OSX fix empty message queue handling

For some (unknown) reason [NSApp postEvent: ... atStart: NO]
doesn't append the event, if the message queue is empty
(AKA [NSApp nextEventMatchingMask .. ] returns nil).
Due to nextEventMatchingMask usage, these postEvents have to
run in the main thread.

Using performSelectorOnMainThread deadlocks, since the calling
thread may have locked the Yield mutex, so we simply defer the
call using an NSEvent, like the Windows backend.

So we have to peek at the queue and if it's empty simply prepend
the event using [.. atStart: YES].

In the end this make the vcl_timer unit test pass on OSX.

Change-Id: Ib41186425b2f76faa0e9f116f47fdcd60d878099

3 files changed, 47 insertions, 53 deletions

diff --git a/vcl/osx/salinst.cxx b/vcl/osx/salinst.cxx
index 5936c0618805..bff9c3816d22 100644
--- a/vcl/osx/salinst.cxx
+++ b/vcl/osx/salinst.cxx
@@ -368,23 +368,7 @@ void AquaSalInstance::wakeupYield()
 {
     // wakeup :Yield
     if( mbWaitingYield )
-    {
-        SalData::ensureThreadAutoreleasePool();
-SAL_WNODEPRECATED_DECLARATIONS_PUSH
-    // 'NSApplicationDefined' is deprecated: first deprecated in macOS 10.12
-        NSEvent* pEvent = [NSEvent otherEventWithType: NSApplicationDefined
-                                   location: NSZeroPoint
-                                   modifierFlags: 0
-                                   timestamp: 0
-                                   windowNumber: 0
-                                   context: nil
-                                   subtype: AquaSalInstance::YieldWakeupEvent
-                                   data1: 0
-                                   data2: 0 ];
-SAL_WNODEPRECATED_DECLARATIONS_POP
-        if( pEvent )
-            [NSApp postEvent: pEvent atStart: NO];
-    }
+        ImplNSAppPostEvent( AquaSalInstance::YieldWakeupEvent, YES );
 }
 
 void AquaSalInstance::PostUserEvent( AquaSalFrame* pFrame, SalEvent nType, void* pData )
@@ -554,14 +538,6 @@ void AquaSalInstance::handleAppDefinedEvent( NSEvent* pEvent )
     };
 }
 
-class ReleasePoolHolder
-{
-    NSAutoreleasePool* mpPool;
-    public:
-    ReleasePoolHolder() : mpPool( [[NSAutoreleasePool alloc] init] ) {}
-    ~ReleasePoolHolder() { [mpPool release]; }
-};
-
 bool AquaSalInstance::DoYield(bool bWait, bool bHandleAllCurrentEvents, sal_uLong const nReleased)
 {
     (void) nReleased;
@@ -627,9 +603,11 @@ bool AquaSalInstance::DoYield(bool bWait, bool bHandleAllCurrentEvents, sal_uLon
 
 SAL_WNODEPRECATED_DECLARATIONS_PUSH
     // 'NSAnyEventMask' is deprecated: first deprecated in macOS 10.12
-            pEvent = [NSApp nextEventMatchingMask: NSAnyEventMask untilDate: nil
+            pEvent = [NSApp nextEventMatchingMask: NSAnyEventMask
 SAL_WNODEPRECATED_DECLARATIONS_POP
-                            inMode: NSDefaultRunLoopMode dequeue: YES];
+                            untilDate: nil
+                            inMode: NSDefaultRunLoopMode
+                            dequeue: YES];
             if( pEvent )
             {
                 [NSApp sendEvent: pEvent];
@@ -648,9 +626,11 @@ SAL_WNODEPRECATED_DECLARATIONS_POP
             NSDate* pDt = AquaSalTimer::pRunningTimer ? [AquaSalTimer::pRunningTimer fireDate] : [NSDate distantFuture];
 SAL_WNODEPRECATED_DECLARATIONS_PUSH
     // 'NSAnyEventMask' is deprecated: first deprecated in macOS 10.12
-            pEvent = [NSApp nextEventMatchingMask: NSAnyEventMask untilDate: pDt
+            pEvent = [NSApp nextEventMatchingMask: NSAnyEventMask
 SAL_WNODEPRECATED_DECLARATIONS_POP
-                            inMode: NSDefaultRunLoopMode dequeue: YES];
+                            untilDate: pDt
+                            inMode: NSDefaultRunLoopMode
+                            dequeue: YES];
             if( pEvent )
                 [NSApp sendEvent: pEvent];
             [NSApp updateWindows];
diff --git a/vcl/osx/salnstimer.mm b/vcl/osx/salnstimer.mm
index 9c3264295d60..c9867cf7a79e 100644
--- a/vcl/osx/salnstimer.mm
+++ b/vcl/osx/salnstimer.mm
@@ -26,24 +26,13 @@
 #include "svdata.hxx"
 
 @implementation TimerCallbackCaller
+
 -(void)timerElapsed:(NSTimer*)pTimer
 {
     (void)pTimer;
-SAL_WNODEPRECATED_DECLARATIONS_PUSH
-// 'NSApplicationDefined' is deprecated: first deprecated in macOS 10.12
-    NSEvent* pEvent = [NSEvent otherEventWithType: NSApplicationDefined
-SAL_WNODEPRECATED_DECLARATIONS_POP
-                               location: NSZeroPoint
-                               modifierFlags: 0
-                               timestamp: [NSDate timeIntervalSinceReferenceDate]
-                               windowNumber: 0
-                               context: nil
-                               subtype: AquaSalInstance::DispatchTimerEvent
-                               data1: 0
-                               data2: 0 ];
-    assert( pEvent );
-    [NSApp postEvent: pEvent atStart: YES];
+    ImplNSAppPostEvent( AquaSalInstance::DispatchTimerEvent, YES );
 }
+
 @end
 
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/vcl/osx/saltimer.cxx b/vcl/osx/saltimer.cxx
index 415ad1284af8..3cf74529a301 100644
--- a/vcl/osx/saltimer.cxx
+++ b/vcl/osx/saltimer.cxx
@@ -31,22 +31,45 @@ NSTimer* AquaSalTimer::pRunningTimer = nil;
 
 static void ImplSalStopTimer();
 
-static inline void ImplPostEvent( short nEventId, bool bAtStart, int nUserData = 0 )
+void ImplNSAppPostEvent( short nEventId, BOOL bAtStart, int nUserData )
 {
-    SalData::ensureThreadAutoreleasePool();
+    ReleasePoolHolder aPool;
 SAL_WNODEPRECATED_DECLARATIONS_PUSH
 // 'NSApplicationDefined' is deprecated: first deprecated in macOS 10.12
     NSEvent* pEvent = [NSEvent otherEventWithType: NSApplicationDefined
 SAL_WNODEPRECATED_DECLARATIONS_POP
                                location: NSZeroPoint
                                modifierFlags: 0
-                               timestamp: [NSDate timeIntervalSinceReferenceDate]
+                               timestamp: 0
                                windowNumber: 0
                                context: nil
                                subtype: nEventId
                                data1: nUserData
-                               data2: 0 ];
+                               data2: 0];
     assert( pEvent );
+    if ( nil == pEvent )
+        return;
+    if ( NO == bAtStart )
+    {
+        // nextEventMatchingMask has to run in the main thread!
+        assert([NSThread isMainThread]);
+
+        // Posting an event to the end of an empty queue fails,
+        // so we peek the queue and post to the start, if empty.
+        // Some Qt bugs even indicate nextEvent without dequeue
+        // sometimes blocks, so we dequeue and re-add the event.
+SAL_WNODEPRECATED_DECLARATIONS_PUSH
+// 'NSAnyEventMask' is deprecated: first deprecated in macOS 10.12
+        NSEvent* pPeekEvent = [NSApp nextEventMatchingMask: NSAnyEventMask
+SAL_WNODEPRECATED_DECLARATIONS_POP
+                               untilDate: nil
+                               inMode: NSDefaultRunLoopMode
+                               dequeue: YES];
+        if ( nil == pPeekEvent )
+            bAtStart = YES;
+        else
+            [NSApp postEvent: pPeekEvent atStart: YES];
+    }
     [NSApp postEvent: pEvent atStart: bAtStart];
 }
 
@@ -54,14 +77,18 @@ static void ImplSalStartTimer( sal_uLong nMS )
 {
     SalData* pSalData = GetSalData();
 
-    if ( 0 == nMS )
+    if( !pSalData->mpFirstInstance->IsMainThread() )
     {
-        ImplSalStopTimer();
-        ImplPostEvent( AquaSalInstance::DispatchTimerEvent, false );
+        ImplNSAppPostEvent( AquaSalInstance::AppStartTimerEvent, YES, nMS );
         return;
     }
 
-    if( pSalData->mpFirstInstance->IsMainThread() )
+    if ( 0 == nMS )
+    {
+        ImplSalStopTimer();
+        ImplNSAppPostEvent( AquaSalInstance::DispatchTimerEvent, NO );
+    }
+    else
     {
         NSTimeInterval aTI = double(nMS) / 1000.0;
         if( AquaSalTimer::pRunningTimer != nil )
@@ -89,8 +116,6 @@ static void ImplSalStartTimer( sal_uLong nMS )
             [[NSRunLoop currentRunLoop] addTimer: AquaSalTimer::pRunningTimer forMode: NSEventTrackingRunLoopMode];
         }
     }
-    else
-        ImplPostEvent( AquaSalInstance::AppStartTimerEvent, true, nMS );
 }
 
 static void ImplSalStopTimer()