crossAxisGlobalOrigin property

@override double get crossAxisGlobalOrigin

Global x of the tree sliver's own cross-axis origin, i.e. where sliver-local x = 0 lands on screen, or 0.0 when isLaidOut is false.

NOT the viewport's left edge: a SliverPadding (or any sliver that insets its child in the cross axis) shifts the tree's band inside the viewport, and a presentation layer that anchors on the viewport paints the drag proxy in a frame the rows do not live in.

Implementation

@override
double get crossAxisGlobalOrigin {
  // getTransformTo asserts `attached`, and there is no frame to speak
  // of before the first layout. The ancestor chain applies each
  // sliver's paint offset (a SliverPadding's cross-axis inset included)
  // and the viewport's own placement; taking only `.dx` is safe because
  // performLayout refuses every non-vertical, non-forward configuration.
  if (geometry == null || !attached) {
    return 0.0;
  }
  return MatrixUtils.transformPoint(getTransformTo(null), Offset.zero).dx;
}