bug#6078: 23.1.90; switch-to-buffer does not redisplay until an event occurs

[Dimitri Fontaine]

The following code, an attempt to have a visual window switching
facility, is failing to provide the visual clue it's meant to give. That
seems to be because switch-to-buffer won't redisplay until some event
occurred, and neither using sit-for nor redisplay helps.

Here's the code:

(defun dim:switch-window-display-number (win num)
  "prepare a temp buffer to diplay in the window while choosing"
  (let ((buf (get-buffer-create
              (concat " *" (number-to-string num) "*"))))
    (with-current-buffer buf
      (insert (concat "\n\n    " (number-to-string num)))
      (text-scale-adjust 12))

    ;; when it works we'll choose one or the other
    (set-window-buffer win buf)
    (select-window win)
    (switch-to-buffer buf 'non-record)
    buf))

(defun dim:switch-window ()
  "Display an overlay in each window showing a unique key, then
ask user for the window where move to"
  (interactive)
  (let ((config (current-window-configuration))
        (num 1)
        (redisplay-dont-pause t)
        key
        buffers)
    
    (dolist (win (window-list))
      (setq buffers (cons (dim:switch-window-display-number win num) buffers))
      (setq num (1+ num)))

    ;(redisplay 1)
    (sit-for 0)
    (while (not key)
      (let ((input (event-basic-type (read-event "Move to window: " nil 5))))
        (when (and (not (symbolp input)) (<= 49 input) (>= 57 input))
          (setq key (- input 48)))))
    (message "%S" key)

    (dolist (buf buffers)
      (kill-buffer buf))

    (set-window-configuration config)

    (setq num 1)
    (dolist (win (window-list))
      (when (eq num key)
        (select-window win))
      (setq num (1+ num)))))


In GNU Emacs 23.1.90.1 (x86_64-apple-darwin10.2.0, NS apple-appkit-1038.25)
 of 2010-03-25 on proton.local
Windowing system distributor `Apple', version 10.3.1038
configured using `configure  '--without-dbus' '--with-ns' 'CFLAGS=-pipe -O2 
-march=nocona''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: nil
  value of $XMODIFIERS: nil
  locale-coding-system: nil
  default enable-multibyte-characters: t

Major mode: Emacs-Lisp

Minor modes in effect:
  savehist-mode: t
  desktop-save-mode: t
  nxhtml-global-minor-mode: t
  iswitchb-mode: t
  diff-auto-refine-mode: t
  global-hl-line-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
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t
  auto-fill-mode: 1

Recent input:
a r y : : SPC t h e SPC o n y <backspace> l y SPC c 
h a n g e SPC i s SPC h o w SPC t o SPC d o SPC i t 
, SPC n o t SPC w h a t SPC e r <backspace> <backspace> 
w e C-a M-f M-f M-f SPC p r o p o s e d C-e SPC c u 
r r e n <M-backspace> d o . C-x C-s C-a C-c C-c q p 
<return> M-` M-` C-n n M-` c o l u m n s , SPC s o 
r r y <return> a h SPC o <backspace> y s <backspace> 
e s <return> C-c C-b <return> w g a t <backspace> <backspace> 
<backspace> h a t s <backspace> ' s SPC t h a t SPC 
l i n g SPC h a s M-b M-b M-b <M-backspace> <backspace> 
SPC h a s SPC C-e <M-backspace> <backspace> <backspace> 
k SPC t SPC <backspace> o SPC d o SPC h e r e ? SPC 
: ) <return> M-` M-` i <backspace> l k <backspace> 
i k e SPC q <backspace> a <M-backspace> <M-backspace> 
a SPC 1 0 SPC h o u r s SPC t <backspace> p l a n e 
SPC t r p <backspace> i p SPC f o r SPC t h a t ? SPC 
n o SPC t h a n s <backspace> k s SPC : ) <return> 
M-` SPC n SPC n M-1 M-` <S-right> <S-up> C-h C-g C-x 
h M-w M-x e m <tab> a s <tab> c s <backspace> <backspace> 
<backspace> c s <tab> - r e <tab> <M-backspace> <M-backspace> 
r e p o <tab> r <tab> e m <backspace> <backspace> b 
<tab> <return>

Recent messages:
Fetching headers for nnimap+hm.local:PostgreSQL.hackers...done
Generating summary...done
Auto-saving...
20:23 You were mentioned by yonkeltron in #emacs [2 times]
20:24 You were mentioned by yonkeltron in #emacs [2 times]
Mark set [2 times]
Saved text until "+ num)))))

(provide 'dim-switch-window)"
Making completion list... [2 times]

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Features:
(shadow emacsbug flow-fill multi-isearch bbdb-hooks w3m-form w3m-symbol
w3m doc-view image-mode w3m-hist w3m-fb w3m-ems w3m-ccl ccl w3m-favicon
w3m-image w3m-proc w3m-util dim-switch-window bbdb-gui gnus-cite smiley
ansi-color gnus-agent gnus-srvr nnvirtual gnus-async gnus-bcklg
gnus-score score-mode sort gnus-ml gnus-msg tar-mode face-remap ffap
gnus-topic nndoc gnus-cache nnfolder utf-7 utf7 auth-source nnimap imap
nndraft nnmh bbdb-gnus bbdb-snarf mail-extr bbdb-com warnings nnnil nntp
bbdb-autoloads bbdb timezone gnus-art mm-uu mml2015 epg-config mm-view
smime dig gnus-sum nnoo gnus-group gnus-undo nnmail mail-source
format-spec dim-gnus-imap-count gnus-start gnus-spec gnus-int gnus-range
gnus-win gnus gnus-ems flyspell ispell hideshow mlinks rx nxml-uchnm
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dim-muse dim-muse-hack muse-context muse-journal muse-book muse-latex
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emacs)

-- 
Dimitri Fontaine