NIC 9929                                                Ira Cotton
NWG/RFC #336                                            Mitre
Level 0 Graphic Input Protocol                          5 May 1972

        Level 0 Graphic Input Protocol

           At its meeting on April 16-18 the network Graphics working
           group began to consider the definition of levels of protocol
           for graphic Input Protocol.  The following describes the
           Level 0 graphics input protocol.

           The philosophy guiding the establishment of this protocol is
           the same as suggested in RFC #178, "Network Graphic Attention
           Handling." Briefly, all input will be described by type,
           origin, and length, followed by the actual data.

           Only two types of input are defined at Level 0: text and
           simple position.

              Text Input

                  Text input will be conveyed in the following format:

                   TEXTIN : DEVICE : COUNT: Text String



                 TEXTIN is a protocol code indicating the nature of this
                 input string.  For the present this code is defined to
                 be 1.

                 DEVICE is a code indicating the device from which the
                 input originated.  The following codes are presently
                 defined:

                      0 - unspecified device
                      1 - primary keyboard
                      2 - tablet
                      3 - mouse
                      4 - joystick
                      5 - lightpen
                      6 - cursor
                      7 - keyset
                      8 - mouse & keyset







                                                                [Page 1]

NIC 9929
NWG/RFC# 336
Level 0 Graphic Input Protocol

                 Count is an integer number indicating the number of
                 characters (bytes) which follow.

                 Text String is a string of "Count" bytes of characters
                 in network ASCII.

              Position Input

                   Simple position data will be conveyed in the
              following format:

                   POSIT : DEVICE : COUNT : x : y

                 POSIT is a protocol code indicating that this string
                 contains position data.  For the present this code is
                 defined to be 2.

                 DEVICE is a code indicating the input device on which
                 this data was generated.  The codes are as defined
                 above.

                 COUNT is an integer number indicating the number of
                 bytes of data which follow.  This includes data for
                 both x and y coordinates.  Thus, the number of bytes of
                 x coordinate data is COUNT divided by 2.  At level 0,
                 COUNT should always be 4, since at this level all
                 coordinates are expressed in 2 bytes of data.

                 x and y coordinate data are represented as signed
                 fractions in the same fashion that position data is
                 represented in the Level 0 graphic output protocol.

           It should be emphasized that input data from a level 0
           graphics user which is not in a format described above should
           be sent on a different link than the graphics input link.
           This may be desirable for certain applications to avoid the
           overhead of the protocol.

       [ This RFC was put into machine readable form for entry ]
       [ into the online RFC archives by BBN Corp. under the   ]
       [ direction of Alex McKenzie.                   12/96   ]






                                                                [Page 2]