General font information decoded from the TFM data can be individually retrieved via a number of font accessors described below.
name: computed by TFM as base name of the file the font was
loaded from (for example "cmr10").
file: the argument to load-font.
checksum: part of the TFM format, provided by Metafont.
frozen: whether the font is frozen (see Freezing).
design-size: in units of TeX point. For example, the design
size of cmr10 (the Computer Modern 10pt roman font) is 10. Apart
from the slant (see below), all other dimensions are given in
design size units, not TeX point units (unless the font has been
frozen; See Freezing). See also Scaling for ways to override
the font’s original design size.
original-design-size: the fon’t original design size.
TFM is able to decode Xerox PARC headers when provided (see TeX
Font Metric Files, David Fuchs, TUGboat Volume 2, n.1, pages 12–16
and PLtoPF[9,10]). The following information is extracted from them, and
defaults to nil otherwise. Note that when a header of sufficient
length is available, it is in fact impossible to tell for sure whether
it is a Xerox PARC one or not. TFM simply assumes it is. As no other
kind of header has been encountered yet (and the whole TeX Live
distribution has been tested), it is a pretty safe assumption. Finally,
if a header size is greater than that of a Xerox PARC one, TFM
discards what’s left of it.
encoding: the font’s character coding scheme if known (an
informal BCPL string, that is, plain ASCII and no parentheses). The
class TFM instantiates when loading a font depends on this string
(see TFM Files), and in particular, on the specific (case
insensitive) values "TeX math symbols" and "TeX math
extension".
family: another BCPL string, if known (for example "CMR").
7bits-safe 0 or 1 if known. When 1, it means that no character of
code lesser than 128 can lead to a character of code greater than 128 by
ways of ligatures or extension recipes.
face-number a number identifying the font, if known.
weight, slope, expansion, and face-code:
decoded from, and filled in when face-number is lesser than 18
(see also TFtoPL[10]). The weight is :medium, :bold, or
:light. The slope is :roman or :italic. The expansion is
:regular, :condensed, or :extended. Finally, the face
code is the concatenation of the upcased first letters of these values.
For example, "MRR" stands for “medium roman regular”.
A font also contains a number of properties extracted from the so-called “parameters” section. They all default to 0.
slant: a scalar ratio (not in design size units; that’s the only
exception).
interword-space, interword-stretch, and
interword-shrink: the font’s normal interword “glue” as three
separate values.
em and ex: TeX’s usual font-dependent units.
extra-space: the font’s additional space to put at the end of
sentences.
TeX math symbols and extension fonts have respectively 15 and 6 additional parameters which are also accessible.
num1..3, denom1..2, sup1..3, sub1..2,
subdrop, supdrop, delim1..2, and axis-height
are available in the math-symbols-font subclass.
default-rule-thickness and big-op-spacing1..5 are
available in the math-extension-font subclass.
Finally, if the font has any parameters left, they are collected in an
array of numeric values, accessible via the parameters function.