CHAPTER 5
396
Text
text position is changed after the glyph is painted in writing mode 0; its vertical
component is always 0.
•
The center diagram illustrates writing mode 1, vertical writing.
w1
is the dis-
placement vector for writing mode 1; its horizontal component is always 0.
•
In the right diagram,
v
is a position vector defining the position of origin 1 rel-
ative to origin 0.
ur
Origin 1
Origin 1
Origin
0
ll
w0
v
Origin
0
New text
position
w1
New text position
Writing mode 0
(horizontal)
Writing mode 1
(vertical)
Mode 1 relative to mode 0
FIGURE 5.5
Metrics for horizontal and vertical writing modes
Glyph metric information is also available separately in the form of Adobe font
metrics (AFM) and Adobe composite font metrics (ACFM) files. These files are
for use by application programs that generate PDF page descriptions and must
make formatting decisions based on the widths and other metrics of glyphs. Also
available in the AFM and ACFM files is kerning information, which allows an
application generating a PDF file to determine spacing adjustments between
glyphs depending on context. Specifications for the AFM and ACFM file formats
are available in Adobe Technical Note #5004,
Adobe Font Metrics File Format
Specification;
the files can be obtained from the Adobe Solutions Network Web
site (see the Bibliography).
5.2 Text State Parameters and Operators
The
text state
comprises those graphics state parameters that only affect text.
There are nine parameters in the text state (see Table 5.1).