bug#74019: [PATCH] Optionally preserve selected candidate across *Completions* update

[Spencer Baugh]

Tags: patch


Add completion-preserve-selection, a defcustom which allows keeping the
same selected candidate after *Completions* is updated by
minibuffer-completion-help.

This works correctly with choose-completion-deselect-if-after: If point
is after a completion (such that choose-completion-deselect-if-after=t
means it won't be treated as selected), point will still be after that
completion after updating the list.

This feature is primarily motivated by the fact that some other
completion UIs (e.g. ido, vertico, etc) effectively have this behavior:
whenever they update the list of completions, they preserve whatever
candidate is selected.

Since the default UI doesn't (yet) have support for auto-updating the
list of completions, preserving the selected candidate is less
significant.  But it might be an interesting feature on its own, and
it's very non-invasive, so maybe we can turn it on by default.

In GNU Emacs 29.2.50 (build 5, x86_64-pc-linux-gnu, X toolkit, cairo
 version 1.15.12, Xaw scroll bars) of 2024-10-15 built on
 igm-qws-u22796a
Repository revision: 16a2e41014c6ea0f3cf268be8d37fe09aeac231e
Repository branch: emacs-29
Windowing system distributor 'The X.Org Foundation', version 11.0.12011000
System Description: Rocky Linux 8.10 (Green Obsidian)

Configured using:
 'configure --with-x-toolkit=lucid --without-gpm --without-gconf
 --without-selinux --without-imagemagick --with-modules --with-gif=no
 --with-tree-sitter --with-native-compilation=aot
 PKG_CONFIG_PATH=/usr/local/home/garnish/libtree-sitter/0.22.6-1/lib/pkgconfig/'

0001-Optionally-preserve-selected-candidate-across-Comple.patch
Description: Text Data