diff options
Diffstat (limited to 'lisp')
| -rw-r--r-- | lisp/font-lock.el | 30 |
1 files changed, 29 insertions, 1 deletions
diff --git a/lisp/font-lock.el b/lisp/font-lock.el index 7eb5a414fe3..88bd6cbc5b6 100644 --- a/lisp/font-lock.el +++ b/lisp/font-lock.el @@ -254,6 +254,23 @@ decoration for buffers in C++ mode, and level 1 decoration otherwise." (integer :tag "level" 1))))) :group 'font-lock) +(defcustom font-lock-large-files t + "How to fontify large files. +When t, apply highlighting without restriction. + +When its a cons with car equal to `head', fontify the first (cdr +value) number of characters only. + +When its a cons with car equal to `narrow', narrow the buffer +to (cdr value) characters around point. That speeds up +fontification at the expense of possible misdetection of syntax +context." + :type '(choice (const :tag "full" t) + (cons :tag "head" + (const head) (integer :tag "length" 1000000)) + (cons :tag "narrow" + (const narrow) (integer :tag "width" 15000)))) + (defcustom font-lock-ignore nil "Rules to selectively disable fontifications due to `font-lock-keywords'. If non-nil, the value should be a list of condition sets of the form @@ -996,7 +1013,18 @@ If LOUDLY is non-nil, print status messages while fontifying. This works by calling `font-lock-fontify-region-function'." (font-lock-set-defaults) (save-restriction - (unless font-lock-dont-widen (widen)) + (pcase-exhaustive font-lock-large-files + (`t nil) + (`(head . ,length) + (setq beg (min length beg) + end (min length end))) + (`(narrow . ,width) + (narrow-to-region (max (point-min) (* (1- (/ beg width)) width)) + (min (point-max) (* (1+ (/ beg width)) width))) + (setq end (min end (point-max))))) + (unless (or font-lock-dont-widen + (eq (car-safe font-lock-large-files) 'narrow)) + (widen)) (funcall font-lock-fontify-region-function beg end loudly))) (defun font-lock-unfontify-region (beg end) |