RGB 0..=1 fill, or null when unfilled.
RGB 0..=1 stroke, or null when unstroked.
Optionalfill_Full gradient fill (PPTX/ODP gradFill). Primes over the flat fill,
which keeps the first stop's colour as the fallback. Present since 0.117.0.
OptionalshadowOuter drop shadow (a:outerShdw). Present since 0.117.0.
A vector shape: a path with fill/stroke styling (mirror of
model::Shape).