atContentPosition
Anchors one direct overlay child at a source content coordinate.
The owning tiled image consumes only the innermost anchor on the direct child's modifier chain. Changing the anchor invalidates overlay geometry but leaves the retained tile paint layer and its image observations intact.
Receiver
modifier chain applied to one direct overlay child.
Return
this chain with one active parent-data provider appended.
Parameters
finite source content coordinate.
placement of the child's extent relative to the transformed coordinate.
Throws
when this scope has escaped its callback or constructing thread.
Anchors one direct overlay child at an independently revisioned source content coordinate.
The source is observed only while the retained child is attached. Notifications may arrive on any thread and commit at the shared frame cutoff; only parent measurement and overlay placement are invalidated, while tile observations, images, and paint remain unchanged. Replacing the source identity closes the previous observation before subscribing to the replacement, and detach or close drops every pending position without closing the externally owned source.
Receiver
modifier chain applied to one direct overlay child.
Return
this chain with one active revisioned parent-data provider appended.
Parameters
externally owned revision history of finite source content coordinates.
placement of the child's extent relative to the committed transformed coordinate.
Throws
when this scope has escaped its callback or constructing thread.
when attachment or source replacement cannot establish an observation, or when replacement, detach, or close cannot release one.