Draw our own base map and make it a mariner preference

[bkeepers]

The chart's base map is now drawn by our own style layers instead of @versatiles/style's colorful() builder, and everything that isn't chart content sits behind a new basemap option — a mariner preference, on by default — at style generation time (style({ basemap }), ?basemap=true|false on the worker's style.json, ?basemap=false in the viewer). The VersaTiles infrastructure stays: shortbread tiles, glyphs, and elevation are still the data; only the styling is ours.

Why

colorful() is a general-purpose topographic style, and a chart wants nearly the opposite: land as a subdued background in a small palette, most land detail omitted, and the mariner deciding how much context to show. Getting there meant maintaining a growing patch layer keyed to colorful's internal layer ids, which broke silently on upstream renames — and the palette could never reach the base map at all, which matters for the planned dusk/night modes. The owned layer set is small (charts omit most of what a topographic map draws), written once against the stable shortbread schema.

What's in the base map now

Always-on chart topography, drawn even with basemap=false: urban extent, airports, bridges over navigable water, glaciers, national boundaries, and place names — including island and locality names, which closes #29. Behind the preference: roads and railways, minor streets, buildings, landcover, beaches, and street names, all styled subdued so they never compete with chart content. Shortbread POIs, ferries, piers, transit symbols, and addresses are deliberately not ported.

Base-map labels place before chart labels, so chart labels win every collision.

New chart portrayals

With the palette reaching the whole style, a few portrayals moved to their chart conventions (S-4/INT1/S-52):

• Water with no depth data draws grey with sparse dashes (the partly-surveyed convention) from seascape's depare polygons, replacing the invented blue-stipple pattern.
• The tiles' wetland layer — carried since the fork but never drawn by any style — now renders: salt marshes as a tuft-pattern overlay, tidal flats in the drying tint. Salt-marsh estuaries no longer read as solid dry land.
• Glaciers draw white with scattered blue strokes (the paper convention) instead of vanishing into water or land fills.
• Fill patterns fade in between z6 and z8: fixed-size pattern glyphs read as noise at small scales, so overview zooms get the flat tint alone.

Known issue

Hairline seams and shore slivers are visible in partly-surveyed water (Great Salt Lake, Lake Peipus, Icelandic coast). These are geometry gaps in the seascape depare tiles — polygons stopping short of tile edges and of the OSM coastline — newly exposed because the old style painted a second water fill underneath. A seascape fix is in progress; nothing in this PR changes when it lands.

Follow-ups

Filed as issues: #24 (bridges and their clearances), #64 (overhead crossings and their clearances), #66 (cliffs), #68 (maritime boundaries), #69 (water-body names).

[Copilot]

Pull request overview

This PR replaces the previously imported VersaTiles “colorful” base-map style builder with an in-repo set of MapLibre style layers, and introduces a new basemap mariner preference (default on) that toggles non-chart land context while keeping chart topography always rendered.

Changes:

• Add basemap as a style-generation option and propagate it end-to-end (style({ basemap }), worker ?basemap=true|false, viewer ?basemap=false).
• Author new owned style layers for chart topography and optional base-map context; add wetlands portrayals and new fill-pattern sprites.
• Remove the @versatiles/style dependency and update sprite generation/tests accordingly.

Reviewed changes

Copilot reviewed 13 out of 19 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
worker/src/route.ts	Adds basemap parsing/validation to the style query parser.
worker/src/route.test.mjs	Adds test coverage for basemap query parsing.
worker/src/index.ts	Documents ?basemap=true|false on /style.json and relies on spreading validated query options into style generation.
viewer/src/main.js	Adds ?basemap=false support and passes basemap through to style().
style/sprites/icons/unsurveyed.svg	Removes the old unsurveyed stipple pattern sprite.
style/sprites/icons/partly-surveyed.svg	Adds the new partly-surveyed dash pattern sprite.
style/sprites/icons/marsh.svg	Adds marsh tuft pattern sprite for wetland rendering.
style/sprites/icons/glacier.svg	Adds glacier stroke pattern sprite.
style/README.md	Updates package description, options list, and documents new layer modules/topography vs basemap split.
style/package.json	Removes @versatiles/style dependency.
style/layers/wetlands.ts	Introduces wetlands layers (tidal flats fill + marsh overlay pattern).
style/layers/topography.ts	Adds always-on chart topography layers sourced from shortbread tiles, including island/locality labels.
style/layers/palette.ts	Extends the day palette with new land/topography/basemap colors and no-data/glacier/intertidal colors.
style/layers/index.ts	Integrates wetlands into chart layer ordering (tidal flats under areas; marsh overlay under hazards).
style/layers/basemap.ts	Adds optional basemap preference layers (roads/rails/buildings/landcover/street labels).
style/index.ts	Rebuilds whole-style assembly without @versatiles/style, adds basemap option and new sources/layers wiring.
style/index.test.ts	Updates tests for new patterns, hillshade behavior, layer ordering, and basemap preference toggling.
style/bin/sprites	Updates the list of pattern icons to include newly introduced pattern sprites.
package-lock.json	Removes @versatiles/style and transitive deps from the lockfile.

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