17 of 25 library components that ship motion carried no reduced-motion rule, so
they animated regardless of the reader's OS setting.
The reason it cannot be fixed once, centrally: a @media (prefers-reduced-motion)
rule in the host document does not cross a shadow boundary, and these render
inside one. Measured while surveying: NO generated leaf page ships such a rule
at all — 0 occurrences across the whole built tree — so there was not even a
page rule to inherit. Each component owns its own.
CSS-ONLY AND ADDITIVE. Nothing but new @media blocks; no existing rule changed.
Verified by diff: 0 real removals across 17 files. The two lines git reports as
removed are a trailing comma moving as a new string was chained onto an existing
concatenation, and both original rules are still present — checked by grepping
for them, not by reading the diff.
WHERE MOTION CARRIES MEANING, it is kept rather than hidden:
· SemanticTreeLegend's spinner MEANS "loading". Stopped dead it is a static
ring that says nothing, so it is slowed to a step crawl (2.4s, steps(8)) —
visibly working, no smooth spin.
· LegendProgressBar's only motion is a hover filter, so it simply stops; the
bar's FILL is geometry, not animation, and still reports its value.
The rule goes where each component's styles actually go, and that varies more
than expected: 13 append into a useShadowStyles template literal, 3 into
string-concatenated sheets, and VerticalTabsLayout into its VTL_SHADOW_CSS
constant AND its duplicate <style> block, because its own header says the two
copies must stay identical.
check:reduced-motion asserts both halves, each mutation-tested to fail before I
trusted a pass: strip the rule from an animating component and it fails; move a
rule from the injected sheet into a <style> block and it fails too, because on a
useShadowStyles component that rule would never reach the shadow root. Both
mutated files restored byte-identical.
Two of my own errors caught by tooling rather than by review, and worth naming:
my first patch asserted useShadowStyles existed in every target and RAISED on
VerticalTabsLayout instead of silently skipping it — the assert-the-anchor habit
from the last registration failure working as intended. Then I appended CSS
after the label argument on two concat-built sheets, corrupting the injection
key; check:shadow-css-parses named both files and the fix was to insert before
the label. A gate I did not write caught what I got wrong.
Registered in all three places and verified by re-reading the parsed
package.json.
