new line
             int       tabmode;    // TM_NONE, TM_FORWARD, TM_BACKWARD
             };
         typedef union {                     // event argument
             struct newlinevent EvtNewline;  // newline event data
             } EVTargs;
 
     For the newline event, PWB calls your handler after creating the
     new line and passes the handle of the file, the filename extension
     (suffix) of the file, and the new line number.
 
     Your handler should define a text switch that lists the suffixes
     for which your handler should process newline events. If the suffix
     at the time of the event is listed in your handler's list, then it
     should fill in the event argument structure and return TRUE. If the
     suffix is not in the list, your handler should return FALSE.
 
     To handle a newline event, your handler should set the newcol
     member to the new column and the tabmode member to one of the
     following values:
 
     tabmode        Action
 
     TM_NONE        Place cursor at 'newcol'
     TM_FORWARD     Place cursor 1 backtab from 'newcol'
     TM_BACKWARD    Place cursor 1 tab from 'newcol'
 
     For an example of a newline event handler, see the INDENT.C example
     extension.
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