C++ (Qt)
#include "mainwindow.h"
 
#include <QPlainTextEdit>
#include <QDebug>
#include <QScrollBar>
#include <QApplication>
#include <QTranslator>
 
static QtMsgHandler oldMsgHandler = 0;
 
static void logMsgHandler(QtMsgType type, const char *msg)
{
    MainWindow::instance()->log(msg);
    oldMsgHandler(type, msg);
}
 
MainWindow *MainWindow::self = 0;
 
MainWindow *MainWindow::instance()
{
    if (!MainWindow::self) {
        MainWindow::self = new MainWindow();
    }
    return MainWindow::self;
}
 
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , logView(new QPlainTextEdit(this))
{
    self = this;
    setCentralWidget(logView);
    logView->setReadOnly(true);
    logView->setMaximumBlockCount(1000);
 
    oldMsgHandler = qInstallMsgHandler(logMsgHandler);
 
    QTranslator *translator = new QTranslator(this);
    if (translator->load(QString(":/translations/test_%2.qm").arg(QLocale::system().name())))
        qApp->installTranslator(translator);
    else delete translator;
 
    QString text = tr("Test from qDebug");
    qDebug() << text.toLocal8Bit().constData();
    text = tr("Test from code");
    log(text);
}
 
MainWindow::~MainWindow()
{
    qInstallMsgHandler(oldMsgHandler);
}
 
void MainWindow::log(const QString &msg)
{
    logView->appendPlainText(msg);
    logView->verticalScrollBar()->setValue(logView->verticalScrollBar()->maximum());
}