1LJ4_FONT(5)                   File Formats Manual                  LJ4_FONT(5)
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NAME

6       lj4_font - groff fonts for use with devlj4
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DESCRIPTION

9       Nominally,  all  Hewlett-Packard  LaserJet  4-series and newer printers
10       have the same internal fonts:  45  scalable  fonts  and  one  bitmapped
11       Lineprinter  font.   The  scalable fonts are available in sizes between
12       0.25  points  and  999.75  points,  in   0.25-point   increments;   the
13       Lineprinter font is available only in 8.5-point size.
14
15       The  LaserJet  font  files included with groff assume that all printers
16       since the LaserJet 4 are identical.  There are some differences between
17       fonts in the earlier and more recent printers, however.  The LaserJet 4
18       printer used Agfa Intellifont technology for 35 of the  internal  scal‐
19       able  fonts;  the remaining 10 scalable fonts were TrueType.  Beginning
20       with the LaserJet 4000-series printers introduced in 1997, all scalable
21       internal fonts have been TrueType.  The number of printable glyphs dif‐
22       fers slightly between Intellifont and TrueType  fonts  (generally,  the
23       TrueType  fonts  include more glyphs), and there are some minor differ‐
24       ences in glyph metrics.  Differences among printer models are described
25       in  the  PCL 5 Comparison Guide and the PCL 5 Comparison Guide Addendum
26       (for printers introduced since approximately 2001).
27
28       LaserJet printers reference a glyph by a  combination  of  a  256-glyph
29       symbol  set and an index within that symbol set.  Many glyphs appear in
30       more than one symbol set; all combinations of symbol set and index that
31       reference  the  same glyph are equivalent.  For each glyph, hpftodit(1)
32       searches a list of symbol sets, and selects the first set that contains
33       the  glyph.  The printing code generated by hpftodit is an integer that
34       encodes a numerical value for the symbol set in the high  byte(s),  and
35       the  index  in the low byte.  See groff_font(5) for a complete descrip‐
36       tion of the font file format; symbol sets are described in greater  de‐
37       tail in the PCL 5 Printer Language Technical Reference Manual.
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39       Two of the scalable fonts, Symbol and Wingdings, are bound to 256-glyph
40       symbol sets; the remaining scalable fonts, as well as  the  Lineprinter
41       font,  support  numerous  symbol sets, sufficient to enable printing of
42       more than 600 glyphs.
43
44       The metrics generated by hpftodit assume that the  DESC  file  contains
45       values  of  1200  for  res  and  6350 for unitwidth, or any combination
46       (e.g., 2400 and 3175) for which res × unitwidth = 7620000.  Although HP
47       PCL  5  LaserJet  printers support an internal resolution of 7200 units
48       per inch, they use a 16-bit signed integer for cursor  positioning;  if
49       devlj4  is to support U.S. ledger paper (11 in × 17 in; in = inch), the
50       maximum usable resolution is 32767 ÷ 17, or 1927 units per inch,  which
51       rounds down to 1200 units per inch.  If the largest required paper size
52       is less (e.g., 8.5 in × 11 in,  or  A5),  a  greater  res  (and  lesser
53       unitwidth) can be specified.
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LIMITATIONS

56       Font  metrics for Intellifont fonts were provided by Tagged Font Metric
57       (TFM) files originally developed by Agfa/Compugraphic.  The  TFM  files
58       provided  for these fonts supported 600+ glyphs and contained extensive
59       lists of kerning pairs.
60
61       To accommodate developers who had become accustomed to  TFM  files,  HP
62       also  provided  TFM  files  for  the  10 TrueType fonts included in the
63       LaserJet 4.  The TFM files for TrueType fonts generally  included  less
64       information  than the Intellifont TFMs, supporting fewer glyphs, and in
65       most cases, providing no kerning information.  By the time  the  Laser‐
66       Jet  4000 printer was introduced, most developers had migrated to other
67       means of obtaining font metrics, and support for new TFM files was very
68       limited.   The  TFM files provided for the TrueType fonts in the Laser‐
69       Jet 4000 support only the Latin 2 (ISO 8859-2) symbol set, and  include
70       no  kerning information; consequently, they are of little value for any
71       but the most rudimentary documents.
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73       Because the Intellifont TFM files contain  considerably  more  informa‐
74       tion,  they generally are preferable to the TrueType TFM files even for
75       use with the TrueType fonts in the newer printers.  The metrics for the
76       TrueType  fonts  are very close, though not identical, to those for the
77       earlier Intellifont fonts of the same names.  Although most output  us‐
78       ing  the  Intellifont  metrics with the newer printers is quite accept‐
79       able, a few glyphs may fail to print as expected.  The  differences  in
80       glyph  metrics  may be particularly noticeable with composite parenthe‐
81       ses, brackets, and braces used by eqn(1).  A script, located  in  /usr/
82       share/groff/1.22.4/font/devlj4/generate, can be used to adjust the met‐
83       rics for these glyphs in the special font “S”  for  use  with  printers
84       that have all TrueType fonts.
85
86       At  the  time HP last supported TFM files, only version 1.0 of the Uni‐
87       code standard was available.  Consequently,  many  glyphs  lacking  as‐
88       signed  code  points were assigned by HP to the Private Use Area (PUA).
89       Later versions of the Unicode standard included code points outside the
90       PUA  for  many of these glyphs.  The HP-supplied TrueType TFM files use
91       the PUA assignments; TFM files generated from more recent TrueType font
92       files require the later Unicode values to access the same glyphs.  Con‐
93       sequently, two different mapping files may be required: one for the HP-
94       supplied TFM files, and one for more recent TFM files.
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FILES

97       /usr/share/groff/1.22.4/font/devlj4/DESC
98              device description file
99
100       /usr/share/groff/1.22.4/font/devlj4/F
101              font description file for font F
102
103       /usr/share/groff/1.22.4/font/devlj4/generate
104              corrects  Intellifont-based height metrics for several glyphs in
105              the special font  for  TrueType  CG  Times  (LaserJet  4000  and
106              later).
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SEE ALSO

109       groff(1), hpftodit(1), grolj4(1), groff_font(5)
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113groff 1.22.4                     22 July 2021                      LJ4_FONT(5)
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