lj4_font - groff fonts for use with devlj4
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.
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.
- /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).
groff(1),
hpftodit(1),
grolj4(1),
groff_font(5)