groff: Font Positions
5.19.3 Font Positions
---------------------
To support typeface indirection through abstract styles, and for
compatibility with AT&T 'troff', the formatter maintains a list of font
"positions" at which fonts required by a document are "mounted". An
output device's description file 'DESC' typically configures a set of
pre-mounted fonts; see ⇒Device and Font Description Files. A
font need not be explicitly mounted before it is selected; GNU 'troff'
will search 'GROFF_FONT_PATH' for it by name and mount it at the first
free mounting position on demand.
-- Request: .fp pos id [font-description-file-name]
-- Register: \n[.f]
-- Register: \n[.fp]
Mount a font under the name ID at mounting position POS, a
non-negative integer. When the formatter starts up, it reads the
output device's description to mount an initial set of faces, and
selects font position 1. Position 0 is unused by default. Unless
the FONT-DESCRIPTION-FILE-NAME argument is given, ID should be the
name of a font description file stored in a directory corresponding
to the selected output device. GNU 'troff' does not traverse
directories to locate the font description file.
The optional third argument enables font names to be aliased, which
can be necessary in compatibility mode since AT&T 'troff' syntax
affords no means of identifying fonts with names longer than two
characters, like 'TBI' or 'ZCMI', in a font selection escape
sequence. ⇒Compatibility Mode. You can also alias fonts on
mounting for convenience or abstraction. (See below regarding the
'.fp' register.)
.fp \n[.fp] SC ZCMI
Send a \f(SChand-written\fP thank-you note.
.fp \n[.fp] Emph TI
.fp \n[.fp] Strong TB
Are \f[Emph]these names\f[] \f[Strong]comfortable\f[]?
'DESC', 'P', and non-negative integers are not usable as font
identifiers.
The position of the currently selected font (or abstract style) is
available in the read-only register '.f'. It is associated with
the environment (⇒Environments).
You can copy the value of '.f' to another register to save it for
later use.
.nr saved-font \n[.f]
... text involving many font changes ...
.ft \n[saved-font]
The index of the next (non-zero) free font position is available in
the read-only register '.fp'. Fonts not listed in the 'DESC' file
are automatically mounted at position '\n[.fp]' when selected with
the 'ft' request or '\f' escape sequence. When mounting a font at
a position explicitly with the 'fp' request, this same practice
should be followed, although GNU 'troff' does not enforce this
strictly.
Info Catalog
groff: Font Families
groff: Using Fonts
groff: Using Symbols