migrate: Qt5/C++11 app to Qt6/C++23 with tests and modern Qt APIs

Entire-Checkpoint: c1ee98dc34a3

qt6-after/qt6-migrated-benchmark/MainWindow.cpp

@@ -0,0 +1,55 @@
+#include "MainWindow.h"
+
+#include "ui_MainWindow.h"
+
+#include <QApplication>
+#include <QPixmap>
+#include <QScreen>
+#include <QString>
+
+MainWindow::MainWindow(QWidget* parent)
+    : QMainWindow(parent), ui(new Ui::MainWindow), pattern(QRegularExpression(R"(^[A-Za-z]+\d+$)"))
+{
+    ui->setupUi(this);
+
+    // Qt6 uses UTF-8 by default; no codec needed
+    setWindowTitle(QString::fromUtf8("Qt6 Migrated Benchmark"));
+    ui->label->setText(QString::fromUtf8("Bitte Text wie Test123 eingeben."));
+    ui->iconLabel->setPixmap(QPixmap(":/icons/app.png").scaled(48, 48));
+
+    // Modern function-pointer connect syntax
+    connect(ui->validateButton, &QPushButton::clicked, this, &MainWindow::onValidateClicked);
+    connect(ui->screenButton, &QPushButton::clicked, this, &MainWindow::onScreenInfoClicked);
+}
+
+MainWindow::~MainWindow()
+{
+    delete ui;
+}
+
+void MainWindow::onValidateClicked()
+{
+    const QString text = ui->lineEdit->text();
+
+    if (pattern.match(text).hasMatch())
+    {
+        ui->resultLabel->setText(QString::fromUtf8("Match"));
+    }
+    else
+    {
+        ui->resultLabel->setText(QString::fromUtf8("No match"));
+    }
+}
+
+void MainWindow::onScreenInfoClicked()
+{
+    // Qt6: Use QScreen instead of deprecated QDesktopWidget
+    const QScreen* screen = QApplication::primaryScreen();
+    if (screen)
+    {
+        const QRect screenGeometry = screen->geometry();
+        const QString info =
+            QString::fromUtf8("Screen: %1x%2").arg(screenGeometry.width()).arg(screenGeometry.height());
+        ui->resultLabel->setText(info);
+    }
+}