rfc746.txt

RFC 相关的技术文档

   Thus, the way for a program to work on all terminals with %TQBNK,
   whether they know about sets or not, is:  to write a bliniking
   picture, select some set other than your normal one (set 1 will do),
   do %GOBNK, output the picture, and reselect set 0.  The picture will
   blink, while you draw things in set 0.  To draw more blinking
   objects, you must reselect set 1 and do another %GOBNK.  Simply
   reselecting set 1 will not work on terminals which don't really
   support sets, since they don't remember that the blinking objects are
   "in set 1" and not "in set 0".

   Erasing a blinking object should make it disappear, on any terminal
   which implements blinking.  On bit matrix terminals, blinking MUST
   always be done by XORing, so that the non-blinking background is not
   destroyed.

   %GOCLS, on a terminal which supports blinking but not sets, should
   delete all blinking objects.  Then, the convention for deleting all
   blinking objects is to select set 1, do a %GOCLS, and reselect set 0.
   This has the desired effect on all terminals.  This definition of
   %GOCLS causes no trouble on non-set terminals, since %GOCLS would
   otherwise be meaningless to them.

   To make blinking objects stop blinking but remain visible is possible
   with a %GOVIS on a terminal which supports sets.  But in general the
   only way to do it is to delete them and redraw them as permanent.



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NWG/RFC# 746                                         RMS 17-MAR-78 43976
The SUPDUP Graphics Extension



Rectangles and XOR

   Bit matrix terminals have their own operations that display list
   terminals cannot duplicate.  First of all, they have XOR mode, in
   which objects drawn cancel existing objects when they overlap.  In
   this mode, drawing an object and erasing it are identical operations.
   All %GOD.. commands act IDENTICALLY to the corresponding %GOE..'s.
   XOR mode is entered with a %GOXOR and left with a %GOIOR.  Display
   list terminals will ignore both commands.  For that reason, the
   program should continue to distinguish draw commands from erase
   commands even in XOR mode.  %TQXOR indicates a terminal which
   implements XOR mode.  XOR mode, when set, remains set even if
   graphics mode is left and re-entered.  However, it is wise to
   re-specify it from time to time, in case output is lost.

   Bit matrix terminals can also draw solid rectangles.  They can thus
   implement the commands %GODRR, %GODRA, %GOERR, and %GOERA.  A
   rectangle is specified by taking the current cursor position to be
   one corner, and providing the address of the opposite corner.  That
   can be done with either a relative address or an absolute one.  The
   %TQREC bit indicates that the terminal implements rectangle commands.

   Of course, a sufficiently intelligent bit matrix terminal can provide
   all the features of a display list terminal by remembering display
   lists which are redundant with the bit matrix, and using them to
   update the matrix when a %GOMSR or %GOVIS is done.  However, most bit
   matrix terminals are not expected to go to such lengths.

























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NWG/RFC# 746                                         RMS 17-MAR-78 43976
The SUPDUP Graphics Extension



How Several Process Can Draw On One Terminal Without Interfering With
Each Other:

   If we define "input-stream state" information to be whatever
   information which can affect the action of any command, other than
   what is contained in the command, then each of the several processes
   must have its own set of input-stream state variables.

   This is accomplished by providing the %GOPSH command.  The %GOPSH
   command saves all such input-stream information, to be restored when
   graphics mode is exited.  If the processes can arrange to output
   blocks of characters uninterruptibly, they can begin each block with
   a %GOPSH followed by commands to initialize the input-stream state
   information as they desire.  Each block of graphics output should be
   ended by a %TDNOP, leaving the terminal in its "normal" state for all
   the other processes, and at the same time popping the what the %GOPSH
   pushed.

      The input-stream state information consists of:

         The cursor position
         the state of XOR mode (default is OFF)
         the selected set (default is 0)
         the co-ordinate unit in use (physical dots, or virtual)
            (default is physical)
         whether output is going to the display screen or to a hardcopy
            device (default is to the screen)
         what portion of the screen is in use
            (see "Using Only Part of the Screen")
            (default is all)

   Each unit of input-stream status has a default value for the sake of
   programs that do not know that the information exists; the exception
   is the cursor position, since all programs must know that it exists.
   A %TDINI or %TDRST command should set all of the variables to their
   default values.

   The state of the current set (whether it is visible, and where its
   center is) is not part of the input-stream state information, since
   it would be hard to say what it would mean if it were.  Besides, the
   current set number is part of the input-stream state information, so
   different processes can use different sets.  The allocation of sets
   to processes is the server host's own business.









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NWG/RFC# 746                                         RMS 17-MAR-78 43976
The SUPDUP Graphics Extension



Using Only Part of the Screen:

   It is sometimes desirable to use part of the screen for picture and
   part for text.  Then one may wish to clear the picture without
   clearing the text.  On display list terminals, %GOCLR should do this.
   On bit matrix terminals, however, %GOCLR can't tell which bits were
   set by graphics and which by text display.  For their sake, the
   %GOLMT command is provided.  This command takes two cursor positions
   as arguments, specifying a rectangle.  It declares that graphics will
   be limited to that rectangle, so %GOCLR should clear only that part
   of the screen.  %GOLMT need not do anything on a terminal which can
   remember graphics output as distinct from text output and clear the
   former selectively, although it would be a desirable feature to
   process it even on those terminals.

   %GOLMT can be used to enable one of several processes which divide up
   the screen among themselves to clear only the picture that it has
   drawn, on a bit matrix terminal.  By using both %GOLMT and distinct
   sets, it is possible to deal successfully with almost any terminal,
   since bit matrix terminals will implement %GOLMT and display list
   terminals almost always implement sets.

   The %TDCLR command should clear the whole screen, including graphics
   output, ignoring %GOLMT.

Errors:

   In general, errors in graphics commands should be ignored.

   Since the output and input streams are not synchronized unless
   trouble is taken, there is no simple way to report an error well
   enough for the program that caused it to identify just which command
   was invalid.  So it is better not to try.

   Errors which are not the fault of any individual command, such as
   running out of memory for display lists, should also be ignored as
   much as possible.  This does NOT mean completely ignoring the
   commands that cannot be followed; it means following them as much as
   possible: moving the cursor, selecting sets, etc. as they specify, so
   that any subsequent commands which can be executed are executed as
   intended.











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NWG/RFC# 746                                         RMS 17-MAR-78 43976
The SUPDUP Graphics Extension



Extensions:

   This protocol does not attempt to specify commands for dealing with
   every imaginable feature which a picture-drawing device can have.
   Additional features should be left until they are needed and well
   understood, so that they can be done right.

Storage of Graphics Commands in Files:

   This can certainly be done.  Since graphics commands are composed
   exclusively of the ASCII characters 0 - 177, any file that can hold
   ASCII text can hold the commands to draw a picture.  This is less
   useful than you might think, however.  Any program for editing, in
   whatever loose sense, a picture, will have its own internal data
   which determine the relationships between the objects depicted, and
   control the interpretation of the programs commands, and this data
   will all be lost in the SUPDUP graphics commands for displaying the
   picture. Thus, each such program will need to have its own format for
   storing pictures in files, suitable for that program's internal data
   structure.  Inclusion of actual graphics commands in a file will be
   useful only when the sole purpose of the file is to be displayed.































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NWG/RFC# 746                                         RMS 17-MAR-78 43976
The SUPDUP Graphics Extension



Note: the values of these commands are represented as 8.-bit octal
bytes.  Arguments to the commands are in lower case inside angle
brackets.

The Draw commands are:

Value   Name   Arguments

101     %GODLR <p>
                Draw line relative, from the cursor to <p>.
102     %GODPR <p>
                Draw point relative, at <p>.
103     %GODRR <p>
                Draw rectangle relative, corners at <p> and at the
                current cursor position.
104     %GODCH <string> <0>
                Display the chars of <string> starting at the current
                graphics cursor position.
121     %GODLA <p>
                Draw line absolute, from the cursor to <p>. The same
                effect as %GODLR, but the arg is an absolute address.
122     %GODPA <p>
                Draw point absolute, at <p>.
123     %GODRA <p>
                Draw rectangle absolute, corners at <p> and at the
                current cursor position.

The Erase commands are:

Value   Name   Arguments

141     %GOELR <p>
                Erase line relative, from the cursor to <p>.
142     %GOEPR <p>
                Erase point relative, at <p>.
143     %GOERR <p>
                Erase rectangle relative, corners at <p> and at the
                current cursor position.
144     %GOECH <string> <0>
                Erase the chars of <string> starting at the current
                graphics cursor position.
161     %GOELA <p>
                Erase line absolute, from the cursor to <p>.
162     %GOEPA <p>
                Erase point absolute, at <p>.
163     %GOERA <p>
                Erase rectangle absolute, corners at <p> and at the
                current cursor position.




                                  -13-

NWG/RFC# 746                                         RMS 17-MAR-78 43976
The SUPDUP Graphics Extension



The miscellaneous commands are:

Value   Name   Arguments

001     %GOMVR <p>
                Move cursor to point <p>
021     %GOMVA <p>
                Move cursor to point <p>, absolute address.
002     %GOXOR
                Turn on XOR mode.  Bit matrix terminals only.
022     %GOIOR
                Turn off XOR mode.
003     %GOSET <n>
                Select set.  <n> is a 1-character set number, 0 - 177.
004     %GOMSR <p>
                Move set origin to <p>.  Display list terminals only.
024     %GOMSA <p>
                Move set origin to <p>, absolute address.
006     %GOINV
                Make current set invisible.
026     %GOVIS
                Make current set visible.
007     %GOBNK
                Make current set blink.  Canceled by %GOINV or %GOVIS.
010     %GOCLR
                Erase whole screen.
030     %GOCLS
                Erase entire current set (display list terminals).
011     %GOPSH
                Push all input-stream status information, to be restored
                when graphics mode is exited.
012     %GOVIR
                Start using virtual co-ordinates
032     %GOPHY
                Resume giving co-ordinates in units of dots.
013     %GOHRD <n>
                Divert output to output subdevice <n>. <n>=0 reselects
                the main display screen.
014     %GOGIN <n>
                Request graphics input (mouse, tablet, etc). <n> is the
                reply code to include in the answer.
015     %GOLMT <p1> <p2>
                Limits graphics to a subrectangle of the screen. %GOCLR
                will clear only that area.  This is for those who would
                use the rest for text.







                                  -14-

NWG/RFC# 746                                         RMS 17-MAR-78 43976
The SUPDUP Graphics Extension



Bits in the SMARTS Variable Related to Graphics:

Note: the values of these bits are represented as octal 36.-bit words,
with the left and right 18.-bit halfword separated by two commas as in
the normal PDP-10 convention.

Name    Value      Description

%TQGRF  000001,,0  terminal understands graphics protocol.

%TQSET  000002,,0  terminal supports multiple sets.

%TQREC  000004,,0  terminal implements rectangle commands.

%TQXOR  000010,,0  terminal implements XOR mode.

%TQBNK  000020,,0  terminal implements blinking.

%TQVIR  000040,,0  terminal implements virtual co-ordinates.

%TQWID  001700,,0  character width, in dots.

%TQHGT  076000,,0  character height, in dots.

%TRGIN  0,,400000  terminal can provide graphics input.

%TRGHC  0,,200000  terminal has a hard-copy device to which output can
                   be diverted.
























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