Per-source-material state: the compile-time fingerprint the keepers were built
against, the keepers pinning the programs, the objects sharing the material,
and the material's dispose listener.
Program variants this source USES (variant fingerprint → blend mode),
whether it owns the keeper for them or shares one compiled for an
identical material on another node. Released in clearSource.
Per-source-material state: the compile-time fingerprint the keepers were built against, the keepers pinning the programs, the objects sharing the material, and the material's
disposelistener.