bug#1488: 23.0.60; dired-pop-to-buffer: use fit-window-to-buffer

[Stephen Berman]

In GNU Emacs 23.0.60.21 (i686-pc-linux-gnu, GTK+ Version 2.12.9)
 of 2008-12-03 on escher

1. emacs -Q

2. Eval this:
   (define-minor-mode my-mm ()
     "My minor mode."
     :global t
     (if my-mm
         (setq default-header-line-format
               '(:eval (propertize "test" 'face '(:overline t))))
       (setq default-header-line-format nil)))

3. Enable my-mm.

4. C-x d foo (where `foo' is some directory with at least three files,
   e.g. emacs/lisp).

5. Mark three files in foo.

6. Type `C'
   ==> The popped up buffer *Marked Files* shows only two of the three
   marked files.

Likewise if the value of the 'face property in my-mm has a non-nil :box
attribute.  In contrast, if the value of the 'face property is
'(:underline t) (but not '(:underline t :overline t)), then in step 6
all three marked files are shown, though with no room to spare.

I guess the basic problem here is that Emacs calculates window-height in
integral equally sized line numbers.  But less fundamentally and more
directly, this problem arises, AFAICT, because dired-pop-to-buffer's
shrink-to-fit code fails to account for header lines.  To fix this it
would suffice to add this sexp above the last sexp in
dired-pop-to-buffer: 
    (with-current-buffer buf 
      (and header-line-format
           (progn (select-window w2) (enlarge-window 1))))

However, unless I'm missing something, fit-window-to-buffer does what
dired-pop-to-buffer's shrink-to-fit code does, and moreover also handles
header lines.  From perusing the change logs, I found several instances
where fit-window-to-buffer replaces library-specific code, and this
appears to be another candidate (dired-pop-to-buffer was introduced many
years before fit-window-to-buffer), in addition to fixing the above bug.
I'm not able to fix the display code to let window-height return
fractional line numbers, so I propose the following patch:

*** emacs/lisp/dired.el.~1.414.~        2008-12-03 10:17:51.000000000 +0100
--- emacs/lisp/dired.el                 2008-12-04 10:11:05.000000000 +0100
***************
*** 2678,2721 ****
  
  (defun dired-pop-to-buffer (buf)
    ;; Pop up buffer BUF.
    ;; If dired-shrink-to-fit is t, make its window fit its contents.
!   (if (not dired-shrink-to-fit)
!       (pop-to-buffer (get-buffer-create buf))
!     ;; let window shrink to fit:
!     (let ((window (selected-window))
!         target-lines w2)
!       (cond ;; if split-height-threshold is enabled, use the largest window
!             ((and (> (window-height (setq w2 (get-largest-window)))
!                    split-height-threshold)
!                 (window-full-width-p w2))
!            (setq window w2))
!           ;; if the least-recently-used window is big enough, use it
!           ((and (> (window-height (setq w2 (get-lru-window)))
!                    (* 2 window-min-height))
!                 (window-full-width-p w2))
!            (setq window w2)))
!       (save-excursion
!       (set-buffer buf)
!       (goto-char (point-max))
!       (skip-chars-backward "\n\r\t ")
!       (setq target-lines (count-lines (point-min) (point)))
!       ;; Don't forget to count the last line.
!       (if (not (bolp))
!           (setq target-lines (1+ target-lines))))
!       (if (<= (window-height window) (* 2 window-min-height))
!         ;; At this point, every window on the frame is too small to split.
!         (setq w2 (display-buffer buf))
!       (setq w2 (split-window window
!                 (max window-min-height
!                      (- (window-height window)
!                         (1+ (max window-min-height target-lines)))))))
!       (set-window-buffer w2 buf)
!       (if (< (1- (window-height w2)) target-lines)
!         (progn
!           (select-window w2)
!           (enlarge-window (- target-lines (1- (window-height w2))))))
!       (set-window-start w2 1)
!       )))
  
  (defcustom dired-no-confirm nil
    "A list of symbols for commands Dired should not confirm.
--- 2678,2687 ----
  
  (defun dired-pop-to-buffer (buf)
    ;; Pop up buffer BUF.
+   (pop-to-buffer (get-buffer-create buf))
    ;; If dired-shrink-to-fit is t, make its window fit its contents.
!   (when dired-shrink-to-fit
!     (fit-window-to-buffer (get-buffer-window buf))))
  
  (defcustom dired-no-confirm nil
    "A list of symbols for commands Dired should not confirm.

(Note that if the frame is shrunk so that not all marked file names fit
in the *Marked Files* window, then without an oversized header line as
is my-mm, dired-pop-to-buffer fails with the error "Attempt to delete
minibuffer or sole ordinary window"; whereas with an oversized header
line, this error is raised only if not even one file name can be shown.
But I see this difference in behavior whether or not the above patch is
applied.)

Steve Berman