Qt5 log to both stdout/stderr and textEdit with qInfo qDebug etc

main.cpp

#include "mainwindow.h"
#include <QApplication>
#include <QDateTime>

void myMessageOutput(QtMsgType type, const QMessageLogContext &context, const QString &msg);

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    qInstallMessageHandler(myMessageOutput);

    MainWindow w;
    w.show();

    return a.exec();
}


void myMessageOutput(QtMsgType type, const QMessageLogContext &context, const QString &msg)
{
    QByteArray localMsg = msg.toLocal8Bit();
    const char *file = context.file ? context.file : "未知文件";
    const char *function = context.function ? context.function : "未知函数";
    
    const char * timeStr = qUtf8Printable(QDateTime::currentDateTime().toString("HH:mm:ss"));
    
    QString qstr   ;
    
    switch (type) {
        case QtDebugMsg:
            fflush(stderr);
            qstr = QString("DBG: %1\t( %2 来自文件 %3 的第 %4 行, 函数 %5 )")
                .arg( localMsg.constData() )
                .arg( timeStr)
                .arg( file)
                .arg( context.line)
                .arg( function ) ;
            fprintf(stdout, qUtf8Printable(qstr+'\n') );
            fflush(stdout);
            break;
        case QtInfoMsg:
            fflush(stderr);
            qstr = QString(localMsg.constData());
            fprintf(stdout, qUtf8Printable(qstr+'\n') );
            fflush(stdout);
            break;
        case QtWarningMsg:
            fflush(stdout);
            qstr = QString(localMsg.constData());
            fprintf(stderr, qUtf8Printable(qstr+'\n') );
            fflush(stderr);
            break;
        case QtCriticalMsg:
            fflush(stdout);
            qstr = QString("CRITICAL: %1 (%2:%3, %4)")
                .arg( localMsg.constData() )
                .arg( file)
                .arg( context.line)
                .arg( function ) ;
            fprintf(stderr, qUtf8Printable(qstr+'\n') );
            fflush(stderr);
            break;
        case QtFatalMsg:
            fflush(stdout);
            qstr = QString("FATAL: %1 (%2:%3, %4)")
                .arg( localMsg.constData() )
                .arg( file)
                .arg( context.line)
                .arg( function ) ;
            fprintf(stderr, qUtf8Printable(qstr+'\n') );
            fflush(stderr);
            break;
    }
    
    MainWindow::teLog->append(qstr);
    
}