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 point 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(1) 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(1) 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″ × 17″), 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″
× 11″ or A5), a greater resolution (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 kern 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/1.22.2/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 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/1.22.2/font/devlj4/DESC
- Device description file.
- /usr/share/groff/1.22.2/font/devlj4/F
- Font description file for font F.
SEE ALSO¶
groff(1),
groff_diff(1),
hpftodit(1),
grolj4(1),
groff_font(5)