* lisp/play/life.el (life-mode): Use define-derived-mode. Derive from

special-mode.
(life): Let-bind inhibit-read-only.
(life-setup): Avoid `setq'.  Use `life-mode'.

2 files changed, 35 insertions, 31 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index b866f4f93aa..404e9bfa8a6 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,5 +1,10 @@
 2013-09-17  Stefan Monnier  <monnier@iro.umontreal.ca>
 
+        * play/life.el (life-mode): Use define-derived-mode.  Derive from
+        special-mode.
+        (life): Let-bind inhibit-read-only.
+        (life-setup): Avoid `setq'.  Use `life-mode'.
+
         * emacs-lisp/package.el (package-generate-autoloads): Remove `require'
         which should not be needed any more.
         (package-menu-refresh, package-menu-describe-package): Use user-error.
diff --git a/lisp/play/life.el b/lisp/play/life.el
index a73f3a58e66..438ff92c402 100644
--- a/lisp/play/life.el
+++ b/lisp/play/life.el
@@ -122,33 +122,32 @@ generations (this defaults to 1)."
   (life-setup)
   (catch 'life-exit
     (while t
-      (let ((inhibit-quit t))
+      (let ((inhibit-quit t)
+            (inhibit-read-only t))
         (life-display-generation sleeptime)
         (life-grim-reaper)
         (life-expand-plane-if-needed)
         (life-increment-generation)))))
 
-(defalias 'life-mode 'life)
-(put 'life-mode 'mode-class 'special)
+(define-derived-mode life-mode special-mode "Life"
+  "Major mode for the buffer of `life'."
+  (setq-local case-fold-search nil)
+  (setq-local truncate-lines t)
+  (setq-local show-trailing-whitespace nil)
+  (setq-local life-current-generation 0)
+  (setq-local life-generation-string "0")
+  (setq-local mode-line-buffer-identification '("Life: generation "
+                                                life-generation-string))
+  (setq-local fill-column (1- (window-width)))
+  (setq-local life-window-start 1)
+  (buffer-disable-undo))
 
 (defun life-setup ()
-  (let (n)
-    (switch-to-buffer (get-buffer-create "*Life*") t)
-    (erase-buffer)
-    (kill-all-local-variables)
-    (setq case-fold-search nil
-          mode-name "Life"
-          major-mode 'life-mode
-          truncate-lines t
-          show-trailing-whitespace nil
-          life-current-generation 0
-          life-generation-string "0"
-          mode-line-buffer-identification '("Life: generation "
-                                            life-generation-string)
-          fill-column (1- (window-width))
-          life-window-start 1)
-    (buffer-disable-undo (current-buffer))
-    ;; stuff in the random pattern
+  (switch-to-buffer (get-buffer-create "*Life*") t)
+  (erase-buffer)
+  (life-mode)
+  ;; stuff in the random pattern
+  (let ((inhibit-read-only t))
     (life-insert-random-pattern)
     ;; make sure (life-life-char) is used throughout
     (goto-char (point-min))
@@ -156,18 +155,18 @@ generations (this defaults to 1)."
       (replace-match (life-life-string) t t))
     ;; center the pattern horizontally
     (goto-char (point-min))
-    (setq n (/ (- fill-column (line-end-position)) 2))
-    (while (not (eobp))
-      (indent-to n)
-      (forward-line))
+    (let ((n (/ (- fill-column (line-end-position)) 2)))
+      (while (not (eobp))
+        (indent-to n)
+        (forward-line)))
     ;; center the pattern vertically
-    (setq n (/ (- (1- (window-height))
-                  (count-lines (point-min) (point-max)))
-               2))
-    (goto-char (point-min))
-    (newline n)
-    (goto-char (point-max))
-    (newline n)
+    (let ((n (/ (- (1- (window-height))
+                   (count-lines (point-min) (point-max)))
+                2)))
+      (goto-char (point-min))
+      (newline n)
+      (goto-char (point-max))
+      (newline n))
     ;; pad lines out to fill-column
     (goto-char (point-min))
     (while (not (eobp))