🚀 go-pugleaf

I have found a bizarre bug in Postscript 47.0 on a Laserwriter II NT.
Is this a known bug?  Is there is a rom update available from Apple?
Does it occur on other printers or versions?

I sent a table genereated by TeX to a Laserwriter II NT (Postscript
version 47.0) and noticed that line segments forming the vertical rules
were slightly out of alignment.  Experimentation determined that the
horizontal position of a line segment (rectangle) was affected by its
vertical dimension.  The same result was obtained on a second 
Laserwriter II NT.

The same postscript file produced perfectly aligned rules on a 
Laserwriter Plus (Postscript 38.0) and on a DEC PrintServer 40
(Postscript 48.1).

Below is a short Postscript program to illustrate the problem.
It generates eight pairs of joined vertical line segments.
The leftmost four pairs are out of alignment by one pixel, the rest
are not.  The bottom eight line segments are all 88 pixels high.
The top line segments vary from 73 to 80 pixels high.  Between 76 and
77 pixels, the horizontal alignment changes.

----- Postscript Program Follows -----
%!
/resolution 300 def % Try 288, 299, 301 for different results.
/Mtrx 6 array def   % Save the CTM
gsave

72 resolution div dup neg scale
0  resolution 11 mul neg translate 

newpath
  892 1249 moveto 2 0 rlineto 0 -72 rlineto -2 0 rlineto closepath fill
  892 1336 moveto 2 0 rlineto 0 -88 rlineto -2 0 rlineto closepath fill
  992 1249 moveto 2 0 rlineto 0 -73 rlineto -2 0 rlineto closepath fill
  992 1336 moveto 2 0 rlineto 0 -88 rlineto -2 0 rlineto closepath fill
 1092 1249 moveto 2 0 rlineto 0 -74 rlineto -2 0 rlineto closepath fill
 1092 1336 moveto 2 0 rlineto 0 -88 rlineto -2 0 rlineto closepath fill
 1192 1249 moveto 2 0 rlineto 0 -75 rlineto -2 0 rlineto closepath fill
 1192 1336 moveto 2 0 rlineto 0 -88 rlineto -2 0 rlineto closepath fill
 1292 1249 moveto 2 0 rlineto 0 -76 rlineto -2 0 rlineto closepath fill
 1292 1336 moveto 2 0 rlineto 0 -88 rlineto -2 0 rlineto closepath fill
 1392 1249 moveto 2 0 rlineto 0 -77 rlineto -2 0 rlineto closepath fill
 1392 1336 moveto 2 0 rlineto 0 -88 rlineto -2 0 rlineto closepath fill
 1492 1249 moveto 2 0 rlineto 0 -78 rlineto -2 0 rlineto closepath fill
 1492 1336 moveto 2 0 rlineto 0 -88 rlineto -2 0 rlineto closepath fill
 1592 1249 moveto 2 0 rlineto 0 -79 rlineto -2 0 rlineto closepath fill
 1592 1336 moveto 2 0 rlineto 0 -88 rlineto -2 0 rlineto closepath fill
 1692 1249 moveto 2 0 rlineto 0 -80 rlineto -2 0 rlineto closepath fill
 1692 1336 moveto 2 0 rlineto 0 -88 rlineto -2 0 rlineto closepath fill

% The damage is done, the rest is for information

Mtrx currentmatrix
grestore
/Times-Roman findfont 12 scalefont setfont
72 288 moveto (Resolution is ) show resolution 10 string cvs show
72 252 moveto (Transform is ) show
   Mtrx 0 get 10 string cvs show (, ) show
   Mtrx 1 get 10 string cvs show (, ) show
   Mtrx 2 get 10 string cvs show (, ) show
   Mtrx 3 get 10 string cvs show (, ) show
   Mtrx 4 get 10 string cvs show (, ) show
   Mtrx 5 get 10 string cvs show
72 216 moveto (Postscript version ) show version show
showpage
----- Postscript Program Precedes -----

Edgar Butt (301) 454-2946 butt@umd2.umd.edu