PACKETSEL, found by exp-shepherd: the prayer packet printed the first 50 of EVERY people group whatever
was selected, so a reader who had narrowed the map to one language family got a packet about somebody
else. I carried that behaviour through verbatim when I moved the packet to the shared printer — it was
already wrong and I preserved it, which is worth saying plainly.
The rows now come from the pins currently SELECTED: the layer's own filter decides which pins render,
`_pinMatchExpr` decides which of those are lit (the affinity tab dims rather than filters), and both
must match — a pin at opacity 0 is not what the reader is looking at.
★ ASKED OF THE MAP'S FEATURES, NOT OF THE ROWS, and this is the part that had to be got right rather
than guessed. Pin properties are DERIVED from rows: useMapLayers fills languageFamily in when the API
returns null for all 2,069 groups, and canonicalizes doxaRegion onto the palette's key forms precisely
so setFilter matches. So evaluating a pin filter against a raw data row is wrong in a way that NEVER
THROWS — it just selects a different, plausible-looking subset. The features the map holds are the only
place the two vocabularies agree.
Answering that question already existed, privately, inside useMapFly: zoomToLegendRow has to solve it to
fit the camera to a legend row, including the reason it cannot use querySourceFeatures (viewport-clipped,
so an off-screen region silently selects nothing). Those three functions move VERBATIM to
library/maps/pin-selection.js and useMapFly imports them, so there is one evaluator rather than two —
and country-posters, which prints the same kind of packet from the same kind of selection, has the same
helper to reach for instead of a second copy.
Two failure modes are distinguished rather than collapsed: pins selected but NO row matching them is an
id mismatch, so it prints the full list and warns; a genuinely empty selection still reaches the shared
printer's own "that list resolved to no records", which is honest. And when the 50-row safety cap bites,
the cover now says "— 50 of 214" instead of quietly being a different packet than the one asked for.
Verified: gates:pre 13/13, check:composite-interop PASS. Needs eyes: rega — select one language family,
print, and check the cards are that family and the cover carries the count.
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