bug#18195: 24.3.92; window-screen-lines is not accurate

[martin rudalics]

>> There is no other buffer.  Everything is done in the buffer where the
>> overlay is supposed to appear.
>
> How do you prevent the overlay from momentarily flashing in the
> window?

I'd instantaneously file a bug report.  Seriously, why should

(let ((overlay (make-overlay (point-min) (point-max))))
  (overlay-put overlay 'display "???????")
  (prog1
      (window-text-pixel-size)
    (delete-overlay overlay)))

cause a "momentarily flashing in the window"?

martin