Re: feature/completions-highlight-modifications e3c5b99 3/6: Add completions-highlight-mode initial implementation.

[Juri Linkov]

> The code is extremely simple, so, if you think you could improve
> anything it is more tan welcome.

The branch contains many different features with different problems,
so here is a short summary for these 4 separate features:

1. feature of setting minibuffer-tab-through-completions-function to
   completions-highlight-minibuffer-tab-through-completions:

The problem is that such TAB cycling is limited only to the case
when the whole *Completions* buffer is visible.

The original behavior of multiple presses of TAB is limited too:
its browsing is uni-directional, there is no way to use S-TAB
to scroll completions backwards.

So I don't see how relying on TAB could improve navigation in completions.

2. completion-set-suffix sometimes doesn't work;

3. commands that dispatch navigation keys from the minibuffer to the
   *Completions* buffer: this doesn't cover other navigation keys.

Maybe like windmove-default-keybindings defines modifiers,
a similar function could set up modifiers for scrolling completions
from the minibuffer, then the users could choose whether to use
e.g. 'M-' modifier for scrolling completions, or no modifier at all.

4. the feature of using completions-highlight-overlay often fails to
   update highlighting when point is moved in the *Completions* buffer
   by other navigation commands.

To fix this, it could work like hl-line-mode, but instead of
highlighting the whole line, it could highlight only completions.

Then completion highlighting would be useful on its own.
A new defcustom e.g. 'completion-highlight' (disabled by default)
could add a post-command-hook like hl-line-mode does.
Then other completion commands could enable this variable locally.