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Emacs: mct version 0.4.0

Below are the release notes. If you have no idea what mct is, it is a very thin layer of interactivity on top of the default completion user interface. Watch the video demo of the initial release.


This entry outlines the changes to the “Minibuffer and Completions in Tandem” (mct package) since the release of version 0.3.0 on 2021-11-19. There have been more than 120 commits in the meantime.

For further details, please consult the manual online: https://protesilaos.com/emacs/mct. Or evaluate the following expression if you already have mct installed:

(info "(mct) Top")

As most changes pertain to optimisations in the code base, we limit this log to what is of interest to the end-user.

Minibuffer Confines Transcended (aka mct-region-mode)

Emacs distinguishes between two types of completion: one that involves the minibuffer and another for text expansion inside regular buffers. MCT has supported the former case since its inception, as hinted by its original name (“Minibuffer and Completions in Tandem”), but would not work as intended for in-buffer completion.

This changes with the introduction of a new global minor mode: mct-region-mode. What once was mct-mode is now defined as mct-minibuffer-mode to better denote the scope of the given functionality.

With mct-region-mode enabled, users get a simplified subset of the familiar MCT functionality when typing TAB or C-M-i to complete the text-at-point in any major-mode that supports completion-at-point-functions (e.g. programming modes or Org).

mct-region-mode is considered experimental and unstable. Users are encouraged to report any bugs as well as recommend ways to improve its functionality or interaction model. The manual has been updated to cover all the relevant details.

Daniel Mendler, who is the developer of the vertico and corfu packages (alternatives to mct-minibuffer-mode and mct-region-mode, respectively), was intstrumental in making mct-region-mode happen. Daniel’s patches helped with everything from (i) the proper functioning of mct-region-mode, (ii) the separation between mct-minibuffer-mode and mct-region-mode, (iii) the overall setup of the minor modes, and (iv) lots of other crucial details of the overall design of MCT. In short: there would be no mct-region-mode without Daniel’s contributions. Any remaining errors or omissions are my own.

Given this new functionality, we can now joke that “MCT” stands for “Minibuffer Confines Transcended”.