bug#56102: 29.0.50; fit-frame-to-buffer's window-text-pixel-size calculation can be incorrect when only is set to vertically

[Eli Zaretskii <eliz@gnu.org>]

> From: Aaron Jensen <aaronjensen@gmail.com>
> Date: Sun, 19 Jun 2022 23:03:14 -0400
> 
> 
> To repro, open emacs -Q and resize your frame so that the ";; This
> buffer..." text wraps (this repro assumes your monitor has more than
> enough space for it to not wrap if the frame was big enough).
> 
> Add a few more lines of text and then:
> 
> M-: (fit-frame-to-buffer nil nil nil nil nil 'vertically)
> 
> You should see that the frame's height is too short and does not contain
> all the lines. It contains one fewer line for each wrapped line.
> 
> Screenshots:
> 
> https://share.cleanshot.com/huexHe
> https://share.cleanshot.com/dnhKex
> 
> The problem appears to be the lines:
> 
> (size
>             (window-text-pixel-size window from to max-width max-height))
> 
> As the max-width will be larger than the current frame (meaning the
> height calculation will not take wrapping into account).
> 
> One possible fix is to set min/max height/width based on `only' to
> (frame-parameter frame 'width) / (frame-parameter frame 'height) but I
> do not know if that is the best fix.
> 
> If that is done, then it may be possible to remove the rest of the
> special handling for `only' that sets width/height to nil and handles that.

I think you're right, but I'd like to hear if Martin has any comments.

Thanks.