Make messageThreadID atomic (#26)

Author: kunitoki

modules/juce_events/messages/juce_MessageManager.cpp

@@ -252,18 +252,16 @@ void MessageManager::deregisterBroadcastListener (ActionListener* const listener
 //==============================================================================
 bool MessageManager::isThisTheMessageThread() const noexcept
 {
-    const std::lock_guard<std::mutex> lock { messageThreadIdMutex };
-
-    return Thread::getCurrentThreadId() == messageThreadId;
+    return Thread::getCurrentThreadId() == messageThreadId.get();
 }
 
 void MessageManager::setCurrentThreadAsMessageThread()
 {
     auto thisThread = Thread::getCurrentThreadId();
 
-    const std::lock_guard<std::mutex> lock { messageThreadIdMutex };
+    messageThreadId.exchange(thisThread);
 
-    if (std::exchange (messageThreadId, thisThread) != thisThread)
+    if (messageThreadId.get() != thisThread)
     {
 #if JUCE_WINDOWS
         // This is needed on windows to make sure the message window is created by this thread
@@ -276,7 +274,7 @@ void MessageManager::setCurrentThreadAsMessageThread()
 bool MessageManager::currentThreadHasLockedMessageManager() const noexcept
 {
     auto thisThread = Thread::getCurrentThreadId();
-    return thisThread == messageThreadId || thisThread == threadWithLock.get();
+    return thisThread == messageThreadId.get() || thisThread == threadWithLock.get();
 }
 
 bool MessageManager::existsAndIsLockedByCurrentThread() noexcept

modules/juce_events/messages/juce_MessageManager.h

@@ -147,7 +147,7 @@ class JUCE_API MessageManager final
         (Best to ignore this method unless you really know what you're doing..)
         @see setCurrentThreadAsMessageThread
     */
-    Thread::ThreadID getCurrentMessageThread() const noexcept { return messageThreadId; }
+    Thread::ThreadID getCurrentMessageThread() const noexcept { return messageThreadId.get(); }
 
     /** Returns true if the caller thread has currently got the message manager locked.
 
@@ -352,9 +352,8 @@ class JUCE_API MessageManager final
 
     std::unique_ptr<ActionBroadcaster> broadcaster;
     Atomic<int> quitMessagePosted { 0 }, quitMessageReceived { 0 };
-    Thread::ThreadID messageThreadId;
+    Atomic<Thread::ThreadID> messageThreadId;
     Atomic<Thread::ThreadID> threadWithLock;
-    mutable std::mutex messageThreadIdMutex;
 
     static bool postMessageToSystemQueue (MessageBase*);
     static void* exitModalLoopCallback (void*);