ezu-features

GIS feature parsing for the ezu workspace.

Parses tile / feature formats into a flat, owned representation that downstream paint code can iterate over without implementing any format-specific traits. Remote fetching is intentionally out of scope — input is always raw bytes / strings handed in by the caller (e.g. an example, ezu serve, the WASM bindings).

Submodules

All decoders produce the same crate-root types:

pub struct FeatureLayer {
    pub name: String,
    pub extent: u32,            // tile-local coord range, typically 4096 for MVT
    pub features: Vec<Feature>,
}
pub struct Feature {
    pub id: Option<u64>,
    pub geometry: Geometry,
    pub properties: HashMap<String, Value>,
}
pub struct Geometry {
    pub points: Vec<(i32, i32)>,
    pub lines: Vec<Vec<(i32, i32)>>,
    pub polygons: Vec<Polygon>,
}
pub struct Polygon { pub exterior: Vec<(i32, i32)>, pub holes: Vec<Vec<(i32, i32)>> }
pub enum Value { String, Float, Double, Int, UInt, SInt, Bool, Null }

Coordinates are integer (i32, i32) pairs. For MVT this is the spec-defined tile-local [0, extent] (y-down); for GeoJSON the caller is responsible for any projection / quantization into the same coordinate space before parsing. All three geometry kinds coexist on a single feature — single-vs-multi is expressed by element count, and a GeoJSON GeometryCollection flattens into whichever combination its children produce.

MVT example

let decoded = ezu_features::mvt::decode(mvt_bytes)?;
if let Some(water) = decoded.layer("water") {
    for f in &water.features {
        for poly in &f.geometry.polygons {
            // paint
        }
    }
}

Polygon rings are classified as exterior / hole via signed shoelace area following the MVT spec.

Hand-off to the renderer

ezu-paint consumes feature data through the generic AssetLoader interface, not by importing this crate directly. Hosts decode their bytes into [FeatureLayer] and bind each layer under a tile.<layer-name> name via ezu_paint::host::TileLoader before rendering; the style's features node samples the binding by name like a shader uniform. This keeps the source-format choice (MVT today, GeoJSON or anything else tomorrow) on the host side — no node code changes when the wire format does.

License

MIT or Apache-2.0, at your option.