Fold the visible stamped leaves under root into one
SubtreeDisplayProgress, or null when the subtree contains no
stamped leaf at all (nothing committed yet / not a geometry subtree) — the
gate treats null as "unknown" and refuses to hold, preserving today's
behavior for shapes it cannot reason about.
Arbitrary nesting depth is supported by construction (partition-of-leaves,
lod-of-partition, lod-of-lod, ...): every shape bottoms out in stamped
leaves, and inner lod_groups' own visibility toggling makes the fold count
exactly the levels that would render.
Fold the visible stamped leaves under
rootinto one SubtreeDisplayProgress, ornullwhen the subtree contains no stamped leaf at all (nothing committed yet / not a geometry subtree) — the gate treatsnullas "unknown" and refuses to hold, preserving today's behavior for shapes it cannot reason about.Arbitrary nesting depth is supported by construction (partition-of-leaves, lod-of-partition, lod-of-lod, ...): every shape bottoms out in stamped leaves, and inner lod_groups' own visibility toggling makes the fold count exactly the levels that would render.