applyStickyChildOffset static method

void applyStickyChildOffset(RenderBoxModel scrollContainer, RenderBoxModel child)

Implementation

static void applyStickyChildOffset(RenderBoxModel scrollContainer, RenderBoxModel child) {
  RenderPositionPlaceholder childRenderPositionHolder = child.renderPositionPlaceholder!;
  RenderLayoutParentData childPlaceHolderParentData = childRenderPositionHolder.parentData as RenderLayoutParentData;
  // Original offset of sticky child in relative status
  Offset childOriginalOffset = childPlaceHolderParentData.offset;

  // Offset of sticky child to scroll container
  Offset childToScrollContainerOffset =
      childRenderPositionHolder.localToGlobal(Offset.zero, ancestor: scrollContainer);

  bool isVerticalFixed = false;
  bool isHorizontalFixed = false;
  RenderStyle childRenderStyle = child.renderStyle;

  if (childRenderStyle.left.isNotAuto || childRenderStyle.right.isNotAuto) {
    isHorizontalFixed =
        _applyStickyChildHorizontalOffset(scrollContainer, child, childOriginalOffset, childToScrollContainerOffset);
  }
  if (childRenderStyle.top.isNotAuto || childRenderStyle.bottom.isNotAuto) {
    isVerticalFixed =
        _applyStickyChildVerticalOffset(scrollContainer, child, childOriginalOffset, childToScrollContainerOffset);
  }

  if (isVerticalFixed || isHorizontalFixed) {
    // Change sticky status to fixed
    child.stickyStatus = StickyPositionType.fixed;
    child.markNeedsPaint();
  } else {
    // Change sticky status to relative
    if (child.stickyStatus == StickyPositionType.fixed) {
      child.stickyStatus = StickyPositionType.relative;
      // Reset child offset to its original offset
      child.markNeedsPaint();
    }
  }
}