Look up a cached ladder snapshot for view — FULL or PREFIX — or null on
miss / disabled / empty. Most loaders use one payload per level, while Lines
may fold several loaded levels into one cumulative payload and store the
logical depth separately. A prefix restores progress so loading resumes from
startLevel = depth instead of re-streaming level 0; a full ladder
short-circuits the whole load. Shared by all three progressive loaders.
The returned elements are the cache entry's own read-only objects; worker
projection structured-clones its inputs, so downstream processing does not
mutate them. A loader that will push more levels must still shallow-copy the
CONTAINER first so it never mutates the cache's payload array.
Look up a cached ladder snapshot for
view— FULL or PREFIX — or null on miss / disabled / empty. Most loaders use one payload per level, while Lines may fold several loaded levels into one cumulative payload and store the logical depth separately. A prefix restores progress so loading resumes fromstartLevel = depthinstead of re-streaming level 0; a full ladder short-circuits the whole load. Shared by all three progressive loaders. The returned elements are the cache entry's own read-only objects; worker projection structured-clones its inputs, so downstream processing does not mutate them. A loader that will push more levels must still shallow-copy the CONTAINER first so it never mutates the cache's payload array.