**Topic: Custom Widgets and Components** In this example, we'll create a custom "Slider With Preview" widget using PyQt6. This widget will have a slider that displays a preview of the current value, which can be especially useful for media players or other applications that require users to adjust a value within a specific range. **slider_with_preview.py** ```python import sys from PyQt6.QtCore import Qt, QObject, pyqtSlot from PyQt6.QtGui import QPainter, QBrush, QColor from PyQt6.QtWidgets import QApplication, QWidget, QSlider, QHBoxLayout class SliderWithPreview(QSlider): def __init__(self, parent=None): super().__init__(parent) self._preview_value = self.minimum() self._preview_rect = None def paintEvent(self, event): super().paintEvent(event) self._paint_preview(event) def _paint_preview(self, event): painter = QPainter(self) painter.setRenderHint(painter.Antialiasing) preview_x = self._preview_rect.x() if self._preview_rect else 0 preview_y = self._preview_rect.y() if self._preview_rect else 0 preview_w = self._preview_rect.width() if self._preview_rect else 0 preview_h = self._preview_rect.height() if self._preview_rect else 0 if preview_w == 0: preview_w = 20 preview_h = 20 preview_x = self.width() - preview_w - 5 preview_y = 5 painter.setPen(QColor('black')) painter.setBrush(QColor('lightblue')) painter.drawRoundedRect(preview_x, preview_y, preview_w, preview_h, 5, 5) painter.setPen(QColor('black')) painter.drawText(preview_x + 5, preview_y + 15, f"{self._preview_value}") def resizeEvent(self, event): super().resizeEvent(event) self._update_preview_rect() def _update_preview_rect(self): slider_height = self.height() preview_w = 20 preview_h = 20 preview_x = self.width() - preview_w - 5 preview_y = (slider_height - preview_h) // 2 self._preview_rect = (preview_x, preview_y, preview_w, preview_h) def _calculate_preview_value(self): range_value = self.maximum() - self.minimum() slider_value = self.value() - self.minimum() preview_value = self.minimum() + int((slider_value / range_value) * range_value) return preview_value @pyqtSlot(int) def on_slider_value_changed(self, value): self._preview_value = self._calculate_preview_value() self.update() class CustomWidget(QWidget): def __init__(self, parent=None): super().__init__(parent) self.slider = SliderWithPreview() self.slider.setRange(0, 100) layout = QHBoxLayout() layout.addWidget(self.slider) self.setLayout(layout) self.slider.valueChanged.connect(self.slider.on_slider_value_changed) if __name__ == "__main__": app = QApplication(sys.argv) widget = CustomWidget() widget.show() sys.exit(app.exec()) ``` **Explanation** We create a custom `SliderWithPreview` widget by subclassing `QSlider`. This custom widget will display a preview of the current value next to the slider. **_paint_preview method** This method is responsible for painting the preview. It creates a `QPainter` object, sets its render hint to `Antialiasing` for a smoother preview, and then draws a lightblue rounded rectangle with the current value. **resizeEvent and _update_preview_rect methods** When the slider's size is updated, we update the position and size of the preview rectangle. **on_slider_value_changed slot** When the slider's value changes, we calculate the new preview value and update the widget to display the new preview. **CustomWidget** We create a `CustomWidget` that creates an instance of the `SliderWithPreview` widget, adds a layout, and sets the connections between the slider's `valueChanged` signal and the `on_slider_value_changed` slot. **Output** When you run this code, you should see a custom slider widget with a preview of the current value. **Design Considerations** To enhance app design and development, you can further customize this widget by adding additional features, such as: 1. Customizable fonts and colors. 2. Rounded rectangle edges or other shapes for the preview. 3. The ability to set a specific width or height for the preview. 4. Additional preview layouts for horizontal or vertical sliders. These design considerations will help create a more modern and user-friendly widget that enhances the overall app design and user experience.