GNU-devel ELPA - corfu


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corfu-, 2022-Jan-24, 130 KiB
Daniel Mendler <>
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To install this package, run in Emacs:

M-x package-install RET corfu RET

Full description


1 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 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, Eglot and 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 Cape package.

NOTE: Corfu uses child frames to show the popup. For now Corfu falls back to the default setting of the completion-in-region-function on non-graphical displays.

2 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 (configuable via corfu-preview-current).
  • The selected candidate automatically committed on further input by default (configurable via corfu-commit-predicate).
  • The Orderless completion style is supported. The filter string can contain arbitrary characters, including spaces, if corfu-quit-at-boundary is nil.
  • Deferred completion style highlighting for performance.
  • Jumping to location/documentation of current candidate.
  • Show candidate documentation/signature string in the echo area.
  • Deprecated candidates are crossed out in the display.
  • Support for annotations (annotation-function, affixation-function).
  • Icons can be provided by an external package via margin formatter functions.

3 Installation and Configuration

Corfu is available from GNU ELPA, such that it can be installed directly via package-install. After installation, the global minor mode can be enabled with M-x corfu-global-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. For filtering I recommend to give Orderless completion a try, which 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. See also the Corfu Wiki for additional configuration tips. In particular the Lsp-mode configuration is documented in the Wiki.

Here is an example configuration:

(use-package corfu
  ;; Optional customizations
  ;; :custom
  ;; (corfu-cycle t)                ;; Enable cycling for `corfu-next/previous'
  ;; (corfu-auto t)                 ;; Enable auto completion
  ;; (corfu-commit-predicate nil)   ;; Do not commit selected candidates on next input
  ;; (corfu-quit-at-boundary t)     ;; Automatically quit at word boundary
  ;; (corfu-quit-no-match t)        ;; Automatically quit if there is no match
  ;; (corfu-preview-current nil)    ;; Disable current candidate preview
  ;; (corfu-preselect-first nil)    ;; Disable candidate preselection
  ;; (corfu-echo-documentation nil) ;; Disable documentation in the echo area
  ;; (corfu-scroll-margin 5)        ;; Use scroll margin

  ;; You may want to 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-/).

;; Optionally use the `orderless' completion style. See `+orderless-dispatch'
;; in the Consult wiki for an advanced Orderless style dispatcher.
;; Enable `partial-completion' for files to allow path expansion.
;; You may prefer to use `initials' instead of `partial-completion'.
(use-package orderless
  ;; 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)
	completion-category-defaults nil
	completion-category-overrides '((file (styles . (partial-completion))))))

;; Use dabbrev with Corfu!
(use-package dabbrev
  ;; Swap M-/ and C-M-/
  :bind (("M-/" . dabbrev-completion)
	 ("C-M-/" . dabbrev-expand)))

;; A few more useful configurations...
(use-package emacs
  ;; 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))

See also the Corfu Wiki for additional configuration tips. For more general documentation read the chapter about completion in the Emacs manual. If you want to create your own Capfs, you can find documentation about completion in the Elisp manual.

3.1 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, corfu-global-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.

(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)

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.

(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)

3.2 Completing with Corfu in the Shell or Eshell

When completing in the Eshell I recommend conservative local settings, no auto completion, quitting at boundary and quitting if there is no match.

(add-hook 'eshell-mode-hook
	  (lambda ()
	    (setq-local corfu-quit-at-boundary t
			corfu-quit-no-match t
			corfu-auto nil)

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 blog post, which shows how to configure pcomplete for git commands. Unfortunately pcomplete has a few technical issues, which we can work around with the 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.

;; 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)

3.3 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.

(use-package corfu
  ;; TAB-and-Go customizations
  (corfu-cycle t)             ;; Enable cycling for `corfu-next/previous'
  (corfu-preselect-first nil) ;; Disable candidate preselection

  ;; Use TAB for cycling, default is `corfu-complete'.
  (:map corfu-map
	("TAB" . corfu-next)
	([tab] . corfu-next)
	("S-TAB" . corfu-previous)
	([backtab] . corfu-previous))


4 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-show-location
  • M-h -> corfu-show-documentation
  • C-g -> corfu-quit
  • keyboard-escape-quit -> corfu-reset

5 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.

  • Orderless: Cofu supports completion styles, including the advanced Orderless completion style, where the filtering expressions are separated by spaces (see corfu-quit-at-boundary).
  • Cape: I collect additional Capf backends and completion-in-region commands in my Cape package. The package provides a file path, a dabbrev completion backend and a backend which allows you to enter unicode characters in the form of TeX commands. Cape provides an adapter to reuse Company backends in Corfu. Furthermore the function cape-super-capf can merge/groups multiple Capfs, such that the candidates of multiple Capfs are displayed together at the same time.
  • kind-icon: Icons are supported by Corfu via an external package. For example the kind-icon package provides beautifully styled SVG icons based on monochromatic icon sets like material design.
  • corfu-doc: The corfu-doc package by @galeo allows you to display the candidate documentation in a popup next to the Corfu popup, similar to company-quickhelp. Note that the corfu-doc package is new and still work in progress.
  • Tempel: Tiny template/snippet package which can be used in conjunction with Corfu.
  • Vertico: You may also want to look into my Vertico package. Vertico is the minibuffer completion counterpart of Corfu.

6 Alternatives

  • 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. Furthermore 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 to display the popup in contrast to the child frames used by Corfu. Overall both packages work well. Company is more mature but the integration into Emacs is a bit less tight, since for example the completion-at-point command (or the completion-in-region function) does not invoke Company.
  • 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.
  • 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 Vertico takes over. If you prefer to perform all your completions in the minibuffer consult-completion-in-region is your best option.

7 Caveats

Corfu is robust in most scenarios. There are a few known technical caveats.

  • Corfu uses child frames to show the popup. For now Corfu falls back to the default setting of the completion-in-region-function on non-graphical displays. You can use one of the alternatives in terminals.
  • Corfu does not sort by history, since completion-at-point does not maintain a history (See branch history for a possible solution).

8 Contributions

Since this package is part of GNU ELPA contributions require a copyright assignment to the FSF.

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