Next: Overview of MCT [Index]
Copyright (C) 2021 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with the Front-Cover Texts being “A GNU Manual,” and with the Back-Cover Texts as in (a) below. A copy of the license is included in the section entitled “GNU Free Documentation License.”
(a) The FSF’s Back-Cover Text is: “You have the freedom to copy and modify this GNU manual.”
This manual, written by Protesilaos Stavrou, describes the customization options for ‘mct’ (or ‘mct.el’ and variants), and provides every other piece of information pertinent to it.
The documentation furnished herein corresponds to stable version 1.0.0, released on 2023-09-24. Any reference to a newer feature which does not yet form part of the latest tagged commit, is explicitly marked as such.
Current development target is 1.1.0-dev.
mct
If you are viewing the README.org version of this file, please note that the GNU ELPA machinery automatically generates an Info manual out of it.
Next: Customizations, Previous: Minibuffer Confines Transcended (mct.el), Up: Minibuffer Confines Transcended (mct.el) [Index]
Minibuffer and Completions in Tandem, also known as “MCT”, “Mct”, ‘mct’, or ‘mct.el’, is a package that enhances the default minibuffer and ‘*Completions*’ buffer of Emacs 28 (or higher) so that they work together as part of a unified framework. The idea is to make the presentation and overall functionality be consistent with other popular, vertically aligned completion UIs while leveraging built-in functionality.
The main feature set that unifies the minibuffer and the ‘*Completions*’ buffer consists of commands that cycle between the two, making it seem like they are part of a contiguous space (Basic usage).
MCT tries to find a middle ground between the frugal defaults and the more opinionated completion UIs. This is most evident in its approach on how to present completion candidates. Instead of showing them outright or only displaying them on demand, MCT implements a minimum input threshold as well as a slight delay before it pops up the ‘*Completions*’ buffer and starts updating it to respond to user input.
Next: Usage, Previous: Overview of MCT, Up: Minibuffer Confines Transcended (mct.el) [Index]
MCT is highly configurable to adapt to the varying needs of users. This section documents each user option.
Next: Minimum input threshold, Up: Customizations [Index]
Brief: Control auto-display and live-update of the ‘*Completions*’ buffer.
Symbol: mct-live-completion (‘choice’ type)
Possible values:
nil
t (default)
visible
This user option governs the overall behaviour of MCT with regard to how it uses the Completions’ buffer:
visible, the Completions’ buffer is live updated only if
it is visible (present in a window). The actual display of the
completions is still handled manually. For this reason, the visible
style does not read the mct-minimum-input, meaning that it will always
try to live update the visible completions, regardless of input length
(Minimum input threshold).
mct-minimum-input is met and is hidden if the input
drops below that threshold. While visible, the buffer is updated live
to match the user’s input.
Note that every command or completion category that is declared in the
mct-completion-passlist ignores this option altogether. This means that
every such symbol will always show the Completions’ buffer automatically
and will always update its contents live to match any further user input
(Passlist for commands or completion categories). Same principle for
the mct-completion-blocklist, which will always disable both the
automatic display and live updating of the Completions’ buffer
(Blocklist for commands or completion categories).
Size boundaries of the Completions.
Next: Delay between live updates, Previous: Live completion, Up: Customizations [Index]
Brief: Try to live update completions when input is >= N.
Symbol: mct-minimum-input (‘natnum’ type)
By default, MCT expects the user to type ‘3’ characters before it tries to compute completion candidates, display the ‘*Completions*’ buffer and keep it updated live to match any subsequent input.
Setting this user option to a value greater than 1 can help reduce the total number of candidates that are being computed. That is because the Completions can consist of thousands of items that all need to be rendered at once in a buffer.
In terms of the user experience, the minimum input threshold can make sessions feel less visually demanding when the user (i) knows what they are looking for and (ii) types fast enough so that the ‘*Completions*’ never have the time to pop up.
This variable is ignored for commands or completion categories that are
specified in the mct-completion-passlist and mct-completion-blocklist.
Live updates per command or completion category.
Next: Live updates per command or completion category, Previous: Minimum input threshold, Up: Customizations [Index]
Brief: Delay in seconds before updating the Completions’ buffer.
Symbol: mct-live-update-delay (‘number’ type)
The delay in seconds between live updates of the Completions’ buffer. The default value is ‘0.3’.
This variable is ignored for commands or completion categories that are
specified in the mct-completion-passlist and mct-completion-blocklist.
Live updates per command or completion category.
Next: Size boundaries of the Completions, Previous: Delay between live updates, Up: Customizations [Index]
By default, MCT has the same behaviour across all types of completion.
Specifically, it respects the mct-live-completion option on whether and
when to perform live completion, the mct-minimum-input threshold before
doing so, and the mct-live-update-delay between changes to the
‘*Completions*’ buffer.
A passlist and a blocklist can override those options for the commands or categories specified.
Next: Blocklist for commands or completion categories, Up: Live updates per command or completion category [Index]
Brief: List of symbols where live completions are always enabled.
Symbol: mct-completion-passlist (‘repeat symbol’ type)
The value of this user option is a list of symbols. Those can refer to
commands like find-file or completion categories such as file, buffer,
or what other packages define like Consult’s consult-location category.
Any entry in the passlist ignores the value of mct-live-completion and
the mct-minimum-input. It also bypasses any possible delay introduced
by mct-live-update-delay. In other words, it immediately displays the
‘*Completions*’ buffer and instantly updates it to match user input.
When the mct-completion-blocklist and the mct-completion-passlist
are in conflict, the former takes precedence.
Next: Known completion categories, Previous: Passlist for commands or completion categories, Up: Live updates per command or completion category [Index]
Brief: List of symbols where live completions are always disabled.
Symbol: mct-completion-blocklist (‘repeat symbol’ type)
The value of this user option is a list of symbols. Those can refer to
commands like find-file or completion categories such as file, buffer,
or what other packages define like Consult’s consult-location category.
This means that they ignore mct-live-completion. They do not
automatically display the Completions’ buffer, nor do they update it to
match user input.
The Completions’ buffer can still be accessed with commands that place
it in a window (such as mct-list-completions-toggle,
mct-switch-to-completions-top).
When the mct-completion-blocklist and the mct-completion-passlist
are in conflict, the former takes precedence.
Perhaps a less drastic measure is to set mct-minimum-input to an
appropriate value. Or better use mct-completion-passlist.
Next: Find completion category, Previous: Blocklist for commands or completion categories, Up: Live updates per command or completion category [Index]
Below are the known completion categories that can be added to the
mct-completion-passlist and mct-completion-blocklist (and relevant
custom code). This resource is non-exhaustive and will be updated to
match available information.
bookmark
buffer
charset
coding-system
color
command (e.g. ‘M-x’)
customize-group
environment-variable
expression
face
file
function (the describe-function command bound to ‘C-h f’)
info-menu
imenu
input-method
kill-ring
library
minor-mode
multi-category
package
project-file
symbol (the describe-symbol command bound to ‘C-h o’)
theme
unicode-name (the insert-char command bound to ‘C-x 8 RET’)
variable (the describe-variable command bound to ‘C-h v’)
From the ‘consult’ package:
consult-grep
consult-isearch
consult-isearch
consult-kmacro
consult-location
From the ‘embark’ package:
embark-keybinding
In general, it is best not to add symbols which include several
thousands of candidates to the passlist. So no command, function,
symbol, unicode-name, variable.
When in doubt, do not add a symbol to either the pass- or block- list.
While using a command that provides a minibuffer prompt, type ‘M-:’ (the
eval-expression command) and evaluate ‘(mct--completion-category)’. It
will return the completion category, if any. Note that this only works
when the variable enable-recursive-minibuffers is non-nil.
To review echo area messages, use ‘C-h e’ (view-echo-area-messages).
Next: Dynamic completion tables in mct-mode, Previous: Live updates per command or completion category, Up: Customizations [Index]
Brief: Set the maximum and minimum height of the Completions’ buffer.
Symbol: mct-completion-window-size (‘choice’ type between nil and cons cell)
The value is a cons cell in the form of ‘(max-height . min-height)’ where each value is either a natural number or a function which returns such a number.
The default maximum height of the window is calculated by the function
mct--frame-height-fraction, which finds the closest round number to
1/3 of the frame’s height. While the default minimum height is 1. This
means that during live completions the Completions’ window will shrink
or grow to show candidates within the specified boundaries. To disable
this bouncing effect, set both max-height and min-height to the same
number.
If nil, do not try to fit the Completions’ buffer to its window.
Next: Hide the Completions mode line, Previous: Size boundaries of the Completions, Up: Customizations [Index]
Brief: Whether to keep dynamic completion live.
Symbol: mct-persist-dynamic-completion (‘boolean’ type)
Possible values:
nil
t (default)
Without any intervention from MCT, the default Emacs behavior for
commands such as find-file or for a file completion category is to hide
the ‘*Completions*’ buffer after updating the list of candidates in a
non-exiting fashion (e.g. select a directory and expect to continue
typing the path). This, however, runs contrary to the interaction model
of MCT when it performs live completions, because the user expects the
Completions’ buffer to remain visible while typing out the path to the
file (Live completion).
When this user option is non-nil (the default) it makes all non-exiting commands keep the ‘*Completions*’ visible when updating the list of candidates.
This applies to prompts in the file completion category whenever the
user selects a candidate with mct-choose-completion-no-exit,
mct-edit-completion, minibuffer-complete, minibuffer-force-complete
(i.e. any command that does not exit the minibuffer).
Selecting candidates with mct-mode.
The two exceptions are (i) when the current completion
session runs a command or category that is blocked by the
mct-completion-blocklist or (ii) the user option mct-live-completion is
nil.
Blocklist for commands or completion categories.
The underlying rationale:
Most completion commands present a flat list of candidates to choose
from. Picking a candidate concludes the session. Some prompts,
however, can recalculate the list of completions based on the selected
candidate. A case in point is find-file (or any command with the file
completion category) which dynamically adjusts the completions to show
only the elements which extend the given file system path. We call such
cases “dynamic completion”. Due to their particular nature, these need
to be handled explicitly. The present user option is provided primarily
to raise awareness about this state of affairs.
Next: Remove shadowed file paths, Previous: Dynamic completion tables in mct-mode, Up: Customizations [Index]
Brief: Do not show a mode line in the Completions’ buffer.
Symbol: mct-hide-completion-mode-line (‘boolean’ type)
By default, the ‘*Completions*’ buffer has its own mode line, just like every other window. Set this user option to non-nil to remove the mode line.
Next: MCT in the minibuffer and completion in regular buffers, Previous: Hide the Completions mode line, Up: Customizations [Index]
Brief: Delete shadowed parts of file names from the minibuffer.
Symbol: mct-remove-shadowed-file-names (‘boolean’ type)
When the built-in file-name-shadow-mode is enabled and this user option
is non-nil, MCT will delete the part of the file path that is shadowed
(meaning that it is overriden) by the given input.
For example, if the user types ‘~/’ after a long path name, everything preceding the ‘~/’ is removed so the interactive selection process starts again from the user’s ‘$HOME’.
Previous: Remove shadowed file paths, Up: Customizations [Index]
Emacs draws a distinction between two types of completion sessions:
completion-in-region.
The former scenario is what MCT has supported since its inception.
Enable mct-mode to get started. There was a time where MCT also
supported in-buffer completion but this was discontinued in version
‘1.0.0’ of the package as Emacs 29 gained the requisite capabilities.
To get the familiar MCT key bindings for in-buffer completion, use
these in your init file:
;; Get the key bindings (let ((map completion-in-region-mode-map)) (define-key map (kbd "C-n") #'minibuffer-next-completion) (define-key map (kbd "C-p") #'minibuffer-previous-completion) (define-key map (kbd "RET") #'minibuffer-choose-completion)) ;; Tweak the appearance (setq completions-format 'one-column) (setq completion-show-help nil) (setq completion-auto-help t) ;; Optionally, tweak the appearance further (setq completions-detailed t) (setq completion-show-inline-help nil) (setq completions-max-height 6) (setq completions-highlight-face 'completions-highlight)
Note that the in-buffer completions will produce a new buffer window
below the current one. Some users find this intrusive. In such a
case, the use of a popup box is better. Consider the corfu package
by Daniel Mendler, which uses such a popup (Alternatives).
Next: Installation, Previous: Customizations, Up: Minibuffer Confines Transcended (mct.el) [Index]
This section outlines the various patterns of interaction that MCT establishes.
Next: Selecting candidates with mct-mode, Up: Usage [Index]
When mct-mode is enabled, some new keymaps are activated
which add commands for cycling between the minibuffer and the
completions. Suppose the following standard layout:
----------------- | | | | Buffers| Buf | | | | ----------------- | | | | Buf | Buf | | | | ----------------- ----------------- | | | Completions | | | ----------------- ----------------- | Minibuffer | -----------------
When inside the minibuffer, pressing ‘C-n’ (or down arrow) takes you to
the top of the completions, while ‘C-p’ (or up arrow) moves to the bottom.
The commands are mct-switch-to-completions-top for the former and
mct-switch-to-completions-bottom for the latter. If the ‘*Completions*’
are not shown, then the buffer pops up automatically and point moves to
the given position.
Similarly, while inside the ‘*Completions*’ buffer, ‘C-p’ (or up arrow) at
the top of the buffer switches to the minibuffer, while ‘C-n’ (or down
arrow) at the bottom of the buffer also goes to the minibuffer. If
point is anywhere else inside the buffer, those key bindings perform a
regular line motion (if the ‘*Completions*’ are set to a grid view, then
the left and right arrow keys perform the corresponding lateral
motions). The commands are mct-previous-completion-or-mini and
mct-next-completion-or-mini. Both accept an optional numeric argument.
If the Nth line lies outside the boundaries of the completions’ buffer,
they move the point to the minibuffer.
The display of the ‘*Completions*’ can be toggled at any time from inside
the minibuffer with ‘C-l’ (mnemonic is “[l]ist completions” and the
command is mct-list-completions-toggle).
Previous: Cyclic behaviour for mct-mode, Up: Usage [Index]
There are several ways to select a completion candidate with
mct-mode.
minibuffer-complete). If the match is unique, the text
will be expanded. Otherwise the ‘*Completions*’ buffer will appear.
This does not exit the minibuffer, meaning that it does not confirm
your choice. To confirm your choice, use ‘RET’. If you ever make a
mistake and expand the wrong candidate, just use undo. Lastly note
that if the candidates meet the completion-cycle-threshold hitting
‘TAB’ again will switch between them.
mct-choose-completion-exit). This
works for all types of completion prompts.
mct-choose-completion-no-exit which is bound
to ‘TAB’ in the completions’ buffer. This is particularly useful for
certain contexts where selecting a candidate does not necessarily
mean that the process has to be finalised (e.g. when using
find-file). In those cases, the event triggered by ‘TAB’ is followed
by the renewal of the list of completions, where relevant (e.g. ‘TAB’
over a directory in find-file, which then shows the contents of that
directory).
The command can correctly expand completion candidates even when the
active style in completion-styles is ‘partial-completion’. In other
words, if the minibuffer contains input like ‘~/G/P/m’ and the point is
in the completions’ buffer over ‘Git/Projects/mct/’ the minibuffer’
contents will become ‘~/Git/Projects/mct/’ and then show the contents
of that directory.
mct-edit-completion) in the completions’ buffer to place
the current candidate in the minibuffer, without exiting the session.
This allows you to edit the text before confirming it. If point is
in the minibuffer before performing this action, the current
candidate is either the one at the top of the completions’ buffer or
that which is under the last known point in said buffer (the last
known position is reset when the window is deleted). Internally,
mct-edit-completion uses mct-choose-completion-no-exit to expand the
completion candidate, so it retains its behaviour (as explained right
above).
Sometimes there is a need to switch to the minibuffer without
selecting the candidate at point, such as to retype some part of the
input. In those cases, type ‘e’ in the completions’ buffer to move to
the minibuffer. The command is called mct-focus-minibuffer, which
can also be assigned to the global keymap, though MCT leaves such a
decision up to the user (same for mct-focus-mini-or-completions).
completing-read-multiple function) using ‘M-RET’
(mct-choose-completion-dwim) in the ‘*Completions*’ will append the
candidate at point to the list of selections and keep the completions
available so that another item may be selected. Any of the
aforementioned applicable methods can confirm the final selection.
If, say, you want to pick a total of three candidates, do ‘M-RET’ for
the first two and ‘RET’ (mct-choose-completion-exit) for the last one.
In contexts that are not CRM-powered, the ‘M-RET’ has the same effect
as ‘TAB’ (mct-choose-completion-no-exit).
mct-complete-and-exit), which
has the same effect as first completing with ‘TAB’ and then
immediately exit the minibuffer with the completed candidate as the
selected one.
mct-next-completion-group)
and ‘M-p’ (mct-previous-completion-group) to move to the next or
previous one, respectively (also work with they keys for
forward-paragraph and backward-paragraph). Both commands accept
an optional numeric argument. For the sake of avoiding surprises,
these commands do not cycle between the completions and the
minibuffer: they stop at the first or last heading.
Next: Sample setup, Previous: Usage, Up: Minibuffer Confines Transcended (mct.el) [Index]
Next: Manual installation method, Up: Installation [Index]
‘mct’ is available on the official GNU ELPA archive for users of Emacs version 27 or higher. One can install the package without any further configuration. The following commands shall suffice:
M-x package-refresh-contents M-x package-install RET mct
A package is also available via Guix:
guix package -i emacs-mct
Previous: Install the package, Up: Installation [Index]
Assuming your Emacs files are found in ‘~/.emacs.d/’, execute the following commands in a shell prompt:
cd ~/.emacs.d # Create a directory for manually-installed packages mkdir manual-packages # Go to the new directory cd manual-packages # Clone this repo and name it "mct" git clone https://git.sr.ht/~protesilaos/mct mct
Finally, in your ‘init.el’ (or equivalent) evaluate this:
;; Make Elisp files in that directory available to the user. (add-to-list 'load-path "~/.emacs.d/manual-packages/mct")
Everything is in place to set up the package.
Next: Keymaps, Previous: Installation, Up: Minibuffer Confines Transcended (mct.el) [Index]
Minimal setup for the minibuffer and in-buffer completion:
(require 'mct) (mct-mode 1)
And with more options:
(require 'mct)
(setq mct-completion-window-size (cons #'mct-frame-height-third 1))
(setq mct-remove-shadowed-file-names t) ; works when `file-name-shadow-mode' is enabled
(setq mct-hide-completion-mode-line t)
(setq mct-minimum-input 3)
(setq mct-live-completion t)
(setq mct-live-update-delay 0.6)
(setq mct-persist-dynamic-completion t)
;; This is for commands or completion categories that should always pop
;; up the completions' buffer. It circumvents the default method of
;; waiting for some user input (see `mct-minimum-input') before
;; displaying and updating the completions' buffer.
(setq mct-completion-passlist
'(;; Some commands
Info-goto-node
Info-index
Info-menu
vc-retrieve-tag
;; Some completion categories
imenu
file
buffer
kill-ring
consult-location))
;; The blocklist follows the same principle as the passlist, except it
;; disables live completions altogether.
(setq mct-completion-blocklist nil)
(mct-mode 1)
Other useful extras from the Emacs source code (read their doc strings):
(setq completion-styles
'(basic substring initials flex partial-completion))
(setq completion-category-overrides
'((file (styles . (basic partial-completion initials substring)))))
(setq completion-cycle-threshold 2)
(setq completion-ignore-case t)
(setq completion-show-inline-help nil)
(setq completions-detailed t)
(setq enable-recursive-minibuffers t)
(setq minibuffer-eldef-shorten-default t)
(setq read-buffer-completion-ignore-case t)
(setq read-file-name-completion-ignore-case t)
(setq resize-mini-windows t)
(setq minibuffer-eldef-shorten-default t)
(file-name-shadow-mode 1)
(minibuffer-depth-indicate-mode 1)
(minibuffer-electric-default-mode 1)
;; Do not allow the cursor in the minibuffer prompt
(setq minibuffer-prompt-properties
'(read-only t cursor-intangible t face minibuffer-prompt))
(add-hook 'minibuffer-setup-hook #'cursor-intangible-mode)
;;; Minibuffer history
(require 'savehist)
(setq savehist-file (locate-user-emacs-file "savehist"))
(setq history-length 500)
(setq history-delete-duplicates t)
(setq savehist-save-minibuffer-history t)
(add-hook 'after-init-hook #'savehist-mode)
;;; Third-party extensions
;;;; Enable Consult previews in the Completions buffer.
;; Requires the `consult' package.
(add-hook 'completion-list-mode-hook #'consult-preview-at-point-mode)
;;;; Setup for Orderless
;; Requires the `orderless' package
;; We make the SPC key insert a literal space and the same for the
;; question mark. Spaces are used to delimit orderless groups, while
;; the quedtion mark is a valid regexp character.
(let ((map minibuffer-local-completion-map))
(define-key map (kbd "SPC") nil)
(define-key map (kbd "?") nil))
;; Because SPC works for Orderless and is trivial to activate, I like to
;; put `orderless' at the end of my `completion-styles'. Like this:
(setq completion-styles
'(basic substring initials flex partial-completion orderless))
(setq completion-category-overrides
'((file (styles . (basic partial-completion orderless)))))
Next: User-level tweaks or custom code, Previous: Sample setup, Up: Minibuffer Confines Transcended (mct.el) [Index]
MCT defines its own keymaps, which extend those that are active in the minibuffer and the ‘*Completions*’ buffer, respectively:
mct-completion-list-mode-map
mct-minibuffer-local-completion-map
You can invoke describe-keymap to learn more about them.
If you want to edit any key bindings, do it in these keymaps, not in those they extend and override (the names of the original ones are the same as above, minus the ‘mct-’ prefix).
Next: Third-party extensions, Previous: Keymaps, Up: Minibuffer Confines Transcended (mct.el) [Index]
In this section we cover custom code that builds on what MCT offers.
Starting with Emacs 29 (current development target), the user option
completions-sort controls the sorting method of candidates in the
‘*Completions*’ buffer. Beside the default of using string-lessp, it
accepts a custom function. Consider any of the following examples:
;; Some sorting functions...
(defun my-sort-by-alpha-length (elems)
"Sort ELEMS first alphabetically, then by length."
(sort elems (lambda (c1 c2)
(or (string-version-lessp c1 c2)
(< (length c1) (length c2))))))
(defun my-sort-by-history (elems)
"Sort ELEMS by minibuffer history.
Use `mct-sort-sort-by-alpha-length' if no history is available."
(if-let ((hist (and (not (eq minibuffer-history-variable t))
(symbol-value minibuffer-history-variable))))
(minibuffer--sort-by-position hist elems)
(my-sort-by-alpha-length elems)))
(defun my-sort-multi-category (elems)
"Sort ELEMS per completion category."
(pcase (mct--completion-category)
('nil elems) ; no sorting
('kill-ring elems)
('project-file (my-sort-by-alpha-length elems))
(_ (my-sort-by-history elems))))
;; Specify the sorting function.
(setq completions-sort #'my-sort-multi-category)
Next: Ido-style navigation through directories, Previous: Sort completion candidates on Emacs 29, Up: User-level tweaks or custom code [Index]
Previous versions of MCT would prepend a ‘[CRM]’ tag to the minibuffer
prompt of commands powered by completing-read-multiple. While this is a
nice usability enhancement, it is not specific to MCT and thus should
not be part of ‘mct.el’. Use this in your init file instead:
;; Add prompt indicator to `completing-read-multiple'. We display
;; [`completing-read-multiple': <separator>], e.g.,
;; [`completing-read-multiple': ,] if the separator is a comma. This
;; is adapted from the README of the `vertico' package by Daniel
;; Mendler. I made some small tweaks to propertize the segments of
;; the prompt.
(defun crm-indicator (args)
(cons (format "[`crm-separator': %s] %s"
(propertize
(replace-regexp-in-string
"\\`\\[.*?]\\*\\|\\[.*?]\\*\\'" ""
crm-separator)
'face 'error)
(car args))
(cdr args)))
(advice-add #'completing-read-multiple :filter-args #'crm-indicator)
Next: Alternatives, Previous: User-level tweaks or custom code, Up: Minibuffer Confines Transcended (mct.el) [Index]
MCT only tweaks the default minibuffer. To get more out of it, consider these exceptionally well-crafted extras:
Adds several commands that make interacting with the minibuffer more powerful. There also are multiple packages that build on it, such as consult-dir by Karthik Chikmagalur and consult-notmuch by José Antonio Ortega Ruiz.
Provides configurable contextual actions for completions and many other constructs inside buffers. A genius package!
Displays informative annotations for all known types of completion candidates.
A completion style that matches a variety of patterns (regexp, flex, initialism, etc.) regardless of the order they appear in.
Glue code that adds icons from the ‘all-the-icons’ package to the ‘*Completions*’ buffer. It can make things prettier and/or more informative, while it can also be combined with Marginalia.
MCT does not support the use-case of completion-in-region. This is
the kind of completion session that is done inside the buffer and does
not involve the minibuffer. However, you may prefer:
An interface for the completion-in-region
which uses a child frame (basically a pop-up) at the position of the
cursor to display candidates. As with all of Daniel’s packages, Corfu
aims for a clean implementation that does the right thing by being
consistent with core Emacs mechanisms.
Additional completion-at-point-functions
(CAPFs) that extend those of core Emacs. These backends can be used
by packages that visualise completion-in-region.
Up: Third-party extensions [Index]
One of the nice features of the Consult package is the ability to preview the candidate at point. All we need to enable it in the ‘*Completions*’ buffer is the following snippet:
(add-hook 'completion-list-mode-hook #'consult-preview-at-point-mode)
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In the grand scheme of things, it may be helpful to think of MCT as proof-of-concept on how the default Emacs completion can become more expressive. MCT’s value rests in its potential to inspire developers to (i) patch Emacs so that its out-of-the-box completion is more interactive, and (ii) expose the shortcomings in the current implementation of the ‘*Completions*’ buffer, which should again provide an impetus for further changes to Emacs. Otherwise, MCT is meant for users who can tolerate the status quo and simply want a thin layer of interactivity for minibuffer completion, in-buffer completion, and their intersection with the Completions’ buffer.
Like MCT, these alternatives provide a thin layer of functionality over the built-in infrastructure. Unlike MCT, they are not constrained by the design of the ‘*Completions*’ buffer and concomitant functionality. They all make for a natural complement to the standard Emacs experience (also Extensions).
this is a more mature and feature-rich package with a large user base and a highly competent maintainer.
Vertico has some performance optimizations on how candidates are
sorted and presented, which means that it displays results right away
without any noticeable performance penalty. Whereas MCT does not
change the underlying behaviour of how candidates are displayed. As
such, MCT will be slower in scenaria where there are lots of
candidates because core Emacs lacks those optimizations. One such
case is with the describe-symbol (‘C-h o’) prompt. If the user asks for
the completions’ buffer without inputting any character (so without
narrowing the list), there will be a noticeable delay before the
buffer is rendered. This is mitigated in MCT by the requirement for
mct-minimum-input, though the underlying mechanics remain intact.
In terms of the interaction model, the main difference between Vertico and MCT is that the former uses the minibuffer by default and shows the completions there. The minibuffer is expanded to show the candidates in a vertical list. Whereas MCT keeps the ‘*Completions*’ buffer and the minibuffer as separate entities, the way standard Emacs does it.
The presence of a fully fledged buffer means that the user can invoke all relevant commands at their disposal, such as to write the buffer to a file for future review, use Isearch to move around, copy a string or rectangle to a register, and so on.
Vertico has official extensions which can make it work exactly like
MCT without any of MCT’s drawbacks. These extensions can also expand
Vertico’s powers such as by providing granular control over the exact
style of presentation for any given completion category (e.g. display
Imenu in a separate buffer, show the switch-to-buffer list
horizontally in the minibuffer, and present find-file in a vertical
list—whatever the user wants).
All things considered, there is no compelling reason why one may prefer MCT over Vertico in terms of the available functionality: Vertico is better.
Icomplete is
closer in spirit to Vertico, as it too uses the minibuffer to display
completion candidates. By default, it presents the list horizontally,
though there exists icomplete-vertical-mode (and fido-vertical-mode).
For our purposes, Icomplete and Fido are the same in terms of the
paradigm they follow. The latter is a re-spin of the former, as it
adjusts certain variables and binds some commands for the convenience
of the end-user. fido-mode and its accoutrements are defined in
‘icomplete.el’.
What MCT borrows from Icomplete is for the input delay (explained elsewhere in this document). Internally, I also learnt how to extend local keymaps by studying ‘icomplete.el’.
I had used Icomplete for several months before moving to what now has become ‘mct.el’. I think it is excellent at providing a thin layer over the built-in infrastructure.
Next: Official sources, Previous: Alternatives, Up: Minibuffer Confines Transcended (mct.el) [Index]
MCT is meant to be a collective effort. Every bit of help matters.
Protesilaos Stavrou.
Daniel Mendler, James Norman Vladimir Cash, José Antonio Ortega Ruiz, Juri Linkov, Philip Kaludercic, Tomasz Hołubowicz.
Andrew Tropin, Benjamin (@zealotrush), Case Duckworth, Chris Burroughs, Jonathan Irving, José Antonio Ortega Ruiz, Kostadin Ninev, Manuel Uberti, Morgan Willcock, Philip Kaludercic, Theodor Thornhill, Tomasz Hołubowicz, Z.Du. As well as users: danrobi11.
Andrew Tropin and Nicolas Goaziou (Guix).
‘icomplete.el’ (built-in—multiple authors), Daniel Mendler (‘vertico’), Omar Antolín Camarena (‘embark’, ‘live-completions’).
Next: GNU Free Documentation License, Previous: Acknowledgements, Up: Minibuffer Confines Transcended (mct.el) [Index]
Next: Indices, Previous: Official sources, Up: Minibuffer Confines Transcended (mct.el) [Index]
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