refs #467 Mechanism for processes to notify each other of which log patterns they are subscribed to.

src/blackmisc/blackmiscfreefunctions.cpp

@@ -24,6 +24,7 @@
 #include "pixmap.h"
 #include "iconlist.h"
 #include "identifierlist.h"
+#include "logpattern.h"
 #include <QtNetwork/QHostInfo>
 #include <QProcessEnvironment>
 #include <QSysInfo>
@@ -83,6 +84,7 @@ void BlackMisc::registerMetadata()
     CIconList::registerMetadata();
     CLogCategory::registerMetadata();
     CLogCategoryList::registerMetadata();
+    CLogPattern::registerMetadata();
     CPixmap::registerMetadata();
     CIdentifier::registerMetadata();
     CIdentifierList::registerMetadata();

src/blackmisc/loghandler.cpp

@@ -57,7 +57,7 @@ namespace BlackMisc
         auto it = std::find_if(m_patternHandlers.begin(), m_patternHandlers.end(), finder);
         if (it == m_patternHandlers.end())
         {
-            auto *handler = new CLogPatternHandler(this);
+            auto *handler = new CLogPatternHandler(this, pattern);
             topologicallySortedInsert(m_patternHandlers, PatternPair(pattern, handler), comparator);
             return handler;
         }
@@ -149,8 +149,21 @@ namespace BlackMisc
         }
     }
 
-    CLogPatternHandler::CLogPatternHandler(CLogHandler *parent) :
-        QObject(parent), m_parent(parent)
+    QList<CLogPattern> CLogHandler::getAllSubscriptions() const
+    {
+        QList<CLogPattern> result;
+        for (const auto &pair : m_patternHandlers)
+        {
+            if (pair.second->isSignalConnected(QMetaMethod::fromSignal(&CLogPatternHandler::messageLogged)))
+            {
+                result.push_back(pair.first);
+            }
+        }
+        return result;
+    }
+
+    CLogPatternHandler::CLogPatternHandler(CLogHandler *parent, const CLogPattern &pattern) :
+        QObject(parent), m_parent(parent), m_pattern(pattern)
     {
         connect(&m_subscriptionUpdateTimer, &QTimer::timeout, this, &CLogPatternHandler::updateSubscription);
         m_subscriptionUpdateTimer.start(1);
@@ -163,7 +176,20 @@ namespace BlackMisc
             m_subscriptionNeedsUpdate = false;
             bool isSubscribed = isSignalConnected(QMetaMethod::fromSignal(&CLogPatternHandler::messageLogged));
 
-            if (m_inheritFallThrough && ! isSubscribed)
+            if (isSubscribed != m_isSubscribed)
+            {
+                m_isSubscribed = isSubscribed;
+                if (m_isSubscribed)
+                {
+                    emit m_parent->subscriptionAdded(m_pattern);
+                }
+                else
+                {
+                    emit m_parent->subscriptionRemoved(m_pattern);
+                }
+            }
+
+            if (m_inheritFallThrough && ! m_isSubscribed)
             {
                 m_parent->removePatternHandler(this);
             }

src/blackmisc/loghandler.h

@@ -63,6 +63,9 @@ namespace BlackMisc
             return handlerForPattern(CLogPattern::exactMatch(CLogCategory::validation()).withSeverityAtOrAbove(CStatusMessage::SeverityWarning));
         }
 
+        //! Returns all log patterns for which there are currently subscribed log pattern handlers.
+        QList<CLogPattern> getAllSubscriptions() const;
+
     signals:
         //! Emitted when a message is logged in this process.
         void localMessageLogged(const BlackMisc::CStatusMessage &message);
@@ -70,6 +73,12 @@ namespace BlackMisc
         //! Emitted when a log message is relayed from a different process.
         void remoteMessageLogged(const BlackMisc::CStatusMessage &message);
 
+        //! Emitted when an object subscribes to a pattern of log messages.
+        void subscriptionAdded(const BlackMisc::CLogPattern &pattern);
+
+        //! Emitted when an object unsubscribes from a pattern of log messages.
+        void subscriptionRemoved(const BlackMisc::CLogPattern &pattern);
+
     public slots:
         //! Called by our QtMessageHandler to log a message.
         void logLocalMessage(const BlackMisc::CStatusMessage &message);
@@ -178,11 +187,13 @@ namespace BlackMisc
 
     private:
         friend class CLogHandler;
-        CLogPatternHandler(CLogHandler *parent);
+        CLogPatternHandler(CLogHandler *parent, const CLogPattern &pattern);
         CLogHandler *m_parent = nullptr;
+        CLogPattern m_pattern;
         bool m_inheritFallThrough = true;
         bool m_enableFallThrough = true;
-        std::atomic<bool> m_subscriptionNeedsUpdate = false;
+        bool m_isSubscribed = false;
+        std::atomic<bool> m_subscriptionNeedsUpdate { false };
         QTimer m_subscriptionUpdateTimer;
         void updateSubscription();
     };