Add :after-hook facility to define-derived-mode.

This allow a form to be evaluated _after_ a major mode's hooks have been run.
It is needed to solve some problems in CC Mode, including bug #16759 and
bug #23476.

* lisp/emacs-lisp/derived.el (define-derived-mode): introduce the new argument
`:after-hook', and generate the requisite code for it.
(derived-mode-make-docstring): Take account of the possibility of :after-hook.

* lisp/subr.el (delayed-after-hook-forms): New variable.
(run-mode-hooks): As the last thing evaluate the forms in
delayed-after-hook-forms.

* doc/lispref/modes.texi (Derived Modes): Document :after-hook.
(Mode Hooks): Document the new feature in run-mode-hooks.

* etc/NEWS: Note the new feature.

1 files changed, 12 insertions, 3 deletions

diff --git a/lisp/emacs-lisp/derived.el b/lisp/emacs-lisp/derived.el
index a615f9a5854..0f7691af0f4 100644
--- a/lisp/emacs-lisp/derived.el
+++ b/lisp/emacs-lisp/derived.el
@@ -137,6 +137,9 @@ BODY can start with a bunch of keyword arguments.  The following keyword
 :abbrev-table TABLE
 	Use TABLE instead of the default (CHILD-abbrev-table).
 	A nil value means to simply use the same abbrev-table as the parent.
+:after-hook FORM
+	A single lisp form which is evaluated after the mode hooks have been
+	run.  It should not be quoted.
 
 Here is how you could define LaTeX-Thesis mode as a variant of LaTeX mode:
 
@@ -184,7 +187,8 @@ See Info node `(elisp)Derived Modes' for more details."
 	(declare-abbrev t)
 	(declare-syntax t)
 	(hook (derived-mode-hook-name child))
-	(group nil))
+	(group nil)
+        (after-hook nil))
 
     ;; Process the keyword args.
     (while (keywordp (car body))
@@ -192,6 +196,7 @@ See Info node `(elisp)Derived Modes' for more details."
 	(`:group (setq group (pop body)))
 	(`:abbrev-table (setq abbrev (pop body)) (setq declare-abbrev nil))
 	(`:syntax-table (setq syntax (pop body)) (setq declare-syntax nil))
+        (`:after-hook (setq after-hook (pop body)))
 	(_ (pop body))))
 
     (setq docstring (derived-mode-make-docstring
@@ -272,7 +277,11 @@ No problems result if this variable is not bound.
 	  ,@body
 	  )
 	 ;; Run the hooks, if any.
-         (run-mode-hooks ',hook)))))
+         (run-mode-hooks ',hook)
+         ,@(when after-hook
+             `((if delay-mode-hooks
+                   (push ',after-hook delayed-after-hook-forms)
+                 ,after-hook)))))))
 
 ;; PUBLIC: find the ultimate class of a derived mode.
 
@@ -344,7 +353,7 @@ which more-or-less shadow%s %s's corresponding table%s."
 			 (format "`%s' " parent))
 		       "might have run,\nthis mode "))
 		    (format "runs the hook `%s'" hook)
-		    ", as the final step\nduring initialization.")))
+		    ", as the final or penultimate step\nduring initialization.")))
 
     (unless (string-match "\\\\[{[]" docstring)
       ;; And don't forget to put the mode's keymap.