bug#43572: Feature request: make it possible to choose whether the first lines of the minibuffer should be displayed instead of the last ones

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 24 Sep 2020 14:52:38 +0000
> From: Gregory Heytings <ghe@sdf.org>
> cc: monnier@iro.umontreal.ca, 43572@debbugs.gnu.org
> 
> >> - "master-icomplete-vertical-after-tab.png" is what a user would see 
> >> with icomplete-mode activated and (setq icomplete-separator "\n") after 
> >> having completed the last directory name with a TAB: the prompt and 
> >> their input is completely hidden
> >
> > Thanks, this subtle issue should now be fixed on master.
> 
> It is not, the only difference is that instead of "the prompt and their 
> input is completely hidden" one should now write "the prompt and the 
> largest part of their input is completely hidden".

I mean the issue with the prompt being hidden after one TAB, but
appear after another TAB.

All the rest is just the consequence of the current policy to show the
last part of the stuff in the mini-window.  (Note that with your
changes, one of the candidates isn't shown in the mini-window.)

There might be a misunderstanding here: I'm not claiming that the
changes I made yesterday and today are supposed to produce the same
effect as your proposed patch.  I'm just making the display with
overlay-string behave (as much as possible) like display with normal
buffer text, that's all.  Per bug#43519.  I'm not saying that my
changes implement the feature you are asking for here.

> Again, could you please provide a recipe which would demonstrate a problem 
> with the technique I propose?

I already explained why your design is problematic.  And so did
Stefan.  So I don't see why a recipe would be needed.

Implementation of such a feature should use text and/or overlay
properties to communicate the intent to the display code.  That would
be much cleaner and safer.