Emacs: icomplete mode, fido mode

This page is for emacs 28 (year 2022) [see Emacs Version History]

icomplete-mode enhances emacs's name completion when in minibuffer prompts.

icomplete does completion for any command that prompts for a list of choices. Here's some of the commands that icomplete has effect:

• execute-extended-command
• find-file
• switch-to-buffer
• describe-function

icomplete-mode vs fido-mode

icomplete-mode has several variations. They all turn on icomplete-mode, but they differ in how they display choices, and string matching method.

icomplete-mode

The most basic. Press Tab to complete, type some more and press Tab to complete more, untill there's only one choice left, then press Enter to finish and exit. You must type the char that matches the beginning of the command/file name you want. Or, you can type a * to stand for any char.

fido-mode

activates icomplete-mode, but use flex match. That is, you can type any char that are contained in the command/file name you want. No need to press Tab. Press Enter will select the first matched choice and exit.

icomplete-vertical-mode vs fido-vertical-mode

These simply display choices vertically.

icomplete-vertical-mode

activates icomplete-mode, and changes settings to show result vertically.

fido-vertical-mode

activates fido-mode, and changes settings to show result vertically.

I recommend just turn on fido-vertical-mode

Icomplete Mode Setup

Put this in your Emacs Init File:

(if (version< emacs-version "28.1")
    (progn
      (progn
        ;; make buffer switch command do suggestions, also for find-file command
        (require 'ido)
        (ido-mode 1)
        ;; show choices vertically
        (setf (nth 2 ido-decorations) "\n")
        ;; show any name that has the chars you typed
        (setq ido-enable-flex-matching t)
        ;; use current pane for newly opened file
        (setq ido-default-file-method 'selected-window)
        ;; use current pane for newly switched buffer
        (setq ido-default-buffer-method 'selected-window)
        )
      (progn
        ;; minibuffer enhanced completion icomplete
        (require 'icomplete)
        (icomplete-mode 1)
        ;; show choices vertically
        (setq icomplete-separator "\n")
        (setq icomplete-hide-common-prefix nil)
        (setq icomplete-in-buffer t)
        (define-key icomplete-minibuffer-map (kbd "<right>") 'icomplete-forward-completions)
        (define-key icomplete-minibuffer-map (kbd "<left>") 'icomplete-backward-completions)))
  (fido-vertical-mode 1))

history of icomplete mode

icomplete is originally written by Ken Manheimer, first released in 1993. (Ken Manheimer's home page: http://myriadicity.net/ • [2014-06-11 https://twitter.com/myriadicity ] )

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