Don't overflow the message queue in wxEventLoop::WakeUp() in wxOSX.

First, don't add any events at all to it unless it's empty. Second, post new
events with low priority instead of high one, we really don't care about them
getting processed, other, real, events should take priority.

Closes #14256.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@78319 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/osx/carbon/evtloop.cpp

@@ -84,12 +84,17 @@ int wxGUIEventLoop::DoDispatchTimeout(unsigned long timeout)
 
 void wxGUIEventLoop::WakeUp()
 {
+    // If there's already one or more events in the queue then there's no need
+    // to post another one.
+    if ( GetNumEventsInQueue( GetMainEventQueue() ) > 0 )
+        return;
+
     OSStatus err = noErr;
     wxMacCarbonEvent wakeupEvent;
     wakeupEvent.Create( 'WXMC', 'WXMC', GetCurrentEventTime(),
                         kEventAttributeNone );
     err = PostEventToQueue(GetMainEventQueue(), wakeupEvent,
-                            kEventPriorityHigh );
+                            kEventPriorityLow );
 }
 
 void wxGUIEventLoop::OSXDoRun()