Position buffer contents at bottom of window

Hi list,

I've been trying to create a function that fills a buffer and then
positions the last line of the buffer at the bottom of the window.

Doing this manually works just fine:

```
(defun my--recenter-window-to-bottom (&optional window)
  "Align contents of BUFFER to the bottom of WINDOW."
  (interactive (list (selected-window)))
  (when (window-live-p window)
    (with-current-buffer (window-buffer window)
      (when-let* ((_ (>= (window-end window t) (point-max)))
                  (edges (window-body-pixel-edges window))
                  (window-top (nth 1 edges))
                  (window-bottom (nth 3 edges))
                  (text-height (cdr (window-text-pixel-size window (window-start window))))
                  (dy (- window-bottom window-top text-height)))
        (message "↑%d ↓%d ↕%d dy%d" window-top window-bottom text-height dy)
        (pixel-scroll-precision-scroll-up dy)))))
```

I can bind this to a key and then calling this function does exactly what I
want it to do.

The problem is that it does not seem to work from Lisp, at least not in the
context I'm using it. Specifically, I have a function in the buffer-local
value of `window-buffer-change-functions` that basically erases the buffer
and fills it with content. At the end, it calls `(goto-char (point-max))`
and then sets a timer for 0 seconds to run the function above.

I'm using the timer because the buffer-fill functions is called from
`window-buffer-change-functions` which, AFAIU, is called during redisplay,
so I was hoping the timer would ensure that redisplay is done before
`my--recenter-window-to-bottom` is called.

Things, however, just don't work... The numbers reported in the `message`
call are different than when I call the function interactively, and the
window is scrolled incorrectly, or not at all.

I'm probably doing something very wrong here, but I'm unsure what. If
anyone can cast an eye and point me in the right direction, I'd be
grateful.

TIA

Joost



-- 
Joost Kremers
Life has its moments