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

[Stefan Monnier]

> Not necessarily: there are the w->optional_new_start and
> w-> force_start flags, which determine what redisplay does with
> window-start in these cases.
> Also, the window-start could be set to a value that leaves point out
> of the displayed area, in which case it won't be in effect.

Right, but these fall back into the case where redisplay performs
a second pass trough the window/buffer, so it's similar to the scrolling
case, right?

>> 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