Emacs: fido-mode for Name Completion

What is fido-mode • fido-vertical-mode

• fido-mode is a feature that does name completion in minibuffer. fido-mode emulates ido mode behavior. (fido is a nickname for “fake-ido”) fido-mode is new in Emacs 27 (Released 2020-08)
• fido-vertical-mode is like fido-mode, but show choices vertically. fido-vertical-mode is new in Emacs 28 (Released 2022-04)

fido-mode and fido-vertical-mode are part of icomplete-mode. They first turn on icomplete-mode. [see Emacs: icomplete, Name Completion]

Difference between fido-mode and icomplete-mode

There are two aspects of difference, submission and match method.

Submit Choice Difference

• icomplete-mode requires you to complete first, then submit your answer. Two distinct steps.
• fido-mode always just select the closest match and submit it.

• The disadvantage of icomplete-mode way is that it's one more keystroke.
• The disadvantage of fido-mode way is that if you are creating a new file (new name), it always submits a existing file name. You have to specifically press some key to tell it you don't want any existing choices. Or answer a prompt that ask you if you want to overwrite. (RISKY)

Matching Method Difference

• icomplete-mode does not use flex match by default. You have to type the starting letter of a name in order to complete.
• fido-mode use flex match (it matches any substring or subset of chars in order.). Usually saves a lot keystrokes.

Copy or Rename File in Dired Overwrites

🛑 WARNING: with fido mode on, when creating a file, or copying a file, etc in dired , be sure to press Ctrl+d to select current dir. Otherwise, if you press Enter, it selects current file choice and prompt to override file.

fido-vertical-mode keys

Ctrl+d

do not use any suggestion, but use the current typed. This is important, when you want to create a new file, dir, or dired for copy file, rename file. (corresponding command is badly named icomplete-fido-delete-char)

Enter

Select current choice

Alt+j

icomplete-fido-exit “Attempt to exit minibuffer immediately with current input.”

Alt+t

icomplete-force-complete “Complete the icomplete minibuffer.”

Ctrl+j

icomplete-force-complete-and-exit “Complete the minibuffer with the longest possible match and exit. Use the first of the matches if there are any displayed, and use the default otherwise.”

→

next choice

←

Prev choice

↓

next choice

↑

Prev choice

Ctrl+s

next choice

Ctrl+r

Prev choice

Ctrl+.

next choice

Ctrl+,

Prev choice

Ctrl+n

next choice

Ctrl+p

Prev choice

Alt+<

icomplete-vertical-goto-first

Alt+>

icomplete-vertical-goto-last