Subject: bug#35006: 27.0.50; Minibuffer sometimes unexpectedly does not grow

From: Eli Zaretskii <[email-masked]>
Date: Wed, 27 Mar 2019 19:55:32 +0200

> From: Markus Triska <[email-masked]>
> Date: Tue, 26 Mar 2019 18:31:03 +0100
> 
> Please start Emacs with "emacs -Q", and then evaluate in the
> *scratch* buffer the following form:
> 
>     (with-selected-window (minibuffer-window)
>       (erase-buffer)
>       (insert (propertize "hello" 'face '(:height 2.0)))
>       (read-key)
>       (erase-buffer))
> 
> This shows "hello" in the minibuffer, and the minibuffer grows as
> expected. Please press a key (or C-g) to continue.
> 
> Next, please make a frame, say "F", with the form:
> 
>     (make-frame '((name . "F")))
> 
> In F, please press:
> 
>     M-x C-g
> 
> This simply enters and exits the minibuffer.
> 
> Then, in the original frame, evaluate again the form above, i.e.:
> 
>     (with-selected-window (minibuffer-window)
>       (erase-buffer)
>       (insert (propertize "hello" 'face '(:height 2.0)))
>       (read-key)
>       (erase-buffer))
> 
> Unexpectedly, the minibuffer is now no longer grown in the (selected)
> frame where this form is evaluated (again), and therefore the inserted
> text is now not fully visible, in contrast to the first time.

I think you expect resize-mini-windows to do what it was never
designed to do.

This feature is supposed to resize mini-windows for the purposes of
interacting with the user, i.e. for displaying messages in the
echo-area, and for prompting the user for input and receiving input in
response.  You are doing something different: you insert arbitrary
text into a mini-window's buffer, which is a normal buffer operation
not specific to mini-windows.  The text you insert is displayed as
part of normal redisplay of all the windows, not as user interaction
via the mini-window.  So in that case, the mini-window is just like
any other window, and those don't resize automatically to accommodate
the text you inserted when they are redisplayed.

Maybe it's a flaw that should be fixed by enhancing the design and
making the implementation follow suit, but currently the code works as
designed, AFAICT.