Re: [Emacs-diffs] /srv/bzr/emacs/trunk r103444: * lisp/facemenu.el (list-colors-display): Use with-help-window (Bug#8048).

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

> Suppose we rewrote `with-output-to-temp-buffer' in Elisp then we would

Find below the definition of with-output-to-temp-buffer on the
lexbind branch (which BTW is getting pretty close to ready for
inclusion).


        Stefan


(defmacro with-output-to-temp-buffer (bufname &rest body)
  "Bind `standard-output' to buffer BUFNAME, eval BODY, then show that buffer.

This construct makes buffer BUFNAME empty before running BODY.
It does not make the buffer current for BODY.
Instead it binds `standard-output' to that buffer, so that output
generated with `prin1' and similar functions in BODY goes into
the buffer.

At the end of BODY, this marks buffer BUFNAME unmodifed and displays
it in a window, but does not select it.  The normal way to do this is
by calling `display-buffer', then running `temp-buffer-show-hook'.
However, if `temp-buffer-show-function' is non-nil, it calls that
function instead (and does not run `temp-buffer-show-hook').  The
function gets one argument, the buffer to display.

The return value of `with-output-to-temp-buffer' is the value of the
last form in BODY.  If BODY does not finish normally, the buffer
BUFNAME is not displayed.

This runs the hook `temp-buffer-setup-hook' before BODY,
with the buffer BUFNAME temporarily current.  It runs the hook
`temp-buffer-show-hook' after displaying buffer BUFNAME, with that
buffer temporarily current, and the window that was used to display it
temporarily selected.  But it doesn't run `temp-buffer-show-hook'
if it uses `temp-buffer-show-function'."
  (let ((old-dir (make-symbol "old-dir"))
        (buf (make-symbol "buf")))
    `(let ((,old-dir default-directory))
       (with-current-buffer (get-buffer-create ,bufname)
         (kill-all-local-variables)
         ;; FIXME: delete_all_overlays
         (setq default-directory ,old-dir)
         (setq buffer-read-only nil)
         (setq buffer-file-name nil)
         (setq buffer-undo-list t)
         (let ((,buf (current-buffer)))
           (let ((inhibit-read-only t)
                 (inhibit-modification-hooks t))
             (erase-buffer)
             (run-hooks 'temp-buffer-setup-hook))
           (let ((standard-output ,buf))
             (prog1 (progn ,@body)
               (internal-temp-output-buffer-show ,buf))))))))