bug#59935: 29.0.60; project-list-buffers is slow

[Dmitry Gutov]

On 11/12/2022 19:07, Juri Linkov wrote:
> +(defvar-local Buffer-menu-buffer-list-function nil
> +  "Function to return buffers for the buffer list.")
>
>         (setq Buffer-menu-files-only
>             (and files-only (>= (prefix-numeric-value files-only) 0)))
> -      (setq Buffer-menu-filter-predicate filter-predicate)
> +      (when (functionp buffer-list)
> +        (setq Buffer-menu-buffer-list-function buffer-list))

Here's an idea: when 'list-buffers-noselect' received a plain list of 
buffers in its BUFFER-LIST argument, it doesn't save that anywhere.

That seems like a bug, doesn't it? That hitting 'g' in such a 
buffer-list buffer resets its contents to all buffer (except hidden, etc).

So it probably makes sense to save it as well.

Long story short, I suggest to name the new variable 
Buffer-menu-buffer-list, and save the value of the BUFFER-LIST argument 
to it no matter what. And, likewise, use it. But when the value is a 
function, call it to obtain the actual list.

One side-effect of this, though, is that the BUFFER-LIST argument to 
list-buffers--refresh will have no purpose anymore.