bug#15189: 24.3.50; display-buffer does not work well with custom frames.

[Keith David Bershatsky]

The documentation for (display-buffer) uses an example with (get-buffer-create 
"*foo*"):

http://www.gnu.org/software/emacs/manual/html_node/elisp/Display-Action-Functions.html

This does not work well with find-file in conjunction with several frames 
because find-file is executed BEFORE custom frame functions are run.  The 
result is that the buffer that initially had focus ends up getting buried even 
though the file being opened is in a new frame.  The only reliable workaround 
appears to be calling the find-file command AFTER the custom frame functions 
are run, which (in my lay opinion) defeats the purpose of using display-buffer.

If the display-buffer function was never intended by the developers to be used 
with find-file and custom frames, then perhaps this email could be treated as a 
feature request "wish-list" instead of being treated as a bug report.

Below is a detailed example that demonstrates what I am experiencing -- just 
plug it in and run the function "example".

Here is a link to a working example that does not use display-buffer:

http://stackoverflow.com/questions/18346785/how-to-intercept-a-file-before-it-opens-and-decide-which-frame

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(defun example ()
  (interactive)
  (custom-find-file "*bar*")
  (set-frame-position (selected-frame) 0 0)
  (mark-whole-buffer)
  (delete-region (region-beginning) (region-end))
  (insert "\*bar\* is about to be buried.")
  (message "\*bar\* is about to be buried.")
  (sit-for 3)
  (custom-find-file "foo.txt")
  (set-frame-position (selected-frame) 100 100)
  (mark-whole-buffer)
  (delete-region (region-beginning) (region-end))
  (insert "\"foo.txt\" is about to be buried.")
  (message "\"foo.txt\" is about to be buried.")
  (sit-for 3)
  (custom-find-file "doe.org")
  (set-frame-position (selected-frame) 200 200)
  (mark-whole-buffer)
  (delete-region (region-beginning) (region-end))
  (insert "\"doe.org\" is about to be buried.")
  (message "\"doe.org\" is about to be buried.")
  (sit-for 3)
  (custom-find-file "*undefined*")
  (set-frame-position (selected-frame) 300 300)
  (mark-whole-buffer)
  (delete-region (region-beginning) (region-end))
  (insert "\*undefined\* is now visible in two (2) frames.")
  (message "\*undefined\* is now visible in two (2) frames.") )

(defvar lawlist-system-buffer-regexp nil
  "Regexps matching `buffer-filename` for frame name `SYSTEM`.")
(setq lawlist-system-buffer-regexp '("*scratch*" "*bar*"))

(defvar lawlist-main-buffer-regexp nil
  "Regexps matching `buffer-filename` for frame name `MAIN`.")
(setq lawlist-main-buffer-regexp '("\\.txt" "\\.tex" "\\.el" "\\.yasnippet"))

(defvar lawlist-org-buffer-regexp nil
  "Regexps matching `buffer-filename` for frame name `ORG`.")
(setq lawlist-org-buffer-regexp '("[*]todo-list[*]" "\\.org_archive" "\\.org"))

(defun lawlist-regexps-match-p (regexps string)
  (catch 'matched
    (dolist (regexp regexps)
      (if (string-match regexp string)
        (throw 'matched t)))))

(defvar buffer-filename nil)

(defun custom-find-file (&optional buffer-filename)
  "Locate or create a specific frame, and then open the file."
  (interactive)
  (unless buffer-filename (setq buffer-filename (read-file-name "Select File: 
")))
  (if buffer-filename
    (display-buffer
      (find-file buffer-filename))))


(defun lawlist-display-buffer-function (&optional buffer flag)
  (if buffer-filename (progn
    (when (lawlist-regexps-match-p lawlist-org-buffer-regexp buffer-filename)
      (if (frame-exists "ORG")
          (switch-to-frame "ORG")
        ;; If unnamed frame exists, then take control of it.
        (catch 'break (dolist (frame (frame-list))
          (if (and
              (not (equal "MAIN" (frame-parameter frame 'name)))
              (not (equal "SYSTEM" (frame-parameter frame 'name)))
              (not (equal "ORG" (frame-parameter frame 'name)))
              (not (equal "WANDERLUST" (frame-parameter frame 'name)))
              (not (equal "MISCELLANEOUS" (frame-parameter frame 'name))) )
            (throw 'break (progn
              (switch-to-frame (frame-parameter frame 'name))
              (set-frame-name "ORG"))))))
        ;; If dolist found no unnamed frame, then create / name it.
        (if (not (frame-exists "ORG"))
          (progn
            (make-frame)
            (set-frame-name "ORG"))) ))
    (when (lawlist-regexps-match-p lawlist-main-buffer-regexp buffer-filename)
      (if (frame-exists "MAIN")
          (switch-to-frame "MAIN")
        ;; If unnamed frame exists, then take control of it.
        (catch 'break (dolist (frame (frame-list))
          (if (and
              (not (equal "MAIN" (frame-parameter frame 'name)))
              (not (equal "SYSTEM" (frame-parameter frame 'name)))
              (not (equal "ORG" (frame-parameter frame 'name)))
              (not (equal "WANDERLUST" (frame-parameter frame 'name)))
              (not (equal "MISCELLANEOUS" (frame-parameter frame 'name))) )
            (throw 'break (progn
              (switch-to-frame (frame-parameter frame 'name))
              (set-frame-name "MAIN"))))))
        ;; If dolist found no unnamed frame, then create / name it.
        (if (not (frame-exists "MAIN"))
          (progn
            (make-frame)
            (set-frame-name "MAIN"))) ))
    (when (lawlist-regexps-match-p lawlist-system-buffer-regexp buffer-filename)
      (if (frame-exists "SYSTEM")
          (switch-to-frame "SYSTEM")
        ;; If unnamed frame exists, then take control of it.
        (catch 'break (dolist (frame (frame-list))
          (if (and
              (not (equal "MAIN" (frame-parameter frame 'name)))
              (not (equal "SYSTEM" (frame-parameter frame 'name)))
              (not (equal "ORG" (frame-parameter frame 'name)))
              (not (equal "WANDERLUST" (frame-parameter frame 'name)))
              (not (equal "MISCELLANEOUS" (frame-parameter frame 'name))) )
            (throw 'break (progn
              (switch-to-frame (frame-parameter frame 'name))
              (set-frame-name "SYSTEM"))))))
        ;; If dolist found no unnamed frame, then create / name it.
        (if (not (frame-exists "SYSTEM"))
          (progn
            (make-frame)
            (set-frame-name "SYSTEM"))) ))
    (when (and (not (lawlist-regexps-match-p lawlist-org-buffer-regexp 
buffer-filename))
            (not (lawlist-regexps-match-p lawlist-main-buffer-regexp 
buffer-filename))
            (not (lawlist-regexps-match-p lawlist-system-buffer-regexp 
buffer-filename)) )
      (if (frame-exists "MISCELLAENOUS")
          (switch-to-frame "MISCELLAENOUS")
        ;; If unnamed frame exists, then take control of it.
        (catch 'break (dolist (frame (frame-list))
          (if (and
              (not (equal "MAIN" (frame-parameter frame 'name)))
              (not (equal "SYSTEM" (frame-parameter frame 'name)))
              (not (equal "ORG" (frame-parameter frame 'name)))
              (not (equal "WANDERLUST" (frame-parameter frame 'name)))
              (not (equal "MISCELLANEOUS" (frame-parameter frame 'name))) )
            (throw 'break (progn
              (switch-to-frame (frame-parameter frame 'name))
              (set-frame-name "MISCELLAENEOUS"))))))
        ;; If dolist found no unnamed frame, then create / name it.
        (if (not (frame-exists "MISCELLAENEOUS"))
          (progn
            (make-frame)
            (set-frame-name "MISCELLAENEOUS"))))))))

(setq display-buffer-function 'lawlist-display-buffer-function)


(defun frame-exists (frame-name)
  (not (eq nil (get-frame frame-name))))

(defun get-frame-name (&optional frame)
  "Return the string that names FRAME (a frame).  Default is selected frame."
  (unless frame (setq frame (selected-frame)))
  (if (framep frame)
      (cdr (assq 'name (frame-parameters frame)))
    (error "Function `get-frame-name': Argument not a frame: `%s'" frame)))

(defun get-frame (frame)
  "Return a frame, if any, named FRAME (a frame or a string).
  If none, return nil.
  If FRAME is a frame, it is returned."
  (cond ((framep frame) frame)
        ((stringp frame)
         (catch 'get-a-frame-found
           (dolist (fr (frame-list))
             (when (string= frame (get-frame-name fr))
               (throw 'get-a-frame-found fr)))
           nil))
        (t
         (error
          "Function `get-frame-name': Arg neither a string nor a frame: `%s'"
          frame))))

(defun switch-to-frame (frame-name)
  (let ((frames (frame-list)))
    (catch 'break
      (while frames
        (let ((frame (car frames)))
          (if (equal (frame-parameter frame 'name) frame-name)
              (throw 'break (select-frame-set-input-focus frame))
            (setq frames (cdr frames))))))))


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In GNU Emacs 24.3.50.1 (x86_64-apple-darwin10.8.0, NS apple-appkit-1038.36)
 of 2013-08-22 on MP.local
Bzr revision: 113971 monnier@iro.umontreal.ca-20130822040645-0fc4fi87eir72jnb
Windowing system distributor `Apple', version 10.3.1038
Configured using:
 `configure --with-ns'

Important settings:
  locale-coding-system: nil
  default enable-multibyte-characters: t

Major mode: Text

Minor modes in effect:
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  yas-global-mode: t
  yas-minor-mode: t
  global-highlight-parentheses-mode: t
  global-linum-mode: t
  linum-mode: t
  delete-selection-mode: t
  flyspell-mode: t
  frame-bufs-mode: t
  tabbar-mode: t
  highlight-parentheses-mode: t
  osx-key-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  global-visual-line-mode: t
  visual-line-mode: t
  transient-mark-mode: t

Recent input:
<escape> x e x a m p l e <return> s-w s-w s-w s-w s-w 
s-w s-w y s-w s-w s-w y s-w s-w s-w s-w s-w s-w s-o 
<menu-bar> <help-menu> <send-emacs-bug-report>

Recent messages:
Word wrapping enabled
*beep*
Beginning of buffer
*beep*
Beginning of buffer

Load-path shadows:
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