bug#54800: 28.1; calc: Cursor positioned at weird position in calc stack

[Christoph Arenz]

On 11.04.22 13:45, Eli Zaretskii wrote:
> > > I noticed that while the patch fixes the problem in most cases,
> > > depending on the height of the calc stack window, there can be the case
> > > that the cursor is not positioned on the top-of-stack symbol `.' but one
> > > line
> > > above, at the beginning of the line with the first stack entry.
> > >
> > > This can be changed by using the number 4 instead of 3 in the patch.
> > > Not sure if this is the best fix.
> > >
> > > (vertical-motion (- 4 (window-height win)))
> > Can you show a reproducible recipe starting from "emacs -Q", so I
> > could investigate?
> And while at that, would the below fix the problem in the rare cases
> where you saw them?
>
>    (vertical-motion (- 3 (window-height win 'ceiling)))
>
> That is, ask window-height to produce the smallest integer number
> greater than the window's height (in case the height in line units is
> not integer)?

Seems 'ceiling does not fix it, but 'floor does, like so:

  (vertical-motion (- 3 (window-height win 'floor)))

How to reproduce -- I could not find a way to do so automatically,
here is for a manual way:

1. emacs -Q
2. C-x * *
3. enter some numbers to fill calc stack window, and some more
4. o (calc-realign)
5. watch where the cursor is placed: on the top-of-stack symbol, or
on the beginning of the line with the first stack entry.
6. increase the stack window height by minimally moving the mode line
above the stack window with the mouse; only increase height by
sub-line-height amount
7. repeat 4. to 6. until you can observe the symptom