**Course Title:** PyQt6 Application Development **Section Title:** Styling and Theming in PyQt6 **Topic:** Implementing dark mode **Objective:** By the end of this topic, you will learn how to implement dark mode in a PyQt6 application, providing users with an alternative visual theme that can improve readability and reduce eye strain in low-light environments. **Introduction:** Dark mode, also known as dark theme or night mode, is a user interface theme that uses a predominantly dark color scheme, often with lighter-colored text and accents. Implementing dark mode in a PyQt6 application involves modifying the application's stylesheets to use dark colors, as well as configuring the application to switch between light and dark modes seamlessly. **Step 1: Creating a Dark Mode Stylesheet:** To create a dark mode stylesheet, you will need to define a new stylesheet with dark colors. Here is an example of a basic dark mode stylesheet: ```css /* dark_mode.css */ QPushButton { background-color: #2b2b2b; color: #ffffff; border: 1px solid #6c6c6c; } QPushButton:hover { background-color: #4b4b4b; } QPushButton:pressed { background-color: #575757; } QLabel { color: #ffffff; } QLineEdit { background-color: #3b3b3b; color: #ffffff; border: 1px solid #6c6c6c; } ``` This stylesheet sets the background color of QPushButtons to a dark gray (`#2b2b2b`), with white text and a light gray border. QLabel and QLineEdit widgets are also styled to have white text on a dark gray background. **Step 2: Loading the Dark Mode Stylesheet:** To load the dark mode stylesheet in your PyQt6 application, you can use the `setqStyleSheet()` method. For example: ```python import sys from PyQt6.QtCore import * from PyQt6.QtGui import * from PyQt6.QtWidgets import * class MainWindow(QMainWindow): def __init__(self): super(MainWindow, self).__init__() self.setStyleSheet(open("dark_mode.css").read()) ``` This code loads the `dark_mode.css` stylesheet when the `MainWindow` is initialized. **Step 3: Switching Between Light and Dark Modes:** To allow users to switch between light and dark modes, you can create a menu option or button that toggles the stylesheet. Here is an example: ```python class MainWindow(QMainWindow): def __init__(self): super(MainWindow, self).__init__() self.menu = self.menuBar() self.view_menu = self.menu.addMenu("View") self.toggle_dark_mode_action = QAction("Toggle Dark Mode", self) self.toggle_dark_mode_action.triggered.connect(self.toggle_dark_mode) self.view_menu.addAction(self.toggle_dark_mode_action) self.dark_mode = False def toggle_dark_mode(self): if not self.dark_mode: self.setStyleSheet(open("dark_mode.css").read()) self.dark_mode = True else: self.setStyleSheet("") self.dark_mode = False ``` This code creates a "Toggle Dark Mode" menu option that toggles the stylesheet when clicked. **Conclusion:** In this topic, you learned how to implement dark mode in a PyQt6 application. You created a dark mode stylesheet, loaded it into your application, and configured a toggle button to switch between light and dark modes. **Practical Takeaways:** * Use a consistent color scheme in your dark mode stylesheet to ensure readability and visual coherence. * Consider using a separate stylesheet for each mode to simplify switching between modes. * Use the `setqStyleSheet()` method to load and switch between stylesheets. **External Resources:** * Qt Stylesheets documentation: [https://doc.qt.io/qt-6/stylesheet.html](https://doc.qt.io/qt-6/stylesheet.html) * Qt Color Palette generator: [https://doc.qt.io/qt-6/qpaintdevice.html#color](https://doc.qt.io/qt-6/qpaintdevice.html#color) **Leave a comment or ask for help:** If you have any questions or need further clarification on implementing dark mode in a PyQt6 application, please leave a comment below. In the next topic, we will explore dynamic theming: switching themes at runtime.