bug#19576: write-file writes the wrong buffer

[Johan Bockgård]

Eli Zaretskii <eliz@gnu.org> writes:

>> The fact remains that a window where window-start equals point-max
>> (i.e. a window displaying nothing) do recenter itself from time to
>> time.
>
> I could only understand that if whatever you do following a call to
> set-window-start includes resizing of windows or creation/deletion of
> windows.  Or maybe you meant editing in that window?  Even then at
> least the simple commands I tried don't do that.
>
> The display engine generally doesn't do anything unless the screen
> should change.  So if you work outside of the window whose starting
> point you forced, Emacs should never do anything with that window.

E.g. the following cause a recenter of *scratch*:

emacs -Q
M-: (set-window-start (selected-window) (point-max) t) RET
C-x 2
Click mouse in other window

or

emacs -Q
M-: (set-window-start (selected-window) (point-max) t) RET
C-x 2
C-x o
C-h i

or

emacs -Q
M-: (set-window-start (selected-window) (point-max) t) RET
Resize frame

or...