dotemacs

README.org (24968B)

---

 #+title: corfu.el - Completion Overlay Region FUnction
 #+author: Daniel Mendler
 #+language: en
 #+export_file_name: corfu.texi
 #+texinfo_dir_category: Emacs misc features
 #+texinfo_dir_title: Corfu: (corfu).
 #+texinfo_dir_desc: Completion Overlay Region FUnction
 
 #+html: <a href="https://www.gnu.org/software/emacs/"><img alt="GNU Emacs" src="https://github.com/minad/corfu/blob/screenshots/emacs.svg?raw=true"/></a>
 #+html: <a href="http://elpa.gnu.org/packages/corfu.html"><img alt="GNU ELPA" src="https://elpa.gnu.org/packages/corfu.svg"/></a>
 #+html: <a href="http://elpa.gnu.org/devel/corfu.html"><img alt="GNU-devel ELPA" src="https://elpa.gnu.org/devel/corfu.svg"/></a>
 
 * Introduction
 
 Corfu enhances completion at point with a small completion popup. The current
 candidates are shown in a popup below or above the point. Corfu is the
 minimalistic ~completion-in-region~ counterpart of the [[https://github.com/minad/vertico][Vertico]] minibuffer UI.
 
 Corfu is a small package, which relies on the Emacs completion facilities and
 concentrates on providing a polished completion UI. Completions are either
 provided by commands like ~dabbrev-completion~ or by pluggable backends
 (~completion-at-point-functions~, Capfs). Most programming language major modes
 implement a Capf. Furthermore the language server packages, [[https://github.com/joaotavora/eglot][Eglot]] and [[https://github.com/emacs-lsp/lsp-mode][Lsp-mode]],
 use Capfs which talk to the LSP server to retrieve the completions. Corfu does
 not include its own completion backends. The Emacs built-in Capfs and the Capfs
 provided by other programming language packages are usually sufficient. A few
 additional Capfs and completion utilities are provided by the [[https://github.com/minad/cape][Cape]] package.
 
 *NOTE*: Corfu uses child frames to show the popup and falls back to the default
 setting of the ~completion-in-region-function~ on non-graphical displays. There is
 a [[https://codeberg.org/akib/emacs-corfu-popup][package in the works]] which uses overlays for the popup such that Corfu can be
 used when Emacs is running in a terminal.
 
 [[https://github.com/minad/corfu/blob/screenshots/light.png?raw=true]]
 
 [[https://github.com/minad/corfu/blob/screenshots/dark.png?raw=true]]
 
 * Features
 
 - Timer-based auto-completions (/off/ by default, set ~corfu-auto~).
 - Popup display with scrollbar indicator and arrow key navigation.
 - The popup can be summoned explicitly by pressing =TAB= at any time.
 - The current candidate is inserted with =TAB= and selected with =RET=.
 - Candidates sorting by prefix, string length and alphabetically.
 - The selected candidate is previewed (configurable via ~corfu-preview-current~).
 - The selected candidate automatically committed on further input by default.
   (configurable via ~corfu-preview-current~).
 - The [[https://github.com/oantolin/orderless][Orderless]] completion style is supported. The filter string can contain
   arbitrary characters, after inserting a space via =M-SPC= (configurable via
   ~corfu-quit-at-boundary~ and ~corfu-separator~).
 - Deferred completion style highlighting for performance.
 - Support for candidate annotations and documentation in the echo area.
 - Deprecated candidates are crossed out in the display.
 - Icons can be provided by an external package via margin formatter functions.
 - Extensions: Quick keys, Index keys, Sorting by history, Candidate documentation
 
 * Installation and Configuration
 
 Corfu is available from [[http://elpa.gnu.org/packages/corfu.html][GNU ELPA]], such that it can be installed directly via
 ~package-install~. After installation, the global minor mode can be enabled with
 =M-x global-corfu-mode=. In order to configure Corfu and other packages in your
 init.el, you may want to use ~use-package~.
 
 Corfu is highly flexible and customizable via ~corfu-*~ customization variables,
 such that you can adapt it precisely to your requirements. However in order to
 quickly try out the Corfu completion package, it should be sufficient to
 activate ~global-corfu-mode~. You can experiment with manual completion for
 example in an Elisp buffer or in an Eshell or Shell buffer. For auto completion,
 set ~corfu-auto=t~ before turning on ~global-corfu-mode~.
 
 Here is an example configuration:
 
 #+begin_src emacs-lisp
   (use-package corfu
     ;; Optional customizations
     ;; :custom
     ;; (corfu-cycle t)                ;; Enable cycling for `corfu-next/previous'
     ;; (corfu-auto t)                 ;; Enable auto completion
     ;; (corfu-separator ?\s)          ;; Orderless field separator
     ;; (corfu-quit-at-boundary nil)   ;; Never quit at completion boundary
     ;; (corfu-quit-no-match nil)      ;; Never quit, even if there is no match
     ;; (corfu-preview-current nil)    ;; Disable current candidate preview
     ;; (corfu-preselect-first nil)    ;; Disable candidate preselection
     ;; (corfu-on-exact-match nil)     ;; Configure handling of exact matches
     ;; (corfu-echo-documentation nil) ;; Disable documentation in the echo area
     ;; (corfu-scroll-margin 5)        ;; Use scroll margin
 
     ;; Enable Corfu only for certain modes.
     ;; :hook ((prog-mode . corfu-mode)
     ;;        (shell-mode . corfu-mode)
     ;;        (eshell-mode . corfu-mode))
 
     ;; Recommended: Enable Corfu globally.
     ;; This is recommended since Dabbrev can be used globally (M-/).
     ;; See also `corfu-excluded-modes'.
     :init
     (global-corfu-mode))
 
   ;; A few more useful configurations...
   (use-package emacs
     :init
     ;; TAB cycle if there are only few candidates
     (setq completion-cycle-threshold 3)
 
     ;; Emacs 28: Hide commands in M-x which do not apply to the current mode.
     ;; Corfu commands are hidden, since they are not supposed to be used via M-x.
     ;; (setq read-extended-command-predicate
     ;;       #'command-completion-default-include-p)
 
     ;; Enable indentation+completion using the TAB key.
     ;; `completion-at-point' is often bound to M-TAB.
     (setq tab-always-indent 'complete))
 #+end_src
 
 Dabbrev completion is based on =completion-in-region= and can be used with Corfu.
 You may want to swap the =dabbrev-completion= with the =dabbrev-expand= key for
 easier access, if you prefer completion. Also take a look at the =cape-dabbrev=
 completion at point function provided by my [[https://github.com/minad/cape][Cape]] package.
 
 #+begin_src emacs-lisp
   ;; Use Dabbrev with Corfu!
   (use-package dabbrev
     ;; Swap M-/ and C-M-/
     :bind (("M-/" . dabbrev-completion)
            ("C-M-/" . dabbrev-expand))
     ;; Other useful Dabbrev configurations.
     :custom
     (dabbrev-ignored-buffer-regexps '("\\.\\(?:pdf\\|jpe?g\\|png\\)\\'")))
 #+end_src
 
 If you start to configure the package more deeply, I recommend to give the
 Orderless completion style a try for filtering. Orderless completion is
 different from the familiar prefix TAB completion. Corfu can be used with the
 default completion styles. The use of Orderless is not a necessity.
 
 #+begin_src emacs-lisp
   ;; Optionally use the `orderless' completion style.
   (use-package orderless
     :init
     ;; Configure a custom style dispatcher (see the Consult wiki)
     ;; (setq orderless-style-dispatchers '(+orderless-dispatch)
     ;;       orderless-component-separator #'orderless-escapable-split-on-space)
     (setq completion-styles '(orderless basic)
           completion-category-defaults nil
           completion-category-overrides '((file (styles . (partial-completion))))))
 #+end_src
 
 The =basic= completion style is specified as fallback in addition to =orderless= in
 order to ensure that completion commands which rely on dynamic completion
 tables, e.g., ~completion-table-dynamic~ or ~completion-table-in-turn~, work
 correctly. See =+orderless-dispatch= in the [[https://github.com/minad/consult/wiki][Consult wiki]] for an advanced Orderless
 style dispatcher. Additionally enable =partial-completion= for file path
 expansion. =partial-completion= is important for file wildcard support. Multiple
 files can be opened at once with =find-file= if you enter a wildcard. You may also
 give the =initials= completion style a try.
 
 See also the [[https://github.com/minad/corfu/wiki][Corfu Wiki]] for additional configuration tips. In particular the
 Lsp-mode configuration is documented in the wiki. For more general documentation
 read the chapter about completion in the [[https://www.gnu.org/software/emacs/manual/html_node/emacs/Completion.html][Emacs manual]]. If you want to create
 your own Capfs, you can find documentation about completion in the [[https://www.gnu.org/software/emacs/manual/html_node/elisp/Completion.html][Elisp manual]].
 
 ** Auto completion
 
 Auto completion is disabled by default, but can be enabled by setting
 ~corfu-auto=t~. Furthermore you may want to configure Corfu to quit completion
 eagerly, such that the completion popup stays out of your way when it appeared
 unexpectedly.
 
 #+begin_src emacs-lisp
   ;; Enable auto completion and configure quitting
   (setq corfu-auto t
         corfu-quit-no-match 'separator) ;; or t
 #+end_src
 
 In general, I recommend to experiment a bit with the various settings and key
 bindings to find a configuration which works for you. There is no one size fits
 all solution. Some people like auto completion, some like manual completion,
 some want to cycle with TAB and some with the arrow keys...
 
 ** Completing with Corfu in the minibuffer
 
 Corfu can be used for completion in the minibuffer, since it relies on child
 frames to display the candidates. By default, ~global-corfu-mode~ does not
 activate ~corfu-mode~ in the minibuffer, to avoid interference with specialised
 minibuffer completion UIs like Vertico or Mct. However you may still want to
 enable Corfu completion for commands like ~M-:~ (~eval-expression~) or ~M-!~
 (~shell-command~), which read from the minibuffer. Activate ~corfu-mode~ only if
 ~completion-at-point~ is bound in the minibuffer-local keymap to achieve this
 effect.
 
 #+begin_src emacs-lisp
   (defun corfu-enable-in-minibuffer ()
     "Enable Corfu in the minibuffer if `completion-at-point' is bound."
     (when (where-is-internal #'completion-at-point (list (current-local-map)))
       ;; (setq-local corfu-auto nil) Enable/disable auto completion
       (corfu-mode 1)))
   (add-hook 'minibuffer-setup-hook #'corfu-enable-in-minibuffer)
 #+end_src
 
 You can also enable Corfu more generally for every minibuffer, as long as no
 other completion UI is active. If you use Mct or Vertico as your main minibuffer
 completion UI, the following snippet should yield the desired result.
 
 #+begin_src emacs-lisp
   (defun corfu-enable-always-in-minibuffer ()
     "Enable Corfu in the minibuffer if Vertico/Mct are not active."
     (unless (or (bound-and-true-p mct--active)
                 (bound-and-true-p vertico--input))
       ;; (setq-local corfu-auto nil) Enable/disable auto completion
       (corfu-mode 1)))
   (add-hook 'minibuffer-setup-hook #'corfu-enable-always-in-minibuffer 1)
 #+end_src
 
 ** Completing with Corfu in the Eshell or Shell
 
 When completing in the Eshell I recommend conservative local settings without
 auto completion, such that the completion behavior is similar to widely used
 shells like Bash, Zsh or Fish.
 
 #+begin_src emacs-lisp
   (add-hook 'eshell-mode-hook
             (lambda ()
               (setq-local corfu-auto nil)
               (corfu-mode)))
 #+end_src
 
 When pressing =RET= while the Corfu popup is visible, the ~corfu-insert~ command
 will be invoked. This command does inserts the currently selected candidate, but
 it does not send the prompt input to Eshell or the comint process. Therefore you
 often have to press =RET= twice which feels like an unnecessary double
 confirmation. Fortunately it is easy to improve this! In my configuration I
 define the advice ~corfu-send-shell~ which sends the candidate after insertion.
 
 #+begin_src emacs-lisp
   (defun corfu-send-shell (&rest _)
     "Send completion candidate when inside comint/eshell."
     (cond
      ((and (derived-mode-p 'eshell-mode) (fboundp 'eshell-send-input))
       (eshell-send-input))
      ((and (derived-mode-p 'comint-mode)  (fboundp 'comint-send-input))
       (comint-send-input))))
 
   (advice-add #'corfu-insert :after #'corfu-send-shell)
 #+end_src
 
 Shell completion uses the flexible ~pcomplete~ mechanism internally, which allows
 you to program the completions per shell command. If you want to know more, look
 into this [[https://www.masteringemacs.org/article/pcomplete-context-sensitive-completion-emacs][blog post]], which shows how to configure pcomplete for git commands. I
 recommend the [[https://github.com/JonWaltman/pcmpl-args.el][pcmpl-args]] package which extends Pcomplete with completion support
 and helpful annotation support for more commands. Similar to the Fish shell,
 pcmpl-args uses man page parsing and --help output parsing to dynamically
 generate completions. This package brings Eshell completion to another level!
 
 Unfortunately Pcomplete has a few technical issues, which we can work around
 with the [[https://github.com/minad/cape][Cape]] library (Completion at point extensions). Cape provides wrappers,
 which sanitize the pcomplete function. Ideally the bugs in pcomplete should be
 fixed upstream. *For now these two advices are strongly recommended to achieve a
 sane Eshell experience.*
 
 #+begin_src emacs-lisp
   ;; Silence the pcomplete capf, no errors or messages!
   (advice-add 'pcomplete-completions-at-point :around #'cape-wrap-silent)
 
   ;; Ensure that pcomplete does not write to the buffer
   ;; and behaves as a pure `completion-at-point-function'.
   (advice-add 'pcomplete-completions-at-point :around #'cape-wrap-purify)
 #+end_src
 
 ** Orderless completion
 
 [[https://github.com/oantolin/orderless][Orderless]] is an advanced completion style that supports multi-component search
 filters separated by a configurable character (space, by default). Normally,
 entering characters like space which lie outside the completion region
 boundaries (words, typically) causes Corfu to quit. This behavior is helpful
 with auto-completion, which may pop-up when not desired, e.g. on entering a new
 variable name. Just keep typing and Corfu will get out of the way.
 
 But orderless search terms can contain arbitrary characters; they are also
 interpreted as regular expressions. To use orderless, set ~corfu-separator~ (a
 space, by default) to the primary character of your orderless component
 separator.
 
 Then, when a new orderless component is desired, use =M-SPC=
 (~corfu-insert-separator~) to enter the /first/ component separator in the input,
 and arbitrary orderless search terms and new separators can be entered
 thereafter.
 
 To treat the entire input as Orderless input, you can set the customization
 option ~corfu-quit-at-boundary=t~. This disables the predicate which checks if the
 current completion boundary has been left. In contrast, if you /always/ want to
 quit at the boundary, simply set ~corfu-quit-at-boundary=nil~. By default
 ~corfu-quit-at-boundary~ is set to ~separator~ which quits at completion boundaries
 as long as no separator has been inserted with ~corfu-insert-separator~.
 
 Finally, there exists the user option ~corfu-quit-no-match~ which is set to
 =separator= by default. With this setting Corfu stays alive as soon as you start
 advanced filtering with a ~corfu-separator~ even if there are no matches, for
 example due to a typo. As long as no separator character has been inserted with
 ~corfu-insert-separator~, Corfu will still quit if there are no matches. This
 ensures that the Corfu popup goes away quickly if completion is not possible.
 
 In the following we show two configurations, one which works best with auto
 completion and one which may work better with manual completion if you prefer to
 always use =SPC= to separate the Orderless components.
 
  #+begin_src emacs-lisp
    ;; Auto completion example
    (use-package corfu
      :custom
      (corfu-auto t)          ;; Enable auto completion
      ;; (corfu-separator ?_) ;; Set to orderless separator, if not using space
      :bind
      ;; Another key binding can be used, such as S-SPC.
      ;; (:map corfu-map ("M-SPC" . corfu-insert-separator))
      :init
      (global-corfu-mode))
 
    ;; Manual completion example
    (use-package corfu
      :custom
      ;; (corfu-separator ?_) ;; Set to orderless separator, if not using space
      :bind
      ;; Configure SPC for separator insertion
      (:map corfu-map ("SPC" . corfu-insert-separator))
      :init
      (global-corfu-mode))
 #+end_src
 
 ** TAB-and-Go completion
 
 You may be interested in configuring Corfu in TAB-and-Go style. Pressing TAB
 moves to the next candidate and further input will then commit the selection.
 Note that further input will not expand snippets or templates, which may not be
 desired but which leads overall to a more predictable behavior. In order to
 force snippet expansion, confirm a candidate explicitly with ~RET~.
 
 #+begin_src emacs-lisp
   (use-package corfu
     ;; TAB-and-Go customizations
     :custom
     (corfu-cycle t)             ;; Enable cycling for `corfu-next/previous'
     (corfu-preselect-first nil) ;; Disable candidate preselection
 
     ;; Use TAB for cycling, default is `corfu-complete'.
     :bind
     (:map corfu-map
           ("TAB" . corfu-next)
           ([tab] . corfu-next)
           ("S-TAB" . corfu-previous)
           ([backtab] . corfu-previous))
 
     :init
     (global-corfu-mode))
 #+end_src
 
 ** Transfer completion to the minibuffer
 
 Sometimes it is useful to transfer the Corfu completion session to the
 minibuffer, since the minibuffer offers richer interaction features. In
 particular, [[https://github.com/oantolin/embark][Embark]] is available in the minibuffer, such that you can act on the
 candidates or export/collect the candidates to a separate buffer. Hopefully we
 can also add Corfu-support to Embark in the future, such that at least
 export/collect is possible directly from Corfu. But in my opinion having the
 ability to transfer the Corfu completion to the minibuffer is an even better
 feature, since further completion can be performed there.
 
 The command ~corfu-move-to-minibuffer~ is defined here in terms of
 ~consult-completion-in-region~, which uses the minibuffer completion UI via
 ~completing-read~.
 
 #+begin_src emacs-lisp
   (defun corfu-move-to-minibuffer ()
     (interactive)
     (let ((completion-extra-properties corfu--extra)
           completion-cycle-threshold completion-cycling)
       (apply #'consult-completion-in-region completion-in-region--data)))
   (define-key corfu-map "\M-m" #'corfu-move-to-minibuffer)
 #+end_src
 
 * Key bindings
 
 Corfu uses a transient keymap ~corfu-map~ which is active while the popup is
 shown. The keymap defines the following remappings and bindings:
 
 - ~beginning-of-buffer~ -> ~corfu-first~
 - ~end-of-buffer~ -> ~corfu-last~
 - ~scroll-down-command~ -> ~corfu-scroll-down~
 - ~scroll-up-command~ -> ~corfu-scroll-up~
 - ~next-line~, =down=, =M-n= -> ~corfu-next~
 - ~previous-line~, =up=, =M-p= -> ~corfu-previous~
 - ~completion-at-point~, =TAB= -> ~corfu-complete~
 - =RET= -> ~corfu-insert~
 - =M-g= -> ~corfu-info-location~
 - =M-h= -> ~corfu-info-documentation~
 - =M-SPC= -> ~corfu-insert-separator~
 - =C-g= -> ~corfu-quit~
 - ~keyboard-escape-quit~ -> ~corfu-reset~
 
 * Extensions
 :properties:
 :custom_id: extensions
 :end:
 
 We maintain small extension packages to Corfu in this repository in the
 subdirectory [[https://github.com/minad/corfu/tree/main/extensions][extensions/]]. The extensions are installed together with Corfu if
 you pull the package from ELPA. The extensions are inactive by default and can
 be enabled manually if desired. Furthermore it is possible to install all of the
 files separately, both ~corfu.el~ and the ~corfu-*.el~ extensions. Currently the
 following extensions come with the Corfu ELPA package:
 
 - [[https://github.com/minad/corfu/blob/main/extensions/corfu-history.el][corfu-history]]: =corfu-history-mode= to remember selected candidates and to improve sorting.
 - [[https://github.com/minad/corfu/blob/main/extensions/corfu-indexed.el][corfu-indexed]]: =corfu-indexed-mode= to select indexed candidates with prefix arguments.
 - [[https://github.com/minad/corfu/blob/main/extensions/corfu-info.el][corfu-info]]: Candidate actions to access the candidate location and documentation.
 - [[https://github.com/minad/corfu/blob/main/extensions/corfu-quick.el][corfu-quick]]: Commands to select using Avy-style quick keys.
 
 * Complementary packages
 
 Corfu works well together with all packages providing code completion via the
 ~completion-at-point-functions~. Many modes and packages already provide a Capf
 out of the box. Nevertheless you may want to look into complementary packages to
 enhance your setup.
 
 - [[https://github.com/oantolin/orderless][Orderless]]: Corfu supports completion styles, including the advanced
   [[https://github.com/oantolin/orderless][Orderless]] completion style, where the filtering expressions are separated by
   spaces or another character (see ~corfu-separator~).
 
 - [[https://github.com/minad/cape][Cape]]: Additional Capf backends and =completion-in-region= commands
   are provided by the [[https://github.com/minad/cape][Cape]] package. Among others, the package supplies a file
   path and a dabbrev completion backend. Cape provides the ~cape-company-to-capf~
   adapter to reuse Company backends in Corfu. Furthermore the function
   ~cape-super-capf~ can merge multiple Capfs, such that the candidates of multiple
   Capfs are displayed together at the same time.
 
 - [[https://github.com/jdtsmith/kind-icon][kind-icon]]: Icons are supported by Corfu via an external package. For example
   the [[https://github.com/jdtsmith/kind-icon][kind-icon]] package provides beautifully styled SVG icons based on
   monochromatic icon sets like material design.
 
 - [[https://github.com/galeo/corfu-doc][corfu-doc]]: The corfu-doc package displays the candidate documentation in a
   popup next to the Corfu popup, similar to =company-quickhelp=.
 
 - [[https://github.com/JonWaltman/pcmpl-args.el][pcmpl-args]]: Extend the Eshell/Shell Pcomplete mechanism with support for many
   more commands. Similar to the Fish shell, Pcomplete uses man page parsing to
   dynamically retrieve the completions and helpful annotations. This package
   brings Eshell completions to another level!
 
 - [[https://github.com/minad/tempel][Tempel]]: Tiny template/snippet package with templates in Lisp syntax, which
   can be used in conjunction with Corfu.
 
 - [[https://github.com/minad/vertico][Vertico]]: You may also want to look into my [[https://github.com/minad/vertico][Vertico]] package. Vertico is the
   minibuffer completion counterpart of Corfu.
 
 * Alternatives
 
 - [[https://github.com/company-mode/company-mode][Company]]: Company is a widely used and mature completion package, which
   implements a similar interaction model and popup UI as Corfu. While Corfu
   relies exclusively on the standard Emacs completion API (Capfs), Company
   defines its own API for the backends. Company includes its completion
   backends, which are incompatible with the Emacs completion infrastructure. As
   a result of this design, Company is a more complex package than Corfu. Company
   by default uses overlays for the popup in contrast to the child frames used by
   Corfu. Overall both packages work well, but Company integrates less tightly
   with Emacs. The ~completion-styles~ support is more limited and the
   ~completion-at-point~ command and the ~completion-in-region~ function do not
   invoke Company.
 
 - [[https://git.sr.ht/~protesilaos/mct][Mct]]: Protesilaos' Minibuffer Confines Transcended package supports both
   minibuffer completion and completion in region. It reuses the default
   completion UI for this purpose and installs a timer which live updates the
   completion buffer. The main advantage of Mct is that you work with a regular
   Emacs buffer instead of with a popup. You can take advantage of the usual
   Emacs commands to navigate in the completions buffer. On top, Mct enhances the
   movement such that you can quickly switch between the completions buffer and
   the minibuffer or the region which is being completed. Mct does not support
   timer-based auto completion, but the integration into Emacs is naturally
   tight.
 
 - [[https://github.com/minad/consult][consult-completion-in-region]]: The Consult package provides the function
   ~consult-completion-in-region~ which can be set as ~completion-in-region-function~
   such that it handles ~completion-at-point~. The function works by transferring
   the in-buffer completion to the minibuffer. In the minibuffer, the minibuffer
   completion UI, for example [[https://github.com/minad/vertico][Vertico]] takes over. If you prefer to perform all
   your completions in the minibuffer ~consult-completion-in-region~ is your best
   option.
 
 * Contributions
 
 Since this package is part of [[http://elpa.gnu.org/packages/corfu.html][GNU ELPA]] contributions require a copyright
 assignment to the FSF.