From: Richard M. Stallman <rms@gnu.org>
Date: Wed, 12 Dec 2001 09:26:43 +0000 (+0000)
Subject: (derived-mode-p): Moved here from derived.el.
X-Git-Tag: ttn-vms-21-2-B4~17772
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=31ca596b970d838877353b06df675c7a4fdeddb2;p=emacs.git

(derived-mode-p): Moved here from derived.el.
---

diff --git a/lisp/subr.el b/lisp/subr.el
index 4232fd77e09..4029b7fa334 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -1294,6 +1294,16 @@ Only affects hooks run in the current buffer."
      (let ((delay-mode-hooks t))
        ,@body)))
 
+;; PUBLIC: find if the current mode derives from another.
+
+(defun derived-mode-p (&rest modes)
+  "Non-nil if the current major mode is derived from one of MODES.
+Uses the `derived-mode-parent' property of the symbol to trace backwards."
+  (let ((parent major-mode))
+    (while (and (not (memq parent modes))
+		(setq parent (get parent 'derived-mode-parent))))
+    parent))
+
 (defmacro with-syntax-table (table &rest body)
   "Evaluate BODY with syntax table of current buffer set to a copy of TABLE.
 The syntax table of the current buffer is saved, BODY is evaluated, and the