**Course Title:** PySide6 Application Development **Section Title:** Styling and Theming Applications **Topic:** Dynamic theming (switch between themes at runtime) **Introduction** In this topic, we'll explore the concept of dynamic theming in PySide6 applications. Dynamic theming allows you to switch between different themes at runtime, providing an enhanced user experience and flexibility in your application's appearance. We'll discuss how to implement dynamic theming, and provide practical examples to help you understand the process. **Understanding Dynamic Theming** Dynamic theming involves switching between different themes or stylesheets at runtime, without requiring a restart of the application. This allows users to customize the appearance of the application to their preference, or to adapt to different environments (e.g., dark mode). **Implementing Dynamic Theming** To implement dynamic theming in PySide6, you'll need to follow these steps: 1. **Create themes**: Create separate stylesheets for each theme you want to implement. For example, you can have a `light.qss` stylesheet for a light theme and a `dark.qss` stylesheet for a dark theme. 2. **Load stylesheets**: Load the stylesheets into your application using the `QApplication.setStyleSheet()` method or the `setStyleSheet()` method of individual widgets. 3. **Create theme switcher**: Create a mechanism to switch between themes, such as a button or a menu item. **Example Code** Here's an example code snippet that demonstrates how to implement dynamic theming: ```python import sys from PySide6.QtCore import Slot from PySide6.QtWidgets import QApplication, QWidget, QPushButton, QVBoxLayout class DynamicThemingExample(QWidget): def __init__(self): super().__init__() self.light_stylesheet = "styles/light.qss" self.dark_stylesheet = "styles/dark.qss" self.current_theme = "light" self.create_widgets() self.create_layout() self.load_theme() def create_widgets(self): self.button = QPushButton("Switch Theme") self.button.clicked.connect(self.switch_theme) def create_layout(self): layout = QVBoxLayout() layout.addWidget(self.button) self.setLayout(layout) def load_theme(self): if self.current_theme == "light": self.style_sheet = self.light_stylesheet else: self.style_sheet = self.dark_stylesheet with open(self.style_sheet, "r") as f: qss = f.read() self.setStyleSheet(qss) @Slot() def switch_theme(self): if self.current_theme == "light": self.current_theme = "dark" else: self.current_theme = "light" self.load_theme() if __name__ == "__main__": app = QApplication(sys.argv) window = DynamicThemingExample() window.show() sys.exit(app.exec()) ``` In this example, we create a simple window with a button that, when clicked, switches the theme between light and dark. **Key Concepts** * **Stylesheets**: Stylesheets are used to define the visual appearance of your application. * **QApplication.setStyleSheet()**: This method sets the stylesheet for the entire application. * **setStyleSheet()**: This method sets the stylesheet for individual widgets. **Practical Takeaways** * **Use stylesheets to define themes**: Stylesheets provide an easy way to define and switch between themes. * **Use signal-slot connections to switch themes**: Signal-slot connections provide an easy way to connect theme switching functionality to buttons or other widgets. **Example Use Cases** * **Dark mode implementation**: Dynamic theming can be used to implement dark mode in your application, providing an enhanced user experience for users who prefer a darker UI. * **Customizable themes**: Dynamic theming allows users to customize the appearance of your application, providing a personalized experience. **Additional Resources** * [Qt Stylesheets](https://doc.qt.io/qt-5/stylesheet-syntax.html) * [Qt Style Sheet Reference](https://doc.qt.io/qt-5/stylesheet-reference.html) **Exercise** Create a simple application that demonstrates dynamic theming. Implement at least two themes: light and dark. Use a button to switch between themes. **Leave a Comment/Ask for Help** If you have any questions or need help with implementing dynamic theming, feel free to leave a comment below.

import sys
from PySide6.QtCore import Slot
from PySide6.QtWidgets import QApplication, QWidget, QPushButton, QVBoxLayout

class DynamicThemingExample(QWidget):
    def __init__(self):
        super().__init__()

        self.light_stylesheet = "styles/light.qss"
        self.dark_stylesheet = "styles/dark.qss"

        self.current_theme = "light"

        self.create_widgets()
        self.create_layout()
        self.load_theme()

    def create_widgets(self):
        self.button = QPushButton("Switch Theme")

        self.button.clicked.connect(self.switch_theme)

    def create_layout(self):
        layout = QVBoxLayout()
        layout.addWidget(self.button)
        self.setLayout(layout)

    def load_theme(self):
        if self.current_theme == "light":
            self.style_sheet = self.light_stylesheet
        else:
            self.style_sheet = self.dark_stylesheet

        with open(self.style_sheet, "r") as f:
            qss = f.read()
            self.setStyleSheet(qss)

    @Slot()
    def switch_theme(self):
        if self.current_theme == "light":
            self.current_theme = "dark"
        else:
            self.current_theme = "light"

        self.load_theme()

if __name__ == "__main__":
    app = QApplication(sys.argv)

    window = DynamicThemingExample()
    window.show()

    sys.exit(app.exec())