Using the m_FeedbackFDs is now apparently necessary also on iOS

The below commit message is relevant for the behaviour fixed by this
change in the Collabora branch cp-6.0 (or core) and collabora-online-4
(of online). The behaviour here in master is broken in different ways,
though, and I am not entirely sure whether this change fixes anything
here. But let's apply it here, too, for consistency.

Until recently we had managed without them on iOS, but that changed
with the recent "Unipoll" work, I think. (Without this change, the iOS
app now runs into assertion failures early on. But note that this
change is not enough to make it work fully again.)

Change-Id: I09d25326ba73ce897da5c91f30530f5b3d5fd272

vcl/headless/svpinst.cxx

@@ -77,9 +77,7 @@ SvpSalInstance::SvpSalInstance( std::unique_ptr<SalYieldMutex> pMutex )
     m_nTimeoutMS            = 0;
 
     m_MainThread = osl::Thread::getCurrentIdentifier();
-#ifndef IOS
     CreateWakeupPipe(true);
-#endif
     if( s_pDefaultInstance == nullptr )
         s_pDefaultInstance = this;
 #if !defined(ANDROID) && !defined(IOS)
@@ -91,13 +89,9 @@ SvpSalInstance::~SvpSalInstance()
 {
     if( s_pDefaultInstance == this )
         s_pDefaultInstance = nullptr;
-#ifndef IOS
     CloseWakeupPipe(true);
-#endif
 }
 
-#ifndef IOS
-
 void SvpSalInstance::CloseWakeupPipe(bool log)
 {
     SvpSalYieldMutex *const pMutex(dynamic_cast<SvpSalYieldMutex*>(GetYieldMutex()));
@@ -153,8 +147,6 @@ void SvpSalInstance::CreateWakeupPipe(bool log)
     }
 }
 
-#endif
-
 void SvpSalInstance::TriggerUserEventProcessing()
 {
     Wakeup();
@@ -343,11 +335,7 @@ void SvpSalYieldMutex::doAcquire(sal_uInt32 const nLockCount)
                 m_bNoYieldLock = true;
                 bool const bEvents = pInst->DoYield(false, request == SvpRequest::MainThreadDispatchAllEvents);
                 m_bNoYieldLock = false;
-#ifdef IOS
-                (void)bEvents;
-#else
                 write(m_FeedbackFDs[1], &bEvents, sizeof(bool));
-#endif
             }
         }
         while (true);
@@ -507,11 +495,9 @@ bool SvpSalInstance::DoYield(bool bWait, bool bHandleAllCurrentEvents)
                 : SvpRequest::MainThreadDispatchOneEvent);
 
         bool bDidWork(false);
-#ifndef IOS
         // blocking read (for synchronisation)
         auto const nRet = read(pMutex->m_FeedbackFDs[0], &bDidWork, sizeof(bool));
         assert(nRet == 1); (void) nRet;
-#endif
         if (!bDidWork && bWait)
         {
             // block & release YieldMutex until the main thread does something

vcl/inc/headless/svpinst.hxx

@@ -73,9 +73,7 @@ private:
     // at least one subclass of SvpSalInstance (GTK3) that doesn't use them.
     friend class SvpSalInstance;
     // members for communication from main thread to non-main thread
-#ifndef IOS
     int                     m_FeedbackFDs[2];
-#endif
     osl::Condition          m_NonMainWaitingYieldCond;
     // members for communication from non-main thread to main thread
     bool                    m_bNoYieldLock = false; // accessed only on main thread