Tracker for JTS implementation

[willcohen]

Current Status

This is a proof-of-concept wrapper providing basic JTS functionality compiled to WebAssembly. Many JTS features are not yet exposed through the JavaScript API.

What's available now:

• Basic geometry operations (buffer, union, intersection, difference, convexHull)
• Spatial predicates (contains, intersects, covers, equalsTopo, etc.)
• STRtree spatial indexing
• PreparedGeometry for optimized queries
• WKT/WKB I/O with 2D/3D/4D support
• LineMerger, CascadedPolygonUnion, OffsetCurveBuilder
• Minimum bounding rectangles and circles

What's not available: The underlying WASM binary includes the full JTS 1.20.0 library, but most of it isn't exposed to JavaScript yet. Adding new functionality requires:

• Creating Java wrapper methods in API.java
• Exporting them to JavaScript using annotations
• Handling Java-JavaScript type conversions

This isn't particularly difficult but it still isn't fully automatic.

Please use this issue to make requests for additional JTS functionality you'd like to see wrapped.

[bjornharrtell]

I'd like to see the GeoJSON I/O included - https://github.com/locationtech/jts/tree/master/modules/io/common/src/main/java/org/locationtech/jts/io/geojson.

[willcohen]

I was just poking around at adding io-common. Something about the JSON library JTS in particular depends on made web-image choke. Till the graal parsing matures a little more I might have to just either re-implement or find something lightweight on the JS side that already does WKT to GeoJSON.

On the other hand, I haven’t tried jts2geojson in web-image yet either, of course, and it would definitely be easier than reimplementing…

[bjornharrtell]

Ah yes I forgot I made that 😄

[willcohen]

@bjornharrtell geojson support added semi-manually (by passing back out to JSON.stringify/parse), and now available on the web page demo and in 0.1.0-alpha2. Doesn't do CRS or forceCCW or precision calcs yet, so it's not quite a mirror of JTS's reader/writer.

[willcohen]

Exposing some of the internals of JTS has uncovered at least one potential bug in web-image (currently fixed on main branch here by building graal with a bug fix PR branch): oracle/graal#12676

There’s definitely some familiarity with the evolving web-image API I need to still gain, but there may well be a few more bugs lurking in the parts of JTS I was struggling with exposing at all before. CoordinateSequenceFilters appear almost done.

[willcohen]

With oracle/graal#12707 merged, json-simple works again, meaning I will be able to fully expose the geojson functions. Still need to rework, but it'll be in my next commit when I get a chance.

[willcohen]

JTS's GeoJSON I/O included in 0.1.0-alpha3, released today.