Method renderWithShadow

app/src/UI/Widgets/PainterContext.cpp:1790–1823

* @brief Renders the given draw callback as a coloured drop shadow. */

 * @brief Renders the given draw callback as a coloured drop shadow.
 */
void Widgets::PainterContext::renderWithShadow(const std::function<void(QPainter*)>& draw,
                                               const QRectF& bounds)
{
  if (!active() || bounds.isEmpty())
    return;

  const qreal pad = qMax<qreal>(2.0, m_state.shadowBlur);
  QRectF padded   = bounds.adjusted(-pad, -pad, pad, pad);
  const QSize sz(qMax(1, int(std::ceil(padded.width()))), qMax(1, int(std::ceil(padded.height()))));

  QImage shadow(sz, QImage::Format_ARGB32_Premultiplied);
  shadow.fill(Qt::transparent);

  {
    QPainter sp(&shadow);
    sp.setRenderHint(QPainter::Antialiasing, true);
    sp.translate(-padded.topLeft());
    draw(&sp);

    sp.setCompositionMode(QPainter::CompositionMode_SourceIn);
    sp.fillRect(shadow.rect(), m_state.shadowColor);
  }

  if (m_state.shadowBlur > 0.0) {
    const int radius = qBound(1, int(std::ceil(m_state.shadowBlur)), 32);
    applyBoxBlur(shadow, radius);
  }

  m_painter->save();
  m_painter->setOpacity(m_state.globalAlpha);
  m_painter->drawImage(padded.topLeft() + QPointF(m_state.shadowOffsetX, m_state.shadowOffsetY),
                       shadow);
  m_painter->restore();
}

/**
 * @brief Pushes the current fill brush onto the active painter.