Variable: whitespace-space-before-tab-regexp
whitespace-space-before-tab-regexp is a customizable variable defined
in whitespace.el.gz.
Value
"\\( +\\)\\( +\\)"
Documentation
Specify SPACEs before TAB regexp.
Used when whitespace-style includes space-before-tab,
space-before-tab::tab or space-before-tab::space.
Source Code
;; Defined in /usr/src/emacs/lisp/whitespace.el.gz
(defcustom whitespace-space-before-tab-regexp "\\( +\\)\\(\t+\\)"
"Specify SPACEs before TAB regexp.
Used when `whitespace-style' includes `space-before-tab',
`space-before-tab::tab' or `space-before-tab::space'."
:type '(regexp :tag "SPACEs Before TAB")
:group 'whitespace)