Adds lat/lon/zoom URL params to /weather so reload / share-link
restores the exact map state. The existing ?layer= param keeps
working alongside.
LiveView side:
- mount() reads lat/lon/zoom from query params, clamps to valid
ranges (lat -90..90, lon -180..180, zoom 4..10), and falls back
to DFW@z7 when missing or invalid. Initial values flow to the
hook via three new data attributes.
- handle_event("viewport_changed", ...) accepts {lat, lon, zoom}
pushed by the hook on debounced moveend, clamps + rounds, and
push_patches the URL with replace: true so browser history
doesn't grow an entry per pan tick.
- build_path/2 helper centralises URL construction so select_layer
and viewport_changed both produce a deterministic param order
(layer, lat, lon, zoom). Tests assert exact URLs.
JS hook side:
- mounted() reads data-initial-lat/lon/zoom from the el dataset
with parseFloat/parseInt + Number.isFinite gates, then seeds
Leaflet's center/zoom from those instead of the previous
hardcoded (32.897, -97.038, 7).
- moveend handler now also schedules a 400 ms-debounced
pushEvent("viewport_changed", {lat, lon, zoom}) so the URL
catches up with whatever the user panned/zoomed to. Separate
debounce timer from the cells fetch since the URL push and the
network fetch have different cadence sweet spots.
Tests cover: initial seeding from URL params, clamping of bad
values, viewport_changed event producing the right patched URL,
and the original layer-shareability test (now expecting the full
viewport in the URL).
Graham McIntire
aa8b789d2e