This is summary of related mail on emacs-devel (an updated patch is attached):

On 2020-08-31 14:44, Boruch Baum wrote:
> Back in version 21, emacs introduced a static 'header-line' that could
> be inserted at the top of any buffer. Calc mode is one emacs package
> that does not use it and could benefit from it, so the attached patch
> offers that feature. The main benefit is that the 'calc trail' buffer
> (what some greybeards from the mechanical age would remember as the
> 'tape reel') no longer has its title line scroll off the visible
> window. The patch also includes:
>
> 1) Width-sensitive text for the header line, so that it is readable for
>    very narrow windows, and scales to very wide windows.
>
> 2) Display of the 'calc trail' buffer when invoking calc from a frame
>    that is split vertically (C-x 3, M-x split-window-right).
>
> 3) My version of emacs includes a unicode character at 'C-x 8 <return>
>    POCKET CALCULATOR', that I did not include in the header line as the
>    mode's icon, but that could be done.
>
> The patch was diff'ed against the version of emacs that I have: the
> latest-and-greatest that debian is distributing ... v26.1


On 2020-09-07 14:01, Boruch Baum wrote:
> First, congratulations on assuming your new responsibilities.
>
> On 2020-09-07 17:00, Lars Ingebrigtsen wrote:
> > The patch doesn't apply to Emacs 28, so I've respun it (included below).
>
> Oops. I didn't think there would be a difference. I'm using emacs 26.1
> in debian and I didn't download the v28 calc.el
>
> > This is somewhat inscrutable, and is repeated twice (once for the calc
> > buffer and once for the trail buffer).
> >
> > It just centres whatever the string like "--- this ---", so it seems
> > like it should land in a single function for reuse.

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