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Diffstat (limited to 'lisp/completion-preview.el')
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diff --git a/lisp/completion-preview.el b/lisp/completion-preview.el new file mode 100644 index 00000000000..e827da43a08 --- /dev/null +++ b/lisp/completion-preview.el @@ -0,0 +1,419 @@ +;;; completion-preview.el --- Preview completion with inline overlay -*- lexical-binding: t; -*- + +;; Copyright (C) 2023-2024 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 a completion suggestion for the symbol at point in an +;; overlay after point. Check out the customization group +;; `completion-preview' for user options that you may want to tweak. +;; +;; To enable Completion Preview mode, use `completion-preview-mode'. +;; To accept the completion suggestion, press TAB. 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. +;; +;; The commands `completion-preview-next-candidate' and +;; `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 M-n and M-p in `completion-preview-active-mode-map' to +;; have them handy whenever the preview is visible. +;; +;; If you set the user option `completion-preview-exact-match-only' to +;; non-nil, Completion Preview mode only suggests a completion +;; candidate when its the only possible completion for the (partial) +;; symbol at point. The user option `completion-preview-commands' +;; says which commands should trigger the completion preview. The +;; user option `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 "foo", but typing just "fo" doesn't show the preview. + +;;; Code: + +(require 'mwheel) + +(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 when there is exactly one completion candidate that +matches the symbol at point. Otherwise, if this option is nil, +when there are multiple matching candidates the preview shows the +first candidate, and you can cycle between the candidates with +\\[completion-preview-next-candidate] and +\\[completion-preview-prev-candidate]." + :type 'boolean + :version "30.1") + +(defcustom completion-preview-commands '(self-insert-command + insert-char + delete-backward-char + backward-delete-char-untabify + analyze-text-conversion) + "List of commands that should trigger completion preview." + :type '(repeat (function :tag "Command" :value self-insert-command)) + :version "30.1") + +(defcustom completion-preview-minimum-symbol-length 3 + "Minimum length of the symbol at point for showing completion preview." + :type 'natnum + :version "30.1") + +(defcustom completion-preview-message-format + "Completion suggestion %i out of %n" + "Message to show after cycling the completion preview suggestion. + +If the value is a string, `completion-preview-next-candidate' and +`completion-preview-prev-candidate' display this string in the +echo area, after substituting \"%i\" with the 1-based index of +the completion suggestion that the preview is showing, and \"%n\" +with the total number of available completion suggestions for the +text around point. + +If this option is nil, these commands do not display any message." + :type '(choice (string :tag "Message format") + (const :tag "No message" nil)) + :version "30.1") + +(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." + :version "30.1") + +(defface completion-preview-exact + '((((supports :underline t)) + :underline t :inherit completion-preview) + (((supports :weight bold)) + :weight bold :inherit completion-preview) + (t :background "gray")) + "Face for exact completion preview overlay." + :version "30.1") + +(defface completion-preview-highlight + '((t :inherit highlight)) + "Face for highlighting the completion preview when the mouse is over it." + :version "30.1") + +(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-keymap completion-preview--mouse-map + :doc "Keymap for mouse clicks on the completion preview." + "<down-mouse-1>" #'completion-preview-insert + "C-<down-mouse-1>" #'completion-at-point + "<down-mouse-2>" #'completion-at-point + ;; BEWARE: `mouse-wheel-UP-event' corresponds to `wheel-DOWN' events + ;; and vice versa!! + "<wheel-up>" #'completion-preview-prev-candidate + "<wheel-down>" #'completion-preview-next-candidate + (key-description (vector mouse-wheel-up-event)) + #'completion-preview-next-candidate + (key-description (vector mouse-wheel-down-event)) + #'completion-preview-prev-candidate) + +(defvar-local completion-preview--overlay nil) + +(defvar completion-preview--internal-commands + '(completion-preview-next-candidate + completion-preview-prev-candidate + ;; Don't dismiss or update the preview when the user scrolls. + mwheel-scroll) + "List of commands that manipulate the completion preview. + +Completion Preview mode avoids updating the preview after these commands.") + +(defsubst completion-preview--internal-command-p () + "Return non-nil if `this-command' manipulates the completion preview." + (memq this-command completion-preview--internal-commands)) + +(defsubst 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." + (let ((bounds (bounds-of-thing-at-point 'symbol))) + (and bounds (<= completion-preview-minimum-symbol-length + (- (cdr bounds) (car bounds)))))) + +(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 preview overlay showing STRING at POS, or move existing preview there." + (if completion-preview--overlay + (move-overlay completion-preview--overlay pos pos) + (setq completion-preview--overlay (make-overlay pos pos)) + (overlay-put completion-preview--overlay 'window (selected-window))) + (let ((previous (overlay-get completion-preview--overlay 'after-string))) + (unless (and previous (string= previous string) + (eq (get-text-property 0 'face previous) + (get-text-property 0 'face string))) + (add-text-properties 0 1 '(cursor 1) string) + (overlay-put completion-preview--overlay 'after-string string)) + completion-preview--overlay)) + +(defsubst completion-preview--get (prop) + "Return property PROP of the completion preview overlay." + (overlay-get completion-preview--overlay prop)) + +(defun completion-preview--window-selection-change (window) + "Hide completion preview in WINDOW after switching to another window. +Completion Preview mode adds this function to +`window-selection-change-functions', which see." + (unless (or (eq window (selected-window)) + (eq window (minibuffer-selected-window))) + (with-current-buffer (window-buffer window) + (completion-preview-active-mode -1)))) + +(define-minor-mode completion-preview-active-mode + "Mode for when the completion preview is shown." + :interactive nil + (if completion-preview-active-mode + (add-hook 'window-selection-change-functions + #'completion-preview--window-selection-change nil t) + (remove-hook 'window-selection-change-functions + #'completion-preview--window-selection-change t) + (completion-preview-hide))) + +(defun completion-preview--try-table (table beg end props) + "Check TABLE for a completion matching the text between BEG and END. + +PROPS is a property list with additional information about TABLE. +See `completion-at-point-functions' for more details. + +If TABLE contains a matching completion, return a list +\(PREVIEW BEG END ALL BASE EXIT-FN) where PREVIEW is the text to +show in the completion preview, ALL is the list of all matching +completion candidates, BASE is a common prefix that TABLE elided +from the start of each candidate, and EXIT-FN is either a +function to call after inserting PREVIEW or nil. If TABLE does +not contain matching completions, or if there are multiple +matching completions and `completion-preview-exact-match-only' is +non-nil, return nil instead." + (let* ((pred (plist-get props :predicate)) + (exit-fn (plist-get props :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)) + (prefix (substring string base))) + (when last + (setcdr last nil) + (when-let ((sorted (funcall sort-fn + (delete prefix (all-completions prefix all))))) + (unless (and (cdr sorted) completion-preview-exact-match-only) + (list (propertize (substring (car sorted) (length prefix)) + 'face (if (cdr sorted) + 'completion-preview + 'completion-preview-exact) + 'mouse-face 'completion-preview-highlight + 'keymap completion-preview--mouse-map) + (+ beg base) end sorted + (substring string 0 base) exit-fn)))))) + +(defun completion-preview--capf-wrapper (capf) + "Translate return value of CAPF to properties for completion preview overlay." + (let ((res (ignore-errors (funcall capf)))) + (and (consp res) + (not (functionp res)) + (seq-let (beg end table &rest plist) res + (or (completion-preview--try-table table beg end plist) + (unless (eq 'no (plist-get plist :exclusive)) + ;; Return non-nil to exclude other capfs. + '(nil))))))) + +(defun completion-preview--update () + "Update completion preview." + (seq-let (preview beg end all base exit-fn) + (run-hook-wrapped + 'completion-at-point-functions + #'completion-preview--capf-wrapper) + (when preview + (let ((ov (completion-preview--make-overlay end preview))) + (overlay-put ov 'completion-preview-beg beg) + (overlay-put ov 'completion-preview-end end) + (overlay-put ov 'completion-preview-index 0) + (overlay-put ov 'completion-preview-cands all) + (overlay-put ov 'completion-preview-base base) + (overlay-put ov 'completion-preview-exit-fn exit-fn) + (completion-preview-active-mode))))) + +(defun completion-preview--show () + "Show a new completion preview. + +Call `completion-at-point-functions' in order to obtain and +display a completion candidate for the text around point. + +If the preview is already shown, first check whether the +suggested candidate remains a valid completion for the text at +point. If so, update the preview according the new text at +point, otherwise hide it." + (when completion-preview-active-mode + ;; We were already showing a preview before this command, so we + ;; check if the text before point is still a prefix of the + ;; candidate that the preview suggested, and if so we first update + ;; existing preview according to the changes made by this command, + ;; and only then try to get a new candidate. This ensures that we + ;; never display a stale preview and that the preview doesn't + ;; flicker, even with slow completion backends. + (let* ((beg (completion-preview--get 'completion-preview-beg)) + (end (max (point) (overlay-start completion-preview--overlay))) + (cands (completion-preview--get 'completion-preview-cands)) + (index (completion-preview--get 'completion-preview-index)) + (cand (nth index cands)) + (after (completion-preview--get 'after-string)) + (face (get-text-property 0 'face after))) + (if (and (<= beg (point) end (1- (+ beg (length cand)))) + (string-prefix-p (buffer-substring beg end) cand)) + ;; The previous preview is still applicable, update it. + (overlay-put (completion-preview--make-overlay + end (propertize (substring cand (- end beg)) + 'face face + 'mouse-face 'completion-preview-highlight + 'keymap completion-preview--mouse-map)) + 'completion-preview-end end) + ;; The previous preview is no longer applicable, hide it. + (completion-preview-active-mode -1)))) + ;; Run `completion-at-point-functions' to get a new candidate. + (while-no-input (completion-preview--update))) + +(defun completion-preview--post-command () + "Create, update or delete completion preview post last command." + (if (and (completion-preview-require-certain-commands) + (completion-preview-require-minimum-symbol-length)) + ;; We should show the preview. + (or + ;; If we're called after a command that itself updates the + ;; preview, don't do anything. + (completion-preview--internal-command-p) + ;; Otherwise, show the preview. + (completion-preview--show)) + (completion-preview-active-mode -1))) + +(defun completion-preview-insert () + "Insert the completion candidate that the preview is showing." + (interactive) + (if completion-preview-active-mode + (let* ((pre (completion-preview--get 'completion-preview-base)) + (end (completion-preview--get 'completion-preview-end)) + (ind (completion-preview--get 'completion-preview-index)) + (all (completion-preview--get 'completion-preview-cands)) + (efn (completion-preview--get 'completion-preview-exit-fn)) + (aft (completion-preview--get 'after-string)) + (str (concat pre (nth ind all)))) + (completion-preview-active-mode -1) + (goto-char end) + (insert (substring-no-properties aft)) + (when (functionp efn) (funcall efn str 'finished))) + (user-error "No current completion preview"))) + +(defun completion-preview-prev-candidate () + "Cycle the candidate that the preview is showing to the previous suggestion." + (interactive) + (completion-preview-next-candidate -1)) + +(defun completion-preview-next-candidate (direction) + "Cycle the candidate that the preview is showing in direction DIRECTION. + +DIRECTION should be either 1 which means cycle forward, or -1 +which means cycle backward. Interactively, DIRECTION is the +prefix argument and defaults to 1." + (interactive "p") + (when completion-preview-active-mode + (let* ((beg (completion-preview--get 'completion-preview-beg)) + (end (completion-preview--get 'completion-preview-end)) + (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))) + (while (or (<= (+ beg (length str)) end) + (not (string-prefix-p (buffer-substring beg end) str))) + (setq new (mod (+ new direction) len) str (nth new all))) + (let ((aft (propertize (substring str (- end beg)) + 'face (if (< 1 len) + 'completion-preview + 'completion-preview-exact) + 'mouse-face 'completion-preview-highlight + 'keymap completion-preview--mouse-map))) + (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)) + (when completion-preview-message-format + (message (format-spec completion-preview-message-format + `((?i . ,(1+ new)) (?n . ,len)))))))) + +(defun completion-preview--active-p (_symbol buffer) + "Check if the completion preview is currently shown in BUFFER." + (buffer-local-value 'completion-preview-active-mode buffer)) + +(dolist (cmd '(completion-preview-insert + completion-preview-prev-candidate + completion-preview-next-candidate)) + (put cmd 'completion-predicate #'completion-preview--active-p)) + +;;;###autoload +(define-minor-mode completion-preview-mode + "Show in-buffer completion suggestions in a preview as you type. + +This mode automatically shows and updates the completion preview +according to the text around point. +\\<completion-preview-active-mode-map>\ +When the preview is visible, \\[completion-preview-insert] +accepts the completion suggestion, +\\[completion-preview-next-candidate] cycles forward to the next +completion suggestion, and \\[completion-preview-prev-candidate] +cycles backward." + :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 |