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LIB2648(3X)                                                        LIB2648(3X)

       lib2648 - subroutines for the HP 2648 graphics terminal

       #include <&lt;stdio.h>&gt;

       typedef char *bitmat;
       FILE *trace;

       cc file.c -l2648

       Lib2648 is a general purpose library of subroutines useful for interac-
       tive graphics on the Hewlett-Packard 2648 graphics terminal.  To use it
       you  must call the routine ttyinit() at the beginning of execution, and
       done() at the end of execution.  All terminal input and output must  go
       through the routines rawchar, readline, outchar, and outstr.

       Lib2648  does  the  necessary  ^E/^F  handshaking  if  getenv(``TERM'')
       returns ``hp2648'', as it will if set by  tset(1).   Any  other  value,
       including for example ``2648'', will disable handshaking.

       Bit  matrix  routines  are provided to model the graphics memory of the
       2648.  These routines are generally useful, but are specifically useful
       for the update function which efficiently changes what is on the screen
       to what is supposed to be on the screen.  The primative bit matrix rou-
       tines are newmat, mat, and setmat.

       The  file  trace,  if  non-null, is expected to be a file descriptor as
       returned by fopen.  If so, lib2648 will trace the progress of the  out-
       put by writing onto this file.  It is provided to make debugging output
       feasible for graphics programs without messing up  the  screen  or  the
       escape sequences being sent.  Typical use of trace will include:
            switch (argv[1][1]) {
            case 'T':
                 trace = fopen("trace", "w");
            if (trace)
                 fprintf(trace, "x is %d, y is %s\n", x, y);
            dumpmat("before update", xmat);

       agoto(x, y)
              Move  the  alphanumeric cursor to position (x, y), measured from
              the upper left corner of the screen.

       aoff() Turn the alphanumeric display off.

       aon()  Turn the alphanumeric display on.

       areaclear(rmin, cmin, rmax, cmax)
              Clear the area on the graphics screen bordered by the four argu-
              ments.   In normal mode the area is set to all black, in inverse
              video mode it is set to all white.

       beep() Ring the bell on the terminal.

       bitcopy(dest, src, rows, cols) bitmat dest, src;
              Copy a rows by cols bit matrix from src to (user provided) dest.

              Clear the alphanumeric display.

              Clear the graphics display.  Note that the 2648 will only  clear
              the part of the screen that is visible if zoomed in.

              Turn the graphics cursor off.

              Turn the graphics cursor on.

       dispmsg(str, x, y, maxlen) char *str;
              Display  the  message  str  in graphics text at position (x, y).
              The maximum message length is given by maxlen, and is needed  to
              for  dispmsg to know how big an area to clear before drawing the
              message.  The lower left corner of the first character is at (x,

       done() Should  be called before the program exits.  Restores the tty to
              normal, turns off graphics screen, turns on alphanumeric screen,
              flushes the standard output, etc.

       draw(x, y)
              Draw a line from the pen location to (x, y).  As with all graph-
              ics coordinates, (x, y) is measured from the bottom left  corner
              of  the screen.  (x, y) coordinates represent the first quadrant
              of the usual Cartesian system.

       drawbox(r, c, color, rows, cols)
              Draw a rectangular box on the graphics screen.  The  lower  left
              corner  is  at  location  (r, c).  The box is rows rows high and
              cols columns wide.  The box is drawn if color is  1,  erased  if
              color  is 0.  (r, c) absolute coordinates represent row and col-
              umn on the screen, with the origin at the lower left.  They  are
              equivalent to (x, y) except for being reversed in order.

       dumpmat(msg, m, rows, cols) char *msg; bitmat m;
              If  trace  is non-null, write a readable ASCII representation of
              the matrix m on trace.  Msg is a label to identify the output.

       emptyrow(m, rows, cols, r) bitmat m;
              Returns 1 if row r of matrix m is  all  zero,  else  returns  0.
              This  routine  is  provided  because  it can be implemented more
              efficiently with a knowledge of the internal representation than
              a series of calls to mat.

       error(msg) char *msg;
              Default error handler.  Calls message(msg) and returns.  This is
              called by certain routines in lib2648.  It is also suitable  for
              calling  by  the user program.  It is probably a good idea for a
              fancy graphics program to supply its own error  procedure  which
              uses setjmp(3) to restart the program.

              Set the terminal to the default graphics modes.

       goff() Turn the graphics display off.

       gon()  Turn the graphics display on.

       koff() Turn the keypad off.

       kon()  Turn  the  keypad  on.  This means that most special keys on the
              terminal (such as the alphanumeric arrow keys) will transmit  an
              escape sequence instead of doing their function locally.

       line(x1, y1, x2, y2)
              Draw a line in the current mode from (x1, y1) to (x2, y2).  This
              is equivalent to move(x1, y1); draw(x2, y2); except that  a  bug
              in  the terminal involving repeated lines from the same point is
              compensated for.

              Move the alphanumeric cursor to the lower left (home down) posi-

       mat(m, rows, cols, r, c) bitmat m;
              Used  to  retrieve an element from a bit matrix.  Returns 1 or 0
              as the value of the [r, c] element of the rows by cols matrix m.
              Bit  matrices  are numbered (r, c) from the upper left corner of
              the matrix, beginning at (0, 0).  R represents the  row,  and  c
              represents the column.

       message(str) char *str;
              Display  the  text  message  str  at  the bottom of the graphics

       minmax(g, rows, cols, rmin, cmin, rmax, cmax) bitmat g;
         int *rmin, *cmin, *rmax, *cmax;
              Find the smallest rectangle that contains all the  1  (on)  ele-
              ments  in the bit matrix g.  The coordinates are returned in the
              variables pointed to by rmin, cmin, rmax, cmax.

       move(x, y)
              Move the pen to location (x, y).  Such motion  is  internal  and
              will not cause output until a subsequent sync().

       movecurs(x, y)
              Move the graphics cursor to location (x, y).

       bitmat newmat(rows, cols)
              Create  (with  malloc(3)) a new bit matrix of size rows by cols.
              The value created (e.g. a pointer  to  the  first  location)  is
              returned.  A bit matrix can be freed directly with free.

       outchar(c) char c;
              Print the character c on the standard output.  All output to the
              terminal should go through this routine or outstr.

       outstr(str) char *str;
              Print the string str on the standard output by repeated calls to

              Print  the graphics display on the printer.  The printer must be
              configured as device 6 (the default) on the HPIB.

       char rawchar()
              Read one character from the terminal and return it.   This  rou-
              tine  or  readline  should be used to get all input, rather than

              Turn the rubber band line off.

       rbon() Turn the rubber band line on.

       char *rdchar(c) char c;
              Return a readable representation of the character c.  If c is  a
              printing  character it returns itself, if a control character it
              is shown in the  ^X  notation,  if  negative  an  apostrophe  is
              prepended.  Space returns ^`, rubout returns ^?.

              NOTE: A pointer to a static place is returned.  For this reason,
              it  will  not  work  to  pass   rdchar   twice   to   the   same
              fprintf/sprintf  call.   You must instead save one of the values
              in your own buffer with strcpy.

       readline(prompt, msg, maxlen) char *prompt, *msg;
              Display prompt on the bottom line of the  graphics  display  and
              read  one  line  of text from the user, terminated by a newline.
              The line is placed in the buffer  msg,  which  has  size  maxlen
              characters.  Backspace processing is supported.

              Set  the display to draw lines in erase mode.  (This is reversed
              by inverse video mode.)

       setmat(m, rows, cols, r, c, val) bitmat m;
              The basic operation to store a value in  an  element  of  a  bit
              matrix.   The [r, c] element of m is set to val, which should be
              either 0 or 1.

              Set the display to draw lines in normal (solid) mode.  (This  is
              reversed by inverse video mode.)

              Set the display to draw lines in exclusive or mode.

       sync() Force  all  accumulated  output  to  be displayed on the screen.
              This should be followed by fflush(stdout).  The  cursor  is  not
              affected  by this function.  Note that it is normally never nec-
              essary to call sync, since rawchar and readline call sync()  and
              fflush(stdout) automatically.

              Toggle  the  state of video.  If in normal mode, go into inverse
              video mode, and vice versa.  The screen is reversed as  well  as
              the internal state of the library.

              Set  up  the  terminal  for  processing.  This routine should be
              called at the beginning of execution.  It places the terminal in
              CBREAK mode, turns off echo, sets the proper modes in the termi-
              nal, and initializes the library.

       update(mold, mnew, rows, cols, baser, basec) bitmat mold, mnew;
              Make whatever changes are needed to make a window on the  screen
              look like mnew.  Mold is what the window on the screen currently
              looks like.  The window has size rows by  cols,  and  the  lower
              left  corner  on  the  screen  of  the window is [baser, basec].
              Note: update was not intended to be used for the entire  screen.
              It would work but be very slow and take 64K bytes of memory just
              for mold and mnew.  It was intended for 100 by 100 windows  with
              objects  in  the center of them, and is quite fast for such win-

              Set inverse video mode.

              Set normal video mode.

       zermat(m, rows, cols) bitmat m;
              Set the bit matrix m to all zeros.

              Set the hardware zoom to value size, which can range from  1  to

              Turn  zoom  off.  This forces the screen to zoom level 1 without
              affecting the current internal zoom number.

              Turn zoom on.  This restores the screen to the previously speci-
              fied zoom size.

       The  routine error is called when an error is detected.  The only error
       currently detected is overflow of the buffer provided to readline.

       Subscripts out of bounds to setmat return without setting anything.



       Mark Horton

       This library is not supported.  It makes no attempt to use all  of  the
       features of the terminal, only those needed by fed.  Contributions from
       users will be accepted for addition to the library.

       The HP 2648 terminal is somewhat unreliable at speeds over  2400  baud,
       even  with the ^E/^F handshaking.  In an effort to improve reliability,
       handshaking is done every 32 characters.  (The manual claims it is only
       necessary  every  80  characters.)   Nonetheless,  I/O errors sometimes
       still occur.

       There is no way to control the amount of debugging output generated  on
       trace without modifying the source to the library.

4th Berkeley Distribution        1 March 1980                      LIB2648(3X)