**Course Title:** PyQt6 Application Development **Section Title:** Styling and Theming in PyQt6 **Topic:** Designing a custom-styled app with dynamic theming, including a dark mode.(Lab topic) **Introduction** In previous topics, we explored how to customize the appearance of widgets using Qt Stylesheets. In this lab topic, we will take it a step further by designing a custom-styled application with dynamic theming, including a dark mode. You will learn how to create a theme management system that allows users to switch between different themes at runtime. **Objectives** By the end of this topic, you will be able to: 1. Design a custom-styled application with a unique look and feel 2. Create a theme management system that allows users to switch between different themes 3. Implement dynamic theming, including a dark mode 4. Use Qt Stylesheets to customize the appearance of widgets **Designing the Application** Before we start coding, let's take some time to design the application. We want to create a simple note-taking application with a unique look and feel. Here's a rough wireframe of what the application could look like: * Main Window: + Header with application logo and theme toggle button + Note list area with scroll bar + Note editor area with text input and buttons + Footer with copyright notice **Theme Management System** To create a theme management system, we will need to define a set of themes that the application can switch between. Let's define two themes for now: a light theme and a dark theme. * Light Theme: + Background color: #FFFFFF + Text color: #000000 + Accent color: #007bff * Dark Theme: + Background color: #212121 + Text color: #FFFFFF + Accent color: #03DAC5 **Implementing the Theme Management System** To implement the theme management system, we will need to create a class that manages the themes and applies them to the application. We will call this class `ThemeManager`. ```python import sys from PyQt6.QtWidgets import QApplication, QWidget, QVBoxLayout, QPushButton from PyQt6.QtGui import QFont from PyQt6.QtCore import Qt class ThemeManager: def __init__(self): self.themes = { 'light': { 'background': '#FFFFFF', 'text': '#000000', 'accent': '#007bff' }, 'dark': { 'background': '#212121', 'text': '#FFFFFF', 'accent': '#03DAC5' } } self.current_theme = 'light' def apply_theme(self, widget): theme = self.themes[self.current_theme] widget.setStyleSheet(f''' background-color: {theme['background']}; color: {theme['text']}; ''') def switch_theme(self, theme): self.current_theme = theme self.apply_theme(self.widget) class MainWindow(QWidget): def __init__(self): super().__init__() self.theme_manager = ThemeManager() self.initUI() def initUI(self): layout = QVBoxLayout() self.setLayout(layout) button = QPushButton('Switch to Dark Theme') button.clicked.connect(self.switch_theme) layout.addWidget(button) self.show() def switch_theme(self): if self.theme_manager.current_theme == 'light': self.theme_manager.switch_theme('dark') else: self.theme_manager.switch_theme('light') if __name__ == '__main__': app = QApplication(sys.argv) window = MainWindow() sys.exit(app.exec()) ``` In this example, we created a `ThemeManager` class that manages the themes and applies them to the application. We also created a `MainWindow` class that uses the `ThemeManager` to switch between themes. **Conclusion** In this lab topic, we designed a custom-styled application with dynamic theming, including a dark mode. We created a theme management system that allows users to switch between different themes at runtime. We also used Qt Stylesheets to customize the appearance of widgets. **What's Next** In the next topic, we will learn how to use `QFileDialog` for file selection. **External Resources** * [Qt Documentation: Stylesheets](https://doc.qt.io/qt-6/stylesheet.html) * [Qt Documentation: QFileDialog](https://doc.qt.io/qt-6/qfiledialog.html) **Do you have any questions or need help?** Leave a comment below and I'll do my best to help.