Method paintEvent

pj_widgets/src/ToggleSwitch.cpp:179–222

}

void ToggleSwitch::paintEvent(QPaintEvent* /*event*/) {
  QPainter painter(this);
  painter.setRenderHint(QPainter::Antialiasing, true);

  // Track: pill (corner radius = half the height). Fill interpolates
  // from the "off" tone to the "on" tone as the thumb moves so the
  // color transition tracks the animation smoothly.
  const QColor off_track(120, 120, 120);
  const QColor on_track(0x11, 0x77, 0xFF);  // blue
  const auto lerp = [](int a, int b, qreal t) { return static_cast<int>(a + ((b - a) * t)); };
  const QColor track_color(
      lerp(off_track.red(), on_track.red(), thumb_position_),
      lerp(off_track.green(), on_track.green(), thumb_position_),
      lerp(off_track.blue(), on_track.blue(), thumb_position_));

  const QRect track = trackRect();
  const qreal radius = track.height() / 2.0;
  painter.setPen(Qt::NoPen);
  painter.setBrush(track_color);
  painter.drawRoundedRect(track, radius, radius);

  // Optional inline label, in the palette text colour (faded when disabled),
  // aligned toward the switch and vertically centred.
  if (!text_.isEmpty()) {
    const QPalette::ColorGroup group = isEnabled() ? QPalette::Active : QPalette::Disabled;
    painter.setPen(palette().color(group, QPalette::WindowText));
    const QRect lr = labelRect();
    const int align = (label_side_ == LabelSide::Left ? Qt::AlignRight : Qt::AlignLeft) | Qt::AlignVCenter;
    const QString elided = fontMetrics().elidedText(text_, Qt::ElideRight, lr.width());
    painter.drawText(lr, align, elided);
  }

  // Both slot backgrounds are always painted; the thumb composites on top.
  // Default impls fade each based on thumb_position_ so only the icon
  // opposite the thumb is visible at rest.
  paintLeftSlot(painter, leftSlotRect(), thumb_position_);
  paintRightSlot(painter, rightSlotRect(), thumb_position_);

  // Thumb: white circle with a faint outer outline for definition.
  const QRect thumb = thumbRect();
  painter.setPen(QPen(QColor(0, 0, 0, 40), 1));
  painter.setBrush(Qt::white);
  painter.drawEllipse(thumb);
}

void ToggleSwitch::paintLeftSlot(QPainter& painter, const QRect& slot_rect, qreal thumb_position) {
  if (left_icon_.isNull()) {