add message hanler functionality

message_handler.cpp

@@ -0,0 +1,97 @@
+#include "message_handler.h"
+
+#include <QDateTime>
+#include <cstring>
+#include <QString>
+#include <QFileInfo>
+#include <QMessageLogContext>
+
+
+static char const *DBG_NAME[] = { "DBG  ", "WARN ", "CRIT ", "FATAL", "INFO " };
+static bool installedMsgHandler = false;
+static int debugLevel = LOG_NOTICE;
+
+int getDebugLevel() { return debugLevel; }
+void setDebugLevel(int newDebugLevel) {
+    debugLevel = newDebugLevel;
+}
+
+bool messageHandlerInstalled() {
+    return installedMsgHandler;
+}
+
+QtMessageHandler atbInstallMessageHandler(QtMessageHandler handler) {
+    installedMsgHandler = (handler != 0);
+    static QtMessageHandler prevHandler = nullptr;
+    if (handler) {
+        prevHandler = qInstallMessageHandler(handler);
+        return prevHandler;
+    } else {
+        return qInstallMessageHandler(prevHandler);
+    }
+}
+
+///
+/// \brief Print message according to given debug level.
+///
+/// \note Install this function using qInstallMsgHandler().
+///
+///  int main(int argc, char **argv) {
+///     installMsgHandler(atbDebugOutput);
+///     QApplication app(argc, argv);
+///     ...
+///     return app.exec();
+///  }
+///
+#if (QT_VERSION > QT_VERSION_CHECK(5, 0, 0) && QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
+void atbDebugOutput(QtMsgType type, const QMessageLogContext &context, const QString &msg) {
+    Q_UNUSED(context);
+    QString const localMsg = QString(DBG_NAME[type]) + msg.toLocal8Bit();
+
+    switch (debugLevel) {
+        case LOG_DEBUG: { // debug-level message
+            syslog(LOG_DEBUG, "%s", localMsg.toStdString().c_str());
+        } break;
+        case LOG_INFO: { // informational message
+            if (type != QtDebugMsg) {
+                syslog(LOG_DEBUG, "%s", localMsg.toStdString().c_str());
+            }
+        } break;
+        case LOG_NOTICE: { // normal, but significant, condition
+            if (type != QtDebugMsg) {
+                syslog(LOG_DEBUG, "%s", localMsg.toStdString().c_str());
+            }
+        } break;
+        case LOG_WARNING: { // warning conditions
+            if (type != QtInfoMsg && type != QtDebugMsg) {
+                syslog(LOG_DEBUG, "%s", localMsg.toStdString().c_str());
+            }
+        } break;
+        case LOG_ERR: { // error conditions
+            if (type != QtInfoMsg && type != QtDebugMsg && type != QtWarningMsg) {
+                syslog(LOG_DEBUG, "%s", localMsg.toStdString().c_str());
+            }
+        } break;
+        case LOG_CRIT: { // critical conditions
+            if (type != QtInfoMsg && type != QtDebugMsg && type != QtWarningMsg) {
+                syslog(LOG_DEBUG, "%s", localMsg.toStdString().c_str());
+            }
+        } break;
+        case LOG_ALERT: { // action must be taken immediately
+            if (type != QtInfoMsg && type != QtDebugMsg && type != QtWarningMsg) {
+                syslog(LOG_DEBUG, "%s", localMsg.toStdString().c_str());
+            }
+        } break;
+        case LOG_EMERG: { // system is unusable
+            if (type != QtInfoMsg && type != QtDebugMsg && type != QtWarningMsg) {
+                syslog(LOG_DEBUG, "%s", localMsg.toStdString().c_str());
+            }
+        } break;
+        default: {
+            //fprintf(stderr, "%s No ErrorLevel defined! %s\n",
+            //    datetime.toStdString().c_str(), msg.toStdString().c_str());
+        }
+    }
+}
+#endif
+

message_handler.h

@@ -0,0 +1,23 @@
+#ifndef MESSAGE_HANDLER_H_INCLUDED
+#define MESSAGE_HANDLER_H_INCLUDED
+
+#include <QtGlobal>
+#ifdef __linux__
+#include <syslog.h>
+#endif
+
+int getDebugLevel();
+void setDebugLevel(int newDebugLevel);
+
+bool messageHandlerInstalled();
+QtMessageHandler atbInstallMessageHandler(QtMessageHandler handler);
+
+#if QT_VERSION < QT_VERSION_CHECK(5, 0, 0)
+// typedef void (*QtMessageHandler)(QtMsgType, const char *);
+void atbDebugOutput(QtMsgType type, const char *msg);
+#elif QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+// typedef void (*QtMessageHandler)(QtMsgType, const QMessageLogContext &, const QString &);
+void atbDebugOutput(QtMsgType type, const QMessageLogContext &context, const QString &msg);
+#endif
+
+#endif // MESSAGE_HANDLER_H_INCLUDED