From 145823ecb2d55a7ea33d4a8482b5941f189d9418 Mon Sep 17 00:00:00 2001
From: Chong Yidong <cyd@gnu.org>
Date: Fri, 7 Sep 2012 18:19:58 +0800
Subject: [PATCH] Let ESC ESC quit in read-char-choice, and use it in
 userlock.el.

* lisp/subr.el (read-char-choice): Allow quitting via ESC ESC.

* lisp/userlock.el (ask-user-about-supersession-threat): Use
read-char-choice.

Fixes: debbugs:12093
---
 lisp/ChangeLog   |  7 +++++++
 lisp/subr.el     | 11 ++++++++---
 lisp/userlock.el | 48 +++++++++++++++++++-----------------------------
 3 files changed, 34 insertions(+), 32 deletions(-)

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 7aae8fd785..d7004237ad 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,10 @@
+2012-09-07  Chong Yidong  <cyd@gnu.org>
+
+	* subr.el (read-char-choice): Allow quitting via ESC ESC.
+
+	* userlock.el (ask-user-about-supersession-threat): Use
+	read-char-choice (Bug#12093).
+
 2012-09-07  Chong Yidong  <cyd@gnu.org>
 
 	* subr.el (buffer-narrowed-p): New function.
diff --git a/lisp/subr.el b/lisp/subr.el
index 621622e70e..a3e0897e9f 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -2237,7 +2237,8 @@ keyboard-quit events while waiting for a valid input."
     (error "Called `read-char-choice' without valid char choices"))
   (let (char done show-help (helpbuf " *Char Help*"))
     (let ((cursor-in-echo-area t)
-          (executing-kbd-macro executing-kbd-macro))
+          (executing-kbd-macro executing-kbd-macro)
+	  (esc-flag nil))
       (save-window-excursion	      ; in case we call help-form-show
 	(while (not done)
 	  (unless (get-text-property 0 'face prompt)
@@ -2261,8 +2262,12 @@ keyboard-quit events while waiting for a valid input."
 	    ;; there are no more events in the macro.  Attempt to
 	    ;; get an event interactively.
 	    (setq executing-kbd-macro nil))
-	   ((and (not inhibit-keyboard-quit) (eq char ?\C-g))
-	    (keyboard-quit))))))
+	   ((not inhibit-keyboard-quit)
+	    (cond
+	     ((and (null esc-flag) (eq char ?\e))
+	      (setq esc-flag t))
+	     ((memq char '(?\C-g ?\e))
+	      (keyboard-quit))))))))
     ;; Display the question with the answer.  But without cursor-in-echo-area.
     (message "%s%s" prompt (char-to-string char))
     char))
diff --git a/lisp/userlock.el b/lisp/userlock.el
index 705d958824..4c003e423a 100644
--- a/lisp/userlock.el
+++ b/lisp/userlock.el
@@ -108,37 +108,27 @@ You can rewrite this to use any criterion you like to choose which one to do.
 The buffer in question is current when this function is called."
   (discard-input)
   (save-window-excursion
-    (let (answer)
+    (let ((prompt
+	   (format "%s changed on disk; \
+really edit the buffer? (y, n, r or C-h) "
+		   (file-name-nondirectory fn)))
+	  (choices '(?y ?n ?r ?? ?\C-h))
+	  answer)
       (while (null answer)
-	(message "%s changed on disk; really edit the buffer? (y, n, r or C-h) "
-		 (file-name-nondirectory fn))
-	(let ((tem (downcase (let ((cursor-in-echo-area t))
-			       (read-char-exclusive)))))
-	  (setq answer
-		(if (= tem help-char)
-		    'help
-		  (cdr (assoc tem '((?n . yield)
-				    (?\C-g . yield)
-				    (?y . proceed)
-				    (?r . revert)
-				    (?? . help))))))
-	  (cond ((null answer)
-		 (beep)
-		 (message "Please type y, n or r; or ? for help")
-		 (sit-for 3))
-		((eq answer 'help)
-		 (ask-user-about-supersession-help)
-		 (setq answer nil))
-		((eq answer 'revert)
-		 (revert-buffer nil (not (buffer-modified-p)))
-					; ask confirmation if buffer modified
-		 (signal 'file-supersession
-			 (list "File reverted" fn)))
-		((eq answer 'yield)
-		 (signal 'file-supersession
-			 (list "File changed on disk" fn))))))
+	(setq answer (read-char-choice prompt choices))
+	(cond ((memq answer '(?? ?\C-h))
+	       (ask-user-about-supersession-help)
+	       (setq answer nil))
+	      ((eq answer ?r)
+	       ;; Ask for confirmation if buffer modified
+	       (revert-buffer nil (not (buffer-modified-p)))
+	       (signal 'file-supersession
+		       (list "File reverted" fn)))
+	      ((eq answer ?n)
+	       (signal 'file-supersession
+		       (list "File changed on disk" fn)))))
       (message
-        "File on disk now will become a backup file if you save these changes.")
+       "File on disk now will become a backup file if you save these changes.")
       (setq buffer-backed-up nil))))
 
 (defun ask-user-about-supersession-help ()
-- 
2.39.2