SECTION 5.6
439
Composite Fonts
may be used with this CIDFont (see Section 5.6.4, “CMaps”). The consumer
application selects glyphs by translating characters from the encoding specified
by the predefined CMap to one of the encodings in the TrueType font’s “cmap”
table. The means by which this is accomplished are implementation-depen-
dent.
Even though the CIDs are sometimes not used to select glyphs in a Type 2
CIDFont, they are always used to determine the glyph metrics, as described in the
next section.
Every CIDFont must contain a glyph description for CID 0, which is analogous to
the
. notdef
character name in simple fonts (see “Handling Undefined Characters”
Glyph Metrics in CIDFonts
As discussed in Section 5.1.3, “Glyph Positioning and Metrics,” the
width
of a
glyph refers to the horizontal displacement between the origin of the glyph and
the origin of the next glyph when writing in horizontal mode. In this mode, the
vertical displacement between origins is always 0. Widths for a CIDFont are de-
fined using the
DW
and
W
entries in the CIDFont dictionary. These widths must
be consistent with the actual widths given in the CIDFont program. (See imple-
The
DW
entry defines the default width, which is used for all glyphs whose widths
are not specified individually. This entry is particularly useful for Chinese, Japa-
nese, and Korean fonts, in which many of the glyphs have the same width.
The
W
array allows the definition of widths for individual CIDs. The elements of
the array are organized in groups of two or three, where each group is in one of
the following two formats:
c
[
w
1
w
2
…
w
n
]
c
first
c
last
w
In the first format,
c
is an integer specifying a starting CID value; it is followed by
an array of
n
numbers that specify the widths for
n
consecutive CIDs, starting
with
c
. The second format defines the same width,
w
, for all CIDs in the range
c
first
to
c
last
.