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+title = "Input Completiton"
+author = ["Michał Sapka"]
+date = 2023-05-26T23:00:00+02:00
+categories = ["emacs"]
+draft = false
+weight = 3004
+image_dir = "emacs"
+image_max_width = 480
+primary_menu = "cool-emacs-appendix"
+abstract = "Icomplete, IDO and FIDO"
+aliases = ["/2023/input-completition-in-emacs/", "/cool-emacs/input-completition-in-emacs/"]
+[menu]
+  [menu.cool-emacs-appendix]
+    weight = 3004
+    identifier = "input-completiton"
++++
+
+Emacs consists of a massive set of tools with a long history.
+Therefore, whatever the problem is, someone likely has already created a package for it.
+In many cases, this package is already baked in Emacs.
+This is great for veterans but very confusing to newcomers - like me.
+
+
+## The three modes {#the-three-modes}
+
+Emacs comes with three modes for input completion: Icomplete, IDO, and FIDO.
+Input completion works with whatever you select in the Minibuffer section.
+For text competition, you must use a different solution, like Company mode[^fn:1].
+
+The oldest one of those is _icomplete_[^fn:2] mode.
+It allows you to select from a list of choices incrementally[^fn:3], so you need to type the beginning, and icomplete will narrow the list of propositions.
+For example, when searching for "magit", the user needs to type "m" first as omitting it and starting with "i" will instead narrow to options beginning with "i".
+Similarly, "mgt" will not limit to "magit" as we're missing"a".
+Newer Emacs versions allowallow us to use "flex" matching with icomplete, but more on this later.
+Incomplete work for all lists using a mini buffer, like filenames or imenu.
+
+Then _IDO_[^fn:4] mode (Interactively Do) came in.
+It uses the aforementioned "flex" matching, where you can search for any part of the word.
+"Magit" would be found with "agit", "mgt" or just "git".
+IDO, however, works only with files and buffers, so \`M-x\` would still fall back to icomplete.
+
+Starting with Emacs 27, we've got _fido_ mode (Fake Ido).
+It combines the best things about icomplete (works anywhere) with flex matching.
+In fact, all Fido does under the hood is to enable Icomplete with flex matching.
+
+There are also other solutions for competition, not baked into emacs, with the most popular being Helm[^fn:5] and Ivy[^fn:6].
+Personally, I always try the default option, and only if their limits become annoying do I look at the alternatives.
+So, I am now a happy FIDO mode user.
+
+
+## Using FIDO {#using-fido}
+
+To start FIDO mode run
+
+```emacs-lisp
+fido-mode
+```
+
+or, if you find a vertical list to be more readable, use
+
+```emacs-lisp
+fido-veritcal-mode
+```
+
+You can also customize variables to have it auto-load in your \`init.el\`:
+
+```emacs-lisp
+(fido-mode t)
+;; or
+(fido-vertical-mode t)
+```
+
+As I've stated above, FIDO is nothing more than flex-enabled Icomplete, so all keybindings work the same.
+For vertical mode:
+
+-   Typing a string will narrow the selection
+-   \`C-n\` and \`C-p\` will select the next/prev element on the list
+-   \`Tab\` will display a buffer with a list of narrowed elements
+-   \`enter\` or \`C-j\` will select the option
+
+One cool thing you can do with FIDO is file deletion (when selecting files) or closing buffers (when selecting buffers) using \`C-k\`.
+
+
+## Customizing the Minibuffer {#customizing-the-minibuffer}
+
+We can, of course, customize how Icomplete looks works[^savanah].
+
+-   _icompleteatches-format_ (default "%s/%s") - how the number of filtered and total options is presented
+-   _complete-first-match_ (default (t :weight bold)) - how the first filtered option is presented
+-   _icomplete-selected-match_ (default (t :inherit highlight)) - the same as above, but for vertical mode
+-   _icomplete-section_ (default (t :inherit shadow :slant italic)) - how the section title for vertical mode is presented
+-   _icomplete-compute-delay_ (default .15) - how fast the filtering will start after a keypress when a larger number of options is presented
+-   _icomplete-delay-completions-threshold_ (default 400) - defines the "large number" for icomplete-compute-delay
+-   _icomplete-max-delay-chars_ (default 2) - maximum number of initial characters before applying _icomplete-compute-delay_. I have no idea what it means, nor have I the knowledge of Elisp to dig into it.
+-   _icomplete-in-buffer_ (default nil) - enables usage of Icomplete outside of the Minibuffer. I have not tested it.
+
+We can also use _icomplete-minibuffer-setup-hook_ hook if needed.
+[^savanah]: list based on [Icomplete source code](https://git.savannah.gnu.org/cgit/emacs.git/tree/lisp/icomplete.el)
+
+
+## Using Completions from Elisp {#using-completions-from-elisp}
+
+The great thing about FIDO is that it, like Icomplete, uses Minibuffer API[^fn:7], so you can simply:
+
+```emacs-lisp
+(completing-read
+ "prompt: "
+ '(("option1" 1) ("option" 2))
+ nil t "default query")
+```
+
+[^fn:1]: [Company-mode website](https://company-mode.github.io/)
+[^fn:2]: [Icomplete documentation](https://www.gnu.org/software/emacs/manual/html_node/emacs/Icomplete.html)
+[^fn:3]: According to a [Reddit comment](https://www.reddit.com/r/emacs/comments/13szol7/comment/jltmaud/?utm_source=reddit&utm_medium=web2x&context=3) this behavior is relatively new.
+    Until recently, Icompelete only showed the narrowed selection in a dedicated buffer, similar to using \`Tab-Tab\` now.
+    The actual input was still up to the user to type in. Thanks for the tidbit
+[^fn:4]: [IDO documentation](https://www.gnu.org/software/emacs/manual/html_mono/ido.html)
+[^fn:5]: [Helm website](https://emacs-helm.github.io/helm/)
+[^fn:6]: [Ivy website](https://oremacs.com/swiper/)
+[^fn:7]: [Guide on Minibuffer completition](https://www.gnu.org/software/emacs/manual/html_node/elisp/Minibuffer-Completion.html)