paperInkDisplayBackdrops function
Display text sits only on the opaque panel (the face draws it, with the grain and the feint rules; the red margin rule stays left of the text): the panel samples are the only backdrops.
Implementation
List<int>? paperInkDisplayBackdrops(
ThemeSpec spec,
List<int> surfaces,
List<int> bgs,
) => paperPanelSamples(
surfaces.first,
spec.background,
accessible: spec.accessible,
);