An appearance is basic with at most one fill and one stroke, none hidden or
with its own opacity, blend mode or effects, and no object effects; Reduce
to Basic keeps the topmost visible fill and stroke. The Layers panel fills
an object's target circle for any non-default transparency (blend mode,
isolation, knockout or an opacity mask: Node::has_default_transparency).
A multi-selection whose objects differ shows "Mixed Appearances" with no
rows. The Appearance panel's object row and the Control bar name the
selection from one source, and type objects are "Type". Expand Appearance
is only in the Object menu. Clear Appearance also resets the object's
opacity and blend mode. Tests cover addFill/addStroke, setItem/removeItem,
clear, reduceToBasic and graphicStyle.apply.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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