Finalization and synchronization

racket-webview-qt.rkt

@@ -316,7 +316,7 @@
 ;RKTWEBVIEW_QT_EXPORT void rkt_webview_register_evt_callback(void (*f)(int));
 (define-rktwebview rkt_webview_register_evt_callback
   (_fun (_fun #:async-apply evt-apply #:atomic? #t
-              _int -> _void) -> _void))
+              _int -> _void) -> _int))
 
 ;RKTWEBVIEW_QT_EXPORT void rkt_webview_init(const char *from);
 (define-rktwebview rkt_webview_init
@@ -526,7 +526,10 @@
 (define (event-callback num)
   (os-async-channel-put events-channel num))
 
-(rkt_webview_register_evt_callback event-callback)
+(void 
+ (while (= (rkt_webview_register_evt_callback event-callback) 0)
+        (sleep 0.1)
+        ))
 
 ;(set! quiet-call (start-event-processing))
 (define evt-cb-hash (make-hash))
@@ -593,7 +596,10 @@
                        (if polling
                            (begin
                              (sleep 0.01)
-                             (os-async-channel-try-get events-channel))
+                             (let ((w (os-async-channel-try-get events-channel)))
+                               (if (eq? w #f)
+                                   0
+                                   w)))
                            (sync events-channel))))
             )
        (letrec
@@ -867,9 +873,14 @@
     (dbg-webview "Start event polling instead of using an event callback")
     (dbg-webview "To make sure the library does not get stuck on a dangling callback")
     (event-callback evt-start-polling)
-    (rkt_webview_register_evt_callback #f)
+
+    ; Set callback to null, but as an event can be in progress,
+    ; we need to check if the mutex lock could be aquired.
+    ; otherwise we wait. 
+    (while (= (rkt_webview_register_evt_callback #f) 0)
+           (sleep 0.1))
     (while (eq? event-processing-kind 'sync)
-           (sleep 0.01))
+           (sleep 0.1))
     (sync-log-webview)
     
     ; When asked to, close all windows