cocoa: yet another hack around weird cocoa behavior

Closes PR 11712
 Merge to 5.1
(cherry picked from commit 845ca2d586)

collects/mred/private/wx/cocoa/slider.rkt

@@ -8,6 +8,7 @@
          "const.rkt"
          "utils.rkt"
          "window.rkt"
+         "queue.rkt"
          "../common/event.rkt"
          "../common/queue.rkt"
          "../common/freeze.rkt"
@@ -158,6 +159,12 @@
   (define/public (update-message [val (get-value)])
     (tellv message-cocoa setTitleWithMnemonic: #:type _NSString (format "~a" val)))
 
+  (inherit get-cocoa-window)
+  (define/override (post-mouse-down)
+    ;; For some reason, dragging a slider disabled mouse-moved
+    ;;  events for the window, so turn them back on:
+    (tellv (get-cocoa-window) setAcceptsMouseMovedEvents: #:type _BOOL #t))
+
   (define/override (maybe-register-as-child parent on?)
     (register-as-child parent on?)))
 

collects/mred/private/wx/cocoa/window.rkt

@@ -98,7 +98,10 @@
   [wxb]
   [-a _void (mouseDown: [_id event]) 
       (unless (do-mouse-event wxb event 'left-down #t #f #f 'right-down)
-        (super-tell #:type _void mouseDown: event))]
+        (super-tell #:type _void mouseDown: event)
+        (let ([wx (->wx wxb)])
+         (when wx
+           (send wx post-mouse-down))))]
   [-a _void (mouseUp: [_id event]) 
       (unless (do-mouse-event wxb event 'left-up #f #f #f 'right-up)
         (super-tell #:type _void mouseUp: event))]
@@ -727,6 +730,8 @@
                              [caps-down #f])
                         #f))
 
+    (define/public (post-mouse-down) (void))
+
     (define/public (on-char s) (void))
     (define/public (on-event m) (void))
     (define/public (queue-on-size) (void))