PRS 10379 and 10377

svn: r15795

original commit: fcfa572e02e8452fd913cbfcdbff820ca046c0af

collects/framework/private/text.ss

@@ -541,14 +541,21 @@ WARNING: printf is rebound in the body of the unit to always
     (define (get-styles-fixed) styles-fixed?)
     (define (set-styles-fixed b) (set! styles-fixed? b))
     
+    (define edition 0)
+    (define/public (get-edition-number) edition)
+    
     (define/augment (on-insert start len)
       (begin-edit-sequence)
       (inner (void) on-insert start len))
     (define/augment (after-insert start len)
+      (set! edition (+ edition 1))
       (when styles-fixed?
         (change-style (get-fixed-style) start (+ start len) #f))
       (inner (void) after-insert start len)
       (end-edit-sequence))
+   (define/augment (after-delete start len)
+     (set! edition (+ edition 1))
+     (inner (void) after-delete start len))
     
     (define/public (move/copy-to-edit dest-edit start end dest-position)
       (split-snip start)

collects/scribblings/framework/text.scrbl

@@ -134,6 +134,14 @@
     @method[text:basic<%> port-name-matches?].
 
   }
+  @defmethod[(get-edition-number) exact-nonnegative-integer?]{
+     Returns a number that increments everytime something in
+     the editor changes. 
+     
+     The number is updated in @xmethod[text% after-insert] and
+     @xmethod[text% after-delete].
+  }
+  
 }
 @defmixin[text:basic-mixin (editor:basic<%> text%) (text:basic<%>)]{
   This mixin implements the basic functionality needed for