Driver: "two finger scrolling on the map should allow me to interact with
the map, but instead it just scrolls down past the map and does not
interact with the map -- that's what the scroll side bars are there for, to
let me interact with the map AND have a way to scroll down past the map."
REPRODUCED before touching anything: wheel over the centre of the map in
research-map-plus-grid moved scrollY 0 -> 480 and the camera never moved.
The map was inert exactly where it is the main control.
CAUSE: _syncScrollZoomToHost disabled scroll-zoom whenever the document or
an ancestor could scroll -- which is ALWAYS true in a composite that stacks
a grid under a map. It was not careless: it fixed
BUG-CANNOT-SCROLL-DOWN-TO-THE-GRID, where the map ate every wheel and the
grid below could not be reached. But that bug already had a second fix --
the .map-scroll-edge gutters, a dedicated page-scroll lane down both sides,
which the Map constructor's own note calls "the single-finger page-scroll
escape". Two fixes for one bug, and the second silently undid the feature
while leaving the first redundant.
So scroll-zoom now stays enabled and the strips carry the page. The
docScrolls/ancestorScrolls probe stays, because the edge affordance keys its
gray indicator off the same question.
MEASURED on the built tree, 1280x900:
wheel x4 over map centre scrollY 0 -> 0 map takes the gesture
wheel x4 over edge strip scrollY 0 -> 480 escape still works
(two strips, 46px wide each)
And the repo's own fitness gate, which exists for this property:
check:fits-screen 17/17 PASS -- including "the grid is reachable" and
"the wheel is targeted", so the bug this replaced has not returned.
DashboardMapPanel carries the same helper and was deliberately NOT changed:
different layout contract (map inside a fixed shell with facet/table/rail
columns), and fits-screen passes it today as "wheel escapes every column".
Flagged in the ledger for the Driver rather than altered on the strength of
a report about a different surface.
gates:pre 0. gates:post 17/18, the single failure being the pre-existing
verify/tables-complete break from the visa-leak fix.
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