update-canna-dics_dir assembles a dics.dir file in the Canna dictionary using one or more alias files
found in a subdirectory of /etc/X11/fonts/. It is typically invoked only from the post-installation and
post-removal scripts of a package containing fonts (that provide aliases for their names) for the X
Window System, but may be invoked at any time to reconstruct fonts.alias files. For each directory,
which is either an absolute path to an X font directory or (preferably) simply the last component of its
path (such as "75dpi" or "misc"), update-canna-dics_dir will assemble
/usr/lib/X11/fonts/directory/fonts.alias from the files found in /etc/X11/fonts/directory/package.alias.
This enables multiple packages to provide aliases for fonts in the same directory. No font package
actually provides the fonts.alias file in the X font directory itself, so there is no danger of
overwriting one package's aliases with those of another.
For instance, the two packages "xfonts-base" and "xfonts-cjk" may both install fonts into the directory
/usr/lib/X11/fonts/misc. They each place their fonts.alias files in /etc/X11/fonts/misc/xfonts-base.alias and /etc/X11/fonts/misc/xfonts-cjk.alias (respectively). update-canna-dics_dir concatenates
these two files (as well as any others that match /etc/X11/fonts/misc/*.alias) into
/usr/lib/X11/fonts/misc/fonts.alias.
The format for fonts.alias files is given in the mkfontdir(1) manual page.
An example of how to use update-canna-dics_dir in package maintainer scripts is provided in the Debian
Policy Manual.