Re: New multi-command facility displays in the wrong echo area.

[Gregory Heytings]

> > At this point you see no indication that I-search has been started. (If 
> > you look close enough, the only thing you can see is a curly arrow in 
> > the right fringe of the miniwindow.) Likewise, if you press C-x C-s, 
> > you see no indication that changes have been saved (or not). And so 
> > forth.
> Right.
>
> > I suggest the following fourth condition in set-minibuffer-message:
> >
> > (< (buffer-size (window-buffer (active-minibuffer-window))) (/ (frame-width 
> > (window-frame (active-minibuffer-window))) 2))
> So you suggest in that case to overwrite the minibuffer prompt, like 
> Emacs 26 did?
Yes, indeed.  That's clearly better than not showing anything at all. 
When there is not enough space on the right of the current minibuffer 
contents, IMO it should be overwritten.
> I'm not sure I like this: it would bring back many problems this feature 
> was supposed to fix.
So far I did not know what problems that feature was supposed to fix, so I 
could not make a judgment on this.  The NEWS item does not indicate what 
these problems were, and I had myself never encountered a situation where 
overwriting the current minibuffer contents was problematic.  It seemed to 
me so far that it was only something more aesthetically pleasing.  Now 
that I've read bug#38457, I see that this is not the case, but I'm not at 
all convinced by the proposed solution.  Something like what eldoc does 
when the minibuffer is active (temporarily displaying the info at the 
beginning of the mode-line) would have been a much better and more robust 
solution.  Otherwise, another solution would be to temporarily add a 
"zeroth" (or "minusoneth") line to the minibuffer with the message.
> In any case, I think the condition could be relaxed: we only care about 
> how much space is left from the minibuffer text's end till the end of 
> the screen line, so "if minibuffer text size modulo window-width is less 
> than something" would be better, I think.  E.g., if you use 70 instead 
> of 67 in your recipe, the problem is mostly gone.
The condition could be refined indeed, but the modulo operation you 
propose would not work with variable pitch faces.  I intentionally 
proposed something simple, which should work in (almost) all cases.  I'm 
an adept of the KISS principle.
> Also, it would be safer to use string-width instead of the number of 
> characters, or even window-text-pixel-size: some people do customize the 
> faces used in the minibuffer.
I won't comment on this.  As I already said elsewhere, it's IMO awful to 
expect any code to do something like this.
> > It is amazing that such a feature got accepted, was included in an 
> > official Emacs release, and became Emacs' default behavior, without 
> > even trying the two obvious cases to test: what happens when there is 
> > not enough free space in the minibuffer? and what happens when the 
> > active minibuffer is not on the same frame?
> This has some history.  You are welcome to read the discussion in 
> bug#38457, especially starting at
>  https://debbugs.gnu.org/cgi/bugreport.cgi?bug=38457#17
>
> You will see that many issues were discussed, the dangers were expected, 
> and as result the change became less invasive, which was especially 
> important because the release cycle was about to start. However, it 
> didn't sound wise to reject the changes outright because they've fixed 
> several important use cases that were an annoyance for a long time.
See above.  I've now read that bug thread, and I'm not at all convinced 
that the chosen solution was TRT, quite the contrary.
> But yes, any significant change in such basic functionality runs a risk 
> to break something, especially in relatively rare use cases 
> (max-mini-window-height set to 1, followed by "C-x o" out of the 
> minibuffer).
As I said to Alan, this recipe is just a recipe, it exhibits a more 
general problem.  The same problem would happen with 
max-mini-window-height set to 2 and a longer text, with a miniwindow only 
frame, with a small enough Emacs frame, and so forth.
> This risk is inherent part of development, and sometimes mistakes are 
> being made.  We try at least not to make the mistakes we know about.
Well... no: the bug#38457 thread contains a message (#317) by Dmitry Gutov 
which points to a problem that is similar to the one I "discovered". 
BTW, he also suggests to use eldoc-minibuffer-message instead of the 
current solution.
> > It is even more amazing that, at the same time, my proposed solution to 
> > display completion candidates in the minibuffer is rejected on the 
> > grounds that it could cause "potential problems", when so far no one 
> > has managed to show a case in which it would create an actual problem.
> Maybe because we are now wiser and don't want to repeat past mistakes?
It seems to me that being wiser would mean taking the time to evaluate a 
proposed solution, instead of rejecting it outright based on a gut 
feeling.