#include <QApplication>
#include <QFrame>
#include <QVBoxLayout>
#include <QPushButton>
#include <QMainWindow>
#include <qevent.h>
#include "./ui_mainwindow.h"

namespace Ui {
    class MainWindow;
}

namespace{

    bool isAltModifierActive() {
        return QGuiApplication::keyboardModifiers() & Qt::AltModifier;
    }

    bool isEventAltModifierActive(QKeyEvent* event) {
        return event->modifiers() & Qt::AltModifier;
    }

    class MainWindow : public QMainWindow
    {
        Q_OBJECT

    public:
        MainWindow(QWidget *parent = nullptr)
            : QMainWindow(parent)
            , ui(new Ui::MainWindow)
            , altPressed(false)
        {
            ui->setupUi(this);
        }

        ~MainWindow()
        {
            delete ui;
        }

    protected:
        void paintEvent(QPaintEvent* event) override
        {
            if (altPressed) {
                qDebug() << "MainWindow redrawn after Alt key press!";
                qDebug() << "    Alt modifier: " << isAltModifierActive();
            }
            QMainWindow::paintEvent(event);
        };

        void keyPressEvent(QKeyEvent* event) override
        {
            if (event->key() == Qt::Key_Alt) {
                qDebug() << "MainWindow - Alt key pressed!";
                qDebug() << "    Alt modifier: " << isAltModifierActive();
                qDebug() << "    event Alt modifier: " << isEventAltModifierActive(event);

                // this->repaint();
            }
            QMainWindow::keyPressEvent(event);
        };

        void keyReleaseEvent(QKeyEvent* event) override
        {
            if (event->key() == Qt::Key_Alt) {
                qDebug() << "MainWindow - Alt key released!";
                qDebug() << "    Alt modifier: " << isAltModifierActive();
                qDebug() << "    event Alt modifier: " << isEventAltModifierActive(event);

                // this->repaint();
            }
            QMainWindow::keyReleaseEvent(event);
        };

    private:
        Ui::MainWindow *ui;

        bool altPressed;
    };

}

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

    MainWindow mainWindow;

    auto* central = new QFrame;
    auto* layout = new QVBoxLayout(central);

    auto* open = new QPushButton("&Open");
    layout->addWidget(open);

    auto* close = new QPushButton("&Close");
    layout->addWidget(close);

    auto* help = new QPushButton("&Help");
    layout->addWidget(help);

    mainWindow.setCentralWidget(central);
    mainWindow.show();

    return a.exec();
}

#include "main.moc"