Variable: font-ccl-encoder-alist

Alist of fontname patterns vs corresponding CCL program.
Each element looks like (REGEXP . CCL-CODE),
where CCL-CODE is a compiled CCL program.
When a font whose name matches REGEXP is used for displaying a character,
CCL-CODE is executed to calculate the code point in the font
from the charset number and position code(s) of the character which are set
in CCL registers R0, R1, and R2 before the execution.
The code point in the font is set in CCL registers R1 and R2
when the execution terminated.
If the font is single-byte font, the register R2 is not used.