Document
A popup anchored to a point in the document — the Compose replacement for the PopupWindow-based PopupToolbar (Phase 4 §4, P2-16). Renders content inside the host composition (no separate window), horizontally centered on the anchor with its bottom edge at the anchor, clamped to the host bounds inset by edgePadding (the View pspdf__popup_toolbar_edge_padding contract).
Place it in a full-size overlay layer above the document. The anchor is a lambda read in the layout phase: a scroll or zoom that moves the anchored point only re-lays the popup out, it never recomposes — this is what replaces the View coordinator's dismiss-on-scroll / delayed-re-show dance with a popup that simply follows the selection.
Parameters
Whether the popup composes at all.
The anchor point in the host's coordinates, read during layout.