Re: Problems fontifying an autoreverting Buffer Menu

[Luc Teirlinck]

   Is any other change needed to make this work right?
   The node Precalculated Fontification seems to say no,
   but maybe it is inaccurate.

I believe that the extra change needed is to make the global-font-lock-mode
implementation (as well as other global minor modes defined with
`define-global-minor-mode') take timers and processes into account.
Apparently, it can currently not handle those.  The current
implementation relies on the assumption that either find-file-hook or
post-command-hook will always run immediately after a major mode
function (see the comments below).  In the case of timers and
processes (and _maybe_ other cases as well), this can be very false.
If you look at the paragraph I deleted from the comments, you see that
it says that one way to implement things more cleanly would be to have
a "major-mode-hook".  We now have such a hook, `after-change-major-mode-hook'.
I believe that the machinery will, for the time being, still have to 
continue to use the two other hooks in addition to
`after-change-major-mode-hook', because not all major modes use
`run-mode-hooks' or otherwise run `after-change-major-mode-hook' yet.

The two small patches to buff-menu.el and easy-mmode.el solve the
auto-reverting Buffer Menu problem.  The comment changes to
font-core.el explain the rationale.

I can install if desired.

===File ~/buff-menu-diff====================================
*** buff-menu.el        19 May 2005 10:46:32 -0500      1.81
--- buff-menu.el        21 May 2005 16:06:59 -0500      
***************
*** 190,196 ****
         #'(lambda (&optional noconfirm) 'fast))
    (setq truncate-lines t)
    (setq buffer-read-only t)
!   (run-hooks 'buffer-menu-mode-hook))
  
  ;; This function exists so we can make the doc string of Buffer-menu-mode
  ;; look nice.
--- 190,196 ----
         #'(lambda (&optional noconfirm) 'fast))
    (setq truncate-lines t)
    (setq buffer-read-only t)
!   (run-mode-hooks 'buffer-menu-mode-hook))
  
  ;; This function exists so we can make the doc string of Buffer-menu-mode
  ;; look nice.
============================================================

===File ~/easy-mmode-diff===================================
*** easy-mmode.el       17 May 2005 10:08:33 -0500      1.62
--- easy-mmode.el       21 May 2005 19:08:35 -0500      
***************
*** 307,314 ****
--- 307,316 ----
         (if ,global-mode
             (progn
               (add-hook 'find-file-hook ',buffers)
+              (add-hook 'after-change-major-mode-hook ',buffers)
               (add-hook 'change-major-mode-hook ',cmmh))
           (remove-hook 'find-file-hook ',buffers)
+          (remove-hook 'after-change-major-mode-hook ',buffers)
           (remove-hook 'change-major-mode-hook ',cmmh))
  
         ;; Go through existing buffers.
============================================================

===File ~/font-core-diff====================================
*** font-core.el        25 Apr 2005 15:51:45 -0500      1.27
--- font-core.el        21 May 2005 17:41:00 -0500      
***************
*** 231,238 ****
  ;; hook is run, the major mode is in the process of being changed and we do 
not
  ;; know what the final major mode will be.  So, `font-lock-change-major-mode'
  ;; only (a) notes the name of the current buffer, and (b) adds our function
! ;; `turn-on-font-lock-if-enabled' to the hook variables `find-file-hook' and
! ;; `post-command-hook' (for buffers that are not visiting files).  By the time
  ;; the functions on the first of these hooks to be run are run, the new major
  ;; mode is assumed to be in place.  This way we get a Font Lock function run
  ;; when a major mode is turned on, without knowing major modes or their hooks.
--- 231,240 ----
  ;; hook is run, the major mode is in the process of being changed and we do 
not
  ;; know what the final major mode will be.  So, `font-lock-change-major-mode'
  ;; only (a) notes the name of the current buffer, and (b) adds our function
! ;; `turn-on-font-lock-if-enabled' to the hook variable
! ;; `after-change-major-mode-hook', as well as to the hook variables
! ;; `find-file-hook' and `post-command-hook' (for modes that do not yet
! ;; run `after-change-major-mode-hook').  By the time
  ;; the functions on the first of these hooks to be run are run, the new major
  ;; mode is assumed to be in place.  This way we get a Font Lock function run
  ;; when a major mode is turned on, without knowing major modes or their hooks.
***************
*** 243,254 ****
  ;; finished, whichever the sooner.  Arguably, any major mode that does not
  ;; follow the convension (a) is broken, and I can't think of any reason why 
(b)
  ;; would not be met (except `gnudoit' on non-files).  However, it is not 
clean.
- ;;
- ;; Probably the cleanest solution is to have each major mode function run some
- ;; hook, e.g., `major-mode-hook', but maybe implementing that change is
- ;; impractical.  I am personally against making `setq' a macro or be advised,
- ;; or have a special function such as `set-major-mode', but maybe someone can
- ;; come up with another solution?
  
  ;; User interface.
  ;;
--- 245,250 ----
============================================================