refs #316 Added CLogHandler which allows to subscribe to log messages.

src/blackmisc/loghandler.h

@@ -0,0 +1,101 @@
+/* Copyright (C) 2014
+ * Swift Project Community / Contributors
+ *
+ * This file is part of Swift Project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution and at http://www.swift-project.org/license.html. No part of Swift Project,
+ * including this file, may be copied, modified, propagated, or distributed except according to the terms
+ * contained in the LICENSE file.
+ */
+
+#ifndef BLACKMISC_LOGHANDLER_H
+#define BLACKMISC_LOGHANDLER_H
+
+//! \file
+
+#include "statusmessage.h"
+#include <QObject>
+#include <QMap>
+
+namespace BlackMisc
+{
+    class CLogCategoryHandler;
+
+    /*!
+     * Class for subscribing to log messages.
+     */
+    class CLogHandler : public QObject
+    {
+        Q_OBJECT
+
+    public:
+        //! \private Constructor.
+        CLogHandler();
+
+        //! \private Destructor.
+        ~CLogHandler();
+
+        //! Return pointer to the CLogHandler singleton.
+        //! \warning This can not be called from within a plugin, because the returned instance will be wrong.
+        static CLogHandler *instance();
+
+        //! Tell the CLogHandler to install itself with qInstallMessageHandler.
+        void install();
+
+        //! Return a category handler for subscribing to all messages whose category string starts with the given prefix.
+        CLogCategoryHandler *handlerForCategory(const QString &prefix);
+
+        //! Enable or disable the default Qt handler.
+        void enableConsoleOutput(bool enable);
+
+    signals:
+        //! Emitted when a message is logged in this process.
+        void localMessageLogged(const BlackMisc::CStatusMessage &message);
+
+        //! Emitted when a log message is relayed from a different process.
+        void remoteMessageLogged(const BlackMisc::CStatusMessage &message);
+
+    public slots:
+        //! Called by our QtMessageHandler to log a message.
+        void logLocalMessage(const BlackMisc::CStatusMessage &message);
+
+        //! Called by the context to relay a message.
+        void logRemoteMessage(const BlackMisc::CStatusMessage &message);
+
+    private:
+        void logMessage(const BlackMisc::CStatusMessage &message);
+        QtMessageHandler m_oldHandler = nullptr;
+        bool m_enableFallThrough = true;
+        bool isFallThroughEnabled(const QList<CLogCategoryHandler *> &handlers) const;
+        QMap<QString, CLogCategoryHandler *> m_categoryHandlers;
+        QList<CLogCategoryHandler *> handlersForCategory(const QString &category) const;
+    };
+
+    /*!
+     * A class for subscribing to log messages in particular categories.
+     * \sa CLogHandler::handlerForCategory
+     */
+    class CLogCategoryHandler : public QObject
+    {
+        Q_OBJECT
+
+    public:
+        /*!
+         * Enable or disable the default Qt handler for messages in relevant categories.
+         * This can override the setting of the parent CLogHandler.
+         */
+        void enableConsoleOutput(bool enable) { m_enableFallThrough = enable; }
+
+    signals:
+        /*!
+         * Emitted when a message is logged in a relevant category.
+         */
+        void messageLogged(const CStatusMessage &message);
+
+    private:
+        friend class CLogHandler;
+        CLogCategoryHandler(QObject *parent, bool enableFallThrough) : QObject(parent), m_enableFallThrough(enableFallThrough) {}
+        bool m_enableFallThrough;
+    };
+}
+
+#endif