class

CallbackRenderer

implements IRenderer

Per-feature dynamic symbol via a callback function. Maximum flexibility — use when other renderers are insufficient.

Constructor

new CallbackRenderer(fn: (feature: Feature, context?: SymbolRenderContext) => Symbol | null)

Parameter	Type		Description
`fn`	`(feature: Feature, context?: SymbolRenderContext) => Symbol \| null`	required	Callback that returns a symbol (or null to skip)

Properties

Name	Type	Access	Description
`type`	`'callback'`	readonly	Renderer type discriminant

Methods

getSymbol()

getSymbol(feature: Feature, context?: SymbolRenderContext): Symbol | null

Invoke user callback to get symbol.

Returns Symbol | null

Example

const renderer = new CallbackRenderer((feature) => {
  const pop = feature.attributes.population as number;
  const size = Math.sqrt(pop / 10000) * 2;
  return {
    type: 'simple-marker',
    color: pop > 1000000 ? [255,0,0,255] : [0,128,255,255],
    size: Math.max(4, Math.min(size, 20)),
  };
});