Subject: bug#27634: 25.2.1; C-g does not quit register-read-with-preview

From: Paul Rankin <[email-masked]>
Date: Mon, 10 Jul 2017 17:20:55 +1000

On Mon, 10 Jul 2017, at 04:33 PM, Tino Calancha wrote:
> How about the following?
> 
> @@ -164,6 +164,8 @@ register-read-with-preview
>  		       help-chars)
>  	    (unless (get-buffer-window buffer)
>  	      (register-preview buffer 'show-empty)))
> +          (when (eq (string-to-char "\C-g") last-input-event)
> +            (keyboard-quit))
>  	  (if (characterp last-input-event) last-input-event
>  	    (error "Non-character input-event")))
>        (and (timerp timer) (cancel-timer timer))

I think that's more a bandaid than fixing the root of the problem, which is that the manual tells the user that register names are alphanumeric characters (and I assume 99% of users only use alphanumeric characters) but the function doesn't test for this. e.g. testing for C-g doesn't catch for ^L or ^M, etc.

If we want to be strict about it, this might work:

@@ -164,8 +164,8 @@
 		       help-chars)
 	    (unless (get-buffer-window buffer)
 	      (register-preview buffer 'show-empty)))
-	  (if (characterp last-input-event) last-input-event
-	    (error "Non-character input-event")))
+	  (if (= (char-syntax last-input-event) 119) last-input-event
+	    (error "Register name must be alphanumeric")))
       (and (timerp timer) (cancel-timer timer))
       (let ((w (get-buffer-window buffer)))
         (and (window-live-p w) (delete-window w)))

That prohibits anything except "a-zA-Z0-9", although users may want to save registers to "$" or "*".