Mac OS X 10.11: disable auto-update for suspended-flush windows

Previous versions of OS X seem to have automatically disabled
update for a window when flushing is disabled, but now we have to
do it ourselves, otherwise text editors can flicker a lot. (The
system change is probably related to the removal of the
`isFlushWindowDisabled` method of `NSWindow` (which was
deprecated in 10.10).

gui-lib/mred/private/wx/cocoa/canvas.rkt

@@ -265,7 +265,9 @@
            [ignored-name #f]
            [gl-config #f])
 
-     (inherit get-cocoa get-cocoa-window
+     (inherit get-cocoa
+              get-cocoa-window
+              get-wx-window
               get-eventspace
               make-graphics-context
               is-shown-to-root?
@@ -319,7 +321,7 @@
      (define/public (queue-paint) (void))
      (define/public (request-canvas-flush-delay)
        (unless is-gl?
-         (request-flush-delay (get-cocoa-window))))
+         (request-flush-delay (get-wx-window))))
      (define/public (cancel-canvas-flush-delay req)
        (unless is-gl?
          (cancel-flush-delay req)))
@@ -365,9 +367,6 @@
      (define/public (end-refresh-sequence)
        (send dc resume-flush))
 
-     (define/public (get-flush-window)
-       (get-cocoa-window))
-
      (define/private (refresh-one)
        (when is-gl?
          (tellv content-cocoa setNeedsDisplay: #:type _BOOL #t))

gui-lib/mred/private/wx/cocoa/frame.rkt

@@ -399,6 +399,22 @@
                   (sync/timeout 1 s))))))
       (atomically
        (direct-show on?)))
+    
+    (define flush-disabled 0)
+    
+    (define/public (disable-flush-window)
+      (when (zero? flush-disabled)
+        (when (version-10.11-or-later?)
+          (tellv cocoa setAutodisplay: #:type _BOOL #f))
+        (tellv cocoa disableFlushWindow))
+      (set! flush-disabled (add1 flush-disabled)))
+
+    (define/public (enable-flush-window)
+      (set! flush-disabled (sub1 flush-disabled))
+      (when (zero? flush-disabled)
+        (tellv cocoa enableFlushWindow)
+        (when (version-10.11-or-later?)
+          (tellv cocoa setAutodisplay: #:type _BOOL #t))))
 
     (define/public (force-window-focus)
       (let ([next (get-app-front-window)])

gui-lib/mred/private/wx/cocoa/window.rkt

@@ -1008,21 +1008,21 @@
     (when wx
       (queue-event (send wx get-eventspace) (lambda () (proc wx))))))
 
-(define (request-flush-delay cocoa-win)
+(define (request-flush-delay wx-win)
   (do-request-flush-delay 
-   cocoa-win
-   (lambda (cocoa-win)
-     (and (tell #:type _bool cocoa-win isVisible)
-          (tellv cocoa-win disableFlushWindow)
+   wx-win
+   (lambda (wx-win)
+     (and (tell #:type _bool (send wx-win get-cocoa-window) isVisible)
+          (send wx-win disable-flush-window)
           #t))
-   (lambda (cocoa-win)
-     (tellv cocoa-win enableFlushWindow))))
+   (lambda (wx-win)
+     (send wx-win enable-flush-window))))
 
 (define (cancel-flush-delay req)
   (do-cancel-flush-delay 
    req
-   (lambda (cocoa-win)
-     (tellv cocoa-win enableFlushWindow))))
+   (lambda (wx-win)
+     (send wx-win enable-flush-window))))
 
 (define (make-init-point x y)
   (make-NSPoint (if (not x)