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

[Markus Triska <triska@metalevel.at>]

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.


In GNU Emacs 27.0.50 (build 1, x86_64-apple-darwin18.0.0, X toolkit, Xaw scroll bars)
 of 2018-11-15 built on mt-computer
Repository revision: b4eb908f858284a7962851fd99c94598f76afa6f
Windowing system distributor 'The X.Org Foundation', version 11.0.11804000