refs #287 Thread safety, fix "memory access violation"

* some improved comments and information
* QMetaObject::invokeMethod in tool.cpp as thread safe invocation
* common base class for threaded readers
* removed event class, using QMetaObject::invoke instead for forcing calls in main event loop
* stop methods for readers, as used for graceful shutdown (preparing for thread safe destruction of objects)
* graceful shutdown for network context
* calls in tool now via inkoke for thread safety (only thread safe methods called directly)

src/blackcore/context_application.h

@@ -9,6 +9,7 @@
 #include "blackcore/context.h"
 #include "blackmisc/statusmessagelist.h"
 #include <QObject>
+#include <QReadWriteLock>
 
 #define BLACKCORE_CONTEXTAPPLICATION_INTERFACENAME "net.vatsim.PilotClient.BlackCore.ContextApplication"
 #define BLACKCORE_CONTEXTAPPLICATION_OBJECTPATH "/Application"
@@ -16,7 +17,7 @@
 namespace BlackCore
 {
     /*!
-     * \brief Application context interface
+     * Application context interface
      */
     class IContextApplication : public CContext
     {
@@ -76,20 +77,21 @@ namespace BlackCore
         virtual ~IContextApplication() {}
 
         //! Output redirection (redirect my output)
-        RedirectionLevel getOutputRedirectionLevel() const { return this->m_outputRedirectionLevel; }
+        //! \threadsafe
+        RedirectionLevel getOutputRedirectionLevel() const;
 
         //! Output redirection (redirect my output)
-        void setOutputRedirectionLevel(RedirectionLevel redirectionLevel) { this->m_outputRedirectionLevel = redirectionLevel; }
+        //! \threadsafe
+        void setOutputRedirectionLevel(RedirectionLevel redirectionLevel);
 
         //! Redirected output generated by others
-        RedirectionLevel getStreamingForRedirectedOutputLevel() const { return this->m_redirectedOutputRedirectionLevel; }
+        //! \threadsafe
+        RedirectionLevel getStreamingForRedirectedOutputLevel() const;
 
         //! Redirected output generated by others
+        //! \threadsafe
         void setStreamingForRedirectedOutputLevel(RedirectionLevel redirectionLevel) ;
 
-        //! Process event, cross thread messages
-        bool event(QEvent *event) override;
-
         //! Reset output redirection
         static void resetOutputRedirection();
 
@@ -144,13 +146,16 @@ namespace BlackCore
         static QtMessageHandler s_oldHandler;
 
         //! Message handler, handles one individual context
+        //! \threadsafe
         void messageHandler(QtMsgType type, const QMessageLogContext &messageContext, const QString &messsage);
 
         //! Handle output dispatch, handles all contexts
+        //! \remarks Can be called in thread, has to be thread safe
         static void messageHandlerDispatch(QtMsgType type, const QMessageLogContext &messageContext, const QString &message);
 
         RedirectionLevel m_outputRedirectionLevel; //!< enable / disable my output
-        RedirectionLevel m_redirectedOutputRedirectionLevel; //!< enable / disable others output
+        RedirectionLevel m_redirectedOutputRedirectionLevel; //!< enable / disable others' output
+        mutable QReadWriteLock m_lock; //!< thread safety
 
     private slots:
         //! Re-stream the redirected output