Build the per-layer cell scope map used by the bind-time fixup passes
that need a per-panel DOM root (buildBoxPlotSelectorsFromDom,
sortLinesByVisualOrder). Works for both facet subplots (after
stampFacetCells has run) and repeat / concat subplots (whose
selectors are class-scoped and need no stamping).
Returns an empty map for single-panel charts, whose subplots carry no
selector.
Build the per-layer cell scope map used by the bind-time fixup passes that need a per-panel DOM root (
buildBoxPlotSelectorsFromDom,sortLinesByVisualOrder). Works for both facet subplots (after stampFacetCells has run) and repeat / concat subplots (whose selectors are class-scoped and need no stamping).Returns an empty map for single-panel charts, whose subplots carry no selector.