diff --git a/collects/mred/private/wx/cocoa/button.rkt b/collects/mred/private/wx/cocoa/button.rkt
index 5cf3a5581a..466382e8c5 100644
--- a/collects/mred/private/wx/cocoa/button.rkt
+++ b/collects/mred/private/wx/cocoa/button.rkt
@@ -25,9 +25,9 @@
 
 (define-objc-class MyButton NSButton
   #:mixins (FocusResponder KeyMouseResponder)
-  [wx]
+  [wxb]
   (-a _void (clicked: [_id sender])
-      (queue-window-event wx (lambda () (send wx clicked)))))
+      (queue-window*-event wxb (lambda (wx) (send wx clicked)))))
 
 (defclass core-button% item%
   (init parent cb label x y w h style font
@@ -99,10 +99,12 @@
                         (tellv button-cocoa setFrame: #:type _NSRect
                                (make-NSRect (make-NSPoint 0 0)
                                             (make-NSSize new-width new-height)))
-                        (set-ivar! button-cocoa wx this)
+                        (set-ivar! button-cocoa wxb (->wxb this))
                         cocoa))
                     button-cocoa))
 
+  (define we (make-will-executor))
+
   (super-new [parent parent]
              [cocoa cocoa]
              [no-show? (memq 'deleted style)]
diff --git a/collects/mred/private/wx/cocoa/canvas.rkt b/collects/mred/private/wx/cocoa/canvas.rkt
index 3ca578d1d3..3faad655bb 100644
--- a/collects/mred/private/wx/cocoa/canvas.rkt
+++ b/collects/mred/private/wx/cocoa/canvas.rkt
@@ -28,37 +28,48 @@
 (import-protocol NSComboBoxDelegate)
 
 ;; Called when a canvas has no backing store ready
-(define (clear-background wx)
-  (let ([bg (send wx get-canvas-background-for-clearing)])
-    (when bg
-      (let ([ctx (tell NSGraphicsContext currentContext)])
-        (tellv ctx saveGraphicsState)
-        (let ([cg (tell #:type _CGContextRef ctx graphicsPort)]
-              [adj (lambda (v) (/ v 255.0))])
-          (CGContextSetRGBFillColor cg
-                                    (adj (color-red bg))
-                                    (adj (color-blue bg))
-                                    (adj (color-green bg))
-                                    1.0)
-          (CGContextFillRect cg (make-NSRect (make-NSPoint 0 0)
-                                             (make-NSSize 32000 32000))))
-        (tellv ctx restoreGraphicsState)))))
+(define (clear-background wxb)
+  (let ([wx (->wx wxb)])
+    (when wx
+      (let ([bg (send wx get-canvas-background-for-clearing)])
+        (when bg
+          (let ([ctx (tell NSGraphicsContext currentContext)])
+            (tellv ctx saveGraphicsState)
+            (let ([cg (tell #:type _CGContextRef ctx graphicsPort)]
+                  [adj (lambda (v) (/ v 255.0))])
+              (CGContextSetRGBFillColor cg
+                                        (adj (color-red bg))
+                                        (adj (color-blue bg))
+                                        (adj (color-green bg))
+                                        1.0)
+              (CGContextFillRect cg (make-NSRect (make-NSPoint 0 0)
+                                                 (make-NSSize 32000 32000))))
+            (tellv ctx restoreGraphicsState)))))))
 
 (define-objc-class MyView NSView 
   #:mixins (FocusResponder KeyMouseResponder) 
-  [wx]
+  [wxb]
   (-a _void (drawRect: [_NSRect r])
-      (unless (send wx paint-or-queue-paint)
-        (clear-background wx)
-        ;; ensure that `nextEventMatchingMask:' returns
-        (post-dummy-event)))
+      (when wxb
+        (let ([wx (->wx wxb)])
+          (when wx
+            (unless (send wx paint-or-queue-paint)
+              (clear-background wxb)
+              ;; ensure that `nextEventMatchingMask:' returns
+              (post-dummy-event))))))
   (-a _void (viewWillMoveToWindow: [_id w])
-      (when wx
-        (queue-window-event wx (lambda () (send wx fix-dc)))))
+      (when wxb
+        (let ([wx (->wx wxb)])
+          (when wx
+            (queue-window-event wx (lambda () (send wx fix-dc)))))))
   (-a _void (onHScroll: [_id scroller])
-      (when wx (send wx do-scroll 'horizontal scroller)))
+      (when wxb 
+        (let ([wx (->wx wxb)])
+          (when wx (send wx do-scroll 'horizontal scroller)))))
   (-a _void (onVScroll: [_id scroller])
-      (when wx (send wx do-scroll 'vertical scroller))))
+      (when wxb 
+        (let ([wx (->wx wxb)])
+          (when wx (send wx do-scroll 'vertical scroller))))))
 
 (define-objc-class FrameView NSView 
   []
@@ -118,22 +129,30 @@
 (define-objc-class MyComboBox NSComboBox
   #:mixins (FocusResponder KeyMouseResponder) 
   #:protocols (NSComboBoxDelegate)
-  [wx]
+  [wxb]
   (-a _void (drawRect: [_NSRect r])
       (super-tell #:type _void drawRect: #:type _NSRect r)
-      (unless (send wx paint-or-queue-paint)
-        (unless (send wx during-menu-click?)
-          (clear-background wx)
-          ;; ensure that `nextEventMatchingMask:' returns
-          (post-dummy-event))))
+      (let ([wx (->wx wxb)])
+        (when wx
+          (unless (send wx paint-or-queue-paint)
+            (unless (send wx during-menu-click?)
+              (clear-background wxb)
+              ;; ensure that `nextEventMatchingMask:' returns
+              (post-dummy-event))))))
   (-a _void (comboBoxWillPopUp: [_id notification])
-      (send wx starting-combo))
+      (let ([wx (->wx wxb)])
+        (when wx
+          (send wx starting-combo))))
   (-a _void (comboBoxWillDismiss: [_id notification])
-      (send wx ending-combo))
+      (let ([wx (->wx wxb)])
+        (when wx
+          (send wx ending-combo))))
   (-a _void (viewWillMoveToWindow: [_id w])
-      (when wx
-        (queue-window-event wx (lambda () (send wx fix-dc))))))
-
+      (when wxb
+        (let ([wx (->wx wxb)])
+          (when wx
+            (queue-window-event wx (lambda () (send wx fix-dc))))))))
+  
 (define-struct scroller (cocoa [range #:mutable] [page #:mutable]))
 (define scroll-width (tell #:type _CGFloat NSScroller scrollerWidth))
 
@@ -247,7 +266,7 @@
          (tell (tell (if is-combo? MyComboBox MyView) alloc) 
                initWithFrame: #:type _NSRect r))))
     (tell #:type _void cocoa addSubview: content-cocoa)
-    (set-ivar! content-cocoa wx this)
+    (set-ivar! content-cocoa wxb (->wxb this))
 
     (when is-combo?
       (tellv content-cocoa setEditable: #:type _BOOL #f)
diff --git a/collects/mred/private/wx/cocoa/choice.rkt b/collects/mred/private/wx/cocoa/choice.rkt
index e94fc82bec..71b7970732 100644
--- a/collects/mred/private/wx/cocoa/choice.rkt
+++ b/collects/mred/private/wx/cocoa/choice.rkt
@@ -20,9 +20,9 @@
 
 (define-objc-class MyPopUpButton NSPopUpButton 
   #:mixins (FocusResponder KeyMouseResponder)
-  [wx]
+  [wxb]
   (-a _void (clicked: [_id sender])
-      (queue-window-event wx (lambda () (send wx clicked)))))
+      (queue-window*-event wxb (lambda (wx) (send wx clicked)))))
 
 (defclass choice% item%
   (init parent cb label
diff --git a/collects/mred/private/wx/cocoa/frame.rkt b/collects/mred/private/wx/cocoa/frame.rkt
index 660a13a038..39b18c8da2 100644
--- a/collects/mred/private/wx/cocoa/frame.rkt
+++ b/collects/mred/private/wx/cocoa/frame.rkt
@@ -30,49 +30,56 @@
 (define dialog-level-counter 0)
 
 (define-objc-mixin (MyWindowMethods Superclass)
-  [wx]
+  [wxb]
   [-a _scheme (getEventspace)
-      (send wx get-eventspace)]
+      (let ([wx (->wx wxb)])
+        (and wx (send wx get-eventspace)))]
   [-a _BOOL (canBecomeKeyWindow)
-      (not (other-modal? wx))]
+      (let ([wx (->wx wxb)])
+        (and wx
+             (not (other-modal? wx))))]
   [-a _BOOL (canBecomeMainWindow) #t]
   [-a _BOOL (windowShouldClose: [_id win])
-      (queue-window-event wx (lambda ()
-                               (unless (other-modal? wx)
-                                 (when (send wx on-close)
-                                   (send wx direct-show #f)))))
+      (queue-window*-event wxb (lambda (wx)
+                                 (unless (other-modal? wx)
+                                   (when (send wx on-close)
+                                     (send wx direct-show #f)))))
       #f]
   [-a _void (windowDidResize: [_id notification])
-      (when wx
-        (queue-window-event wx (lambda ()
-                                 (send wx on-size 0 0)
-                                 (send wx clean-up))))]
+      (when wxb
+        (queue-window*-event wxb (lambda (wx)
+                                   (send wx on-size 0 0)
+                                   (send wx clean-up))))]
   [-a _void (windowDidMove: [_id notification])
-      (when wx
-        (queue-window-event wx (lambda ()
-                                 (send wx on-size 0 0))))]
+      (when wxb
+        (queue-window*-event wxb (lambda (wx)
+                                   (send wx on-size 0 0))))]
   [-a _void (windowDidBecomeMain: [_id notification])
-      (when wx
-        (set! front wx)
-        (send wx install-mb)
-        (send wx notify-responder #t)
-        (queue-window-event wx (lambda ()
-                                 (send wx on-activate #t))))]
+      (when wxb
+        (let ([wx (->wx wxb)])
+          (when wx
+            (set! front wx)
+            (send wx install-mb)
+            (send wx notify-responder #t)
+            (queue-window-event wx (lambda ()
+                                     (send wx on-activate #t))))))]
   [-a _void (windowDidResignMain: [_id notification])
-      (when wx
-        (when (eq? front wx) (set! front #f))
-        (send empty-mb install)
-        (send wx notify-responder #f)
-        (queue-window-event wx (lambda ()
-                                 (send wx on-activate #f))))])
+      (when wxb
+        (let ([wx (->wx wxb)])
+          (when wx
+            (when (eq? front wx) (set! front #f))
+            (send empty-mb install)
+            (send wx notify-responder #f)
+            (queue-window-event wx (lambda ()
+                                     (send wx on-activate #f))))))])
 
 (define-objc-class MyWindow NSWindow
   #:mixins (FocusResponder KeyMouseResponder MyWindowMethods)
-  [wx])
+  [wxb])
 
 (define-objc-class MyPanel NSPanel
   #:mixins (FocusResponder KeyMouseResponder MyWindowMethods)
-  [wx])
+  [wxb])
 
 (set-front-hook! (lambda () (values front
                                     (and front (send front get-eventspace)))))
diff --git a/collects/mred/private/wx/cocoa/gauge.rkt b/collects/mred/private/wx/cocoa/gauge.rkt
index db13bb784f..32241caa46 100644
--- a/collects/mred/private/wx/cocoa/gauge.rkt
+++ b/collects/mred/private/wx/cocoa/gauge.rkt
@@ -19,7 +19,7 @@
 
 (define-objc-class MyProgressIndicator NSProgressIndicator
   #:mixins ()
-  [wx])
+  [wxb])
 
 (defclass gauge% item%
   (init parent
diff --git a/collects/mred/private/wx/cocoa/group-panel.rkt b/collects/mred/private/wx/cocoa/group-panel.rkt
index 73588a0a2e..0b367e474c 100644
--- a/collects/mred/private/wx/cocoa/group-panel.rkt
+++ b/collects/mred/private/wx/cocoa/group-panel.rkt
@@ -16,7 +16,7 @@
 
 (define-objc-class MyBox NSBox
   #:mixins (FocusResponder KeyMouseResponder)
-  [wx])
+  [wxb])
 
 (defclass group-panel% (panel-mixin window%)
   (init parent
diff --git a/collects/mred/private/wx/cocoa/list-box.rkt b/collects/mred/private/wx/cocoa/list-box.rkt
index 7fda6f6e0f..434ef4b8f9 100644
--- a/collects/mred/private/wx/cocoa/list-box.rkt
+++ b/collects/mred/private/wx/cocoa/list-box.rkt
@@ -23,23 +23,29 @@
 
 (define-objc-class MyTableView NSTableView
   #:mixins (FocusResponder KeyMouseResponder)
-  [wx]
+  [wxb]
   [-a _id (preparedCellAtColumn: [_NSInteger column] row: [_NSInteger row])
-      (tell (tell NSCell alloc) initTextCell: #:type _NSString (send wx get-row row))]
+      (let ([wx (->wx wxb)])
+        (tell (tell NSCell alloc) initTextCell: #:type _NSString 
+              (if wx (send wx get-row row) "???")))]
   [-a _void (doubleClicked: [_id sender])
-      (queue-window-event wx (lambda () (send wx clicked 'list-box-dclick)))]
+      (queue-window*-event wxb (lambda (wx) (send wx clicked 'list-box-dclick)))]
   [-a _void (tableViewSelectionDidChange: [_id aNotification])
-      (queue-window-event wx (lambda () (send wx clicked 'list-box)))])
+      (queue-window*-event wxb (lambda (wx) (send wx clicked 'list-box)))])
 
 (define-objc-class MyDataSource NSObject
   #:protocols (NSTableViewDataSource)
-  [wx]
+  [wxb]
   [-a _NSInteger (numberOfRowsInTableView: [_id view])
-      (send wx number)]
+      (let ([wx (->wx wxb)])
+        (send wx number))]
   [-a _NSString (tableView: [_id aTableView]
                             objectValueForTableColumn: [_id aTableColumn]
                             row: [_NSInteger rowIndex])
-      (send wx get-row rowIndex)])
+      (let ([wx (->wx wxb)])
+        (if wx
+            (send wx get-row rowIndex)
+            "???"))])
 
 (define (remove-nth data i)
   (cond
@@ -55,7 +61,7 @@
 
   (define source (as-objc-allocation
                   (tell (tell MyDataSource alloc) init)))
-  (set-ivar! source wx this)
+  (set-ivar! source wxb (->wxb this))
 
   (define items choices)
   (define data (map (lambda (x) (box #f)) choices))
@@ -73,7 +79,7 @@
                                  (tell (tell NSTableColumn alloc) initWithIdentifier: content-cocoa)))
                          (init-font content-cocoa font)
                          content-cocoa))
-  (set-ivar! content-cocoa wx this)
+  (set-ivar! content-cocoa wxb (->wxb this))
 
   (tellv cocoa setDocumentView: content-cocoa)
   (tellv cocoa setHasVerticalScroller: #:type _BOOL #t)
diff --git a/collects/mred/private/wx/cocoa/menu-item.rkt b/collects/mred/private/wx/cocoa/menu-item.rkt
index 29365d24df..2e532ebb44 100644
--- a/collects/mred/private/wx/cocoa/menu-item.rkt
+++ b/collects/mred/private/wx/cocoa/menu-item.rkt
@@ -14,8 +14,11 @@
 (import-class NSMenuItem)
 
 (define-objc-class MyMenuItem NSMenuItem
-  [wx]
-  (-a _void (selected: [_id sender]) (send wx selected)))
+  [wxb]
+  (-a _void (selected: [_id sender]) 
+      (let ([wx (->wx wxb)])
+        (when wx
+          (send wx selected)))))
 
 
 (defclass menu-item% object%
@@ -51,7 +54,7 @@
                           initWithTitle: #:type _NSString (regexp-replace #rx"\t.*" label "")
                           action: #:type _SEL #f
                           keyEquivalent: #:type _NSString "")])
-          (set-ivar! item wx this)
+          (set-ivar! item wxb (->wxb this))
           (tellv menu addItem: item)
           (tellv item setEnabled: #:type _BOOL enabled?)
           (tellv item setTarget: item)
diff --git a/collects/mred/private/wx/cocoa/message.rkt b/collects/mred/private/wx/cocoa/message.rkt
index 68d5cc4474..0fce8fc5eb 100644
--- a/collects/mred/private/wx/cocoa/message.rkt
+++ b/collects/mred/private/wx/cocoa/message.rkt
@@ -33,11 +33,11 @@
 
 (define-objc-class MyTextField NSTextField
   #:mixins (FocusResponder KeyMouseResponder)
-  [wx])
+  [wxb])
 
 (define-objc-class MyImageView NSImageView
   #:mixins (FocusResponder KeyMouseResponder)
-  [wx])
+  [wxb])
 
 (defclass message% item%
   (init parent label
diff --git a/collects/mred/private/wx/cocoa/radio-box.rkt b/collects/mred/private/wx/cocoa/radio-box.rkt
index 211410e68c..fce42e5c8e 100644
--- a/collects/mred/private/wx/cocoa/radio-box.rkt
+++ b/collects/mred/private/wx/cocoa/radio-box.rkt
@@ -25,9 +25,9 @@
 
 (define-objc-class MyMatrix NSMatrix
   #:mixins (FocusResponder KeyMouseResponder)
-  [wx]
+  [wxb]
   (-a _void (clicked: [_id sender])
-      (queue-window-event wx (lambda () (send wx clicked)))))
+      (queue-window*-event wxb (lambda (wx) (send wx clicked)))))
 
 (define-objc-class MyImageButtonCell NSButtonCell
   [img]
diff --git a/collects/mred/private/wx/cocoa/slider.rkt b/collects/mred/private/wx/cocoa/slider.rkt
index c0a8e7804d..92dd980a48 100644
--- a/collects/mred/private/wx/cocoa/slider.rkt
+++ b/collects/mred/private/wx/cocoa/slider.rkt
@@ -23,13 +23,15 @@
 
 (define-objc-class MySlider NSSlider
   #:mixins (FocusResponder KeyMouseResponder)
-  [wx]
+  [wxb]
   (-a _void (changed: [_id sender])
-      (queue-window-event wx (lambda () (send wx changed)))
-      (constrained-reply
-       (send wx get-eventspace)
-       (lambda () (let loop () (pre-event-sync #t) (when (yield) (loop))))
-       (void))))
+      (let ([wx (->wx wxb)])
+        (when wx
+          (queue-window-event wx (lambda () (send wx changed)))
+          (constrained-reply
+           (send wx get-eventspace)
+           (lambda () (let loop () (pre-event-sync #t) (when (yield) (loop))))
+           (void))))))
 
 (defclass slider% item%
   (init parent cb
diff --git a/collects/mred/private/wx/cocoa/tab-panel.rkt b/collects/mred/private/wx/cocoa/tab-panel.rkt
index 175e4d40b0..9a11f8a442 100644
--- a/collects/mred/private/wx/cocoa/tab-panel.rkt
+++ b/collects/mred/private/wx/cocoa/tab-panel.rkt
@@ -20,9 +20,9 @@
 (define-objc-class MyTabView NSTabView
   #:mixins (FocusResponder KeyMouseResponder)
   #:protocols (NSTabViewDelegate)
-  [wx]
+  [wxb]
   (-a _void (tabView: [_id cocoa] didSelectTabViewItem: [_id item-cocoa])
-      (queue-window-event wx (lambda () (send wx do-callback)))))
+      (queue-window*-event wxb (lambda (wx) (send wx do-callback)))))
 
 (defclass tab-panel% (panel-mixin window%)
   (init parent
diff --git a/collects/mred/private/wx/cocoa/utils.rkt b/collects/mred/private/wx/cocoa/utils.rkt
index 132b691ffb..72167b6ccf 100644
--- a/collects/mred/private/wx/cocoa/utils.rkt
+++ b/collects/mred/private/wx/cocoa/utils.rkt
@@ -14,7 +14,9 @@
          as-objc-allocation
          retain release
          with-autorelease
-         clean-menu-label)
+         clean-menu-label
+         ->wxb
+         ->wx)
 
 (define cocoa-lib (ffi-lib (format "/System/Library/Frameworks/Cocoa.framework/Cocoa")))
 (define cf-lib (ffi-lib (format "/System/Library/Frameworks/CoreFoundation.framework/CoreFoundation")))
@@ -50,3 +52,9 @@
 
 (define (clean-menu-label str)
   (regexp-replace* #rx"&(.)" str "\\1"))
+
+(define (->wxb wx)
+  (make-weak-box wx))
+
+(define (->wx wxb)
+  (weak-box-value wxb))
diff --git a/collects/mred/private/wx/cocoa/window.rkt b/collects/mred/private/wx/cocoa/window.rkt
index 0796b38cdd..9361147c42 100644
--- a/collects/mred/private/wx/cocoa/window.rkt
+++ b/collects/mred/private/wx/cocoa/window.rkt
@@ -21,6 +21,7 @@
          KeyMouseResponder
 
          queue-window-event
+         queue-window*-event
          request-flush-delay
          cancel-flush-delay)
 
@@ -29,30 +30,30 @@
 ;; ----------------------------------------
 
 (define-objc-mixin (FocusResponder Superclass)
-  [wx]
+  [wxb]
   [-a _BOOL (acceptsFirstResponder)
       #t]
   [-a _BOOL (becomeFirstResponder)
       (and (super-tell becomeFirstResponder)
-           (begin
-             (send wx is-responder wx #t)
+           (let ([wx (->wx wxb)])
+             (when wx (send wx is-responder wx #t))
              #t))]
   [-a _BOOL (resignFirstResponder)
       (and (super-tell resignFirstResponder)
-           (begin
-             (send wx is-responder wx #f)
+           (let ([wx (->wx wxb)])
+             (when wx (send wx is-responder wx #f))
              #t))])
 
 (define-objc-mixin (KeyMouseResponder Superclass)
-  [wx]
+  [wxb]
   [-a _void (mouseDown: [_id event]) 
-      (unless (do-mouse-event wx event 'left-down #t #f #f 'right-down)
+      (unless (do-mouse-event wxb event 'left-down #t #f #f 'right-down)
         (super-tell #:type _void mouseDown: event))]
   [-a _void (mouseUp: [_id event]) 
-      (unless (do-mouse-event wx event 'left-up #f #f #f 'right-up)
+      (unless (do-mouse-event wxb event 'left-up #f #f #f 'right-up)
         (super-tell #:type _void mouseUp: event))]
   [-a _void (mouseDragged: [_id event]) 
-      (unless (do-mouse-event wx event 'motion #t #f #f)
+      (unless (do-mouse-event wxb event 'motion #t #f #f)
         (super-tell #:type _void mouseDragged: event))]
   [-a _void (mouseMoved: [_id event]) 
       ;; This event is sent to the first responder, instead of the
@@ -69,94 +70,102 @@
                 (loop (tell hit superview))))))]
   [-a _BOOL (doMouseMoved: [_id event]) 
       ;; called by mouseMoved:
-      (do-mouse-event wx event 'motion #f #f #f)]
+      (do-mouse-event wxb event 'motion #f #f #f)]
   [-a _void (mouseEntered: [_id event]) 
-      (unless (do-mouse-event wx event 'enter #f #f #f)
+      (unless (do-mouse-event wxb event 'enter #f #f #f)
         (super-tell #:type _void mouseEntered: event))]
   [-a _void (mouseExited: [_id event]) 
-      (unless (do-mouse-event wx event 'leave #f #f #f)
+      (unless (do-mouse-event wxb event 'leave #f #f #f)
         (super-tell #:type _void mouseExited: event))]
   [-a _void (rightMouseDown: [_id event]) 
-      (unless (do-mouse-event wx event 'right-down #f #f #t)
+      (unless (do-mouse-event wxb event 'right-down #f #f #t)
         (super-tell #:type _void rightMouseDown: event))]
   [-a _void (rightMouseUp: [_id event]) 
-      (unless (do-mouse-event wx event 'right-up #f #f #f)
+      (unless (do-mouse-event wxb event 'right-up #f #f #f)
         (super-tell #:type _void rightMouseUp: event))]
   [-a _void (rightMouseDragged: [_id event]) 
-      (unless (do-mouse-event wx event 'motion #f #f #t)
+      (unless (do-mouse-event wxb event 'motion #f #f #t)
         (super-tell #:type _void rightMouseDragged: event))]
   [-a _void (otherMouseDown: [_id event]) 
-      (unless (do-mouse-event wx event 'middle-down #f #t #f)
+      (unless (do-mouse-event wxb event 'middle-down #f #t #f)
         (super-tell #:type _void otherMouseDown: event))]
   [-a _void (otherMouseUp: [_id event]) 
-      (unless (do-mouse-event wx event 'middle-up #f #f #f)
+      (unless (do-mouse-event wxb event 'middle-up #f #f #f)
         (super-tell #:type _void otherMouseUp: event))]
   [-a _void (otherMouseDragged: [_id event]) 
-      (unless (do-mouse-event wx event 'motion #f #t #f)
+      (unless (do-mouse-event wxb event 'motion #f #t #f)
         (super-tell #:type _void otherMouseDragged: event))]
   
   [-a _void (keyDown: [_id event])
-      (unless (do-key-event wx event)
+      (unless (do-key-event wxb event)
         (super-tell #:type _void keyDown: event))]
   [-a _void (insertText: [_NSString str])
-      (queue-window-event wx (lambda ()
-                               (send wx key-event-as-string str)))])
+      (let ([wx (->wx wxb)])
+        (when wx
+          (queue-window-event wx (lambda ()
+                                   (send wx key-event-as-string str)))))])
 
-(define (do-key-event wx event)
-  (let* ([modifiers (tell #:type _NSUInteger event modifierFlags)]
-         [bit? (lambda (m b) (positive? (bitwise-and m b)))]
-         [pos (tell #:type _NSPoint event locationInWindow)]
-         [str (tell #:type _NSString event characters)])
-    (let-values ([(x y) (send wx window-point-to-view pos)])
-      (let ([k (new key-event%
-                    [key-code (or
-                               (map-key-code (tell #:type _ushort event keyCode))
-                               (if (string=? "" str)
-                                   #\nul
-                                   (string-ref str 0)))]
-                    [shift-down (bit? modifiers NSShiftKeyMask)]
-                    [control-down (bit? modifiers NSControlKeyMask)]
-                    [meta-down (bit? modifiers NSCommandKeyMask)]
-                    [alt-down (bit? modifiers NSAlternateKeyMask)]
-                    [x (->long x)]
-                    [y (->long y)]
-                    [time-stamp (->long (* (tell #:type _double event timestamp) 1000.0))]
-                    [caps-down (bit? modifiers NSAlphaShiftKeyMask)])])
-        (if (send wx definitely-wants-event? k)
-            (begin
-              (queue-window-event wx (lambda ()
-                                       (send wx dispatch-on-char k #f)))
-              #t)
-            (constrained-reply (send wx get-eventspace)
-                               (lambda () (send wx dispatch-on-char k #t))
-                               #t))))))
+(define (do-key-event wxb event)
+  (let ([wx (->wx wxb)])
+    (and
+     wx
+     (let* ([modifiers (tell #:type _NSUInteger event modifierFlags)]
+            [bit? (lambda (m b) (positive? (bitwise-and m b)))]
+            [pos (tell #:type _NSPoint event locationInWindow)]
+            [str (tell #:type _NSString event characters)])
+       (let-values ([(x y) (send wx window-point-to-view pos)])
+         (let ([k (new key-event%
+                       [key-code (or
+                                  (map-key-code (tell #:type _ushort event keyCode))
+                                  (if (string=? "" str)
+                                      #\nul
+                                      (string-ref str 0)))]
+                       [shift-down (bit? modifiers NSShiftKeyMask)]
+                       [control-down (bit? modifiers NSControlKeyMask)]
+                       [meta-down (bit? modifiers NSCommandKeyMask)]
+                       [alt-down (bit? modifiers NSAlternateKeyMask)]
+                       [x (->long x)]
+                       [y (->long y)]
+                       [time-stamp (->long (* (tell #:type _double event timestamp) 1000.0))]
+                       [caps-down (bit? modifiers NSAlphaShiftKeyMask)])])
+           (if (send wx definitely-wants-event? k)
+               (begin
+                 (queue-window-event wx (lambda ()
+                                          (send wx dispatch-on-char k #f)))
+                 #t)
+               (constrained-reply (send wx get-eventspace)
+                                  (lambda () (send wx dispatch-on-char k #t))
+                                  #t))))))))
 
-(define (do-mouse-event wx event kind l? m? r? [ctl-kind kind])
-  (let* ([modifiers (tell #:type _NSUInteger event modifierFlags)]
-         [bit? (lambda (m b) (positive? (bitwise-and m b)))]
-         [pos (tell #:type _NSPoint event locationInWindow)])
-    (let-values ([(x y) (send wx window-point-to-view pos)]
-                 [(control-down) (bit? modifiers NSControlKeyMask)])
-      (let ([m (new mouse-event%
-                    [event-type (if control-down ctl-kind kind)]
-                    [left-down (and l? (not control-down))]
-                    [middle-down m?]
-                    [right-down (or r? (and l? control-down))]
-                    [x (->long x)]
-                    [y (->long y)]
-                    [shift-down (bit? modifiers NSShiftKeyMask)]
-                    [meta-down (bit? modifiers NSCommandKeyMask)]
-                    [alt-down (bit? modifiers NSAlternateKeyMask)]
-                    [time-stamp (->long (* (tell #:type _double event timestamp) 1000.0))]
-                    [caps-down (bit? modifiers NSAlphaShiftKeyMask)])])
-        (if (send wx definitely-wants-event? m)
-            (begin
-              (queue-window-event wx (lambda ()
-                                       (send wx dispatch-on-event m #f)))
-              #t)
-            (constrained-reply (send wx get-eventspace)
-                               (lambda () (send wx dispatch-on-event m #t))
-                               #t))))))
+(define (do-mouse-event wxb event kind l? m? r? [ctl-kind kind])
+  (let ([wx (->wx wxb)])
+    (and
+     wx
+     (let* ([modifiers (tell #:type _NSUInteger event modifierFlags)]
+            [bit? (lambda (m b) (positive? (bitwise-and m b)))]
+            [pos (tell #:type _NSPoint event locationInWindow)])
+       (let-values ([(x y) (send wx window-point-to-view pos)]
+                    [(control-down) (bit? modifiers NSControlKeyMask)])
+         (let ([m (new mouse-event%
+                       [event-type (if control-down ctl-kind kind)]
+                       [left-down (and l? (not control-down))]
+                       [middle-down m?]
+                       [right-down (or r? (and l? control-down))]
+                       [x (->long x)]
+                       [y (->long y)]
+                       [shift-down (bit? modifiers NSShiftKeyMask)]
+                       [meta-down (bit? modifiers NSCommandKeyMask)]
+                       [alt-down (bit? modifiers NSAlternateKeyMask)]
+                       [time-stamp (->long (* (tell #:type _double event timestamp) 1000.0))]
+                       [caps-down (bit? modifiers NSAlphaShiftKeyMask)])])
+           (if (send wx definitely-wants-event? m)
+               (begin
+                 (queue-window-event wx (lambda ()
+                                          (send wx dispatch-on-event m #f)))
+                 #t)
+               (constrained-reply (send wx get-eventspace)
+                                  (lambda () (send wx dispatch-on-event m #t))
+                                  #t))))))))
 
 (define window%
   (class object%
@@ -173,7 +182,7 @@
     (when (eventspace-shutdown? eventspace)
       (error '|GUI object initialization| "the eventspace has been shutdown"))
 
-    (set-ivar! cocoa wx this)
+    (set-ivar! cocoa wxb (->wxb this))
 
     (unless no-show?
       (show #t)) 
@@ -392,8 +401,13 @@
 
 ;; ----------------------------------------
 
-(define (queue-window-event win thunk)
-  (queue-event (send win get-eventspace) thunk))
+(define (queue-window-event wx thunk)
+  (queue-event (send wx get-eventspace) thunk))
+
+(define (queue-window*-event wxb proc)
+  (let ([wx (->wx wxb)])
+    (when wx
+      (queue-event (send wx get-eventspace) (lambda () (proc wx))))))
 
 (define depth 0)
 
diff --git a/collects/mred/private/wx/gtk/button.rkt b/collects/mred/private/wx/gtk/button.rkt
index 8277ffe0e4..41a0388ddc 100644
--- a/collects/mred/private/wx/gtk/button.rkt
+++ b/collects/mred/private/wx/gtk/button.rkt
@@ -29,7 +29,8 @@
   (_fun _GtkWidget -> _void)
   (lambda (gtk)
     (let ([wx (gtk->wx gtk)])
-      (send wx queue-clicked))))
+      (when wx
+        (send wx queue-clicked)))))
 
 (defclass button-core% item%
   (init parent cb label x y w h style font
diff --git a/collects/mred/private/wx/gtk/canvas.rkt b/collects/mred/private/wx/gtk/canvas.rkt
index b847499eeb..cf625f6e53 100644
--- a/collects/mred/private/wx/gtk/canvas.rkt
+++ b/collects/mred/private/wx/gtk/canvas.rkt
@@ -121,7 +121,8 @@
   (_fun _GtkWidget -> _void)
   (lambda (gtk)
     (let ([wx (gtk->wx gtk)])
-      (send wx combo-maybe-clicked))))
+      (when wx
+        (send wx combo-maybe-clicked)))))
 
 (define-gtk gtk_combo_box_set_active (_fun _GtkWidget _int -> _void))
 (define-gtk gtk_combo_box_get_active (_fun _GtkWidget -> _int))
@@ -130,11 +131,12 @@
   (_fun _GtkWidget _GdkEventExpose-pointer -> _gboolean)
   (lambda (gtk event)
     (let ([wx (gtk->wx gtk)])
-      (unless (send wx paint-or-queue-paint)
-        (let ([gc (send wx get-canvas-background-for-clearing)])      
-          (when gc
-            (gdk_draw_rectangle (widget-window gtk) gc #t
-                                0 0 32000 32000)))))
+      (when wx
+        (unless (send wx paint-or-queue-paint)
+          (let ([gc (send wx get-canvas-background-for-clearing)])      
+            (when gc
+              (gdk_draw_rectangle (widget-window gtk) gc #t
+                                  0 0 32000 32000))))))
     #t))
 
 (define-signal-handler connect-expose-border "expose-event"
@@ -165,7 +167,8 @@
 
 (define (do-value-changed gtk dir)
   (let ([wx (gtk->wx gtk)])
-    (queue-window-event wx (lambda () (send wx do-scroll dir))))
+    (when wx
+      (queue-window-event wx (lambda () (send wx do-scroll dir)))))
   #t)
 
 (define-gtk gtk_entry_get_type (_fun -> _GType))
diff --git a/collects/mred/private/wx/gtk/choice.rkt b/collects/mred/private/wx/gtk/choice.rkt
index ce69a6487a..3f1238e84e 100644
--- a/collects/mred/private/wx/gtk/choice.rkt
+++ b/collects/mred/private/wx/gtk/choice.rkt
@@ -26,7 +26,8 @@
   (_fun _GtkWidget -> _void)
   (lambda (gtk)
     (let ([wx (gtk->wx gtk)])
-      (send wx queue-clicked))))
+      (when wx
+        (send wx queue-clicked)))))
 
 (defclass choice% item%
   (init parent cb label
diff --git a/collects/mred/private/wx/gtk/client-window.rkt b/collects/mred/private/wx/gtk/client-window.rkt
index 79b562a3f6..5c34d43c5f 100644
--- a/collects/mred/private/wx/gtk/client-window.rkt
+++ b/collects/mred/private/wx/gtk/client-window.rkt
@@ -17,11 +17,12 @@
   (_fun _GtkWidget _GtkAllocation-pointer -> _gboolean)
   (lambda (gtk a)
     (let ([wx (gtk->wx gtk)])
-      (send wx save-client-size 
-            (GtkAllocation-x a)
-            (GtkAllocation-y a)
-            (GtkAllocation-width a)
-            (GtkAllocation-height a)))
+      (when wx
+        (send wx save-client-size 
+              (GtkAllocation-x a)
+              (GtkAllocation-y a)
+              (GtkAllocation-width a)
+              (GtkAllocation-height a))))
     #t))
 
 (define (client-size-mixin %)
diff --git a/collects/mred/private/wx/gtk/frame.rkt b/collects/mred/private/wx/gtk/frame.rkt
index 64b1e7e4c6..3ba10a7cc8 100644
--- a/collects/mred/private/wx/gtk/frame.rkt
+++ b/collects/mred/private/wx/gtk/frame.rkt
@@ -56,18 +56,20 @@
   (_fun _GtkWidget -> _gboolean)
   (lambda (gtk)
     (let ([wx (gtk->wx gtk)])
-      (queue-window-event wx (lambda () 
-                               (unless (other-modal? wx)
-                                 (when (send wx on-close)
-                                   (send wx direct-show #f))))))))
+      (when wx
+        (queue-window-event wx (lambda () 
+                                 (unless (other-modal? wx)
+                                   (when (send wx on-close)
+                                     (send wx direct-show #f)))))))))
 
 (define-signal-handler connect-configure "configure-event"
   (_fun _GtkWidget _GdkEventConfigure-pointer -> _gboolean)
   (lambda (gtk a)
     (let ([wx (gtk->wx gtk)])
-      (send wx remember-size 
-            (GdkEventConfigure-width a)
-            (GdkEventConfigure-height a)))
+      (when wx
+        (send wx remember-size 
+              (GdkEventConfigure-width a)
+              (GdkEventConfigure-height a))))
     #f))
 
 (define-cstruct _GdkEventWindowState ([type _int]
@@ -81,9 +83,10 @@
   (_fun _GtkWidget _GdkEventWindowState-pointer -> _gboolean)
   (lambda (gtk evt)
     (let ([wx (gtk->wx gtk)])
-      (send wx on-window-state 
-            (GdkEventWindowState-changed_mask evt)
-            (GdkEventWindowState-new_window_state evt)))
+      (when wx
+        (send wx on-window-state 
+              (GdkEventWindowState-changed_mask evt)
+              (GdkEventWindowState-new_window_state evt))))
     #f))
 
 (define frame%
diff --git a/collects/mred/private/wx/gtk/list-box.rkt b/collects/mred/private/wx/gtk/list-box.rkt
index 4544f7780d..7e4f7f282e 100644
--- a/collects/mred/private/wx/gtk/list-box.rkt
+++ b/collects/mred/private/wx/gtk/list-box.rkt
@@ -62,7 +62,8 @@
   (_fun _GtkWidget -> _void)
   (lambda (gtk)
     (let ([wx (gtk->wx gtk)])
-      (send wx queue-changed))))
+      (when wx
+        (send wx queue-changed)))))
 
 (defclass list-box% item%
   (init parent cb
diff --git a/collects/mred/private/wx/gtk/menu-bar.rkt b/collects/mred/private/wx/gtk/menu-bar.rkt
index b1afb74aee..a51a944a38 100644
--- a/collects/mred/private/wx/gtk/menu-bar.rkt
+++ b/collects/mred/private/wx/gtk/menu-bar.rkt
@@ -41,11 +41,12 @@
   (_fun _GtkWidget -> _void)
   (lambda (gtk)
     (let ([wx (gtk->wx gtk)])
-      (let ([frame (send wx get-top-window)])
-        (when frame
-          (constrained-reply (send frame get-eventspace)
-                             (lambda () (send frame on-menu-click))
-                             (void)))))))
+      (when wx
+        (let ([frame (send wx get-top-window)])
+          (when frame
+            (constrained-reply (send frame get-eventspace)
+                               (lambda () (send frame on-menu-click))
+                               (void))))))))
 
 (define top-menu%
   (class widget%
@@ -57,13 +58,15 @@
   (_fun _GtkWidget _GdkEventKey-pointer -> _gboolean)
   (lambda (gtk event)
     (let ([wx (gtk->wx gtk)])
-      (other-modal? wx))))
+      (or (not wx)
+          (other-modal? wx)))))
 
 (define-signal-handler connect-menu-button-press "button-press-event"
   (_fun _GtkWidget _GdkEventButton-pointer -> _gboolean)
   (lambda (gtk event)
     (let ([wx (gtk->wx gtk)])
-      (other-modal? wx))))
+      (or (not wx)
+          (other-modal? wx)))))
 
 (defclass menu-bar% widget%
   (inherit install-widget-parent)
diff --git a/collects/mred/private/wx/gtk/menu.rkt b/collects/mred/private/wx/gtk/menu.rkt
index d3ef2afd87..0698d6a49b 100644
--- a/collects/mred/private/wx/gtk/menu.rkt
+++ b/collects/mred/private/wx/gtk/menu.rkt
@@ -36,13 +36,15 @@
   (_fun _GtkWidget -> _void)
   (lambda (gtk)
     (let ([wx (gtk->wx gtk)])
-      (send wx do-on-select))))
+      (when wx
+        (send wx do-on-select)))))
 
 (define-signal-handler connect-menu-deactivate "deactivate"
   (_fun _GtkWidget -> _void)
   (lambda (gtk)
     (let ([wx (gtk->wx gtk)])
-      (send wx do-no-selected))))
+      (when wx
+        (send wx do-no-selected)))))
 
 (define menu-item-handler%
   (class widget%
diff --git a/collects/mred/private/wx/gtk/radio-box.rkt b/collects/mred/private/wx/gtk/radio-box.rkt
index 68285a9d15..e1c2087931 100644
--- a/collects/mred/private/wx/gtk/radio-box.rkt
+++ b/collects/mred/private/wx/gtk/radio-box.rkt
@@ -31,7 +31,8 @@
   (_fun _GtkWidget -> _void)
   (lambda (gtk)
     (let ([wx (gtk->wx gtk)])
-      (send wx queue-clicked))))
+      (when wx
+        (send wx queue-clicked)))))
 
 (defclass radio-box% item%
   (init parent cb label
diff --git a/collects/mred/private/wx/gtk/slider.rkt b/collects/mred/private/wx/gtk/slider.rkt
index 2ed4cc2e4a..d2280ef35f 100644
--- a/collects/mred/private/wx/gtk/slider.rkt
+++ b/collects/mred/private/wx/gtk/slider.rkt
@@ -26,7 +26,8 @@
   (_fun _GtkWidget -> _void)
   (lambda (gtk)
     (let ([wx (gtk->wx gtk)])
-      (send wx queue-changed))))
+      (when wx
+        (send wx queue-changed)))))
 
 (defclass slider% item%
   (init parent cb
diff --git a/collects/mred/private/wx/gtk/tab-panel.rkt b/collects/mred/private/wx/gtk/tab-panel.rkt
index 8e1bc1b603..c2e304e9aa 100644
--- a/collects/mred/private/wx/gtk/tab-panel.rkt
+++ b/collects/mred/private/wx/gtk/tab-panel.rkt
@@ -35,7 +35,8 @@
   (_fun _GtkWidget _pointer _int -> _void)
   (lambda (gtk ignored i)
     (let ([wx (gtk->wx gtk)])
-      (send wx page-changed i))))
+      (when wx
+        (send wx page-changed i)))))
 
 (define tab-panel%
   (class (client-size-mixin (panel-mixin window%))
diff --git a/collects/mred/private/wx/gtk/widget.rkt b/collects/mred/private/wx/gtk/widget.rkt
index a836f51686..cf40708281 100644
--- a/collects/mred/private/wx/gtk/widget.rkt
+++ b/collects/mred/private/wx/gtk/widget.rkt
@@ -52,14 +52,16 @@
     
     (super-new)
 
-    (let ([cell (malloc-immobile-cell this)])
+    (let ([cell (malloc-immobile-cell (make-weak-box this))])
       (g_object_set_data gtk "wx" cell)
       (for ([gtk (in-list extra-gtks)])
         (g_object_set_data gtk "wx" cell)))))
 
 (define (gtk->wx gtk)
   (let ([ptr (g_object_get_data gtk "wx")])
-    (and ptr (ptr-ref ptr _scheme))))
+    (and ptr 
+         (let ([wb (ptr-ref ptr _scheme)])
+           (and wb (weak-box-value wb))))))
 
 (set-widget-hook! (lambda (gtk)
                     (let loop ([gtk gtk])
diff --git a/collects/mred/private/wx/gtk/window.rkt b/collects/mred/private/wx/gtk/window.rkt
index e6da632d7c..a85982a0a5 100644
--- a/collects/mred/private/wx/gtk/window.rkt
+++ b/collects/mred/private/wx/gtk/window.rkt
@@ -81,13 +81,15 @@
   (_fun _GtkWidget _GdkEventFocus-pointer -> _gboolean)
   (lambda (gtk event)
     (let ([wx (gtk->wx gtk)])
-      (queue-window-event wx (lambda () (send wx on-set-focus)))
+      (when wx
+        (queue-window-event wx (lambda () (send wx on-set-focus))))
       #f)))
 (define-signal-handler connect-focus-out "focus-out-event"
   (_fun _GtkWidget _GdkEventFocus-pointer -> _gboolean)
   (lambda (gtk event)
     (let ([wx (gtk->wx gtk)])
-      (queue-window-event wx (lambda () (send wx on-kill-focus)))
+      (when wx
+        (queue-window-event wx (lambda () (send wx on-kill-focus))))
       #f)))
 (define (connect-focus gtk)
   (connect-focus-in gtk)
@@ -97,47 +99,52 @@
   (_fun _GtkWidget _GtkAllocation-pointer -> _gboolean)
   (lambda (gtk a)
     (let ([wx (gtk->wx gtk)])
-      (send wx save-size 
-            (GtkAllocation-x a)
-            (GtkAllocation-y a)
-            (GtkAllocation-width a)
-            (GtkAllocation-height a)))
+      (when wx
+        (send wx save-size 
+              (GtkAllocation-x a)
+              (GtkAllocation-y a)
+              (GtkAllocation-width a)
+              (GtkAllocation-height a))))
     #t))
 ;; ----------------------------------------
 
 (define-signal-handler connect-key-press "key-press-event"
   (_fun _GtkWidget _GdkEventKey-pointer -> _gboolean)
   (lambda (gtk event)
-    (let* ([wx (gtk->wx gtk)]
-           [modifiers (GdkEventKey-state event)]
-           [bit? (lambda (m v) (positive? (bitwise-and m v)))]
-           [k (new key-event%
-                   [key-code (let ([kv (GdkEventKey-keyval event)])
-                               (or
-                                (map-key-code kv)
-                                (integer->char (gdk_keyval_to_unicode kv))))]
-                   [shift-down (bit? modifiers GDK_SHIFT_MASK)]
-                   [control-down (bit? modifiers GDK_CONTROL_MASK)]
-                   [meta-down (bit? modifiers GDK_META_MASK)]
-                   [alt-down (bit? modifiers GDK_MOD1_MASK)]
-                   [x 0]
-                   [y 0]
-                   [time-stamp (GdkEventKey-time event)]
-                   [caps-down (bit? modifiers GDK_LOCK_MASK)])])
-      (if (send wx handles-events? gtk)
-          (begin
-            (queue-window-event wx (lambda () (send wx dispatch-on-char k #f)))
-            #t)
-          (constrained-reply (send wx get-eventspace)
-                             (lambda () (send wx dispatch-on-char k #t))
-                             #t)))))
+    (let ([wx (gtk->wx gtk)])
+      (and
+       wx
+       (let* ([modifiers (GdkEventKey-state event)]
+              [bit? (lambda (m v) (positive? (bitwise-and m v)))]
+              [k (new key-event%
+                      [key-code (let ([kv (GdkEventKey-keyval event)])
+                                  (or
+                                   (map-key-code kv)
+                                   (integer->char (gdk_keyval_to_unicode kv))))]
+                      [shift-down (bit? modifiers GDK_SHIFT_MASK)]
+                      [control-down (bit? modifiers GDK_CONTROL_MASK)]
+                      [meta-down (bit? modifiers GDK_META_MASK)]
+                      [alt-down (bit? modifiers GDK_MOD1_MASK)]
+                      [x 0]
+                      [y 0]
+                      [time-stamp (GdkEventKey-time event)]
+                      [caps-down (bit? modifiers GDK_LOCK_MASK)])])
+         (if (send wx handles-events? gtk)
+             (begin
+               (queue-window-event wx (lambda () (send wx dispatch-on-char k #f)))
+               #t)
+             (constrained-reply (send wx get-eventspace)
+                                (lambda () (send wx dispatch-on-char k #t))
+                                #t)))))))
 
 (define-signal-handler connect-button-press "button-press-event"
   (_fun _GtkWidget _GdkEventButton-pointer -> _gboolean)
   (lambda (gtk event)
     (unless (gtk_widget_is_focus gtk)
-      (unless (other-modal? (gtk->wx gtk))
-        (gtk_widget_grab_focus gtk)))
+      (let ([wx (gtk->wx gtk)])
+        (when wx
+          (unless (other-modal? wx)
+            (gtk_widget_grab_focus gtk)))))
     (do-button-event gtk event #f #f)))
 
 (define-signal-handler connect-button-release "button-release-event"
@@ -176,67 +183,69 @@
                       (GdkEventButton-type event)))])
     (unless (or (= type GDK_2BUTTON_PRESS)
                 (= type GDK_3BUTTON_PRESS))
-      (let* ([wx (gtk->wx gtk)]
-             [modifiers (if motion?
-                            (GdkEventMotion-state event)
-                            (if crossing?
-                                (GdkEventCrossing-state event)
-                                (GdkEventButton-state event)))]
-             [bit? (lambda (m v) (positive? (bitwise-and m v)))]
-             [type (cond
-                    [(= type GDK_MOTION_NOTIFY)
-                     'motion]
-                    [(= type GDK_ENTER_NOTIFY)
-                     'enter]
-                    [(= type GDK_LEAVE_NOTIFY)
-                     'leave]
-                    [(= type GDK_BUTTON_PRESS)
-                     (case (GdkEventButton-button event)
-                       [(1) 'left-down]
-                       [(3) 'right-down]
-                       [else 'middle-down])]
-                    [else
-                     (case (GdkEventButton-button event)
-                       [(1) 'left-up]
-                       [(3) 'right-up]
-                       [else 'middle-up])])]
-             [m (new mouse-event%
-                     [event-type type]
-                     [left-down (case type
-                                  [(left-down) #t]
-                                  [(left-up) #f]
-                                  [else (bit? modifiers GDK_BUTTON1_MASK)])]
-                     [middle-down (case type
-                                    [(middle-down) #t]
-                                    [(middle-up) #f]
-                                    [else (bit? modifiers GDK_BUTTON2_MASK)])]
-                     [right-down (case type
-                                   [(right-down) #t]
-                                   [(right-up) #f]
-                                   [else (bit? modifiers GDK_BUTTON3_MASK)])]
-                     [x (->long ((if motion? 
-                                     GdkEventMotion-x 
-                                     (if crossing? GdkEventCrossing-x GdkEventButton-x))
-                                 event))]
-                     [y (->long ((if motion? GdkEventMotion-y 
-                                     (if crossing? GdkEventCrossing-y GdkEventButton-y))
-                                 event))]
-                     [shift-down (bit? modifiers GDK_SHIFT_MASK)]
-                     [control-down (bit? modifiers GDK_CONTROL_MASK)]
-                     [meta-down (bit? modifiers GDK_META_MASK)]
-                     [alt-down (bit? modifiers GDK_MOD1_MASK)]
-                     [time-stamp ((if motion? GdkEventMotion-time 
-                                      (if crossing? GdkEventCrossing-time GdkEventButton-time))
-                                  event)]
-                     [caps-down (bit? modifiers GDK_LOCK_MASK)])])
-        (if (send wx handles-events? gtk)
-            (begin
-              (queue-window-event wx (lambda ()
-                                       (send wx dispatch-on-event m #f)))
-              #t)
-            (constrained-reply (send wx get-eventspace)
-                               (lambda () (send wx dispatch-on-event m #t))
-                               #t))))))
+      (let ([wx (gtk->wx gtk)])
+        (and
+         wx
+         (let* ([modifiers (if motion?
+                               (GdkEventMotion-state event)
+                               (if crossing?
+                                   (GdkEventCrossing-state event)
+                                   (GdkEventButton-state event)))]
+                [bit? (lambda (m v) (positive? (bitwise-and m v)))]
+                [type (cond
+                       [(= type GDK_MOTION_NOTIFY)
+                        'motion]
+                       [(= type GDK_ENTER_NOTIFY)
+                        'enter]
+                       [(= type GDK_LEAVE_NOTIFY)
+                        'leave]
+                       [(= type GDK_BUTTON_PRESS)
+                        (case (GdkEventButton-button event)
+                          [(1) 'left-down]
+                          [(3) 'right-down]
+                          [else 'middle-down])]
+                       [else
+                        (case (GdkEventButton-button event)
+                          [(1) 'left-up]
+                          [(3) 'right-up]
+                          [else 'middle-up])])]
+                [m (new mouse-event%
+                        [event-type type]
+                        [left-down (case type
+                                     [(left-down) #t]
+                                     [(left-up) #f]
+                                     [else (bit? modifiers GDK_BUTTON1_MASK)])]
+                        [middle-down (case type
+                                       [(middle-down) #t]
+                                       [(middle-up) #f]
+                                       [else (bit? modifiers GDK_BUTTON2_MASK)])]
+                        [right-down (case type
+                                      [(right-down) #t]
+                                      [(right-up) #f]
+                                      [else (bit? modifiers GDK_BUTTON3_MASK)])]
+                        [x (->long ((if motion? 
+                                        GdkEventMotion-x 
+                                        (if crossing? GdkEventCrossing-x GdkEventButton-x))
+                                    event))]
+                        [y (->long ((if motion? GdkEventMotion-y 
+                                        (if crossing? GdkEventCrossing-y GdkEventButton-y))
+                                    event))]
+                        [shift-down (bit? modifiers GDK_SHIFT_MASK)]
+                        [control-down (bit? modifiers GDK_CONTROL_MASK)]
+                        [meta-down (bit? modifiers GDK_META_MASK)]
+                        [alt-down (bit? modifiers GDK_MOD1_MASK)]
+                        [time-stamp ((if motion? GdkEventMotion-time 
+                                         (if crossing? GdkEventCrossing-time GdkEventButton-time))
+                                     event)]
+                        [caps-down (bit? modifiers GDK_LOCK_MASK)])])
+           (if (send wx handles-events? gtk)
+               (begin
+                 (queue-window-event wx (lambda ()
+                                          (send wx dispatch-on-event m #f)))
+                 #t)
+               (constrained-reply (send wx get-eventspace)
+                                  (lambda () (send wx dispatch-on-event m #t))
+                                  #t))))))))
 
 ;; ----------------------------------------