PA_TryToOpenPrinterSession

version 2003

PA_TryToOpenPrinterSession → char

The routine PA_TryToOpenPrinterSession allows the 4D Extension to have exclusive access to the printer.

If the printer (or hardware/software printing device) is not currently used by any of the processes running within the 4D work session, the routine returns 1, and gives your plug-in exclusive access to the printer. If a process within the 4th Dimension work session is currently printing, the routine returns 0.

A Plug-in cannot perform any print operation until it has exclusive access to the printer.

The plug-in developer MUST "take" the printer before printing.

Another routine of this API, PA_OpenPrinterSession, waits until the printer is not used by any other process; PA_TryToOpenPrinterSession returns immediately, even if the printer is in use.

If the 4D Plug-in directly performs print operations, it must:

A successful (routine returns 0) call to PA_TryToOpenPrinterSession must be counter-balanced by a call to PA_ClosePrinterSession . If this is not done, the PrintManager will be unavailable to all the other processes for the duration of the active 4th Dimension session.

On Macintosh, this routine will call internally PrOpen, so you won't have to call it yourself.

Do not print if the printer is already in use.

 
   void PrintIfFree()
   {
      if ( PA_TryToOpenPrinterSession() )
      {
         /* . . . printing operations . . . */
 
         PA_ClosePrinterSession();
      }
      else
         PA_Alert("PrinterIn use, try later.");
   }

PA_ClosePrinterSession , PA_OpenPrinterSession .