device_drivers

PRSVR/DEVICE_DRIVERS -- User-supplied Print Server Device Drivers     83/08/08


  The Print Server (PRSVR) is capable of handling up to 4 customer-supplied
  device drivers on systems running Software Version SR4.1 or later.  This
  support is in addition to that supplied by Apollo for the NEC Spinwriter,
  Printronix, Versatec, and GE 3000 printers.

  A user device driver may consist of 6 procedures:

  USERn_INIT (sio_line, sio_line_speed)
       is called once to initialize the printer.  This procedure
       typically initializes internal state and opens the
       specified SIO line.  SIO_$CONTROL may be called to set the
       characteristics of the SIO line.  The sio_line_speed parameter
       indicates the line speed of the chosen SIO line (i.e., one
       of SIO_$50, SIO_$75, SIO_$110, ..., SIO_$19200).

  USERn_WRITE (string, length)
       is called to write the specified string to the device.  Any
       number of newline characters (including zero) may be
       present in the string.

  USERn_FLUSH
       is called to flush the output buffer for the device.
       Ignore this call if data for the device is not buffered by
       the driver.

  USERn_SET_MODE (mode, value)
       is called to convey to the device driver any information
       which the user may have specified (via the PRF command)
       at the time the file was printed.  This call may also be
       used by PRSVR to convey information from other sources
       in the future.  Support is currently provided which allows
       the user to specify the following information:

          - point size of desired font
          - weight of desired font
          - draft or letter quality font
          - type of data being sent
            1. text
            2. plot file - bitmap data defined by
               a GMF file
            3. transparent - no interpretation
               of data is done by PRSVR.

  USERn_RETURN_INFO (query, info)
       is called to determine some capability of the device from
       the user supplied device driver.  Currently the only query
       which need be supported is the bits/inch for a plotting device.

  USERn_CLOSE
       is called to close the device prior to exiting from the
       print server.

  (The declarations of these calls and data types used may be found in
  /SYS/INS/PRSVR.INS.PAS.)

  After the device driver has been written, bind it with the Print Server
  as follows:

       $ bind -b prsvr.user /com/prsvr user1.bin

  The binder will complain about undefined symbols for all unsupplied user
  device drivers; ignore these messages.

  Select the device using the DEVICE entry in the configuration file
  (see HELP PRSVR CONFIG).  Specify either SPINWRITER, PRINTRONIX, VERSATEC,
  or GE for the standard Apollo-supported devices, or USER1, USER2, USER3, or
  USER4 for user-supplied device drivers.  The letter "n" in the device
  driver procedure names is replaced by the device number: 1, 2, 3, or 4.

RELATED TOPICS

  More information is available.  Type:

    - HELP PRSVR
      for details about starting the Print Server.

    - HELP PRSVR CONFIG
      for details about device configuration files.

    - HELP PRF
      for details about queueing files to a printer.
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