;;; Commentary:
-; zaaaaaaap
+;; "Electric" has been used in Emacs to refer to different things.
+;; Among them:
+;;
+;; - electric modes and buffers: modes that typically pop-up in a modal kind of
+;; way a transient buffer that automatically disappears as soon as the user
+;; is done with it.
+;;
+;; - electric keys: self inserting keys which additionally perform some side
+;; operation which happens to be often convenient at that time. Examples of
+;; such side operations are: reindenting code, inserting a newline,
+;; ... auto-fill-mode and abbrev-mode can be considered as built-in forms of
+;; electric key behavior.
;;; Code:
+(eval-when-compile (require 'cl))
+
;; This loop is the guts for non-standard modes which retain control
;; until some event occurs. It is a `do-forever', the only way out is
;; to throw. It assumes that you have set up the keymap, window, and
(err nil)
(prompt-string prompt))
(while t
- (if (not (or (stringp prompt) (eq prompt nil) (eq prompt 'noprompt)))
+ (if (functionp prompt)
(setq prompt-string (funcall prompt)))
(if (not (stringp prompt-string))
- (if (eq prompt-string 'noprompt)
- (setq prompt-string nil)
- (setq prompt-string "->")))
+ (setq prompt-string (unless (eq prompt-string 'noprompt) "->")))
(setq cmd (read-key-sequence prompt-string))
(setq last-command-event (aref cmd (1- (length cmd)))
this-command (key-binding cmd t)
(fit-window-to-buffer win max-height))
win)))
+;;; Electric keys.
+
+(defgroup electricity ()
+ "Electric behavior for self inserting keys."
+ :group 'editing)
+
+(defun electric--after-char-pos ()
+ "Return the position after the char we just inserted.
+Returns nil when we can't find this char."
+ (let ((pos (point)))
+ (when (or (eq (char-before) last-command-event) ;; Sanity check.
+ (save-excursion
+ (or (progn (skip-chars-backward " \t")
+ (setq pos (point))
+ (eq (char-before) last-command-event))
+ (progn (skip-chars-backward " \n\t")
+ (setq pos (point))
+ (eq (char-before) last-command-event)))))
+ pos)))
+
+;; Electric indentation.
+
+;; Autoloading variables is generally undesirable, but major modes
+;; should usually set this variable by adding elements to the default
+;; value, which only works well if the variable is preloaded.
+;;;###autoload
+(defvar electric-indent-chars '(?\n)
+ "Characters that should cause automatic reindentation.")
+
+(defun electric-indent-post-self-insert-function ()
+ ;; FIXME: This reindents the current line, but what we really want instead is
+ ;; to reindent the whole affected text. That's the current line for simple
+ ;; cases, but not all cases. We do take care of the newline case in an
+ ;; ad-hoc fashion, but there are still missing cases such as the case of
+ ;; electric-pair-mode wrapping a region with a pair of parens.
+ ;; There might be a way to get it working by analyzing buffer-undo-list, but
+ ;; it looks challenging.
+ (let (pos)
+ (when (and (memq last-command-event electric-indent-chars)
+ ;; Don't reindent while inserting spaces at beginning of line.
+ (or (not (memq last-command-event '(?\s ?\t)))
+ (save-excursion (skip-chars-backward " \t") (not (bolp))))
+ (setq pos (electric--after-char-pos))
+ ;; Not in a string or comment.
+ (not (nth 8 (save-excursion (syntax-ppss pos)))))
+ ;; For newline, we want to reindent both lines and basically behave like
+ ;; reindent-then-newline-and-indent (whose code we hence copied).
+ (when (< (1- pos) (line-beginning-position))
+ (let ((before (copy-marker (1- pos) t)))
+ (save-excursion
+ (unless (memq indent-line-function
+ '(indent-relative indent-relative-maybe))
+ ;; Don't reindent the previous line if the indentation function
+ ;; is not a real one.
+ (goto-char before)
+ (indent-according-to-mode))
+ ;; We are at EOL before the call to indent-according-to-mode, and
+ ;; after it we usually are as well, but not always. We tried to
+ ;; address it with `save-excursion' but that uses a normal marker
+ ;; whereas we need `move after insertion', so we do the
+ ;; save/restore by hand.
+ (goto-char before)
+ ;; Remove the trailing whitespace after indentation because
+ ;; indentation may (re)introduce the whitespace.
+ (delete-horizontal-space t))))
+ (indent-according-to-mode))))
+
+;;;###autoload
+(define-minor-mode electric-indent-mode
+ "Automatically reindent lines of code when inserting particular chars.
+`electric-indent-chars' specifies the set of chars that should cause reindentation."
+ :global t
+ :group 'electricity
+ (if electric-indent-mode
+ (add-hook 'post-self-insert-hook
+ #'electric-indent-post-self-insert-function)
+ (remove-hook 'post-self-insert-hook
+ #'electric-indent-post-self-insert-function))
+ ;; FIXME: electric-indent-mode and electric-layout-mode interact
+ ;; in non-trivial ways. It turns out that electric-indent-mode works
+ ;; better if it is run *after* electric-layout-mode's hook.
+ (when (memq #'electric-layout-post-self-insert-function
+ (memq #'electric-indent-post-self-insert-function
+ (default-value 'post-self-insert-hook)))
+ (remove-hook 'post-self-insert-hook
+ #'electric-layout-post-self-insert-function)
+ (add-hook 'post-self-insert-hook
+ #'electric-layout-post-self-insert-function)))
+
+;; Electric pairing.
+
+(defcustom electric-pair-pairs
+ '((?\" . ?\"))
+ "Alist of pairs that should be used regardless of major mode."
+ :type '(repeat (cons character character)))
+
+(defcustom electric-pair-skip-self t
+ "If non-nil, skip char instead of inserting a second closing paren.
+When inserting a closing paren character right before the same character,
+just skip that character instead, so that hitting ( followed by ) results
+in \"()\" rather than \"())\".
+This can be convenient for people who find it easier to hit ) than C-f."
+ :type 'boolean)
+
+(defun electric-pair-post-self-insert-function ()
+ (let* ((syntax (and (eq (char-before) last-command-event) ; Sanity check.
+ (let ((x (assq last-command-event electric-pair-pairs)))
+ (cond
+ (x (if (eq (car x) (cdr x)) ?\" ?\())
+ ((rassq last-command-event electric-pair-pairs) ?\))
+ (t (char-syntax last-command-event))))))
+ ;; FIXME: when inserting the closer, we should maybe use
+ ;; self-insert-command, although it may prove tricky running
+ ;; post-self-insert-hook recursively, and we wouldn't want to trigger
+ ;; blink-matching-open.
+ (closer (if (eq syntax ?\()
+ (cdr (or (assq last-command-event electric-pair-pairs)
+ (aref (syntax-table) last-command-event)))
+ last-command-event)))
+ (cond
+ ;; Wrap a pair around the active region.
+ ((and (memq syntax '(?\( ?\" ?\$)) (use-region-p))
+ (if (> (mark) (point))
+ (goto-char (mark))
+ ;; We already inserted the open-paren but at the end of the region,
+ ;; so we have to remove it and start over.
+ (delete-char -1)
+ (save-excursion
+ (goto-char (mark))
+ (insert last-command-event)))
+ (insert closer))
+ ;; Backslash-escaped: no pairing, no skipping.
+ ((save-excursion
+ (goto-char (1- (point)))
+ (not (zerop (% (skip-syntax-backward "\\") 2))))
+ nil)
+ ;; Skip self.
+ ((and (memq syntax '(?\) ?\" ?\$))
+ electric-pair-skip-self
+ (eq (char-after) last-command-event))
+ ;; This is too late: rather than insert&delete we'd want to only skip (or
+ ;; insert in overwrite mode). The difference is in what goes in the
+ ;; undo-log and in the intermediate state which might be visible to other
+ ;; post-self-insert-hook. We'll just have to live with it for now.
+ (delete-char 1))
+ ;; Insert matching pair.
+ ((not (or (not (memq syntax `(?\( ?\" ?\$)))
+ overwrite-mode
+ ;; I find it more often preferable not to pair when the
+ ;; same char is next.
+ (eq last-command-event (char-after))
+ (eq last-command-event (char-before (1- (point))))
+ ;; I also find it often preferable not to pair next to a word.
+ (eq (char-syntax (following-char)) ?w)))
+ (save-excursion (insert closer))))))
+
+;;;###autoload
+(define-minor-mode electric-pair-mode
+ "Automatically pair-up parens when inserting an open paren."
+ :global t
+ :group 'electricity
+ (if electric-pair-mode
+ (add-hook 'post-self-insert-hook
+ #'electric-pair-post-self-insert-function)
+ (remove-hook 'post-self-insert-hook
+ #'electric-pair-post-self-insert-function)))
+
+;; Automatically add newlines after/before/around some chars.
+
+(defvar electric-layout-rules '()
+ "List of rules saying where to automatically insert newlines.
+Each rule has the form (CHAR . WHERE) where CHAR is the char
+that was just inserted and WHERE specifies where to insert newlines
+and can be: nil, `before', `after', `around', or a function that returns
+one of those symbols.")
+
+(defun electric-layout-post-self-insert-function ()
+ (let* ((rule (cdr (assq last-command-event electric-layout-rules)))
+ pos)
+ (when (and rule
+ (setq pos (electric--after-char-pos))
+ ;; Not in a string or comment.
+ (not (nth 8 (save-excursion (syntax-ppss pos)))))
+ (let ((end (copy-marker (point) t)))
+ (goto-char pos)
+ (case (if (functionp rule) (funcall rule) rule)
+ ;; FIXME: we used `newline' down here which called
+ ;; self-insert-command and ran post-self-insert-hook recursively.
+ ;; It happened to make electric-indent-mode work automatically with
+ ;; electric-layout-mode (at the cost of re-indenting lines
+ ;; multiple times), but I'm not sure it's what we want.
+ (before (goto-char (1- pos)) (skip-chars-backward " \t")
+ (unless (bolp) (insert "\n")))
+ (after (insert "\n")) ; FIXME: check eolp before inserting \n?
+ (around (save-excursion
+ (goto-char (1- pos)) (skip-chars-backward " \t")
+ (unless (bolp) (insert "\n")))
+ (insert "\n"))) ; FIXME: check eolp before inserting \n?
+ (goto-char end)))))
+
+;;;###autoload
+(define-minor-mode electric-layout-mode
+ "Automatically insert newlines around some chars."
+ :global t
+ :group 'electricity
+ (if electric-layout-mode
+ (add-hook 'post-self-insert-hook
+ #'electric-layout-post-self-insert-function)
+ (remove-hook 'post-self-insert-hook
+ #'electric-layout-post-self-insert-function)))
+
(provide 'electric)
;; arch-tag: dae045eb-dc2d-4fb7-9f27-9cc2ce277be8