QML console.log qDebug() to QML TextEdit object using qInstallMessageHandler

main.cpp

#include <QtMessageHandler>
#include <QQmlApplicationEngine>
#include <QQmlContext>

QObject * s_qml_text_edit = 0;

void myMessageOutput(QtMsgType type, const QMessageLogContext &context, const QString &msg)
{
    if(s_qml_text_edit)
    {
        QString temp = msg;
        // http://doc.qt.io/qt-5/qtqml-cppintegration-interactqmlfromcpp.html#invoking-qml-methods
        QMetaObject::invokeMethod(s_qml_text_edit, "append",
//                Q_RETURN_ARG(QVariant, returnedValue),
                Q_ARG(QString, temp));
//        QByteArray localMsg = msg.toLocal8Bit();
//        fprintf(stderr, "Debug1: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function);
//        break;
    }
    else if(MainWindow::s_textEdit)
    {
        switch (type) {
        case QtDebugMsg:
        case QtWarningMsg:
        case QtCriticalMsg:
            // redundant check, could be removed, or the
            // upper if statement could be removed
            if(MainWindow::s_textEdit != 0)
                MainWindow::appendText(msg);
            break;
        case QtFatalMsg:
            abort();
        }
    }
    else
    {
        QByteArray localMsg = msg.toLocal8Bit();
        switch (type) {
        case QtDebugMsg:
            fprintf(stderr, "Debug: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function);
            break;
        case QtWarningMsg:
            fprintf(stderr, "Warning: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function);
            break;
        case QtCriticalMsg:
            fprintf(stderr, "Critical: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function);
            break;
        case QtFatalMsg:
            fprintf(stderr, "Fatal: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function);
            abort();
        }
    }
}

int main() {
        qInstallMessageHandler(myMessageOutput);
// ...

        QApplication a(argc, argv);// can be changed to QGuiApplication for QML only
        QQmlApplicationEngine engine;

        engine.load(QUrl(QStringLiteral("qrc:/qml/MainWindowForm.qml")));
        
        // get the object with the name "textEdit" and make it accessible by the messageHandler
        s_qml_text_edit = engine.rootObjects().first()->findChild<QObject*>("textEdit");
        QmlMainWindow w(engine.rootObjects().first());

        w.start();
        return a.exec();
}

MainWindowForm.qml

import QtQuick.Window 2.2

Window {
  id: root
  
      Flickable {
             id: flick

             Layout.minimumHeight: 50
             Layout.fillHeight: true
             contentWidth: textEdit.paintedWidth
             contentHeight: textEdit.paintedHeight
             clip: true

             function ensureVisible(r)
             {
                 if (contentX >= r.x)
                     contentX = r.x;
                 else if (contentX+width <= r.x+r.width)
                     contentX = r.x+r.width-width;
                 if (contentY >= r.y)
                     contentY = r.y;
                 else if (contentY+height <= r.y+r.height)
                     contentY = r.y+r.height-height;
             }


             TextEdit {
                 objectName: "textEdit"
                 id: textEdit
                 width: flick.width
                 height: flick.height
                 focus: true
                 wrapMode: TextEdit.Wrap
                 text: qsTr("QML Debug Output")
                 font.pixelSize: 12
                 onCursorRectangleChanged: flick.ensureVisible(cursorRectangle)
                 onTextChanged: cursorPosition = text.length
             }
        }
}