**Topic: Custom Widgets and Components** **Example: RoundProgressBar Widget** In this example, we will create a custom RoundProgressBar widget using PyQt6. This widget will display a circular progress bar that can be used to represent a percentage value. **Source Code:** ```python import sys from PyQt6.QtCore import Qt, QRect, QPoint from PyQt6.QtGui import QPainter, QPen, QBrush, QColor from PyQt6.QtWidgets import QWidget class RoundProgressBar(QWidget): def __init__(self): super().__init__() self._percentage = 0 self._min_value = 0 self._max_value = 100 self._bar_color = QColor(0, 167, 245) # Blue color self._bar_width = 20 def set_percentage(self, percentage): if percentage < self._min_value or percentage > self._max_value: raise ValueError("Invalid percentage value") self._percentage = percentage self.update() def paintEvent(self, event): painter = QPainter(self) painter.setRenderHint(QPainter.RenderHint.Antialiasing) # Draw circle width = self.width() height = self.height() rect = QRect(0, 0, width, height) painter.setPen(QPen(Qt.PenStyle.NoPen)) painter.setBrush(QBrush(QColor(255, 255, 255))) painter.drawEllipse(rect) # Draw progress bar pen = QPen(self._bar_color) pen.setWidth(self._bar_width) painter.setPen(pen) painter.setBrush(QBrush(Qt.BrushStyle.NoBrush)) arc_length = (self._percentage / 100) * 360 painter.drawArc(rect, -90 * 16, arc_length * 16) if __name__ == "__main__": from PyQt6.QtWidgets import QApplication app = QApplication(sys.argv) progress_bar = RoundProgressBar() progress_bar.resize(200, 200) progress_bar.set_percentage(75) progress_bar.show() sys.exit(app.exec()) ``` **Design Best Practices:** * Custom widgets should inherit from QWidget to ensure proper event handling. * Use QPen and QBrush to define colors and styles for drawing shapes. * Use paintEvent to handle painting and updates of the widget. * Use update() method to trigger a repaint when data changes. **Productivity Hacks:** * Use Designer tool to create and design custom widgets visually. * Use StyleSheets to change appearance of widgets instead of modifying code. **Innovative Examples:** * Use animations to smoothly change percentage values. * Incorporate interaction effects, such as tooltips or hover effects. By following these guidelines and best practices, developers can create effective, visually appealing custom widgets to enhance the design and functionality of their applications.