bug#34038: 26.1; set-window-start sometimes fails to set window start

[Alan Mackenzie]

Hello, Martin.

On Sat, Jan 12, 2019 at 09:13:07 +0100, martin rudalics wrote:
>  > A bit of debugging output shows that after (erase-buffer), window-start
>  > is already at 1, not the former point-max.

> 'window-start' returns the position of the window start marker.  When
> you erase a buffer _all_ its markers go to point-min - point-max and
> all window start or point markers included.

Of course!  I don't know what I was thinking at the time.  Markers
behave like markers, and w->start in struct window is just an ordinary
marker.  Sorry for writing rubbish.

>  > After (insert b),
>  > window-start continues to be at 1.

> Because the insertion type of a window start marker is nil.  You can
> use 'insert-before-markers' to override that.

Yes.  The question remains, what is causing the unexpected scrolling in
the OP's scenario?

> martin

-- 
Alan Mackenzie (Nuremberg, Germany).