diff --git a/pkgs/draw-pkgs/draw-doc/scribblings/draw/bitmap-class.scrbl b/pkgs/draw-pkgs/draw-doc/scribblings/draw/bitmap-class.scrbl
index 2bbd8d3fc5..1964f0e3c7 100644
--- a/pkgs/draw-pkgs/draw-doc/scribblings/draw/bitmap-class.scrbl
+++ b/pkgs/draw-pkgs/draw-doc/scribblings/draw/bitmap-class.scrbl
@@ -76,6 +76,18 @@ the bitmap is selected into another DC, attached as a button label, etc.).
 
 }
 
+@defmethod[(get-backing-scale)
+           (>/c 0.0)]{
+
+Gets the number of pixels that correspond to a drawing unit for the
+bitmap, either when the bitmap is used as a target for drawing or when
+the bitmap is drawn into another context.
+
+For example, on Mac OS X when the main monitor is in Retina mode,
+@racket[make-screen-bitmap] returns a bitmap whose backing scale is
+@racket[2.0].}
+
+
 @defmethod[(get-depth)
            exact-nonnegative-integer?]{
 
diff --git a/pkgs/draw-pkgs/draw-doc/scribblings/draw/bitmap-dc-class.scrbl b/pkgs/draw-pkgs/draw-doc/scribblings/draw/bitmap-dc-class.scrbl
index cffce48b0e..7e481d6b52 100644
--- a/pkgs/draw-pkgs/draw-doc/scribblings/draw/bitmap-dc-class.scrbl
+++ b/pkgs/draw-pkgs/draw-doc/scribblings/draw/bitmap-dc-class.scrbl
@@ -90,7 +90,12 @@ If @racket[pre-multiplied?] is true, @racket[just-alpha?] is false,
  are scaled by the corresponding alpha value (i.e., multiplied by the
  alpha value and then divided by 255).
 
-}
+If the bitmap has a backing scale (see @xmethod[bitmap%
+ get-backing-scale]) other than @racket[1.0], the the result of
+ @method[bitmap-dc% get-argb-pixels] is as if the bitmap is drawn to a
+ bitmap with a backing scale of @racket[1.0] and the pixels of the
+ target bitmap are returned.}
+
 
 @defmethod[(get-bitmap)
            (or/c (is-a?/c bitmap%) #f)]{
diff --git a/pkgs/draw-pkgs/draw-doc/scribblings/draw/guide.scrbl b/pkgs/draw-pkgs/draw-doc/scribblings/draw/guide.scrbl
index 23d4125d62..75088f25ac 100644
--- a/pkgs/draw-pkgs/draw-doc/scribblings/draw/guide.scrbl
+++ b/pkgs/draw-pkgs/draw-doc/scribblings/draw/guide.scrbl
@@ -755,8 +755,11 @@ Different kinds of bitmaps can produce different results:
        make-bitmap] uses the same platform-specific drawing operations
        as drawing into a @racket[canvas%] instance. A bitmap produced
        by @racket[make-screen-bitmap] is the same as one produced by
-       @racket[make-platform-bitmap] on Windows or Mac OS X, but it may
-       be sensitive to the X11 server on Unix.
+       @racket[make-platform-bitmap] on Windows or Mac OS X, but it
+       may be sensitive to the X11 server on Unix. On Mac OS X, when
+       the main screen is in Retina mode (at the time that the bitmap
+       is created), the bitmap is also internally scaled so that one
+       drawing unit uses two pixels.
 
        Use @racket[make-screen-bitmap] when drawing to a bitmap as an
        offscreen buffer before transferring an image to the screen, or
diff --git a/pkgs/draw-pkgs/draw-lib/racket/draw/private/bitmap-dc.rkt b/pkgs/draw-pkgs/draw-lib/racket/draw/private/bitmap-dc.rkt
index 5d9e241b7f..b9395f6e98 100644
--- a/pkgs/draw-pkgs/draw-lib/racket/draw/private/bitmap-dc.rkt
+++ b/pkgs/draw-pkgs/draw-lib/racket/draw/private/bitmap-dc.rkt
@@ -21,7 +21,16 @@
     (define b&w? #f)
     
     (when _bm
-      (do-set-bitmap _bm #f))
+      (do-set-bitmap _bm #f)
+      ;; Needed if the bitmap has a device scale:
+      (when c (init-cr-matrix c)))
+
+    (define/override (init-cr-matrix cr)
+      (when bm
+        (define s (send bm get-cairo-device-scale))
+        (unless (= s 1)
+          (cairo_scale cr s s)))
+      (super init-cr-matrix cr))
 
     (define/override (ok?) (and c #t))
 
diff --git a/pkgs/draw-pkgs/draw-lib/racket/draw/private/bitmap.rkt b/pkgs/draw-pkgs/draw-lib/racket/draw/private/bitmap.rkt
index e893897e3c..09067a01bf 100644
--- a/pkgs/draw-pkgs/draw-lib/racket/draw/private/bitmap.rkt
+++ b/pkgs/draw-pkgs/draw-lib/racket/draw/private/bitmap.rkt
@@ -504,6 +504,13 @@
         (let ([p (cairo_get_source cr)])
           (cairo_pattern_reference p)
           (cairo_set_source_surface cr (get-cairo-surface) (- x) (- y))
+          (let ([sc (get-cairo-device-scale)])
+            (unless (= sc 1)
+              (let ([m (make-cairo_matrix_t 0.0 0.0 0.0 0.0 0.0 0.0)])
+                (cairo_matrix_init_translate m 0 0)
+                (cairo_matrix_scale m sc sc)
+                (cairo_matrix_translate m x y)
+                (cairo_pattern_set_matrix (cairo_get_source cr) m))))
           (cairo_new_path cr)
           (cairo_rectangle cr 0 0 w h)
           (cairo_fill cr)
@@ -633,6 +640,10 @@
                 alpha-s))
           (get-empty-surface)))
 
+    (define/public (get-cairo-device-scale) 1.0)
+
+    (define/public (get-backing-scale) (get-cairo-device-scale))
+
     (define/public (get-handle) s)
 
     (define/public (get-argb-pixels x y w h bstr
@@ -912,15 +923,24 @@
 
 (define quartz-bitmap%
   (class bitmap%
-    (init w h [with-alpha? #t])
+    (init w h [with-alpha? #t] [resolution 1.0])
     (super-make-object (make-alternate-bitmap-kind w h))
-
+    
+    (define cocoa-resolution resolution)
+    
+    (define/override (get-cairo-device-scale)
+      cocoa-resolution)
+    
     (define s
       (let ([s (cairo_quartz_surface_create (if with-alpha?
                                                 CAIRO_FORMAT_ARGB32
                                                 CAIRO_FORMAT_RGB24)
-                                            w
-                                            h)])
+                                            (inexact->exact
+                                             (ceiling
+                                              (* cocoa-resolution w)))
+                                            (inexact->exact
+                                             (ceiling
+                                              (* cocoa-resolution h))))])
         ;; initialize bitmap to empty - needed?
         (let ([cr (cairo_create s)])
           (cairo_set_operator cr (if with-alpha?
diff --git a/pkgs/draw-pkgs/draw-lib/racket/draw/private/dc.rkt b/pkgs/draw-pkgs/draw-lib/racket/draw/private/dc.rkt
index bd2bd60e66..b5314e2cc4 100644
--- a/pkgs/draw-pkgs/draw-lib/racket/draw/private/dc.rkt
+++ b/pkgs/draw-pkgs/draw-lib/racket/draw/private/dc.rkt
@@ -1774,6 +1774,15 @@
                                        (send src get-cairo-surface)
                                        (- a-dest-x a-src-x)
                                        (- a-dest-y a-src-y))
+             (let ([sc (send src get-cairo-device-scale)])
+               (unless (= sc 1)
+                 (let ([m (make-cairo_matrix_t 0.0 0.0 0.0 0.0 0.0 0.0)])
+                   (cairo_matrix_init_translate m 0 0)
+                   (cairo_matrix_scale m sc sc)
+                   (cairo_matrix_translate m
+                                           (- (- a-dest-x a-src-x))
+                                           (- (- a-dest-y a-src-y)))
+                   (cairo_pattern_set_matrix (cairo_get_source cr) m))))
              (adjust-pattern-filter (cairo_get_source cr))
              (if mask
                  (stamp-pattern mask a-msrc-x a-msrc-y)
diff --git a/pkgs/draw-pkgs/draw-lib/racket/draw/private/local.rkt b/pkgs/draw-pkgs/draw-lib/racket/draw/private/local.rkt
index 0807f263d8..ab567c965d 100644
--- a/pkgs/draw-pkgs/draw-lib/racket/draw/private/local.rkt
+++ b/pkgs/draw-pkgs/draw-lib/racket/draw/private/local.rkt
@@ -10,6 +10,7 @@
   ;; bitmap%
   get-cairo-surface
   get-cairo-alpha-surface
+  get-cairo-device-scale
   release-bitmap-storage
   get-bitmap-gl-context
   drop-alpha-s
diff --git a/pkgs/draw-pkgs/draw-lib/racket/draw/unsafe/cairo.rkt b/pkgs/draw-pkgs/draw-lib/racket/draw/unsafe/cairo.rkt
index 9365e7d6d0..c60c990360 100644
--- a/pkgs/draw-pkgs/draw-lib/racket/draw/unsafe/cairo.rkt
+++ b/pkgs/draw-pkgs/draw-lib/racket/draw/unsafe/cairo.rkt
@@ -265,6 +265,10 @@
   #:wrap (allocator cairo_surface_destroy))
 (define-cairo cairo_ps_surface_create (_cfun _path _double* _double* -> _cairo_surface_t)
   #:wrap (allocator cairo_surface_destroy))
+(define-cairo cairo_surface_set_fallback_resolution (_cfun _cairo_surface_t _double* _double* -> _void))
+(define-cairo cairo_surface_get_fallback_resolution (_cfun _cairo_surface_t (x : (_ptr o _double)) (y :  (_ptr o _double))
+                                                           -> _void
+                                                           -> (values x y)))
 
 ;; Stream surfaces
 
diff --git a/pkgs/gui-pkgs/gui-doc/scribblings/gui/global-draw-funcs.scrbl b/pkgs/gui-pkgs/gui-doc/scribblings/gui/global-draw-funcs.scrbl
index 78b894fe5c..023550a39a 100644
--- a/pkgs/gui-pkgs/gui-doc/scribblings/gui/global-draw-funcs.scrbl
+++ b/pkgs/gui-pkgs/gui-doc/scribblings/gui/global-draw-funcs.scrbl
@@ -14,13 +14,26 @@ Normally, drawing is automatically flushed to the screen. Use
 other actions depend on updating the display.}
 
 
+@defproc[(get-display-backing-scale [#:monitor monitor exact-nonnegative-integer? 0])
+                                    (or/c (>/c 0.0) #f)]{
+
+Returns the number of pixels that correspond to one drawing unit on a
+monitor.  The result is normally @racket[1.0], but it is @racket[2.0] on
+Mac OS X in Retina display mode.
+
+On Mac OS X, the result can change at any time.  See also
+@xmethod[top-level-window<%> display-changed].
+
+If @racket[monitor] is not less than the current number of available
+ monitors (which can change at any time), the is @racket[#f]. See also
+ @xmethod[top-level-window<%> display-changed].}
+
+
 @defproc[(get-display-count) exact-positive-integer?]{
 Returns the number of monitors currently active. 
 
 On Windows and Mac OS X, the result can change at any time.
-See also @xmethod[top-level-window<%> display-changed].
-
-}
+See also @xmethod[top-level-window<%> display-changed].}
 
 
 @defproc[(get-display-depth)
diff --git a/pkgs/gui-pkgs/gui-doc/scribblings/gui/miscwin-funcs.scrbl b/pkgs/gui-pkgs/gui-doc/scribblings/gui/miscwin-funcs.scrbl
index 2da9618c39..0dfec35ba2 100644
--- a/pkgs/gui-pkgs/gui-doc/scribblings/gui/miscwin-funcs.scrbl
+++ b/pkgs/gui-pkgs/gui-doc/scribblings/gui/miscwin-funcs.scrbl
@@ -275,8 +275,13 @@ environment of the result namespace.}
 Creates a bitmap that draws in a way that is the same as drawing to a
 canvas in its default configuration.
 
-See also @secref[#:doc '(lib "scribblings/draw/draw.scrbl") "Portability"].
-}
+In particular, on Mac OS X when the main monitor is in Retina display
+mode, a drawing unit corresponds to two pixels, and the bitmap
+internally contains four times as many pixels as requested by
+@racket[width] and @racket[height]. See also
+@racket[get-display-backing-scale].
+
+See also @secref[#:doc '(lib "scribblings/draw/draw.scrbl") "Portability"].}
 
 
 @defproc[(play-sound [filename path-string?]
diff --git a/pkgs/gui-pkgs/gui-doc/scribblings/gui/top-level-window-intf.scrbl b/pkgs/gui-pkgs/gui-doc/scribblings/gui/top-level-window-intf.scrbl
index 2820d9a495..0762cfecf6 100644
--- a/pkgs/gui-pkgs/gui-doc/scribblings/gui/top-level-window-intf.scrbl
+++ b/pkgs/gui-pkgs/gui-doc/scribblings/gui/top-level-window-intf.scrbl
@@ -197,8 +197,9 @@ Returns @|void-const|.
     Called when the displays configuration changes.
 
     To determine the new monitor configuration, use
-    @racket[get-display-count], @racket[get-display-size], and
-    @racket[get-display-left-top-inset]. 
+    @racket[get-display-count], @racket[get-display-size],
+    @racket[get-display-left-top-inset], and
+    @racket[get-display-backing-scale].
 
     Note that this method may be invoked multiple times for a single
     logical change to the monitors.
diff --git a/pkgs/gui-pkgs/gui-lib/mred/HISTORY.txt b/pkgs/gui-pkgs/gui-lib/mred/HISTORY.txt
index aab906c1f6..e4c42e8005 100644
--- a/pkgs/gui-pkgs/gui-lib/mred/HISTORY.txt
+++ b/pkgs/gui-pkgs/gui-lib/mred/HISTORY.txt
@@ -1,6 +1,10 @@
+Version 5.90.0.9
+Added get-display-backing-scale
+Added get-backing-scale to bitmap%
+
 Version 5.90.0.5
 
-Fix key-event% get-key-release-code to return 'press instead of 'down
+Fixed key-event% get-key-release-code to return 'press instead of 'down
  for a key-down event
 
 ----------------------------------------
diff --git a/pkgs/gui-pkgs/gui-lib/mred/mred-sig.rkt b/pkgs/gui-pkgs/gui-lib/mred/mred-sig.rkt
index 2f0b39892f..d071cafa9f 100644
--- a/pkgs/gui-pkgs/gui-lib/mred/mred-sig.rkt
+++ b/pkgs/gui-pkgs/gui-lib/mred/mred-sig.rkt
@@ -82,6 +82,7 @@ get-color-from-user
 get-current-mouse-state
 get-default-shortcut-prefix
 get-directory
+get-display-backing-scale
 get-display-count
 get-display-depth
 get-display-left-top-inset
diff --git a/pkgs/gui-pkgs/gui-lib/mred/private/mred.rkt b/pkgs/gui-pkgs/gui-lib/mred/private/mred.rkt
index 669ba84d5a..54f5e53c95 100644
--- a/pkgs/gui-pkgs/gui-lib/mred/private/mred.rkt
+++ b/pkgs/gui-pkgs/gui-lib/mred/private/mred.rkt
@@ -251,6 +251,7 @@
 	   get-display-size
 	   get-display-left-top-inset
 	   get-display-count
+           get-display-backing-scale
 	   get-color-from-user
 	   get-font-from-user
            append-editor-operation-menu-items
diff --git a/pkgs/gui-pkgs/gui-lib/mred/private/wx/cocoa/canvas.rkt b/pkgs/gui-pkgs/gui-lib/mred/private/wx/cocoa/canvas.rkt
index 6613d6cbb0..69be809546 100644
--- a/pkgs/gui-pkgs/gui-lib/mred/private/wx/cocoa/canvas.rkt
+++ b/pkgs/gui-pkgs/gui-lib/mred/private/wx/cocoa/canvas.rkt
@@ -413,7 +413,7 @@
      (define/public (get-dc) dc)
 
      (define/public (make-compatible-bitmap w h)
-       (make-object quartz-bitmap% w h))
+       (make-screen-bitmap w h))
 
      (define/override (fix-dc [refresh? #t])
        (when (dc . is-a? . dc%)
diff --git a/pkgs/gui-pkgs/gui-lib/mred/private/wx/cocoa/dc.rkt b/pkgs/gui-pkgs/gui-lib/mred/private/wx/cocoa/dc.rkt
index 94c463235d..ec8b8effad 100644
--- a/pkgs/gui-pkgs/gui-lib/mred/private/wx/cocoa/dc.rkt
+++ b/pkgs/gui-pkgs/gui-lib/mred/private/wx/cocoa/dc.rkt
@@ -1,5 +1,6 @@
 #lang racket/base
-(require racket/class
+(require "../../syntax.rkt"
+         racket/class
          ffi/unsafe
          ffi/unsafe/objc
          racket/draw/unsafe/cairo
@@ -16,9 +17,11 @@
 
 (provide 
  (protect-out dc%
-              do-backing-flush))
+              do-backing-flush)
+ display-bitmap-resolution
+ make-screen-bitmap)
 
-(import-class NSOpenGLContext)
+(import-class NSOpenGLContext NSScreen)
 (define NSOpenGLCPSwapInterval 222)
 
 (define dc%
@@ -59,7 +62,8 @@
     ;; Use a quartz bitmap so that text looks good:
     (define trans? transparent?)
     (define/override (make-backing-bitmap w h) 
-      (make-object quartz-bitmap% w h trans?))
+      (make-object quartz-bitmap% w h trans? 
+                   (display-bitmap-resolution 0 void)))
     (define/override (can-combine-text? sz) #t)
 
     (define/override (get-backing-size xb yb)
@@ -104,3 +108,23 @@
                  (backing-draw-bm bm cr (unbox w) (unbox h))
                  (cairo_destroy cr))))))
    (tellv ctx restoreGraphicsState)))
+
+(define (display-bitmap-resolution num fail)
+  (let ([r (atomically
+            (with-autorelease
+             (let ([s (if (zero? num)
+                          (tell NSScreen mainScreen)
+                          (let ([screens (tell NSScreen screens)])
+                            (if (num . < . (tell #:type _NSUInteger screens count))
+                                (tell screens objectAtIndex: #:type _NSUInteger num)
+                                #f)))])
+               (and s
+                    (tell #:type _CGFloat s backingScaleFactor)))))])
+    (cond
+     [(not r) (fail)]
+     [(zero? r) 1.0]
+     [else r])))
+
+(define/top (make-screen-bitmap [exact-positive-integer? w]
+                                [exact-positive-integer? h])
+  (make-object quartz-bitmap% w h #t (display-bitmap-resolution 0 void)))
diff --git a/pkgs/gui-pkgs/gui-lib/mred/private/wx/cocoa/platform.rkt b/pkgs/gui-pkgs/gui-lib/mred/private/wx/cocoa/platform.rkt
index 1567a0c7d4..99d3b54d89 100644
--- a/pkgs/gui-pkgs/gui-lib/mred/private/wx/cocoa/platform.rkt
+++ b/pkgs/gui-pkgs/gui-lib/mred/private/wx/cocoa/platform.rkt
@@ -62,6 +62,7 @@
    display-size
    display-origin
    display-count
+   display-bitmap-resolution
    flush-display
    get-current-mouse-state
    fill-private-color
diff --git a/pkgs/gui-pkgs/gui-lib/mred/private/wx/cocoa/procs.rkt b/pkgs/gui-pkgs/gui-lib/mred/private/wx/cocoa/procs.rkt
index 3064355586..d5edd7491f 100644
--- a/pkgs/gui-pkgs/gui-lib/mred/private/wx/cocoa/procs.rkt
+++ b/pkgs/gui-pkgs/gui-lib/mred/private/wx/cocoa/procs.rkt
@@ -53,6 +53,7 @@
   get-highlight-background-color
   get-highlight-text-color
   check-for-break)
+ display-bitmap-resolution
  make-screen-bitmap
  make-gl-bitmap
  show-print-setup
@@ -157,10 +158,6 @@
 (define (id-to-menu-item id) id)
 (define (can-show-print-setup?) #t)
 
-(define/top (make-screen-bitmap [exact-positive-integer? w]
-                                [exact-positive-integer? h])
-  (make-object quartz-bitmap% w h))
-
 (define/top (make-gl-bitmap [exact-positive-integer? w]
                             [exact-positive-integer? h]
                             [gl-config% c])
diff --git a/pkgs/gui-pkgs/gui-lib/mred/private/wx/common/backing-dc.rkt b/pkgs/gui-pkgs/gui-lib/mred/private/wx/common/backing-dc.rkt
index 655da62df5..45c7936298 100644
--- a/pkgs/gui-pkgs/gui-lib/mred/private/wx/common/backing-dc.rkt
+++ b/pkgs/gui-pkgs/gui-lib/mred/private/wx/common/backing-dc.rkt
@@ -214,6 +214,12 @@
 	  (cairo_translate cr dx dy))
         (cairo_pattern_reference s)
         (cairo_set_source_surface cr (send bm get-cairo-surface) 0 0)
+        (let ([sc (send bm get-cairo-device-scale)])
+          (unless (= sc 1)
+            (let ([m (make-cairo_matrix_t 0.0 0.0 0.0 0.0 0.0 0.0)])
+              (cairo_matrix_init_translate m 0 0)
+              (cairo_matrix_scale m sc sc)
+              (cairo_pattern_set_matrix (cairo_get_source cr) m))))
         (cairo_new_path cr)
         (cairo_rectangle cr 0 0 w h)
         (cairo_fill cr)
diff --git a/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/frame.rkt b/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/frame.rkt
index 7ee11f9656..188397f9eb 100644
--- a/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/frame.rkt
+++ b/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/frame.rkt
@@ -22,6 +22,7 @@
               display-origin
               display-size
 	      display-count
+              display-bitmap-resolution
               location->window
               get-current-mouse-state))
 
@@ -558,6 +559,13 @@
 (define (display-count)
   (gdk_screen_get_n_monitors (gdk_screen_get_default)))
 
+(define (display-bitmap-resolution num fail)
+  (if (zero? num)
+      1.0
+      (if (num . < . (gdk_screen_get_n_monitors (gdk_screen_get_default)))
+          1.0
+          (fail))))
+
 (define (location->window x y)
   (for/or ([f (in-hash-keys all-frames)])
     (let ([fx (send f get-x)]
diff --git a/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/platform.rkt b/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/platform.rkt
index 1194feef74..125744392b 100644
--- a/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/platform.rkt
+++ b/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/platform.rkt
@@ -63,6 +63,7 @@
    display-size
    display-origin
    display-count
+   display-bitmap-resolution
    flush-display
    get-current-mouse-state
    fill-private-color
diff --git a/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/procs.rkt b/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/procs.rkt
index cacf3d1829..c9f84e17a5 100644
--- a/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/procs.rkt
+++ b/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/procs.rkt
@@ -48,6 +48,7 @@
  show-print-setup
  display-origin
  display-size
+ display-bitmap-resolution
  flush-display
  location->window
  make-screen-bitmap
diff --git a/pkgs/gui-pkgs/gui-lib/mred/private/wx/platform.rkt b/pkgs/gui-pkgs/gui-lib/mred/private/wx/platform.rkt
index 5c2e0654e1..8029396a56 100644
--- a/pkgs/gui-pkgs/gui-lib/mred/private/wx/platform.rkt
+++ b/pkgs/gui-pkgs/gui-lib/mred/private/wx/platform.rkt
@@ -49,6 +49,7 @@
                 display-size
                 display-origin
 		display-count
+                display-bitmap-resolution
                 flush-display
                 get-current-mouse-state
                 fill-private-color
diff --git a/pkgs/gui-pkgs/gui-lib/mred/private/wx/win32/frame.rkt b/pkgs/gui-pkgs/gui-lib/mred/private/wx/win32/frame.rkt
index 647e13e421..de9cf186f7 100644
--- a/pkgs/gui-pkgs/gui-lib/mred/private/wx/win32/frame.rkt
+++ b/pkgs/gui-pkgs/gui-lib/mred/private/wx/win32/frame.rkt
@@ -22,7 +22,8 @@
  (protect-out frame%
               display-size
               display-origin
-	      display-count))
+	      display-count
+              display-bitmap-resolution))
 
 (define-user32 SetLayeredWindowAttributes (_wfun _HWND _COLORREF _BYTE _DWORD -> _BOOL))
 (define-user32 GetActiveWindow (_wfun -> _HWND))
@@ -152,7 +153,18 @@
     (set-box! yb 0)]))
 
 (define (display-count)
-  (length (get-all-screen-rects)))
+  (let ([pos 0])
+    (EnumDisplayMonitors #f #f (lambda (mon dc r ptr)
+                                 (set! pos (add1 pos))
+                                 #t)
+                         #f)
+    pos))
+
+(define (display-bitmap-resolution num fail)
+  (if (or (zero? num)
+          (num . < . (display-count)))
+      1.0
+      (fail)))
 
 (define mouse-frame #f)
 
diff --git a/pkgs/gui-pkgs/gui-lib/mred/private/wx/win32/platform.rkt b/pkgs/gui-pkgs/gui-lib/mred/private/wx/win32/platform.rkt
index e3d775ef3f..1461b2b100 100644
--- a/pkgs/gui-pkgs/gui-lib/mred/private/wx/win32/platform.rkt
+++ b/pkgs/gui-pkgs/gui-lib/mred/private/wx/win32/platform.rkt
@@ -63,6 +63,7 @@
    display-size
    display-origin
    display-count
+   display-bitmap-resolution
    flush-display
    get-current-mouse-state
    fill-private-color
diff --git a/pkgs/gui-pkgs/gui-lib/mred/private/wx/win32/procs.rkt b/pkgs/gui-pkgs/gui-lib/mred/private/wx/win32/procs.rkt
index 81ef379e7a..e557c4037b 100644
--- a/pkgs/gui-pkgs/gui-lib/mred/private/wx/win32/procs.rkt
+++ b/pkgs/gui-pkgs/gui-lib/mred/private/wx/win32/procs.rkt
@@ -53,6 +53,7 @@
  file-creator-and-type
  display-origin
  display-size
+ display-bitmap-resolution
  make-screen-bitmap
  make-gl-bitmap
  special-control-key
diff --git a/pkgs/gui-pkgs/gui-lib/mred/private/wxtop.rkt b/pkgs/gui-pkgs/gui-lib/mred/private/wxtop.rkt
index 4587579279..ba907c204f 100644
--- a/pkgs/gui-pkgs/gui-lib/mred/private/wxtop.rkt
+++ b/pkgs/gui-pkgs/gui-lib/mred/private/wxtop.rkt
@@ -18,6 +18,7 @@
 	   get-display-size
 	   get-display-left-top-inset
 	   get-display-count
+	   get-display-backing-scale
 	   (protect-out make-top-container%
 			make-top-level-window-glue%
 			wx-frame%
@@ -59,6 +60,12 @@
     (lambda ()
       (wx:display-count)))
 
+  (define get-display-backing-scale
+    (lambda (#:monitor [monitor 0])
+      (unless (exact-nonnegative-integer? monitor)
+	(raise-argument-error 'get-display-backing-scale "exact-nonnegative-integer?" monitor))
+      (wx:display-bitmap-resolution monitor (lambda () #f))))
+
   (define-values (left-margin top-margin init-top-x init-top-y)
     (let-values ([(x y) (get-display-left-top-inset #f)]
 		 [(x2 y2) (get-display-left-top-inset #t)])
diff --git a/racket/src/mac/osx_appl.rkt b/racket/src/mac/osx_appl.rkt
index 3976e33222..e9f83c924e 100644
--- a/racket/src/mac/osx_appl.rkt
+++ b/racket/src/mac/osx_appl.rkt
@@ -15,8 +15,17 @@
 	   racket/file
            racket/path)
 
+  (define (try . l)
+    (or (ormap (lambda (f)
+		 (and (file-exists? f)
+		      f))
+	       l)
+	(car (reverse l))))
+
   (define rez-path (or (getenv "REZ")
-		       "/Developer/Tools/Rez"))
+		       (find-executable-path "Rez")
+		       (try "/Applications/Xcode.app/Contents/Developer/Tools/Rez"
+			    "/Developer/Tools/Rez")))
 
   (define for-3m? (getenv "BUILDING_3M"))
 
@@ -101,7 +110,9 @@
 	   (assoc-pair "CFBundleVersion"
 		       ,(version))
 	   (assoc-pair "CFBundleShortVersionString"
-		       ,(version))))
+		       ,(version))
+	   (assoc-pair "NSPrincipalClass" "NSApplicationMain")
+	   (assoc-pair "NSHighResolutionCapable" (true))))
 
     (create-app (build-path (current-directory) (if for-3m? 'up 'same))
                 (string-append "GRacket" suffix)