Blink Fragment Propagation and Sticky Descendant Boundaries

The provided text explains how Blink's LayoutView manages sticky descendant propagation within the fragment tree. Under standard conditions, sticky elements bubble upward through ancestor fragments until they reach a scroll container, where propagation is terminated. The LayoutView’s root fragment can capture this data, allowing the LocalFrameView to trigger simplified layout updates when viewport-constrained objects change. However, a critical exception occurs during printing or pagination, where a hard propagation barrier is established at the page-border-box boundary. This mechanism ensures that sticky descendants from the document content do not escape into the outer page boxes, regardless of the LayoutView's specific scroll status. Ultimately, the system relies on fragment builders and style predicates to maintain these containment rules during the layout process.