path: root/users/aspen/emacs.d/show-matching-paren.el

;;; -*- lexical-binding: t; -*-

;;; https://with-emacs.com/posts/ui-hacks/show-matching-lines-when-parentheses-go-off-screen/

;; we will call `blink-matching-open` ourselves...
(remove-hook 'post-self-insert-hook
             #'blink-paren-post-self-insert-function)
;; this still needs to be set for `blink-matching-open` to work
(setq blink-matching-paren 'show)

(let ((ov nil)) ; keep track of the overlay
  (advice-add
   #'show-paren-function
   :after
    (defun show-paren--off-screen+ (&rest _args)
      "Display matching line for off-screen paren."
      (when (overlayp ov)
        (delete-overlay ov))
      ;; check if it's appropriate to show match info,
      ;; see `blink-paren-post-self-insert-function'
      (when (and (overlay-buffer show-paren--overlay)
                 (not (or cursor-in-echo-area
                          executing-kbd-macro
                          noninteractive
                          (minibufferp)
                          this-command))
                 (and (not (bobp))
                      (memq (char-syntax (char-before)) '(?\) ?\$)))
                 (= 1 (logand 1 (- (point)
                                   (save-excursion
                                     (forward-char -1)
                                     (skip-syntax-backward "/\\")
                                     (point))))))
        ;; rebind `minibuffer-message' called by
        ;; `blink-matching-open' to handle the overlay display
        (cl-letf (((symbol-function #'minibuffer-message)
                   (lambda (msg &rest args)
                     (let ((msg (apply #'format-message msg args)))
                       (setq ov (display-line-overlay+
                                 (window-start) msg ))))))
          (blink-matching-open))))))

(defun display-line-overlay+ (pos str &optional face)
  "Display line at POS as STR with FACE.

FACE defaults to inheriting from default and highlight."
  (let ((ol (save-excursion
              (goto-char pos)
              (make-overlay (line-beginning-position)
                            (line-end-position)))))
    (overlay-put ol 'display str)
    (overlay-put ol 'face
                 (or face '(:inherit default :inherit highlight)))
    ol))

(setq show-paren-style 'paren
      show-paren-delay 0.03
      show-paren-highlight-openparen t
      show-paren-when-point-inside-paren nil
      show-paren-when-point-in-periphery t)
(show-paren-mode 1)