+ ;; Enable or disable the mechanism.
+ ;; First get rid of the old idle timer.
+ (when show-paren--idle-timer
+ (cancel-timer show-paren--idle-timer)
+ (setq show-paren--idle-timer nil))
+ (setq show-paren--idle-timer (run-with-idle-timer
+ show-paren-delay t
+ #'show-paren-function))
+ (unless show-paren-mode
+ (delete-overlay show-paren--overlay)
+ (delete-overlay show-paren--overlay-1)))
+
+(defun show-paren--unescaped-p (pos)
+ "Determine whether the paren after POS is unescaped."
+ (save-excursion
+ (goto-char pos)
+ (= (logand (skip-syntax-backward "/\\") 1) 0)))
+
+(defun show-paren--categorize-paren (pos)
+ "Determine whether the character after POS has paren syntax,
+and if so, return a cons (DIR . OUTSIDE), where DIR is 1 for an
+open paren, -1 for a close paren, and OUTSIDE is the buffer
+position of the outside of the paren. If the character isn't a
+paren, or it is an escaped paren, return nil."
+ (cond
+ ((and (eq (syntax-class (syntax-after pos)) 4)
+ (show-paren--unescaped-p pos))
+ (cons 1 pos))
+ ((and (eq (syntax-class (syntax-after pos)) 5)
+ (show-paren--unescaped-p pos))
+ (cons -1 (1+ pos)))))
+
+(defun show-paren--locate-near-paren ()
+ "Locate an unescaped paren \"near\" point to show.
+If one is found, return the cons (DIR . OUTSIDE), where DIR is 1
+for an open paren, -1 for a close paren, and OUTSIDE is the buffer
+position of the outside of the paren. Otherwise return nil."
+ (let* ((ind-pos (save-excursion (back-to-indentation) (point)))
+ (eol-pos
+ (save-excursion
+ (end-of-line) (skip-chars-backward " \t" ind-pos) (point)))
+ (before (show-paren--categorize-paren (1- (point))))
+ (after (show-paren--categorize-paren (point))))
+ (cond
+ ;; Point is immediately outside a paren.
+ ((eq (car before) -1) before)
+ ((eq (car after) 1) after)
+ ;; Point is immediately inside a paren.
+ ((and show-paren-when-point-inside-paren before))
+ ((and show-paren-when-point-inside-paren after))
+ ;; Point is in the whitespace before the code.
+ ((and show-paren-when-point-in-periphery
+ (<= (point) ind-pos))
+ (or (show-paren--categorize-paren ind-pos)
+ (show-paren--categorize-paren (1- eol-pos))))
+ ;; Point is in the whitespace after the code.
+ ((and show-paren-when-point-in-periphery
+ (>= (point) eol-pos))
+ (show-paren--categorize-paren (1- eol-pos))))))
+
+(defvar show-paren-data-function #'show-paren--default
+ "Function to find the opener/closer \"near\" point and its match.
+The function is called with no argument and should return either nil
+if there's no opener/closer near point, or a list of the form
+\(HERE-BEG HERE-END THERE-BEG THERE-END MISMATCH)
+Where HERE-BEG..HERE-END is expected to be near point.")
+
+(defun show-paren--default ()
+ (let* ((temp (show-paren--locate-near-paren))
+ (dir (car temp))
+ (outside (cdr temp))
+ pos mismatch here-beg here-end)
+ ;;
+ ;; Find the other end of the sexp.
+ (when dir
+ (setq here-beg (if (eq dir 1) outside (1- outside))
+ here-end (if (eq dir 1) (1+ outside) outside))
+ (save-restriction
+ ;; Determine the range within which to look for a match.
+ (when blink-matching-paren-distance
+ (narrow-to-region
+ (max (point-min) (- (point) blink-matching-paren-distance))
+ (min (point-max) (+ (point) blink-matching-paren-distance))))
+ ;; Scan across one sexp within that range.
+ ;; Errors or nil mean there is a mismatch.
+ (condition-case ()
+ (setq pos (scan-sexps outside dir))
+ (error (setq pos t mismatch t)))
+ ;; Move back the other way and verify we get back to the
+ ;; starting point. If not, these two parens don't really match.
+ ;; Maybe the one at point is escaped and doesn't really count,
+ ;; or one is inside a comment.
+ (when (integerp pos)
+ (unless (condition-case ()
+ (eq outside (scan-sexps pos (- dir)))
+ (error nil))
+ (setq pos nil)))
+ ;; If found a "matching" paren, see if it is the right
+ ;; kind of paren to match the one we started at.
+ (if (not (integerp pos))
+ (if mismatch (list here-beg here-end nil nil t))
+ (let ((beg (min pos outside)) (end (max pos outside)))
+ (unless (eq (syntax-class (syntax-after beg)) 8)
+ (setq mismatch
+ (not (or (eq (char-before end)
+ ;; This can give nil.
+ (cdr (syntax-after beg)))
+ (eq (char-after beg)
+ ;; This can give nil.
+ (cdr (syntax-after (1- end))))
+ ;; The cdr might hold a new paren-class
+ ;; info rather than a matching-char info,
+ ;; in which case the two CDRs should match.
+ (eq (cdr (syntax-after (1- end)))
+ (cdr (syntax-after beg)))))))
+ (list here-beg here-end
+ (if (= dir 1) (1- pos) pos)
+ (if (= dir 1) pos (1+ pos))
+ mismatch)))))))