Re: Strange Emacs crash

[Kim F. Storm]

"Martin Lüthi" <address@hidden> writes:

> Symptoms:
>
> Hi
>
> Emacs crashes consistently when I use iso-accents-mode in the *mail*
> buffer. I could reduce my .emacs to the following two lines
>
> ======= .emacs =======
> (custom-set-variables
>  '(global-font-lock-mode t nil (font-lock))
>  '(mail-archive-file-name "~/mail/sent")
>  )
> ======================
>
> To reproduce the error do the following steps:
>
> - M-x mail                          [enter mail mode]
> - M-x iso-accents-mode              [enter iso-accents-mode]
> - put point on the Subject line
> - enter "u                          [write a 'ü' (u Umlaut)]
> - go to the mail body
> - enter S-h                         [write a upcase 'H']
> - Emacs crashes
>


It turns out that when you hit " iso-accents-mode has setup
a function to be called via key-translation-map with the purpose
of reading the next character and combine them into a single
character.  The problem is that this function modifies the
buffer in a state where emacs expects the window and buffer
contents to be in a consitent state.

The following patch fixes the problem for iso-accents-mode.

This should probably be fixed in emacs' core to handle this situation
in general, but I'm not too familiar with that specific part of the
code.  Richard? Stefan?



*** iso-acc.el  01 Sep 2003 17:45:28 +0200      1.58
--- iso-acc.el  23 Feb 2005 17:00:45 +0100      
***************
*** 290,295 ****
--- 290,305 ----
        (iso-accents-compose prompt)
      (vector last-input-char)))
  
+ 
+ ;; The iso-accents-compose function is called deep inside Emacs' read
+ ;; key sequence machinery, so the call to read-event below actually
+ ;; recurses into that machinery.  Doing that does not cause any
+ ;; problem on its own, but read-event will have marked the window's
+ ;; display matrix to be accurate -- which is broken by the subsequent
+ ;; call to delete-region.  Therefore, we must call force-window-update
+ ;; after delete-region to explicitly clear the accurate state of the
+ ;; window's display matrix.
+ 
  (defun iso-accents-compose (prompt)
    (let* ((first-char last-input-char)
         (list (assq first-char iso-accents-list))
***************
*** 308,314 ****
                            (read-event))
                        (insert first-char)
                        (prog1 (read-event)
!                         (delete-region (1- (point)) (point)))))
         (entry (cdr (assq second-char list))))
      (if entry
        ;; Found it: return the mapped char
--- 318,326 ----
                            (read-event))
                        (insert first-char)
                        (prog1 (read-event)
!                         (delete-region (1- (point)) (point))
!                         ;; Display is no longer up-to-date.
!                         (force-window-update (selected-window)))))
         (entry (cdr (assq second-char list))))
      (if entry
        ;; Found it: return the mapped char

-- 
Kim F. Storm <address@hidden> http://www.cua.dk