added get-button-label method to switchable-button%

original commit: 65579793afbebb705080267a37580ec0b94e1e97

collects/mrlib/scribblings/switchable-button.scrbl

@@ -35,8 +35,10 @@ as little as possible vertical space.
   }
   
   @defmethod[(command) void?]{
-
-Calls the button's callback function.}
-
+    Calls the button's callback function.
   }
   
+  @defmethod[(get-button-label) string?]{
+    Returns the label of this button.
+  }
+}

collects/mrlib/switchable-button.rkt

@@ -56,6 +56,8 @@
                 [alternate-bitmap bitmap]
                 [vertical-tight? #f])
     
+    (define/public (get-button-label) label)
+    
     (when (and (is-a? label bitmap%)
                (not (send label ok?)))
       (error 'switchable-button% "label bitmap is not ok?"))