Re: save-current-buffer

[Andreas Politz <politza@fh-trier.de>]

Nikolaj Schumacher wrote:
> Andreas Politz <politza@fh-trier.de> wrote:
> 
>> Is this a bug, or am I missing something ?
>> Eval this in *scratch* buffer and you end up in the *Help* one.
>>
>> (save-current-buffer
>>   (switch-to-buffer "*Help*"))
> 
> There is a subtle difference between the current-buffer and the window's
> buffer.  Any buffer can be current without being displayed.  The
> function for that is `set-buffer'.
> 
> `switch-to-buffer' changes both the current-buffer and the selected window's
> buffer.
> 
> (progn
>   (message "%s/%s" (current-buffer) (window-buffer (selected-window)))
>   (save-current-buffer
>     (switch-to-buffer "*Help*")
>     (message "%s/%s" (current-buffer) (window-buffer (selected-window))))
>   (message "%s/%s" (current-buffer) (window-buffer (selected-window))))
> 
> will output:
> 
> *scratch*/*scratch*
> *Help*/*Help*
> *scratch*/*Help*
> 
> As you can see, current-buffer is restored, but the window's
> buffer is not.
> 
> Replacing `save-current-buffer' with `save-window-excursion'
> 
> gets you:
> 
> *scratch*/*scratch*
> *Help*/*Help*
> *scratch*/*scratch*
> 
> 
> But generally, `switch-to-buffer' should only be used when the user
> wants to see the new buffer.  Otherwise `set-buffer' is the better choice.
> 
> 
> 
> regards,
> Nikolaj Schumacher
> 
> 

I see. I assume after the form is evaluated, some event will set the current-buffer
to the one switch-to-buffer switched to.

The reason I was asking is some problem I had with the recentf package. It's
really a minor one, but I was just curious what to make of it and how things are working.
The idiom from above is used in one of it's functions.

(require 'recentf)
(run-with-timer 0 nil 'recentf-open-files)

Now pressing 'q' gives a read-only error, though it is
bound to recentf-cancel-dialog. Pressing it twice works fine.

-ap