Re: Navigating completions from minibuffer

[Spencer Baugh <sbaugh@janestreet.com>]

Juri Linkov <juri@linkov.net> writes:
>>> 1. On editing the minibuffer close the completions window as expired.
>>
>> This would make it difficult to narrow the completions by typing in some
>> text from them, though.  I think I relatively often:
>>
>> 1. TAB
>> 2. Look at *Completions*
>> 3. Type in some text from one of them
>>
>> Step 3 would harder if *Completions* disappeared on the first character
>> I typed.
>>
>> Perhaps instead typing a character could deselect the currently selected
>> completion, rather than hide *Completions*?  But it seems nice to
>> maintain the selected completion as you type, as a visual guide, and
>> also my other patch maintains the selected completion between each TAB,
>> which is nice.
>
> In case of completion-auto-update=t the selected completion should be
> maintained as you type indeed.  But when completion-auto-update=nil
> instead of forcing the completions window to be closed it looks better
> just to deselect the current completion.

Yes, agreed on that point.  When completion-auto-update=nil, It is
better to deselect the current completion than close the completions
window.

>> Maybe... we could somehow de-activate the selected completion, visually
>> de-emphasizing it in some way, but still showing its position in some
>> less-significant way?  An underline, perhaps?  And subsequent operations
>> which change the selected completion would reactivate it, making it the
>> selected completion again.  That might be a bit tricky to represent
>> visually in an intuitive way, but it might give us everything we want.
>>
>> Maybe we could represent that visually by moving the selected completion
>> indicator (which in emacs -q is a green highlight) to *the minibuffer*
>> when the "selected" completion is not actually active.  Then the user
>> would quite quickly get the idea: RET submits whatever is highlighted in
>> green.
>
> Usually the active editing area is not highlighted in any way.
> So better would be to use highlighting only in the completions window.

Yes, but I wonder if we could have some simple indicator in the
minibuffer which isn't too visually noisy.  And which is only activated
if the user has previously selected a candidate in *Completions* and
then deselected it by typing.  Maybe highlighting the minibuffer prompt
instead of the text?  Well, not really necessary, just a thought.

> For completions-highlight-face=t it's clear that deselection should
> remove this face.  But what to do for completions-highlight-face=nil
> is not clear.  Maybe just to move point to area with no candidates?

I had been assuming "move point to area with no candidates" was how we
would implement deselection in any case.  Since "point is on a
candidate" is the definition of selection, as it stands.

Maybe we can deselect by moving point to just before (or after) the
selected candidate?  Move point to the whitespace in-between candidates.
Then no candidate is selected, and completions-highlight-face won't
highlight any candidate, but there's still a bit of visual indicator
(window-point) which shows what candidate was previously selected, and
if the user does want to re-select the candidate, the user can just hit
<down> (or <up>) to select the candidate again.

And completion-auto-update could maintain this state, too, just like it
maintains the selected candidate: if point is right before (but not on)
a candidate, it should stay right before (but not on) that candidate as
the user types and *Completions* updates.