map

The high-level engines that wire a core!Scene, a backend, and d3-zoom together: geoMap (a project-once map engine over GeoJSON) and plot (a generic 2D engine driven by per-datum draw callbacks). createBackend selects the rendering backend by BackendType.

import { plot } from "@mapequation/d3gl/map";

plot(el, { width, height }).layer("links", data, {
  draw: (ctx, d) => { ctx.moveTo(d.x0, d.y0); ctx.lineTo(d.x1, d.y1); },
  stroke: "#888",
});

Classes

Class	Description
GeoMap	-
HighlightBuilder	Builder handed to custom hover/highlight draw fns, scoped to ONE source drawable. Everything recorded lands in the overlay group (drawn on top, inheriting the source layer’s clipTo/sizeMode). World coordinates throughout. Geometry comes from the Scene’s already-projected subpaths/circles — no re-projection, no datum re-processing.
LayerHandle	A handle to one registered layer, returned by GeoMap.layer, Plot.layer, and Plot.points. Lets you stream more data into the layer via append without re-projecting or re-building the features already in it.
Plot	-
Tooltip	A single shared, absolutely-positioned, pointer-events-none tooltip div in the host. Created lazily on first show; default inline look unless a className is given (then styling is entirely the caller’s). Always carries d3gl-tooltip.

Interfaces

Interface	Description
BackendHandle	-
BaseEngineOptions	Options every engine shares, owned and consumed once by the BaseEngine constructor. Each engine’s options type (e.g. GeoMapOptions, PlotOptions) extends this and adds only its own fields, so a base-level setting is declared in exactly one place and can’t drift or be silently dropped by an engine that forgot to wire it.
DataLabelOptions	Engine-owned text labels for plot() / geoMap() (#223) — the data-driven analogue of network.labels(). You supply the data and d3-style accessors; the engine measures each label’s text once (no magic-number metrics), places + culls collisions on every pan/zoom (the shared LabelLayer machinery), and routes to the active backend — an HTML overlay on WebGL, native <text>/fillText on SVG/Canvas so labels survive toSVG()/toPNG() export. Styling mirrors network.labels(): a built-in default look, an inline style override, or a full-CSS className. Plain labels are vertically centred on the anchor (offset sits them beside the glyph); set rotationOf for the oriented (rotated) model.
EngineSizing	How an engine is sized. Sizing is responsive by default — the engine observes its host and resizes in place (no teardown), preserving layers, view, and interaction state:
GeoMapOptions	Options every engine shares, owned and consumed once by the BaseEngine constructor. Each engine’s options type (e.g. GeoMapOptions, PlotOptions) extends this and adds only its own fields, so a base-level setting is declared in exactly one place and can’t drift or be silently dropped by an engine that forgot to wire it.
HighlightStyle	Style for highlight-overlay geometry. Unlike bulk StyleOverrides, lineWidth IS allowed: only one item is re-tessellated per hover change.
HoverHit	-
HoverOptions	Hover styling (#162), symmetric with SelectionOptions: hovered = how the hovered item looks (a HighlightStyle redraw / custom draw fn on Scene layers; on instanced lanes the ring uses its stroke), others = fade the non-hovered glyphs — the hover analogue of selection.others, opt-in. The layer hover option accepts either this object OR a bare HoverOption (the flat forms: true / a style / a draw fn) for the common “just style the hovered item” case.
InteractiveLayerOptions	Declarative interaction options shared by every engine’s retained layers. The machinery (hover overlay, tooltip, selection styling, hit-testing) lives entirely in BaseEngine — these options are just the per-layer surface that both BaseEngine.select’s and the hover/tooltip dispatch read. Plot.layer()/Plot.points() and GeoMap.layer() forward them into the LayerSpec via BaseEngine.interactionFields, so the contract has one home.
LayerOptions	Declarative interaction options shared by every engine’s retained layers. The machinery (hover overlay, tooltip, selection styling, hit-testing) lives entirely in BaseEngine — these options are just the per-layer surface that both BaseEngine.select’s and the hover/tooltip dispatch read. Plot.layer()/Plot.points() and GeoMap.layer() forward them into the LayerSpec via BaseEngine.interactionFields, so the contract has one home.
PlotLayerOptions	Declarative interaction options shared by every engine’s retained layers. The machinery (hover overlay, tooltip, selection styling, hit-testing) lives entirely in BaseEngine — these options are just the per-layer surface that both BaseEngine.select’s and the hover/tooltip dispatch read. Plot.layer()/Plot.points() and GeoMap.layer() forward them into the LayerSpec via BaseEngine.interactionFields, so the contract has one home.
PlotOptions	Plot adds no engine-level options of its own — all of BaseEngineOptions (sizing, backend, tooltipClass) apply.
PlotPointOptions	Declarative interaction options shared by every engine’s retained layers. The machinery (hover overlay, tooltip, selection styling, hit-testing) lives entirely in BaseEngine — these options are just the per-layer surface that both BaseEngine.select’s and the hover/tooltip dispatch read. Plot.layer()/Plot.points() and GeoMap.layer() forward them into the LayerSpec via BaseEngine.interactionFields, so the contract has one home.
SelectionOptions	Styles for select(): the selected set and its complement. Defaults: selected keeps the base style (items stand out because the others dim); others is { opacity: 0.3 }.
StyleOverride	Bulk per-drawable style override, composed over the base colors the layer’s fill/stroke accessors produce. Colors only — stroke geometry has its width baked in at tessellation time, so a bulk width change would be O(n) re-tessellation (widths are available in the single-item highlight overlay instead).

Type Aliases

Type Alias	Description
BackendType	Which renderer an engine (GeoMap / Plot, or the React <GeoMap>) draws the core!Scene with. Geometry is projected & tessellated once (backend-independent); the backend only turns it into pixels (or SVG nodes). Defaults to "webgl".
HChild	A minimal hyperscript helper: build a detached DOM element tree declaratively, with no framework and no HTML-string parsing. It’s the un-sugared React.createElement model — handy for the rich content the engine tooltip option accepts ((d) => HTMLElement), or any HTML overlay.
HighlightDraw	-
HoverOption	The hovered-item style payload: true = default style, a style = replay with it, a function = full custom draw of the hovered item.

Functions

Function	Description
createBackend	-
createCanvasBackend	Synchronously create a Canvas backend + its element. Used by the engine’s “auto” mode for an instant (non-async) first paint before the WebGL device is ready.
geoMap	-
h	-
plot	-