In Text mode and related modes, @kbd{M-@key{TAB}} completes words
based on the spell-checker's dictionary. @xref{Spelling}.
+@cindex completion preview
+@cindex preview completion
+@cindex suggestion preview
+@cindex Completion Preview mode
+@findex completion-preview-mode
+@vindex completion-preview-mode
+ Completion Preview mode is a minor mode that shows you symbol
+completion suggestions as type. When you enable Completion Preview
+mode in a buffer (with @kbd{M-x completion-preview-mode}), Emacs
+examines the text around point after certain commands you invoke and
+automatically suggests a possible completion. Emacs displays this
+suggestion with an inline preview right after point, so you see in
+advance exactly how the text will look if you accept the completion
+suggestion---that's why it's called a preview.
+
+For example, suppose that you have an Emacs Lisp buffer with the
+following code:
+
+@lisp
+(defun doit (foobarbaz)
+ fo@point{}
+@end lisp
+
+If you type another @samp{o}, the preview appears after point,
+suggesting that you complete the text to @samp{foobarbaz}:
+
+@lisp
+(defun doit (foobarbaz)
+ foo@point{}barbaz
+@end lisp
+
+Here, the text @samp{barbaz} after point is the completion preview.
+You can accept the completion suggestion with @kbd{@key{TAB}} to
+actually inserts @samp{barbaz} and move point after it:
+
+@lisp
+(defun doit (foobarbaz)
+ foobarbaz@point{}
+@end lisp
+
+If you want to ignore a completion suggestion, just go on editing or
+moving around the buffer. Completion Preview mode continues to update
+the suggestion as you type according to the text around point.
+
+@vindex completion-preview-active-mode-map
+@findex completion-preview-prev-candidate
+@findex completion-preview-next-candidate
+The commands @code{completion-preview-next-candidate} and
+@code{completion-preview-prev-candidate} allow you to cycle the
+completion candidate that the preview suggests. These commands don't
+have a default keybinding, but you can bind them, for example, to
+@kbd{M-n} and @kbd{M-p} in @code{completion-preview-active-mode-map}
+to have them handy whenever the preview is visible.
+
+@vindex completion-preview-exact-match-only
+@vindex completion-preview-commands
+@vindex completion-preview-minimum-symbol-length
+If you set the user option @code{completion-preview-exact-match-only}
+to non-@code{nil}, Completion Preview mode only suggests a completion
+candidate when its the only possible completion for the (partial)
+symbol at point. The user option @code{completion-preview-commands}
+says which commands should trigger the completion preview; by default
+those are only @code{self-insert-command} and
+@code{delete-backward-char}, which correspond to when you type regular
+characters in the buffer or delete them. The user option
+@code{completion-preview-minimum-symbol-length} specifies a minimum
+number of consecutive characters with word or symbol syntax that
+should appear around point for Emacs to suggest a completion. By
+default, this option is set to 3, so Emacs suggests a completion if
+you type @samp{foo}, but typing just @samp{fo} doesn't trigger
+completion preview.
+
+@vindex completion-preview-insert-on-completion
+The user option @code{completion-preview-insert-on-completion}
+controls what happens when you invoke @code{completion-at-point} while
+the completion preview is visible. By default this option is
+@code{nil}, which tells @code{completion-at-point} to ignore the
+completion preview and show the list of completion candidates as
+usual. If you set @code{completion-preview-insert-on-completion} to
+non-@code{nil}, then @code{completion-at-point} inserts the preview
+directly without looking for more candidates. To show the list of
+candidates with this setting while the preview is visible, type
+@kbd{C-g} to dismiss it before invoking @code{completion-at-point}.
+
@node MixedCase Words
@section MixedCase Words
@cindex camel case
--- /dev/null
+;;; completion-preview.el --- Preview completion with inline overlay -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2023 Free Software Foundation, Inc.
+
+;; Author: Eshel Yaron <me@eshelyaron.com>
+;; Maintainer: Eshel Yaron <me@eshelyaron.com>
+;; Keywords: abbrev convenience
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; This library provides the Completion Preview mode. This minor mode
+;; displays the top completion candidate for the symbol at point in an
+;; overlay after point. If you want to enable Completion Preview mode
+;; in all programming modes, add the following to your Emacs init:
+;;
+;; (add-hook 'prog-mode-hook #'completion-preview-mode)
+;;
+;; Also check out the customization group `completion-preview` for
+;; some user options that you may want to tweak.
+
+;;; Code:
+
+(defgroup completion-preview nil
+ "In-buffer completion preview."
+ :group 'completion)
+
+(defcustom completion-preview-exact-match-only nil
+ "Whether to show completion preview only when there is an exact match.
+
+If this option is non-nil, Completion Preview mode only shows the
+preview overlay when there is exactly one completion candidate
+that matches the symbol at point, otherwise it shows the top
+candidate also when there are multiple matching candidates."
+ :type 'boolean)
+
+(defcustom completion-preview-commands '(self-insert-command
+ delete-backward-char
+ backward-delete-char-untabify)
+ "List of commands that should trigger completion preview."
+ :type '(repeat (function :tag "Command" :value self-insert-command)))
+
+(defcustom completion-preview-minimum-symbol-length 3
+ "Minimum length of the symbol at point for showing completion preview."
+ :type 'natnum)
+
+(defcustom completion-preview-hook
+ '(completion-preview-require-certain-commands
+ completion-preview-require-minimum-symbol-length)
+ "Hook for functions that determine whether to show preview completion.
+
+Completion Preview mode calls each of these functions in order
+after each command, and only displays the completion preview when
+all of the functions return non-nil."
+ :type 'hook)
+
+(defcustom completion-preview-insert-on-completion nil
+ "Whether \\[completion-at-point] inserts the previewed suggestion."
+ :type 'boolean)
+
+(defvar completion-preview-sort-function #'minibuffer--sort-by-length-alpha
+ "Sort function to use for choosing a completion candidate to preview.")
+
+(defface completion-preview
+ '((t :inherit shadow))
+ "Face for completion preview overlay.")
+
+(defface completion-preview-exact
+ '((t :underline t :inherit completion-preview))
+ "Face for exact completion preview overlay.")
+
+(defvar-keymap completion-preview-active-mode-map
+ :doc "Keymap for Completion Preview Active mode."
+ "C-i" #'completion-preview-insert
+ ;; "M-n" #'completion-preview-next-candidate
+ ;; "M-p" #'completion-preview-prev-candidate
+ )
+
+(defvar-local completion-preview--overlay nil)
+
+(defvar completion-preview--internal-commands
+ '(completion-preview-next-candidate completion-preview-prev-candidate)
+ "List of commands that manipulate the completion preview.")
+
+(defun completion-preview--internal-command-p ()
+ "Return non-nil if `this-command' manipulates the completion preview."
+ (memq this-command completion-preview--internal-commands))
+
+(defun completion-preview-require-certain-commands ()
+ "Check if `this-command' is one of `completion-preview-commands'."
+ (or (completion-preview--internal-command-p)
+ (memq this-command completion-preview-commands)))
+
+(defun completion-preview-require-minimum-symbol-length ()
+ "Check if the length of symbol at point is at least above a certain threshold.
+`completion-preview-minimum-symbol-length' determines that threshold."
+ (pcase (bounds-of-thing-at-point 'symbol)
+ (`(,beg . ,end)
+ (<= completion-preview-minimum-symbol-length (- end beg)))))
+
+(defun completion-preview-hide ()
+ "Hide the completion preview."
+ (when completion-preview--overlay
+ (delete-overlay completion-preview--overlay)
+ (setq completion-preview--overlay nil)))
+
+(defun completion-preview--make-overlay (pos string)
+ "Make a new completion preview overlay at POS showing STRING."
+ (if completion-preview--overlay
+ (move-overlay completion-preview--overlay pos pos)
+ (setq completion-preview--overlay (make-overlay pos pos)))
+ (add-text-properties 0 1 '(cursor 1) string)
+ (overlay-put completion-preview--overlay 'after-string string)
+ completion-preview--overlay)
+
+(defun completion-preview--get (prop)
+ "Return property PROP of the completion preview overlay."
+ (overlay-get completion-preview--overlay prop))
+
+(define-minor-mode completion-preview-active-mode
+ "Mode for when the completion preview is active."
+ :interactive nil
+ (if completion-preview-active-mode
+ (add-hook 'completion-at-point-functions #'completion-preview--insert -1 t)
+ (remove-hook 'completion-at-point-functions #'completion-preview--insert t)
+ (completion-preview-hide)))
+
+(defun completion-preview--exit-function (func)
+ "Return an exit function that hides the completion preview and calls FUNC."
+ (lambda (&rest args)
+ (completion-preview-active-mode -1)
+ (when func (apply func args))))
+
+(defun completion-preview--update ()
+ "Update completion preview."
+ (pcase (let ((completion-preview-insert-on-completion nil))
+ (run-hook-with-args-until-success 'completion-at-point-functions))
+ (`(,beg ,end ,table . ,plist)
+ (let* ((pred (plist-get plist :predicate))
+ (exit-fn (completion-preview--exit-function
+ (plist-get plist :exit-function)))
+ (string (buffer-substring beg end))
+ (md (completion-metadata string table pred))
+ (sort-fn (or (completion-metadata-get md 'cycle-sort-function)
+ (completion-metadata-get md 'display-sort-function)
+ completion-preview-sort-function))
+ (all (let ((completion-lazy-hilit t))
+ (completion-all-completions string table pred
+ (- (point) beg) md)))
+ (last (last all))
+ (base (or (cdr last) 0))
+ (bbeg (+ beg base))
+ (prefix (substring string base)))
+ (when last
+ (setcdr last nil)
+ (let* ((filtered (remove prefix (all-completions prefix all)))
+ (sorted (funcall sort-fn filtered))
+ (multi (cadr sorted)) ; multiple candidates
+ (cand (car sorted)))
+ (when (and cand (not (and multi completion-preview-exact-match-only)))
+ (let* ((face (if multi 'completion-preview 'completion-preview-exact))
+ (after (propertize (substring cand (length prefix)) 'face face))
+ (ov (completion-preview--make-overlay end after)))
+ (overlay-put ov 'completion-preview-beg bbeg)
+ (overlay-put ov 'completion-preview-end end)
+ (overlay-put ov 'completion-preview-index 0)
+ (overlay-put ov 'completion-preview-cands sorted)
+ (overlay-put ov 'completion-preview-exit-fn exit-fn)
+ (completion-preview-active-mode)))))))))
+
+(defun completion-preview--show ()
+ "Show completion preview."
+ (when completion-preview-active-mode
+ (let* ((beg (completion-preview--get 'completion-preview-beg))
+ (cands (completion-preview--get 'completion-preview-cands))
+ (index (completion-preview--get 'completion-preview-index))
+ (cand (nth index cands))
+ (len (length cand))
+ (end (+ beg len))
+ (cur (point))
+ (face (get-text-property 0 'face (completion-preview--get 'after-string))))
+ (if (and (< beg cur end) (string-prefix-p (buffer-substring beg cur) cand))
+ (overlay-put (completion-preview--make-overlay
+ cur (propertize (substring cand (- cur beg))
+ 'face face))
+ 'completion-preview-end cur)
+ (completion-preview-active-mode -1))))
+ (while-no-input (completion-preview--update)))
+
+(defun completion-preview--post-command ()
+ "Create, update or delete completion preview post last command."
+ (if (run-hook-with-args-until-failure 'completion-preview-hook)
+ (or (completion-preview--internal-command-p)
+ (completion-preview--show))
+ (completion-preview-active-mode -1)))
+
+(defun completion-preview--insert ()
+ "Completion at point function for inserting the current preview."
+ (when (and completion-preview-active-mode
+ completion-preview-insert-on-completion)
+ (list (completion-preview--get 'completion-preview-beg)
+ (completion-preview--get 'completion-preview-end)
+ (list (nth (completion-preview--get 'completion-preview-index)
+ (completion-preview--get 'completion-preview-cands)))
+ :exit-function (completion-preview--get 'completion-preview-exit-fn))))
+
+(defun completion-preview-insert ()
+ "Insert the current completion preview."
+ (interactive)
+ (let ((completion-preview-insert-on-completion t))
+ (completion-at-point)))
+
+(defun completion-preview-prev-candidate ()
+ "Cycle the preview to the previous completion suggestion."
+ (interactive)
+ (completion-preview-next-candidate -1))
+
+(defun completion-preview-next-candidate (direction)
+ "Cycle the preview to the next completion suggestion in DIRECTION.
+
+DIRECTION should be either 1 which means cycle forward, or -1
+which means cycle backward. Interactively, DIRECTION is the
+prefix argument."
+ (interactive "p")
+ (when completion-preview-active-mode
+ (let* ((beg (completion-preview--get 'completion-preview-beg))
+ (all (completion-preview--get 'completion-preview-cands))
+ (cur (completion-preview--get 'completion-preview-index))
+ (len (length all))
+ (new (mod (+ cur direction) len))
+ (str (nth new all))
+ (pos (point)))
+ (while (or (<= (+ beg (length str)) pos)
+ (not (string-prefix-p (buffer-substring beg pos) str)))
+ (setq new (mod (+ new direction) len) str (nth new all)))
+ (let ((aft (propertize (substring str (- pos beg))
+ 'face (if (< 1 len)
+ 'completion-preview
+ 'completion-preview-exact))))
+ (add-text-properties 0 1 '(cursor 1) aft)
+ (overlay-put completion-preview--overlay 'completion-preview-index new)
+ (overlay-put completion-preview--overlay 'after-string aft)))))
+
+;;;###autoload
+(define-minor-mode completion-preview-mode
+ "Show in-buffer completion preview as you type."
+ :lighter " CP"
+ (if completion-preview-mode
+ (add-hook 'post-command-hook #'completion-preview--post-command nil t)
+ (remove-hook 'post-command-hook #'completion-preview--post-command t)
+ (completion-preview-active-mode -1)))
+
+(provide 'completion-preview)
+;;; completion-preview.el ends here
projects / emacs.git / commitdiff