Re: Fundamental mode vs. special mode

[Chong Yidong <cyd@gnu.org>]

Chong Yidong <cyd@gnu.org> writes:

> I think this change is problematic.  IIUC, it introduces a nontrivial
> backward incompatibility: major modes defined with define-derived-mode
> now run fundamental-mode-hook, and thus behave differently from major
> modes that are defined directly according to previous Emacs guidelines
> for major modes (which was to simply call kill-all-local-variables).

I propose to remove the fundamental-mode-hook variable introduced in
that change, and introduce `run-mode-hooks-hook', which `run-mode-hooks'
runs before all the other hooks.  Then minor modes can use
`run-mode-hooks-hook', and the "turning off global modes" feature will
be available to non-derived modes.

=== modified file 'lisp/emacs-lisp/derived.el'
*** lisp/emacs-lisp/derived.el	2011-08-25 05:37:55 +0000
--- lisp/emacs-lisp/derived.el	2011-10-25 02:35:20 +0000
***************
*** 230,236 ****
  					; Run the parent.
  	 (delay-mode-hooks
  
! 	  (,(or parent 'fundamental-mode))
  					; Identify the child mode.
  	  (setq major-mode (quote ,child))
  	  (setq mode-name ,name)
--- 230,236 ----
  					; Run the parent.
  	 (delay-mode-hooks
  
! 	  (,(or parent 'kill-all-local-variables))
  					; Identify the child mode.
  	  (setq major-mode (quote ,child))
  	  (setq mode-name ,name)

=== modified file 'lisp/emacs-lisp/easy-mmode.el'
*** lisp/emacs-lisp/easy-mmode.el	2011-10-19 12:54:24 +0000
--- lisp/emacs-lisp/easy-mmode.el	2011-10-25 03:30:57 +0000
***************
*** 367,377 ****
  	     (progn
  	       (add-hook 'after-change-major-mode-hook
  			 ',MODE-enable-in-buffers)
! 	       (add-hook 'fundamental-mode-hook ',MODE-enable-in-buffers)
  	       (add-hook 'find-file-hook ',MODE-check-buffers)
  	       (add-hook 'change-major-mode-hook ',MODE-cmhh))
  	   (remove-hook 'after-change-major-mode-hook ',MODE-enable-in-buffers)
!            (remove-hook 'fundamental-mode-hook ',MODE-enable-in-buffers)
  	   (remove-hook 'find-file-hook ',MODE-check-buffers)
  	   (remove-hook 'change-major-mode-hook ',MODE-cmhh))
  
--- 367,377 ----
  	     (progn
  	       (add-hook 'after-change-major-mode-hook
  			 ',MODE-enable-in-buffers)
! 	       (add-hook 'run-mode-hooks-hook ',MODE-enable-in-buffers)
  	       (add-hook 'find-file-hook ',MODE-check-buffers)
  	       (add-hook 'change-major-mode-hook ',MODE-cmhh))
  	   (remove-hook 'after-change-major-mode-hook ',MODE-enable-in-buffers)
!            (remove-hook 'run-mode-hooks-hook ',MODE-enable-in-buffers)
  	   (remove-hook 'find-file-hook ',MODE-check-buffers)
  	   (remove-hook 'change-major-mode-hook ',MODE-cmhh))
  

=== modified file 'lisp/simple.el'
*** lisp/simple.el	2011-10-19 12:54:24 +0000
--- lisp/simple.el	2011-10-25 02:35:48 +0000
***************
*** 349,355 ****
  Other major modes are defined by comparison with this one."
    (interactive)
    (kill-all-local-variables)
!   (run-mode-hooks 'fundamental-mode-hook))
  
  ;; Special major modes to view specially formatted data rather than files.
  
--- 349,356 ----
  Other major modes are defined by comparison with this one."
    (interactive)
    (kill-all-local-variables)
!   (unless delay-mode-hooks
!     (run-hooks 'after-change-major-mode-hook)))
  
  ;; Special major modes to view specially formatted data rather than files.
  

=== modified file 'lisp/subr.el'
*** lisp/subr.el	2011-10-06 19:15:19 +0000
--- lisp/subr.el	2011-10-25 03:30:33 +0000
***************
*** 1527,1532 ****
--- 1527,1535 ----
  (defvar after-change-major-mode-hook nil
    "Normal hook run at the very end of major mode functions.")
  
+ (defvar run-mode-hooks-hook nil
+   "Normal hook run before `run-mode-hooks' runs the mode hooks.")
+ 
  (defun run-mode-hooks (&rest hooks)
    "Run mode hooks `delayed-mode-hooks' and HOOKS, or delay HOOKS.
  Execution is delayed if the variable `delay-mode-hooks' is non-nil.
***************
*** 1540,1546 ****
      ;; Normal case, just run the hook as before plus any delayed hooks.
      (setq hooks (nconc (nreverse delayed-mode-hooks) hooks))
      (setq delayed-mode-hooks nil)
!     (apply 'run-hooks hooks)
      (run-hooks 'after-change-major-mode-hook)))
  
  (defmacro delay-mode-hooks (&rest body)
--- 1543,1549 ----
      ;; Normal case, just run the hook as before plus any delayed hooks.
      (setq hooks (nconc (nreverse delayed-mode-hooks) hooks))
      (setq delayed-mode-hooks nil)
!     (apply 'run-hooks (cons 'run-mode-hooks-hook hooks))
      (run-hooks 'after-change-major-mode-hook)))
  
  (defmacro delay-mode-hooks (&rest body)