Technical data

Table 3–1: X Server Options for Tuning the Font-Cache Mechanism
stty Option
Description
-cs cache_size
Defines the number of cache units.
The minimum (and also default) value for this
parameter is 1024. If you specify a cache size
smaller than 1024, font caching is disabled. For
one ideographic language, the recommended value
is the lowest multiple of 1024 that accommodates
the number of frequently used characters in that
language.
If a workstation displays multiple ideographic
languages simultaneously, you must add together
the values required for each language to get the
minimum cache size. Specify an even larger value
if you intend to run applications, such as desktop
publishing software, that require multiple font
styles and sizes for each ideographic character.
-cu unit_size
Defines the size of each cache unit.
The minimum value for unit size is 31 bytes and
the default value is 128 bytes. If you specify a
value smaller than 31 bytes, the value has no
effect. If a particular font requires more memory
space than 128 bytes, the font-cache mechanism
automatically allocates one or more additional
units to store its glyphs.
______________________ Note _______________________
Font caching applies only to uncompressed fonts in pcf format.
Font caching is not applied to any compressed fonts or to fonts
in bdf format. Because font caching cannot be used with
compressed fonts, the 2-byte fonts for Asian languages are not
installed in compressed format.
You can calculate cache unit size with the following formula:
unit_size = ((floor(ceil((double)WIDTH / 8.0) /4.0)) + 1.0) * 4.0 * (double)HEIGHT
Consider the following calculation for a typical font size of 24x24:
unit_size in bytes =
((floor(ceil((double) 24 / 8.0 / 4.0)) + 1.0) * 4.0 * (double) 24 = 96
For 34x34 fonts, the unit size calculation would yield 272 bytes.
Given that 96 bytes are needed to cache a 24x24 font glyph and 272 bytes
are needed to cache a 34x34 font glyph, the default unit size of 128 has the
following implications:
Using Asian Language Support Enhancements for Motif Applications 3–3