rfc553.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

         makes sense if the specified unit is a string or tty unit.

         Errors: Subpicture does not exist, unit does not exist, not a
         string or tty unit.

      DELETE-UNIT(Subpicture, Unit)

         Deletes a unit.









Irby, et. al.                                                  [Page 13]

RFC 553        Draft design for a text/graphics protocol    14 July 1973


      VISIBLE-UNIT(Subpicture, Unit, Flag)

         Makes the Unit visible or invisible as specified by Flag.  If a
         unit which is target sensitive is made invisible, it is no
         longer target sensitive.  However, in the absence of a
         subsequent modifying target sensitive command, the unit becomes
         target sensitive again if it should be made visible.

         Errors: Subpicture does not exist, unit does not exist.

      SET-TARGET-KEY(Subpicture, Unit, Target-Key)

         Sets the target key for the specified unit to the specified
         value.

      SET-STANDOUT-MODE(mode)

         Sets the mode that will be used to make text and/or units stand
         out to blinking, underlining, etc.

         If the terminal does not support the specified mode, the
         terminal should make a best effort or use another method to
         make things stand out.

      STANDOUT-UNIT(Subpicture, unit, yesno)

         makes the specified unit stand out (according to the mode set
         by SET-STANDOUT-MODE) or not, according to "yesno".  If the
         unit which is to stand out is a call-unit, the instance of the
         subpicture which is the result of the call (all the way to the
         terminal nodes) is made to stand out.

      STANDOUT-TEXT(Subpicture, unit, begin-char-count, end-char-count,
      yesno)

         Unit must refer to a string unit.

         Makes the specified text stand out (according to the mode set
         by SET-STANDOUT-MODE) or not, according to "yesno".

      UPDATE-STRUCTURED-DISPLAY()

         This causes any changes that have been made to the display
         file, since the last update or since ICP, to be reflected on
         the screen.






Irby, et. al.                                                  [Page 14]

RFC 553        Draft design for a text/graphics protocol    14 July 1973


      TTY(parameters)

         parameters are:

            position rectangle, visible/invisible, number of lines, mode
            of characters

         This refers to the ICP TTY simulation

      USE-TTY-UNITS(Subpicture1, unit1, ..., Subpicturen, unitn)

         Unescorted characters are to be appended only to the specified
         tty units.

      Errors: Subpicture, unit does not exist.

      RESET(How)

         Case How Of

            =  Permanent

               Immediately resets the terminal to its initial ICP state

            =  Temporary

               Immediately resets the terminal to its initial ICP state
               without destroying the previous state.

            =  Restore state saved from last RESET(Temporary).

Direct Feedback

   It seems extremely desirable, given network speeds, to allow the
   using host to perform direct feedback to the user without
   intervention from the application program in the serving host.  This
   is already done in telnet with local echoing.  We propose extending
   this capability to graphics by allowing "dragging" (attaching a
   subpicture's origin to the position of the cursor), "tracking"
   (following the movement of the mouse, stylus, or light pen with a
   distinctive mark on the screen), "inking" (plotting the trail of the
   cursor on the screen) and "rubber banding" (a straight line attached
   to a fixed point on one end the cursor location on the other).

   These should be seen as allowable extensions of the protocol rather
   than as requirements.  There should, however, be commands available
   in the protocol for determining their existence and controlling them.




Irby, et. al.                                                  [Page 15]

RFC 553        Draft design for a text/graphics protocol    14 July 1973


Data input primitives

   Input Control

      TARGET-SENSATIVE(key1, ..., keyn)

         Arms the units which have the specified keys for target
         selection.

      SET-INPUT-MODE(Device, parameters)

         Selects the mode in which a logical device shall produce input
         and under what conditions.

         the logical devices are specified below as well as their
         possible input formats and conditions.

         Errors: no such device.

   Keyboard input

      The keyboard has only one input mode, in which it sends a
      character whenever a key is struck.

   Binary devices

      Unless otherwise specified, binary devices act as an extension of
      the keyboard and produce 8-bit characters which are not
      distinguishable from keyboard characters by the serving host.

         The algorithm for translating binary devices into characters is
         not specified, but something like the NLS accumulation
         algorithm for mouse-keyset chords is intended.

      Binary devices may also input binary data (according to their
      up/down states), which is transmitted on state changes.  Examples
      of this type of device are function keys and overlay cards, mouse
      and keyset (used independently or together), pen-up/pen/down,
      light pen buttons, etc.

   Coordinate input

      Coordinates may be sent according to any subset of the following
      criteria: with every character in some designated set (e.g.
      control characters, or all characters); with every binary device
      state change input; after some time interval has elapsed; after a
      position change P > (y1-y0) ^2+(x1-x0)^2, etc.




Irby, et. al.                                                  [Page 16]

RFC 553        Draft design for a text/graphics protocol    14 July 1973


      Coordinates may be sent in either or both of "X-Y" or "target"
      format.

         X-Y format is just the location of the cursor relative to the
         screen region assigned to the host.

         Target format is the "call stack" (logical path from the root
         unit - the ICP SUBPICTURE - to the closest unit) plus the
         target-key of that unit plus the count of the closest character
         within the string or the closest line segment or dot or special
         point if appropriate.

            Target input is unavailable for segmented display files.

            In the event of overlapping target sensitive units, it is
            not specified which of the units selected will be returned
            as the hit unit.

   Time input

      Since hosts may wish to consider two events happening sufficiently
      close together to be simultaneous, or to keep detailed interaction
      statistics, it must be possible to request time information to be
      sent with some reasonable subnet of other types of input.

Interrogations

   It must be possible for the serving host to discover its environment
   (e.g. screen size, available devices) and to read back state
   information (display file).

      This is very desirable both for debugging and for redirecting a
      displayed image to another device (e.g. a plotter).

   Environment

      Terminal parameters: screen size and resolution, available input
      devices, terminal type (for device specific control), number of
      lines in the ICP TTY-UNIT.

      Character parameters: available character sizes, special (non-
      ASCII) characters, font characteristics, sub- and super-scripting
      facilities.

   State

      Display file or display file components.




Irby, et. al.                                                  [Page 17]

RFC 553        Draft design for a text/graphics protocol    14 July 1973


      Cursor Position

         It should be possible for the application program to read the
         cursor position at any time.

      Display File Support

         It should be possible to find out if this user process supports
         only segmented or structured display files, or both.

      Command support

         It should be possible to get a matrix from the user process
         which indicates which commands are implemented.  This is a
         necessity to find out which, if any, of the direct feedback
         features are supported, and might be nice to allow for, e.g.,
         the possibility of a text only or graphics only subset of the
         protocol to be implemented.

Encoding Principles

   Commands will have the format : BGC OPCODE DATA EGC where:

      BGC (Begin Graphics Command) places the telnet connection into a
      "read graphics command" mode,

      OPCODE DATA is the specific graphics command and data, and

      EGC (End Graphics Command) restores the telnet connection to its
      normal state.

      Note: This may all have to be bracketed by telnet Begin-8-bit-
      transparent-mode and End-8-bit-transparent-mode commands.

   Numbers in general will have have 7-bits of significance in each byte
   -- if the high order of a byte is on, then the significant bits from
   the next byte should be concatenated onto the low-order end of the
   bits collected so far, etc..

   Subpicture names - shall be 14-bit numbers, assigned by the serving
   host.

   Unit names - shall be 14-bit numbers, assigned by the serving host.

   Strings - shall be 8-bit characters, with an escape convention to
   represent changes of font and mode.





Irby, et. al.                                                  [Page 18]

RFC 553        Draft design for a text/graphics protocol    14 July 1973


      Since the channel is 8-bits wide, there is room for many more than
      128 displayable characters.  However, the interpretation of codes
      200B and above is not standardized!

   Coordinates should be as described in RFC 493.

   Rectangles - shall be specified by the coordinates of the endpoints
   of one of the diagonal.

Encoding

   The actual encoding of this protocol is forthcoming.  Since we expect
   some changes to come about because of the upcoming Network Graphics
   Group Meeting, we have postponed the actual encoding until after this
   meeting.

          [This RFC was put into machine readable form for entry]
           [into the online RFC archives by Via Genie, 12/1999]

































Irby, et. al.                                                  [Page 19]