Re: fix for bug#29935 copyright-update inserts year at random places

[Stefan Monnier <monnier@iro.umontreal.ca>]

>> But this is a fairly normal/common need: display a buffer temporarily.
>> So we should have a "canned" answer.
>> I'm thinking of something like
>>
>>      (let ((x (temporary-display-buffer BUF)))
>
> What kind of object would "x" be?

The kind of object that carries the necessary information from
temporary-display-buffer to temporary-undisplay-buffer so that they
together DTRT.

>>      (temporary-undisplay-buffer x)
>> where hopefully this would handle the case where
>> temporary-display-buffer needs to use a separate frame, as well as the
>> case where BUF is already displayed somewhere.
> If "x" is a window, then `quit-restore-window' should know how to deal
> with it.

If `x` is just a window, how does quit-restore-window know that we want
to hide BUF (and not some other buffer that happens to be displayed
in the window once we get to quit-restore-window)?

If `x` is just a window, how does quit-restore-window know whether BUF was
already displayed in that window before temporary-undisplay-buffer was
called (in order to decide whether to change the window's buffer or not)?

> So please tell what's missing in `with-temp-buffer-window'.

It forces scoping.  IOW it can't be used when the
temporary-undisplay-buffer part needs to be done at some arbitrary later
time (e.g. after the user has run a bunch of commands).


        Stefan