font-lock-beginning-of-syntax-function

font-lock-beginning-of-syntax-function is a variable defined in `font-lock.el'.
Its value is

nil

• This variable is obsolete since 23.3;
  use `syntax-begin-function' instead.
• This variable may be risky if used as a file-local variable.

Documentation:
Non-nil means use this function to move back outside all constructs.
When called with no args it should move point backward to a place which
is not in a string or comment and not within any bracket-pairs (or else,
a place such that any bracket-pairs outside it can be ignored for Emacs
syntax analysis and fontification).

If this is nil, Font Lock uses `syntax-begin-function' to move back
outside of any comment, string, or sexp. This variable is semi-obsolete;
we recommend setting `syntax-begin-function' instead.

This is normally set via `font-lock-defaults'.