bug#32672: 27.0.50; image resize on window resizing

[Eli Zaretskii <eliz@gnu.org>]

> Date: Tue, 25 Sep 2018 19:56:09 +0200
> From: martin rudalics <rudalics@gmx.at>
> CC: juri@linkov.net, 32672@debbugs.gnu.org
> 
>  > Bottom line is what I said up-thread: Lisp programs cannot expect
>  > those hook calls to be too accurate and focused, they need to be
>  > prepared to handle many irrelevant calls, and they had better have
>  > their own bookkeeping regarding window dimensions etc.
> 
> 'window-size-change-functions' is not hypothetical and guards itself
> against running twice for unchanged window sizes.  I don't really
> understand what you doubt here - I rewrote it in its current form
> because you once said (when discussing Bug#21333) that
> 
>  > I believe window-size-change-functions is meant for taking notice of
>  > resizes done by the user or some Lisp code, not for automated resizes
>  > whose sole purpose is to allow some message be read in its entirety.
>  > If you agree, then the current behavior will make sense to you.
>  >
>  > If anything, IMO we should _reduce_ the number of unrelated events
>  > that trigger a call to these functions.  For example, currently any
>  > command that reads from the minibuffer will trigger it, because when
>  > read-from-minibuffer exits, it restores the window configuration by
>  > calling set-window-configuration, which is documented to trigger these
>  > functions.  That just doesn't make any sense to me, since most reads
>  > from the minibuffer don't resize any windows!
> 
> and in a later post you said
> 
>  > I'd say, don't set the "size changed" flag unless the size really
>  > changed.
> 
> and now it seems that you think that a similar argument does not apply
> when running 'window-configuration-change-hook'.

All true and agreed, but it doesn't contradict my main point.  We
could (and do) try to be as accurate as possible, but there are limits
to that that cannot be easily lifted, not without some serious
redesign.

> I'd still need to see a hypothetical example where the same redisplay
> cycle would run 'window-size-change-functions' functions twice when no
> sizes actually changed.

We have better things to do with our free time than discuss
hypothetical examples.