excludeFromScrolling constant
When a top-level SemanticsNode below a RenderAbstractViewport is tagged with excludeFromScrolling it will not be part of the scrolling area for semantic purposes.
This behavior is only active if the RenderAbstractViewport tagged its SemanticsConfiguration with useTwoPaneSemantics. Otherwise, the excludeFromScrolling tag is ignored.
As an example, a RenderSliver that stays on the screen within a Scrollable even though the user has scrolled past it (e.g. a pinned app bar) can tag its SemanticsNode with excludeFromScrolling to indicate that it should no longer be considered for semantic actions related to scrolling.
Implementation
static const SemanticsTag excludeFromScrolling = SemanticsTag('RenderViewport.excludeFromScrolling')