Provided by: groff_1.22.4-8build1_amd64 
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 scalable 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 differs slightly between Intellifont and
TrueType fonts (generally, the TrueType fonts include more glyphs), and there are some
minor differences 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 description of the font file format; symbol sets are
described in greater detail 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
LaserJet 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 LaserJet 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 information, 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 using the
Intellifont metrics with the newer printers is quite acceptable, a few glyphs may fail to
print as expected. The differences in glyph metrics may be particularly noticeable with
composite parentheses, 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 metrics 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 Unicode standard was
available. Consequently, many glyphs lacking assigned 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. Consequently, 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)