On a precomp layer the key covered only the nested comp's size, rate and
duration, so an edit inside the precomp kept a stale analysis. The key now
writes the precomp layer's Essential Properties and what its comp draws, field
by field and recursively. Each comp is written once per key and nesting is
capped, so shared, deep or cyclic precomps are keyed in bounded time. Docs say
what clears an analysis.
Their analyses are made from the layer's input to the effect (masks, then the
effects above it), but the key covered only the layer's frames, so a mask or
effect edit kept a stale analysis. frames_key::analysis_key adds the masks,
the effects above the instance and the Effects switch. Keys saved before
(frames only) stay valid while each edit keeps the input.
arnav-hiwarkar