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>]

> Cc: 43572@debbugs.gnu.org
> Date: Wed, 23 Sep 2020 19:46:18 +0000
> From: Gregory Heytings via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> >> The attached patch does not change the behavior of Emacs in any way, 
> >> unless the feature it introduces is used.
> >
> > I see the following potential problem with it: icomplete will likely 
> > want to set it globally, but that means it will also affect uses of the 
> > mini window where icomplete is not used.  Also, potential other users 
> > may encounter similar difficulties.
> 
> No, if you look at the patch its value is reset to nil whenever the 
> minibuffer is entered.  And the example I gave with icomplete is:
> 
> (add-hook 'icomplete-minibuffer-setup-hook (lambda () (setq start-display-at-beginning-of-minibuffer t)))
> 
> where icomplete-minibuffer-setup-hook is run during minibuffer setup if 
> (and only if) icomplete is active.  So the behavior with M-: for example 
> would not be affected.

There are more callers of resize_mini_widow than just those.  It is
not safe to assume that this can be handled only inside read_minibuf.

So I agree with Stefan that the text inserted into the minibuffer
should itself indicate to the display engine that it wants to be
displayed starting at BOB.  That way we don't have to worry about
inadvertently affecting other users of the mini-window.