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)