[nighthawk]

Why

Maparoni's MCP tools now return map renders as PNGs (maparoni/lambdaroni#285): the Lambda produces SVG through GeoDrawer.drawSVG on Amazon Linux and Phoenix rasterises it with rsvg-convert. drawSVG skipped raster base maps entirely, and all tile compositing lived behind canImport(CoreGraphics), so the chat renders were vector-only.

The way

The per-pixel tile compositor is now pure Swift (renderTiledBaseMapBitmap), shared by the existing CoreGraphics path and by drawSVG, which composites the cached tiles into one bitmap, encodes it as PNG with swift-png and emits an <image> with a base64 data URI beneath the vector content. Embedding rather than linking matters because librsvg refuses remote fetches but happily decodes data URIs.

Along the way the .baseMap / .tiledBaseMap content cases lose their CoreGraphics gate, prefetchTiles(for:) becomes public (with a [Content] overload for callers that just want everything fetched before a sync draw), TileImage.pngDecoder is available on every platform, and the URLTemplateTileSource convenience initialiser falls back to it off Apple platforms. .baseMap is still omitted from SVG.

Swift 5 compilers are dropped. swift-png's dependencies need Swift 6.0 tools, and no older swift-png resolves on 5.10 either, so the Linux CI matrix is now 6.2 and 6.0.

Testing

• swift test on macOS (64 tests) and in swift:6.3-amazonlinux2023 via Docker (77 tests) both pass. The new TiledBaseMapSVGTests render a 2×2 StaticTileSource grid to SVG, check the <image> precedes the <path>, and decode the embedded PNG to confirm the west/east tiles landed where expected.
• Not verified here: an actual rsvg-convert run of the output, and a real slippy-map source end to end. Follow-ups on the Lambda side: /formaggio/run.svg needs to opt into a tiled base map, and GeoLogicKit's GeoJSON+SVG.swift continent-scale minimum bounding box makes small maps render as dots.

🤖 Generated with Claude Code

[nighthawk]

Suggested squash-merge commit message:

feat(drawer): embed tiled base maps in SVG output on every platform

`drawSVG` now composites the cached tiles of a `.tiledBaseMap`, encodes
them as PNG and emits an `<image>` with a base64 data URI (once, via
`xlink:href`) beneath the vector content, so librsvg and other offline
rasterisers show the base map.

- Move the tile compositor off CoreGraphics into a pure-Swift
  `renderTiledBaseMapBitmap` shared by the CGImage path and `drawSVG`.
- Snapshot only the fetched tiles before compositing instead of probing
  the whole 2^z × 2^z grid, which took minutes at street-level zooms.
- Add swift-png for PNG encode/decode on every platform, with
  `TileImage.pngDecoder` as the `URLTemplateTileSource` default off
  Apple platforms.
- Let `URLTemplateTileSource` send extra request headers, for services
  that check the Origin of key-restricted requests.
- Ungate the `.baseMap` and `.tiledBaseMap` content cases from
  CoreGraphics.
- Make `prefetchTiles(for:)` public and add a `[Content]` overload.
- Drop Swift 5 compilers: swift-png's dependencies need Swift 6.0
  tools, so the Linux CI matrix is 6.2 and 6.0.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>