bug#74246: [PATCH] Reuse display windows in image-dired

[martin rudalics]

> I still don't understand how a local variable in one target buffer could
> help to display another buffer in the same window from grep/xref list.

By having grep do the following:

- Issue a first request to display a buffer from that list,

- remember the window used,

- set the local variable in the target buffer to the remembered value
  before calling 'display-buffer' again.

It could do that if it wanted to communicate the window to use in a
buffer local variable thus avoiding to pass an extra value via the
alist.

>> Would you like that?  I think displaying *backtrace* in the same window
>> is always a bad idea.
>
> Only when 'display-buffer-below-selected' fails that is extremely rare.

I assumed that the user had customized it.

>>>> pass the symbol of the function calling 'display-buffer' with some
>>>> unique number identifying the nth call of 'display-buffer' within that
>>>> function.  Everything else is guesswork.
>>>
>>> There is already such a symbol: 'category'.

'category' is much broader.

>> But this one is already handled by 'buffer-match-p'.  We can't set it
>> willy-nilly to some arbitrary value.  Otherwise, that function might
>> match it in an unexpected way.
>
> 'display-buffer-reuse-category-window' could reuse the 'category' symbol.
> Or '(some-window . reuse-category)'.

Let me turn the table and ask you: Both grep/xref know very well which
window was used for displaying the last match.  What speaks again to
have them just remember that window after each call and propose it via a
(some-window . ,window) alist entry in the next call together with
'display-buffer-use-some-window'?  I think the main advantage of such an
approach is that grep/xref would be in complete control of a good
proposal for such a window, something most users could hardly resist.

> Not either, but preferably the last used window.

Not preferably, IMHO.

>> 'image-dired' _is_ different because it always uses the same buffer for
>> showing images stored in different files.  I know of no other function
>> doing that.  Do you?
>
> I don't remember any other function doing such non-standard things.

So IMHO we should exploit that fact in its 'display-buffer' call.

martin