(find-tag-marker-ring-length): New variable.

(find-tag-marker-ring): New variable.
(tags-location-ring): New variable replacing tags-location-ring.
(tags-location-stack): Deleted.
(tags-table-format-hooks): Doc fix.
(initialize-new-tags-table): Init find-tag-marker-ring,
tags-location-ring.
(tags-reset-tags-tables): Doc fix.  Set tags-location-ring,
find-tag-marker-ring.
(find-tag-noselect): Doc fix.  Use tags-location-ring,
find-tag-marker-ring.
(find-tag, find-tag-other-window, find-tag-other-frame,
find-tag-regexp): Doc fix.
(pop-tag-mark): New function.
(esc-map): Bind pop-tag-mark.

1 files changed, 79 insertions, 16 deletions

diff --git a/lisp/progmodes/etags.el b/lisp/progmodes/etags.el
index 3b5a9d6d7b6..e6f081d1df6 100644
--- a/lisp/progmodes/etags.el
+++ b/lisp/progmodes/etags.el
@@ -1,6 +1,5 @@
 ;;; etags.el --- etags facility for Emacs
-
-;; Copyright (C) 1985, 1986, 1988, 1989, 1992, 1993, 1994, 1995
+;; Copyright (C) 1985, 1986, 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1998
 ;;	Free Software Foundation, Inc.
 
 ;; Author: Roland McGrath <roland@gnu.ai.mit.edu>
@@ -25,6 +24,8 @@
 
 ;;; Code:
 
+(require 'ring)
+
 ;;;###autoload
 (defvar tags-file-name nil
   "*File name of tags table.
@@ -106,13 +107,21 @@ Otherwise, `find-tag-default' is used."
   :group 'etags
   :type 'function)
 
+(defcustom find-tag-marker-ring-length 16
+  "*Length of marker rings `find-tag-marker-ring' and `tags-location-ring'."
+  :group 'etags
+  :type 'integer)
+
+(defvar find-tag-marker-ring (make-ring find-tag-marker-ring-length)
+  "Ring of markers which are locations from which \\[find-tag] was invoked.")
+
 (defvar default-tags-table-function nil
   "If non-nil, a function to choose a default tags file for a buffer.
 This function receives no arguments and should return the default
 tags table file to use for the current buffer.")
 
-(defvar tags-location-stack nil
-  "List of markers which are locations visited by \\[find-tag].
+(defvar tags-location-ring (make-ring find-tag-marker-ring-length)
+  "Ring of markers which are locations visited by \\[find-tag].
 Pop back to the last location with \\[negative-argument] \\[find-tag].")
 
 ;; Tags table state.
@@ -135,8 +144,8 @@ nil means it has not yet been computed; use `tags-table-files' to do so.")
 
 (defvar tags-table-format-hooks '(etags-recognize-tags-table
 				  recognize-empty-tags-table)
-  "List of functions to be called in a tags table buffer to identify
-the type of tags table.  The functions are called in order, with no arguments,
+  "List of functions to be called in a tags table buffer to identify the type of tags table.  
+The functions are called in order, with no arguments,
 until one returns non-nil.  The function should make buffer-local bindings
 of the format-parsing tags function variables if successful.")
 
@@ -180,6 +189,8 @@ One argument, the tag info returned by `snarf-tag-function'.")
   (set (make-local-variable 'tags-table-files) nil)
   (set (make-local-variable 'tags-completion-table) nil)
   (set (make-local-variable 'tags-included-tables) nil)
+  (setq find-tag-marker-ring (make-ring find-tag-marker-ring-length))
+  (setq tags-location-ring (make-ring find-tag-marker-ring-length))
   ;; Value is t if we have found a valid tags table buffer.
   (let ((hooks tags-table-format-hooks))
     (while (and hooks
@@ -599,11 +610,19 @@ Returns t if it visits a tags table, or nil if there are no more in the list."
 	(error "File %s is not a valid tags table" local-tags-file-name)))))
 
 (defun tags-reset-tags-tables ()
-  "Reset tags state to cancel effect of any previous \\[visit-tags-table]
-or \\[find-tag]."
+  "Reset tags state to cancel effect of any previous \\[visit-tags-table] or \\[find-tag]."
   (interactive)
   (setq tags-file-name nil
-	tags-location-stack nil
+	tags-location-ring (progn
+			     (mapcar (lambda (m)
+				       (set-marker m nil))
+				     tags-location-ring)
+			     (make-ring find-tag-marker-ring-length))
+	find-tag-marker-ring (progn
+			       (mapcar (lambda (m)
+					 (set-marker m nil))
+				       find-tag-marker-ring)
+			       (make-ring find-tag-marker-ring-length))
 	tags-table-list nil
 	tags-table-computed-list nil
 	tags-table-computed-list-for nil
@@ -738,6 +757,10 @@ or just \\[negative-argument]), pop back to the previous tag gone to.
 
 If third arg REGEXP-P is non-nil, treat TAGNAME as a regexp.
 
+A marker representing the point when this command is onvoked is pushed
+onto a ring and may be popped back to with \\[pop-tag-mark].
+Contrast this with the ring of marks gone to by the command.
+
 See documentation of variable `tags-file-name'."
   (interactive (find-tag-interactive "Find tag: "))
 
@@ -747,19 +770,20 @@ See documentation of variable `tags-file-name'."
   (let ((local-find-tag-hook find-tag-hook))
     (if (eq '- next-p)
 	;; Pop back to a previous location.
-	(if (null tags-location-stack)
+	(if (ring-empty-p tags-location-ring)
 	    (error "No previous tag locations")
-	  (let ((marker (car tags-location-stack)))
-	    ;; Pop the stack.
-	    (setq tags-location-stack (cdr tags-location-stack))
+	  (let ((marker (ring-remove tags-location-ring 0)))
 	    (prog1
 		;; Move to the saved location.
-		(set-buffer (marker-buffer marker))
+		(set-buffer (or (marker-buffer marker)
+                                (error "The marked buffer has been deleted")))
 	      (goto-char (marker-position marker))
 	      ;; Kill that marker so it doesn't slow down editing.
 	      (set-marker marker nil nil)
 	      ;; Run the user's hook.  Do we really want to do this for pop?
 	      (run-hooks 'local-find-tag-hook))))
+      ;; Record whence we came.
+      (ring-insert find-tag-marker-ring (point-marker))
       (if next-p
 	  ;; Find the same table we last used.
 	  (visit-tags-table-buffer 'same)
@@ -787,8 +811,7 @@ See documentation of variable `tags-file-name'."
 	    (not next-p)))
 	  (set-marker marker (point))
 	  (run-hooks 'local-find-tag-hook)
-	  (setq tags-location-stack
-		(cons marker tags-location-stack))
+	  (ring-insert tags-location-ring marker)
 	  (current-buffer))))))
 
 ;;;###autoload
@@ -803,6 +826,12 @@ multiple matches for a tag, more exact matches are found first.  If NEXT-P
 is the atom `-' (interactively, with prefix arg that is a negative number
 or just \\[negative-argument]), pop back to the previous tag gone to.
 
+If third arg REGEXP-P is non-nil, treat TAGNAME as a regexp.
+
+A marker representing the point when this command is onvoked is pushed
+onto a ring and may be popped back to with \\[pop-tag-mark].
+Contrast this with the ring of marks gone to by the command.
+
 See documentation of variable `tags-file-name'."
   (interactive (find-tag-interactive "Find tag: "))
   (switch-to-buffer (find-tag-noselect tagname next-p regexp-p)))
@@ -821,6 +850,12 @@ multiple matches for a tag, more exact matches are found first.  If NEXT-P
 is negative (interactively, with prefix arg that is a negative number or
 just \\[negative-argument]), pop back to the previous tag gone to.
 
+If third arg REGEXP-P is non-nil, treat TAGNAME as a regexp.
+
+A marker representing the point when this command is onvoked is pushed
+onto a ring and may be popped back to with \\[pop-tag-mark].
+Contrast this with the ring of marks gone to by the command.
+
 See documentation of variable `tags-file-name'."
   (interactive (find-tag-interactive "Find tag other window: "))
 
@@ -856,6 +891,12 @@ multiple matches for a tag, more exact matches are found first.  If NEXT-P
 is negative (interactively, with prefix arg that is a negative number or
 just \\[negative-argument]), pop back to the previous tag gone to.
 
+If third arg REGEXP-P is non-nil, treat TAGNAME as a regexp.
+
+A marker representing the point when this command is onvoked is pushed
+onto a ring and may be popped back to with \\[pop-tag-mark].
+Contrast this with the ring of marks gone to by the command.
+
 See documentation of variable `tags-file-name'."
   (interactive (find-tag-interactive "Find tag other frame: "))
   (let ((pop-up-frames t))
@@ -875,12 +916,34 @@ just \\[negative-argument]), pop back to the previous tag gone to.
 
 If third arg OTHER-WINDOW is non-nil, select the buffer in another window.
 
+A marker representing the point when this command is onvoked is pushed
+onto a ring and may be popped back to with \\[pop-tag-mark].
+Contrast this with the ring of marks gone to by the command.
+
 See documentation of variable `tags-file-name'."
   (interactive (find-tag-interactive "Find tag regexp: " t))
   ;; We go through find-tag-other-window to do all the display hair there.
   (funcall (if other-window 'find-tag-other-window 'find-tag)
 	   regexp next-p t))
 ;;;###autoload (define-key esc-map [?\C-.] 'find-tag-regexp)
+
+;;;###autoload (define-key esc-map "*" 'pop-tag-mark)
+
+;;;###autoload
+(defun pop-tag-mark ()
+  "Pop back to where \\[find-tag] was last invoked.
+
+This is distinct from invoking \\[find-tag] with a negative argument
+since that pops a stack of markers at which tags were found, not from
+where they were found."
+  (interactive)
+  (if (ring-empty-p find-tag-marker-ring)
+      (error "No previous locations for find-tag invocation"))
+  (let ((marker (ring-remove find-tag-marker-ring 0)))
+    (switch-to-buffer (or (marker-buffer marker)
+                          (error "The marked buffer has been deleted")))
+    (goto-char (marker-position marker))
+    (set-marker marker nil nil)))
 
 ;; Internal tag finding function.