Don't use callbacks -- use several submit buttons or special return addresses.

scheme/httpd/surflets/web-server/root/surflets/admin-handler.scm

@@ -25,7 +25,7 @@
 			       (td ,number-field) 
 			       (td ,(make-submit-button "Change")))))
 	    (hr)
-	    (URL ,(make-callback return-to-main-page) "Return to main page")))
+	    (URL ,(string-append new-url "?return=") "Return to main page")))
 	 )))
 
     (define (handler-options req . maybe-update-text)
@@ -33,18 +33,26 @@
 				 ,(:optional maybe-update-text "")))
 	     (number-field 
 	      (make-number-input-field `(@ ((value ,(options-instance-lifetime))))))
-	     (req (get-option-change number-field update-text)))
+	     (req (get-option-change number-field update-text))
-	(with-fatal-error-handler
+	     (bindings (get-bindings req)))
-	 (lambda (condition more)
+	(format #t "bindings ~s~%" bindings)
-	   (handler-options req "Please enter a valid, positive integer number"))
+	(cond 
-	 (set-options-instance-lifetime
+	 ((assoc "return" bindings)
-	  (let ((result (input-field-value number-field (get-bindings req))))
+	  (return-to-main-page req))
-	    (if (and (integer? result)
+	 (else
-		     (> result 0))
+
-		(handler-options req 
+	  (with-fatal-error-handler
-				 (format #f "Instance lifetime changed to ~a." 
+	   (lambda (condition more)
-					 (options-instance-lifetime)))
+	     (handler-options req "Please enter a valid, positive integer number"))
-		(error "not a positive integer")))))))
+	   (let ((result (input-field-value number-field bindings)))
+	     (if (and (integer? result)
+		      (> result 0))
+		 (begin
+		   (set-options-instance-lifetime result)
+		   (handler-options req 
+				    (format #f "Instance lifetime changed to ~a." 
+					    (options-instance-lifetime))))
+		  (error "not a positive integer"))))))))
 
     (define (return-to-main-page req)
       (send/finish (make-http-error-response http-status/moved-perm req

scheme/httpd/surflets/web-server/root/surflets/admin-profiling.scm

@@ -17,16 +17,10 @@
     (define counter 0)
     (define gnuplot "/usr/bin/gnuplot")
 
-    (define (reset-profiling-state!)
-      (set! counter 0)
-      (for-each delete-file file-names-to-delete)
-      (delete-file file-name)
-      (set! file-name (create-temp-file "servlet-profiling"))
-      (set! file-names-to-delete '()))
-
     (define (profile req . maybe-update-text)
       (let* ((update-text (:optional maybe-update-text ""))
 	     (input-field (make-text-input-field gnuplot '(@ (size 20))))
+	     (change-button (make-submit-button "Change"))
 	     (req 
 	      (send-html/suspend
 	       (lambda (new-url)
@@ -37,31 +31,46 @@
 			 (font (@ (color "red")) ,update-text)
 			 (p "Currently, there are " ,counter " profiles saved.")
 			 (ul
-			  (li (URL ,(make-callback new-profile) "Create new profile"))
+			  (li (URL ,(string-append new-url "?newprofile=")
-			  (li (URL ,(make-callback result) "Show profile results")
+				   "Create new profile")
+			  (li (URL ,(string-append new-url "?result=")
+				   "Show profile results")
 			      (br)
 			      (servlet-form
 			       ,new-url
 			       (p "This uses " (var "gnuplot") " that is searched at "
-				  ,input-field ,(make-submit-button "Change"))))
+				  ,input-field ,change-button)))
-			       (li (URL ,(make-callback reset) "Delete files and reset profile state.")))
+			  (li (URL ,(string-append new-url "?delete_reset=")
-			      (hr)
+				   "Delete files and reset profile state."))))
-			      (URL ,(make-callback return-to-main-page) 
+			 (hr)
-				   "Return to main page leaving profile state untouched.")
+			 (URL ,(string-append new-url "?return=") 
-			      (br)
+			      "Return to main page leaving profile state untouched.")
-			      (URL ,(make-callback reset-and-return-to-main-page)
+			 (br)
-				   "Return to main page reseting profile-state"))))))
+			 (URL ,(string-append new-url "?reset_return=")
+			      "Return to main page reseting profile-state"))))))
 	     (bindings (get-bindings req)))
-	(let ((new-gnuplot-location (with-fatal-error-handler
+	(cond
-				     (lambda (condition more)
+	 ((assoc "newprofile" bindings)
-				       #f)
+	  (new-profile req))
-				     (input-field-value input-field bindings))))
+	 ((assoc "result" bindings)
-	  (if (and new-gnuplot-location
+	  (result req))
-		   (file-executable? new-gnuplot-location))
+	 ((assoc "delete_reset" bindings)
-	      (begin
+	  (reset req))
-		(set! gnuplot new-gnuplot-location)
+	 ((assoc "return" bindings)
-		(profile req (format #f "Gnuplot is now searched at ~a." gnuplot)))
+	  (reset req))
-	      (profile req "Please enter a file name of an existing executable.")))))
+	 ((assoc "reset_return" bindings)
+	  (reset-and-return-to-main-page req))
+	 (else
+	  (let ((new-gnuplot-location (with-fatal-error-handler
+				       (lambda (condition more)
+					 #f)
+				       (input-field-value input-field bindings))))
+	    (if (and new-gnuplot-location
+		     (file-executable? new-gnuplot-location))
+		(begin
+		  (set! gnuplot new-gnuplot-location)
+		  (profile req (format #f "Gnuplot is now searched at ~a." gnuplot)))
+		(profile req "Please enter a file name of an existing executable.")))))))
 
     (define (new-profile req)
       (profile-space file-name)
@@ -105,15 +114,22 @@ plot '~a' title 'Servlet Profiling ~a' with lines"
 
     (define (reset req)
       (reset-profiling-state!)
-      (profile req))
+      (profile req "Profiling state reseted."))
 
-    (define (return-to-main-page req)
+    (define (reset-profiling-state!)
-      (send/finish (make-http-error-response http-status/moved-perm req
+      (set! counter 0)
-					     "admin.scm" "admin.scm")))    
+      (for-each delete-filesys-object file-names-to-delete)
+      (delete-filesys-object file-name)
+      (set! file-name (create-temp-file "servlet-profiling"))
+      (set! file-names-to-delete '()))
 
     (define (reset-and-return-to-main-page req)
       (reset-profiling-state!)
-      (return-to-main-page req))
+      (return-to-main-page req))    
+
+    (define (return-to-main-page req)
+      (send/finish (make-http-error-response http-status/moved-perm req
+					     "admin.scm" "admin.scm")))
 
     (define (main req)
       (profile req))

scheme/httpd/surflets/web-server/root/surflets/byte-input.scm

@@ -7,7 +7,7 @@
 	scheme)
   (begin
 
-    ;; This uses callbacks.
+    ;; This doesn't use c-a-l-l-b-a-c-k-s anymore.
 
     (define (make-byte-input-fields bits)
       (let ((checkboxes 

scheme/httpd/surflets/web-server/root/surflets/calculate.scm

@@ -7,7 +7,7 @@
 	scheme)
   (begin
 
-    ;; This doesn't use callbacks anymore.
+    ;; This doesn't use c-a-l-l-b-a-c-k-s anymore.
     
     (define *operator-alist*
 	    `(("+" . ,+)