paintingOrder property

List<RenderBox> get paintingOrder

Implementation

List<RenderBox> get paintingOrder {
  if (_paintingOrder != null) {
    return _paintingOrder!;
  }

  if (childCount == 0) {
    // No child.
    return _paintingOrder = const [];
  } else if (childCount == 1) {
    // Only one child.
    final List<RenderBox> order = <RenderBox>[];
    order.add(firstChild!);
    return _paintingOrder = order;
  } else {
    // Sort by zIndex.
    List<RenderBox> children = getChildren();
    if (_childrenNeedsSort) {
      children.sort((RenderBox left, RenderBox right) {
        // @FIXME: Add patch to handle nested fixed element paint priority, need to remove
        // this logic after Kraken has implemented stacking context tree.
        if (left is RenderBoxModel && left.renderStyle.position == CSSPositionType.fixed &&
          right is RenderBoxModel && right.renderStyle.position == CSSPositionType.fixed) {
          // Child element always paint after parent element when their position are both fixed
          // as W3C stacking context specified.
          // Kraken will place these two renderObjects as siblings of the children of HTML renderObject
          // due to lack stacking context support, so it needs to add this patch to handle this case.
          if (right.renderStyle.isAncestorOf(left.renderStyle)) return 1;
          if (left.renderStyle.isAncestorOf(right.renderStyle)) return -1;
        }

        bool isLeftNeedsStacking = left is RenderBoxModel && left.needsStacking;
        bool isRightNeedsStacking = right is RenderBoxModel && right.needsStacking;
        if (!isLeftNeedsStacking && isRightNeedsStacking) {
          return 0 <= (right.renderStyle.zIndex ?? 0) ? -1 : 1;
        } else if (isLeftNeedsStacking && !isRightNeedsStacking) {
          return (left.renderStyle.zIndex ?? 0) < 0 ? -1 : 1;
        } else if (isLeftNeedsStacking && isRightNeedsStacking) {
          return (left.renderStyle.zIndex ?? 0) <= (right.renderStyle.zIndex ?? 0) ? -1 : 1;
        } else {
          return -1;
        }
      });
    }
    return _paintingOrder = children;
  }
}