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

[Ergus]

On Sat, Nov 21, 2020 at 09:30:17PM +0200, Juri Linkov wrote:
> > > > Maybe we should look more how zsh behaves... and try to mimic that as
> > > > much as possible. Because it is already pretty consisten
> > >
> > > Does zsh use arrow keys to navigate in completions?
> > > How then it's possible to get previous/next history item (up/down arrows),
> > > and move the cursor in the command line (left/right arrows)?
> >
> > Similar to what we are doing.
> >
> > 1) When NO completions shown: previous/next history and so on.
> > 2) When completions are shown: navigate completions.
> >
> > Completions are only shown after a "tab request" 1->2 (unlike
> > incomplete)
>
> Trying to mimic the 'zsh' behavior is a good thing.  Using
> 'zsh' as a reference, what do you think about naming the package
> 'zcomplete'.
Ok

> > If you type any letter completions disappear, inserts a space and then
> > the letter, so
> >
> > backspace just hides completions (deletes the inserted space), so goes
> > from 2->1 easily (unlike *Completions*).
>
> If you want to emulate the 'zsh' behavior, then much simpler approach
> would be to allow TAB to pop-up the completions buffer, i.e. to display
> and switch to it.  Then all motion keys will be available by default.
> To display the cursor in the minibuffer is still possible by using
> '(cursor-in-echo-area t)'.  RET will insert the completion under point
> to the minibuffer.  Any self-inserting key could switch back
> to the minibuffer and insert its character.
The real issue with that is not setting, but reseting. Because
completions-list-map uses:

1. \e\e\e delete-completion-window
2. q quit-window
3. z kill-current-buffer

to exit. In principle quit-window-hook works for 2. But for 1 we need
an advise and rebind q and 3 is bind to z. so 

I am not clear what's the best approach or the consequences of changing
them. But my proposal will be then make:
q and z: self-insert (as they will call quit-window in the hook any way).

And rebind
C-g: to kill-current-buffer. (I don't really know the difference between
all them)

The hook for self-insert is trivial. But it won't cover commands like
delete-backward-char, backward-kill-word and so on.

The trick there may be to throw the read-only error and call 1, 2 or
3... to go to the minibuffer when any command tries to modify
"Completions* and try to execute there.

But I don't know if it is possible to do that for a whole buffer or a
map in a clean way and locally to a window/buffer only. Is it?