Fix logger thread so that it doesn't lose messages at startup.

This was particularly noticeable when running for the first time and
selecting OSCAR's data location.

oscar/logger.cpp

@@ -1,5 +1,6 @@
-/* OSCAR Logger module implementation
+/* OSCAR Logger module implementation
  *
+ * Copyright (c) 2020 The OSCAR Team
  * Copyright (c) 2011-2018 Mark Watkins <mark@jedimark.net>
  *
  * This file is subject to the terms and conditions of the GNU General Public
@@ -59,18 +60,32 @@ void MyOutputHandler(QtMsgType type, const QMessageLogContext &context, const QS
 
 }
 
+static QMutex s_LoggerRunning;
+
 void initializeLogger()
 {
+    s_LoggerRunning.lock();  // lock until the thread starts running
     logger = new LogThread();
     otherThreadPool = new QThreadPool();
     bool b = otherThreadPool->tryStart(logger);
+    if (b) {
+        s_LoggerRunning.lock();  // wait until the thread begins running
+        s_LoggerRunning.unlock();  // we no longer need the lock
+    }
     qInstallMessageHandler(MyOutputHandler);
     if (b) {
         qDebug() << "Started logging thread";
     } else {
         qWarning() << "Logging thread did not start correctly";
     }
+}
 
+void LogThread::connectionReady()
+{
+    strlock.lock();
+    connected = true;
+    strlock.unlock();
+    qDebug() << "Logging UI initialized";
 }
 
 void shutdownLogger()
@@ -117,10 +132,11 @@ void LogThread::quit() {
 void LogThread::run()
 {
     running = true;
+    s_LoggerRunning.unlock();  // unlock as soon as the thread begins to run
     do {
         strlock.lock();
         //int r = receivers(SIGNAL(outputLog(QString())));
-        while (!buffer.isEmpty()) {
+        while (connected && !buffer.isEmpty()) {
             QString msg = buffer.takeFirst();
                 fprintf(stderr, "%s\n", msg.toLocal8Bit().data());
                 emit outputLog(msg);

oscar/logger.h

@@ -1,4 +1,4 @@
-#ifndef LOGGER_H
+#ifndef LOGGER_H
 #define LOGGER_H
 
 #include <QDebug>
@@ -16,13 +16,14 @@ class LogThread:public QObject, public QRunnable
 {
     Q_OBJECT
 public:
-    explicit LogThread() : QRunnable() { running = false; logtime.start(); }
+    explicit LogThread() : QRunnable() { running = false; logtime.start(); connected = false; }
     virtual ~LogThread() {}
 
     void run();
     void append(QString msg);
     void appendClean(QString msg);
     bool isRunning() { return running; }
+    void connectionReady();
 
     void quit();
 
@@ -34,6 +35,7 @@ signals:
 protected:
     volatile bool running;
     QTime logtime;
+    bool connected;
 };
 
 extern LogThread * logger;

oscar/main.cpp

@@ -1,5 +1,6 @@
 /* OSCAR Main
  *
+ * Copyright (c) 2019-2020 The OSCAR Team
  * Copyright (c) 2011-2018 Mark Watkins <mark@jedimark.net>
  *
  * This file is subject to the terms and conditions of the GNU General Public
@@ -338,7 +339,6 @@ int main(int argc, char *argv[]) {
     }
 
     initializeLogger();
-    QThread::msleep(50); // Logger takes a little bit to catch up
 
     qDebug().noquote() << "OSCAR starting" << QDateTime::currentDateTime().toString();
 

oscar/mainwindow.cpp

@@ -69,10 +69,10 @@ MainWindow::MainWindow(QWidget *parent) :
     ui(new Ui::MainWindow)
 {
     ui->setupUi(this);
-    ui->logText->setPlainText("00000: Startup: OSCAR Logger initialized");
 
     if (logger) {
         connect(logger, SIGNAL(outputLog(QString)), this, SLOT(logMessage(QString)));
+        logger->connectionReady();
     }
 
     // Bring window to top (useful when language is changed)