Document handleWindowSystemEvent()

Document asynchronous and synchronous mode behavior.

Change-Id: I2dc1256af5b3a8014025c89c65d41480f18f0701
Reviewed-by: Jørgen Lind <jorgen.lind@theqtcompany.com>

src/gui/kernel/qwindowsysteminterface.cpp

@@ -450,6 +450,19 @@ void QWindowSystemInterfacePrivate::postWindowSystemEvent(WindowSystemEvent *ev)
         dispatcher->wakeUp();
 }
 
+/*!
+    Handles a window system event.
+
+    By default this function posts the event on the window system event queue and
+    wakes the Gui event dispatcher. Qt Gui will then handle the event asynchonously
+    at a later point. The return value is not used in asynchronous mode and will
+    always be true.
+
+    In synchronous mode Qt Gui will process the event immediately. The return value
+    indicates if Qt accepted the event.
+
+    \sa flushWindowSystemEvents(), setSynchronousWindowSystemEvents()
+*/
 bool QWindowSystemInterfacePrivate::handleWindowSystemEvent(QWindowSystemInterfacePrivate::WindowSystemEvent *ev)
 {
     bool accepted = true;