**Course Title:** Qt 6 Application Development with C++ **Section Title:** Widgets, Layouts, and Events **Topic:** Building a basic form using Qt widgets, layouts, and event handling.(Lab topic) In this lab topic, we will put together the concepts learned so far to create a basic form using Qt widgets, layouts, and event handling. This exercise will help solidify your understanding of the topics covered in the previous sections and provide hands-on experience in designing and developing simple graphical user interfaces (GUIs) with Qt. **Learning Objectives** By completing this lab, you will be able to: 1. Create a basic form using Qt widgets (e.g., QLabel, QLineEdit, QPushButton) 2. Organize the widgets using different layout managers (e.g., QVBoxLayout, QHBoxLayout) 3. Connect widgets to custom slots using the signal-slot mechanism 4. Handle events and validate user input **Creating the Basic Form** For this example, let's create a simple login form that prompts the user to enter their username and password. We will use the following Qt widgets: * QLabel for displaying labels * QLineEdit for input fields * QPushButton for the login button Here's the code to create the basic form: ```cpp #include <QApplication> #include <QDialog> #include <QVBoxLayout> #include <QHBoxLayout> #include <QLabel> #include <QLineEdit> #include <QPushButton> class LoginForm : public QDialog { Q_OBJECT public: LoginForm(QWidget *parent = nullptr); private slots: void onLoginButtonClicked(); private: QLineEdit *usernameLineEdit; QLineEdit *passwordLineEdit; QPushButton *loginButton; }; LoginForm::LoginForm(QWidget *parent) : QDialog(parent) { QVBoxLayout *mainLayout = new QVBoxLayout; setLayout(mainLayout); QLabel *usernameLabel = new QLabel("Username:"); mainLayout->addWidget(usernameLabel); usernameLineEdit = new QLineEdit; mainLayout->addWidget(usernameLineEdit); QLabel *passwordLabel = new QLabel("Password:"); mainLayout->addWidget(passwordLabel); passwordLineEdit = new QLineEdit; passwordLineEdit->setEchoMode(QLineEdit::Password); mainLayout->addWidget(passwordLineEdit); QHBoxLayout *buttonLayout = new QHBoxLayout; mainLayout->addLayout(buttonLayout); QPushButton *cancelButton = new QPushButton("Cancel"); buttonLayout->addWidget(cancelButton); loginButton = new QPushButton("Login"); buttonLayout->addWidget(loginButton); connect(loginButton, &QPushButton::clicked, this, &LoginForm::onLoginButtonClicked); } void LoginForm::onLoginButtonClicked() { // Get the username and password from the input fields QString username = usernameLineEdit->text(); QString password = passwordLineEdit->text(); // Validate the username and password ( mocked for demonstration purposes) if (username.isEmpty() || password.isEmpty()) { QMessageBox::information(this, "Error", "Please enter both username and password."); } else if (username != "admin" || password != "password") { QMessageBox::information(this, "Error", "Invalid username or password."); } else { QMessageBox::information(this, "Success", "Login successful!"); } } int main(int argc, char *argv[]) { QApplication app(argc, argv); LoginForm loginForm; loginForm.show(); return app.exec(); } ``` In this code, we created a LoginForm class that inherits from QDialog. We used a QVBoxLayout as the main layout and added the widgets to it. We also connected the login button's clicked signal to the onLoginButtonClicked slot. **Key Concepts and Takeaways** * Use a QVBoxLayout as the main layout to organize the widgets vertically. * Use a QHBoxLayout to organize the buttons horizontally. * Connect the widgets to custom slots using the signal-slot mechanism. * Use the QLineEdit::Password EchoMode to display asterisks (*) for password input fields. * Use the QMessageBox to display error messages or success notifications. **Practical Exercise** Modify the LoginForm class to include the following features: * A "Remember me" checkbox that stores the username and password in a QStringList * A "Forgot password" button that displays a message box with a password recovery link **Additional Resources** For more information on Qt widgets, layouts, and event handling, refer to the following resources: * Qt Documentation: [https://doc.qt.io/](https://doc.qt.io/) * Qt Widgets Module: [https://doc.qt.io/qt-6/qtwidgets-module.html](https://doc.qt.io/qt-6/qtwidgets-module.html) **Questions or Need Help?** If you have any questions or need help with this lab, feel free to use the space below to ask and discuss with other students. Please provide your feedback and any questions about this topic before we move on to the next one: 'Exploring advanced widgets: QComboBox, QListWidget, QTableWidget, QTreeView.'