bug#17678: 24.4.50; Feature Request -- calculate new `window-start` & `window-end` before visual redisplay

[Keith David Bershatsky]

The `window-scroll-functions` hook would be more useful if the value of 
`window-start` could be obtained *before* running the `post-command-hook`.  At 
the present time, it would appear that the `post-command-hook` runs *before* 
the `window-scroll-functions` hook.  Therefore, the `post-command-hook` cannot 
presently use the `window-start` value produced from the 
`window-scroll-functions` hook (which occurs *after* the `post-command-hook` 
has already finished).

Keith

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At Fri, 13 Jun 2014 10:14:03 -0400,
Stefan Monnier wrote:

* * *

> >> If OTOH redisplay decides to scroll, it won't re-execute
> >> pre-redisplay-function, so Elisp doesn't get a chance to react to this
> >> new window-start.
> > ??? Then what are those calls to run_window_scroll_functions that
> > redisplay issues?
> 
> Ah, right, I forgot about this.  So maybe window-scroll-functions is the
> answer to the OP's needs!
> 
> 
>         Stefan