LJ4_FONT(5) File Formats Manual LJ4_FONT(5)
NAME
lj4_font - groff fonts for use with devlj4
DESCRIPTION
Nominally, all Hewlett-Packard LaserJet 4-series and newer printers
have the same internal fonts: 45 scalable fonts and one bitmapped
Lineprinter font. The scalable fonts are available in sizes between
0.25 points and 999.75 points, in 0.25-point increments; the
Lineprinter font is available only in 8.5-point size.
The LaserJet font files included with groff assume that all printers
since the LaserJet 4 are identical. There are some differences between
fonts in the earlier and more recent printers, however. The LaserJet 4
printer used Agfa Intellifont technology for 35 of the internal scal-
able fonts; the remaining 10 scalable fonts were TrueType. Beginning
with the LaserJet 4000-series printers introduced in 1997, all scalable
internal fonts have been TrueType. The number of printable glyphs dif-
fers slightly between Intellifont and TrueType fonts (generally, the
TrueType fonts include more glyphs), and there are some minor differ-
ences in glyph metrics. Differences among printer models are described
in the PCL 5 Comparison Guide and the PCL 5 Comparison Guide Addendum
(for printers introduced since approximately 2001).
LaserJet printers reference a glyph by a combination of a 256-glyph
symbol set and an index within that symbol set. Many glyphs appear in
more than one symbol set; all combinations of symbol set and index that
reference the same glyph are equivalent. For each glyph, hpftodit(1)
searches a list of symbol sets, and selects the first set that contains
the glyph. The printing code generated by hpftodit is an integer that
encodes a numerical value for the symbol set in the high byte(s), and
the index in the low byte. See groff_font(5) for a complete descrip-
tion of the font file format; symbol sets are described in greater de-
tail in the PCL 5 Printer Language Technical Reference Manual.
Two of the scalable fonts, Symbol and Wingdings, are bound to 256-glyph
symbol sets; the remaining scalable fonts, as well as the Lineprinter
font, support numerous symbol sets, sufficient to enable printing of
more than 600 glyphs.
The metrics generated by hpftodit assume that the DESC file contains
values of 1200 for res and 6350 for unitwidth, or any combination
(e.g., 2400 and 3175) for which res × unitwidth = 7620000. Although HP
PCL 5 LaserJet printers support an internal resolution of 7200 units
per inch, they use a 16-bit signed integer for cursor positioning; if
devlj4 is to support U.S. ledger paper (11 in × 17 in; in = inch), the
maximum usable resolution is 32767 ÷ 17, or 1927 units per inch, which
rounds down to 1200 units per inch. If the largest required paper size
is less (e.g., 8.5 in × 11 in, or A5), a greater res (and lesser
unitwidth) can be specified.
LIMITATIONS
Font metrics for Intellifont fonts were provided by Tagged Font Metric
(TFM) files originally developed by Agfa/Compugraphic. The TFM files
provided for these fonts supported 600+ glyphs and contained extensive
lists of kerning pairs.
To accommodate developers who had become accustomed to TFM files, HP
also provided TFM files for the 10 TrueType fonts included in the
LaserJet 4. The TFM files for TrueType fonts generally included less
information than the Intellifont TFMs, supporting fewer glyphs, and in
most cases, providing no kerning information. By the time the Laser-
Jet 4000 printer was introduced, most developers had migrated to other
means of obtaining font metrics, and support for new TFM files was very
limited. The TFM files provided for the TrueType fonts in the Laser-
Jet 4000 support only the Latin 2 (ISO 8859-2) symbol set, and include
no kerning information; consequently, they are of little value for any
but the most rudimentary documents.
Because the Intellifont TFM files contain considerably more informa-
tion, they generally are preferable to the TrueType TFM files even for
use with the TrueType fonts in the newer printers. The metrics for the
TrueType fonts are very close, though not identical, to those for the
earlier Intellifont fonts of the same names. Although most output us-
ing the Intellifont metrics with the newer printers is quite accept-
able, a few glyphs may fail to print as expected. The differences in
glyph metrics may be particularly noticeable with composite parenthe-
ses, brackets, and braces used by eqn(1). A script, located in /usr/
share/groff/1.22.4/font/devlj4/generate, can be used to adjust the met-
rics for these glyphs in the special font “S” for use with printers
that have all TrueType fonts.
At the time HP last supported TFM files, only version 1.0 of the Uni-
code standard was available. Consequently, many glyphs lacking as-
signed code points were assigned by HP to the Private Use Area (PUA).
Later versions of the Unicode standard included code points outside the
PUA for many of these glyphs. The HP-supplied TrueType TFM files use
the PUA assignments; TFM files generated from more recent TrueType font
files require the later Unicode values to access the same glyphs. Con-
sequently, two different mapping files may be required: one for the HP-
supplied TFM files, and one for more recent TFM files.
FILES
/usr/share/groff/1.22.4/font/devlj4/DESC
device description file
/usr/share/groff/1.22.4/font/devlj4/F
font description file for font F
/usr/share/groff/1.22.4/font/devlj4/generate
corrects Intellifont-based height metrics for several glyphs in
the special font for TrueType CG Times (LaserJet 4000 and
later).
SEE ALSO
groff(1), hpftodit(1), grolj4(1), groff_font(5)
groff 1.22.4 7 March 2023 LJ4_FONT(5)
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