Function generateShadowCorner

app/src/Platform/CSD.cpp:98–118

* @brief Generates a square shadow corner tile fading from opaque (inner) to transparent (outer). */

 * @brief Generates a square shadow corner tile fading from opaque (inner) to transparent (outer).
 */
QImage generateShadowCorner(int size)
{
  QImage tile(size, size, QImage::Format_ARGB32_Premultiplied);
  tile.fill(Qt::transparent);

  const qreal invSize = size > 0 ? 1.0 / static_cast<qreal>(size) : 0.0;
  for (int y = 0; y < size; ++y) {
    for (int x = 0; x < size; ++x) {
      const qreal dx   = static_cast<qreal>(size - x - 1);
      const qreal dy   = static_cast<qreal>(size - y - 1);
      const qreal dist = qSqrt(dx * dx + dy * dy);

      qreal alpha  = 1.0 - qMin(dist * invSize, 1.0);
      alpha        = alpha * alpha * (3.0 - 2.0 * alpha);
      alpha       *= CSD::ShadowOpacity;
      tile.setPixelColor(x, y, QColor(0, 0, 0, qRound(alpha * 255)));
    }
  }

  return tile;
}

/**
 * @brief Builds the (2r+1)^2 9-slice atlas: corner tiles + 1px edge gradients + transparent center.