Artifact 37da8a7920abe4b110001af5755a0a003acacaceb73f84898a75a0eba6a35f85:

• File psl-1983/emode/vs-support.sl — part of check-in [eb17ceb7f6] at 2020-04-21 19:40:01 on branch master — Add Reduce 3.0 to the historical section of the archive, and some more
  files relating to version sof PSL from the early 1980s. Thanks are due to
  Paul McJones and Nelson Beebe for these, as well as to all the original
  authors.

  git-svn-id: https://svn.code.sf.net/p/reduce-algebra/code/historical@5328 2bfe0521-f11c-4a00-b80e-6202646ff360 (user: arthurcnorman@users.sourceforge.net, size: 2844) [annotate] [blame] [check-ins using] [more...]

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% VS-SUPPORT.SL - "Fast" routines to support the "virtual-screen" package.
% 
% Author:      Alan Snyder
%              Hewlett-Packard/CRC
% Date:        6 August 1982
%
% This revised version takes advantage of TerminalClearEOL.
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

(BothTimes (load fast-vector))

(de RewriteChangedCharacters (oldline newline RowLocation LeftCol RightCol)

  % A rather specialized routine to look for characters that differ between
  % oldline and newline, and to write those out to the screen.  The search is
  % limited to run from LeftCol to RightCol.  RowLocation is simply passed on
  % to WritePhysicalCharacter.

  (prog (last-nonblank-column)

    % Check to see whether a Clear-EOL is appropriate.  It is appropriate if
    % the rightmost changed character has been changed to a BLANK, and the
    % remainder of the line is blank.  If this is the case, we determine the
    % column to clear from, clear out the old line, and (after outputting prior
    % changed characters), do the Clear-EOL.

    % Find out where the rightmost changed character actually is:

    (while (and (WLEQ LeftCol RightCol)
	        (WEQ (igets newline RightCol) (igets oldline RightCol)))
      (setf RightCol (WDifference RightCol 1))
      )
    (if (WGreaterP LeftCol RightCol) (return NIL)) % No change at all!

    % If the rightmost changed character is being changed to a space, then find
    % out if the rest of the line is blank.  If it is, then set the variable
    % LAST-NONBLANK-COLUMN to the appropriate value and clear out OLDLINE in
    % preparation for a later ClearEOL.  Otherwise, LAST-NONBLANK-COLUMN
    % remains NIL.

    (if (WEQ (igets newline RightCol) (char space))
      (progn
        (setf last-nonblank-column (size newline))
        (while (and (WGEQ last-nonblank-column 0)
		    (WEQ (igets newline last-nonblank-column) (char space))
		    )
          (setf last-nonblank-column (WDifference last-nonblank-column 1))
          )
        (if (WLessP last-nonblank-column RightCol)
	    (while (> RightCol last-nonblank-column)
	      (iputs oldline RightCol (char space))
	      (setf RightCol (WDifference RightCol 1))
	      )
	    )))

    % Output all changed characters (other than those that will be taken care
    % of by ClearEOL):

    (while (WLEQ LeftCol RightCol)
      (let ((ch (igets newline LeftCol)))
        (if (WNEQ ch (igets oldline LeftCol))
	  (WritePhysicalCharacter ch RowLocation LeftCol)
	  ))
      (setf LeftCol (wplus2 LeftCol 1))
      )

    % Do the ClearEOL, if that's what we decided to do.

    (if last-nonblank-column
      (progn
	(MoveToPhysicalLocation RowLocation (WPlus2 last-nonblank-column 1))
	(TerminalClearEOL)
	))
  ))