Emacs: icomplete, Name Completion

What is icomplete-mode

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

icomplete does completion for any command that prompts for a list of choices, such as opening a file, switch buffer, calling a command by name.

Examples of commands that icomplete has effect:

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

Alt+x icomplete-mode

Turn on or off enhanced completion in minibuffer.

• Press Tab to complete.
• press Ctrl+j to select current choice and submit.
• press Enter to submit what's in minibuffer.

icomplete-vertical-mode

• Activates icomplete-mode
• Change settings to show choices vertically.
• Call again to toggle vertical display to horizontal.

icomplete-vertical-mode is new in Emacs 28 (Released 2022-04)

icomplete keys

【Tab】

Complete what you typed.

【Space】

Complete up to a word.

【Enter】

Use what you typed so far.

【Ctrl+j】 icomplete-force-complete-and-exit

Use first choice and exit.

【Ctrl+,】 icomplete-backward-completions

complete backward

【Ctrl+.】 icomplete-forward-completions

complete forward

【M-p】

previous-history-element

【M-n】

next-history-element

Completion Styles

you can setup many different completion styles.

here are different styles, from Completion Styles (Emacs Manual)

'basic

• A matching completion alternative must have the same beginning as the text in the minibuffer before point.
• Furthermore, if there is any text in the minibuffer after point, the rest of the completion alternative must contain that text as a substring.

'partial-completion

• This aggressive completion style divides the minibuffer text into words separated by hyphens or spaces, and completes each word separately.
• (For example, when completing command names, em-l-m completes to emacs-lisp-mode.)
• Furthermore, a ‘*’ in the minibuffer text is treated as a “wildcard”—it matches any string of characters at the corresponding position in the completion alternative.

'emacs22

• similar to basic, except that it ignores the text in the minibuffer after point.

'substring

• A matching completion alternative must contain the text in the minibuffer before point, and the text in the minibuffer after point, as substrings (in that same order).
• Thus, if the text in the minibuffer is foobar, with point between foo and bar, that matches AfooBbarC, where A, B, and C can be any string including the empty string.

'flex

if you typed abc it is matched against *a*b*c* where * are any char or no char.

'initials

lch matches list-command-history

Setup completion-styles

completion-styles

variable. List of completion styles to use. The available styles are listed in completion-styles-alist .

;; examples of setting completion styles

;; use flex match.
(setq completion-styles '(flex))

;; default in emacs 29
(setq completion-styles '(basic partial-completion emacs22))