bug#50178: 28.0.50; Size of echo area does not account for line-spacing

[martin rudalics <rudalics@gmx.at>]

 >> It must know and handle every setting that affects line height, current
 >> and future. It would be handy if Emacs provided a function that does
 >> that.
 >
 > We already have it: window-text-pixel-size.

To elaborate:

(1) You first have to calculate the maximum permissible pixel height of
     the echo area window from the character height of the frame where
     you intend to display the completions and the value of
     `max-mini-window-height' height as specified for that frame.  Note
     that for a minibuffer-less frame the echo area window may appear on
     another frame whose character height you have to use here.

(2) You then have to calculate the pixel height of each completion line
     as if it were shown in the echo area window mentioned in (1) using
     `window-text-pixel-size' and add it to some cumulative height until
     you have exhausted the maximum permissible height calculated in (1).

martin