refs #336 Fixed CLogHandler thread safety in swiftcore.

src/blackmisc/loghandler.cpp

@@ -40,10 +40,7 @@ namespace BlackMisc
 
     CLogHandler::~CLogHandler()
     {
-        if (m_oldHandler)
-        {
-            qInstallMessageHandler(m_oldHandler);
-        }
+        qInstallMessageHandler(m_oldHandler);
     }
 
     CLogCategoryHandler *CLogHandler::handlerForCategoryPrefix(const QString &category)

src/blackmisc/loghandler.h

@@ -45,10 +45,6 @@ namespace BlackMisc
         //! \warning This must only be called from the main thread.
         CLogCategoryHandler *handlerForCategoryPrefix(const QString &prefix);
 
-        //! Enable or disable the default Qt handler.
-        //! \warning This must only be called from the main thread.
-        void enableConsoleOutput(bool enable);
-
     signals:
         //! Emitted when a message is logged in this process.
         void localMessageLogged(const BlackMisc::CStatusMessage &message);
@@ -63,6 +59,9 @@ namespace BlackMisc
         //! Called by the context to relay a message.
         void logRemoteMessage(const BlackMisc::CStatusMessage &message);
 
+        //! Enable or disable the default Qt handler.
+        void enableConsoleOutput(bool enable);
+
     private:
         void logMessage(const BlackMisc::CStatusMessage &message);
         QtMessageHandler m_oldHandler = nullptr;
@@ -80,11 +79,10 @@ namespace BlackMisc
     {
         Q_OBJECT
 
-    public:
+    public slots:
         /*!
          * Enable or disable the default Qt handler for messages in relevant categories.
          * This can override the setting of the parent CLogHandler.
-         * \warning This must only be called from the main thread.
          */
         void enableConsoleOutput(bool enable) { Q_ASSERT(thread() == QThread::currentThread()); m_enableFallThrough = enable; }
 

src/blackmisc/worker.h

@@ -14,12 +14,33 @@
 
 #include <QThread>
 #include <QMutex>
+#include <QTimer>
 #include <functional>
 #include <atomic>
 
 namespace BlackMisc
 {
 
+    /*!
+     * Starts a single-shot timer which will run in an existing thread and call a task when it times out.
+     *
+     * Useful when a worker thread wants to push small sub-tasks back to the thread which spawned it.
+     * \see QTimer::singleShot()
+     */
+    template <typename F>
+    void singleShot(int msec, QThread *target, F task)
+    {
+        auto *timer = new QTimer;
+        timer->setSingleShot(true);
+        timer->moveToThread(target);
+        QObject::connect(timer, &QTimer::timeout, [ = ]()
+        {
+            task();
+            timer->deleteLater();
+        });
+        QMetaObject::invokeMethod(timer, "start", Q_ARG(int, msec));
+    }
+
     /*!
      * Just a subclass of QThread whose destructor waits for the thread to finish.
      */