diff --git a/collects/mrlib/graph.rkt b/collects/mrlib/graph.rkt
index 62a702ba2e..b466956d37 100644
--- a/collects/mrlib/graph.rkt
+++ b/collects/mrlib/graph.rkt
@@ -378,7 +378,7 @@
           (let ([old-currently-overs currently-overs])
             (set! currently-overs new-currently-overs)
             
-	    (on-mouse-over-snips currently-overs)
+            (on-mouse-over-snips currently-overs)
             (for-each 
              (lambda (old-currently-over)
                (invalidate-to-children/parents old-currently-over dc))
@@ -387,9 +387,8 @@
              (lambda (new-currently-over)
                (invalidate-to-children/parents new-currently-over dc))
              new-currently-overs))))
-
-      (define/public (on-mouse-over-snips snips)
-	(void))
+      
+      (define/public (on-mouse-over-snips snips) (void))
         
       ;; set-equal : (listof snip) (listof snip) -> boolean
       ;; typically lists will be small (length 1),
@@ -404,37 +403,20 @@
       ;; all of its children and parents.
       (define/private (invalidate-to-children/parents snip dc)
         (when (is-a? snip graph-snip<%>)
-          (unless (eq? last-dc dc)
-            (define-values (w h a s) (send dc get-text-extent "Label" #f #f 0)) 
-            (set! last-dc dc)
-            (set! text-height h))
-          (let* ([parents-and-children (append (get-all-parents snip)
-                                               (get-all-children snip))]
-                 [rects (get-rectangles snip parents-and-children)]
-                 [or/c (or/c-rects rects)]
-                 [invalidate-rect
-                  (lambda (rect)
-                    (save-rectangle-to-invalidate
-                     (- (rect-left rect) text-height)
-                     (- (rect-top rect)  text-height)
-                     (+ (- (rect-right rect)
-                           (rect-left rect))
-                        text-height)
-                     (+ (- (rect-bottom rect)
-                           (rect-top rect))
-                        text-height)))])
-            (cond
-              [(< (rect-area or/c)
-                  (apply + (map (lambda (x) (rect-area x)) rects)))
-               (invalidate-rect or/c)]
-              [else
-               (for-each invalidate-rect rects)]))))
-      (inherit invalidate-bitmap-cache)
-      (define text-height #f)
-      (define last-dc #f)
+          (define-values (_1 text-height _2 _3) (send dc get-text-extent "Label" #f #f 0))
+          (define parents-and-children (append (get-all-parents snip)
+                                               (get-all-children snip)))
+          (define rects (get-rectangles snip parents-and-children))
+          (for ([rect (in-list rects)])
+            (save-rectangle-to-invalidate
+             (- (rect-left rect) text-height)
+             (- (rect-top rect)  text-height)
+             (+ (rect-right rect) text-height)
+             (+ (rect-bottom rect) text-height)))))
       
       (define pending-invalidate-rectangle #f)
       (define pending-invalidate-rectangle-timer #f)
+      (inherit invalidate-bitmap-cache)
       (define/private (run-pending-invalidate-rectangle)
         (define the-pending-invalidate-rectangle pending-invalidate-rectangle)
         (set! pending-invalidate-rectangle #f)
@@ -445,15 +427,16 @@
           (set! pending-invalidate-rectangle-timer 
                 (new timer% [notify-callback
                              (λ () (run-pending-invalidate-rectangle))])))
-        (cond
-          [pending-invalidate-rectangle
-           (match pending-invalidate-rectangle
-             [(list l2 t2 r2 b2)
-              (set! pending-invalidate-rectangle 
-                    (list (min l l2) (min t t2) (max r r2) (max b b2)))])]
-          [else
-           (set! pending-invalidate-rectangle (list l t r b))])
+        (add-to-pending-indvalidate-rectangle l t r b)
         (send pending-invalidate-rectangle-timer start 20 #t))
+      
+      (define/private (add-to-pending-indvalidate-rectangle l t r b)
+        (set! pending-invalidate-rectangle
+              (match pending-invalidate-rectangle
+                [(list l2 t2 r2 b2)
+                 (list (min l l2) (min t t2) (max r r2) (max b b2))]
+                [#f
+                 (list l t r b)])))
 
       ;; get-rectangles : snip (listof snip) -> rect
       ;; computes the rectangles that need to be invalidated for connecting 
@@ -521,7 +504,11 @@
           (let ([old-font (send dc get-font)])
             (when edge-label-font
               (send dc set-font edge-label-font))
-            (unless pending-invalidate-rectangle (draw-edges dc left top right bottom dx dy))
+            (cond
+              [pending-invalidate-rectangle
+               (add-to-pending-indvalidate-rectangle left top right bottom)]
+              [else
+               (draw-edges dc left top right bottom dx dy)])
             (when edge-label-font
               (send dc set-font old-font))))
         (super on-paint before? dc left top right bottom dx dy draw-caret))