The renderer kept the evaluation of each blend, envelope and repeat
while the object and a hash stayed the same: the addresses of the art of
the symbols the object showed and of the patterns it painted with, and
the patterns' tile bounds. When anything else the evaluation reads
changed, such as a pattern's tile type, symbols in symbol art, the
fonts or the color settings, a renderer that had drawn the object went
on drawing the old evaluation. The quads of a gradient mesh were kept
the same way after a change to the color settings, and the art drawn
for a live object with an effect of its own was kept by the object's
address alone.
resources_key now also walks the opacity-mask, symbol and pattern art
it finds. It hashes what it finds, the font generation when it finds
type or a placed document, and the color settings. Mesh quads are made
again when the color settings change. The art drawn for an object's
effects is made again when the hash changes, if it was made from
evaluated live objects.
With other builds running, a temporary release test timed the hash for
400 live objects at 17 to 506 microseconds a frame, against 10 to 16
before.
Docs: docs/target-app-parity.md, docs/gaps.md.
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