Re: set-window-buffer bugs

[John Mastro <john.b.mastro@gmail.com>]

jenia.ivlev <jenia.ivlev@gmail.com> wrote:
> Hello.
>
> Using dired, I want find-buffer-other-window to open in the exact
> same window.
>
> So I made this little program:
>
>
>     (define-key dired-mode-map "o" 'dired-find-file-other-opened-window)
>
>     (defun dired-find-file-other-opened-window ()
>         (interactive)
>         (set-window-buffer (frame-first-window) (dired-get-filename 'no-dir))
>         (dired-find-file-other-window))
>
>
> It turns out that you needed to have visited that file already for
> this to work.

[snip]

> I mean, I don't get it. Why do I need to have visited the file before?
> And in any case, how do I fix this? I just want it to open in the
> (frame-first-window) that's all.

Correct, the second argument to `set-window-buffer' must be a buffer (or
the name of a buffer), not the name of the file.

The distinction between buffers and files is an important one. As one
small practical consideration, there can be many files named "foo.txt",
but only one buffer named "foo.txt".

If you're not sure which (file or buffer) is appropriate for a given
function, check out its documentation (e.g. `C-h f set-window-buffer
RET'). In many cases, as with `set-window-buffer', the name itself gives
a hint.

All that said, I think the command below will do what you want. The
function `find-file-noselect' is the one that visits the file and
creates a buffer. If the file is already open, it returns the existing
buffer. It's a variant of `find-file' (the command bound to `C-x C-f')
with the difference that it doesn't display the buffer - useful to us
here because we want to handle that part ourselves.

(defun dired-find-file-other-opened-window ()
  (interactive)
  (let* ((file (dired-get-filename 'no-dir))
         (buffer (find-file-noselect file)))
    (set-window-buffer (frame-first-window) buffer)))

Hope that helps

-- 
john