57 lines
1.6 KiB
TypeScript
57 lines
1.6 KiB
TypeScript
import { Event } from 'event-target-shim'
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/** An event fired by a context requester to signal it desires a named context. */
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export class ContextEvent<T = unknown> extends Event<'context-request'> {
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constructor(init: ContextEventInit<T>) {
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super('context-request', { bubbles: true, composed: true })
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init = Object(init) as Required<ContextEventInit<T>>
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this.context = init.context
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}
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context!: Context<T>
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multiple!: boolean
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callback!: ContextCallback<Context<T>>
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}
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interface ContextEventInit<T = unknown> {
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context: Context<T>
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multiple?: boolean
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callback: ContextCallback<Context<T>>
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}
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/** A Context object defines an optional initial value for a Context, as well as a name identifier for debugging purposes. */
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export type Context<T = unknown> = {
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name: string
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initialValue?: T
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}
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/** A helper type which can extract a Context value type from a Context type. */
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export type ContextType<T extends Context> = T extends Context<infer Y>
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? Y
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: never
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/** A function which creates a Context value object */
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export function createContext<T>(
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name: string,
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initialValue?: T
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): Readonly<Context<T>> {
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return {
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name,
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initialValue,
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}
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}
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/** A callback which is provided by a context requester and is called with the value satisfying the request. */
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export type ContextCallback<ValueType> = (
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value: ValueType,
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dispose?: () => void
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) => void
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declare global {
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interface HTMLElementEventMap {
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/** A 'context-request' event can be emitted by any element which desires a context value to be injected by an external provider. */
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'context-request': ContextEvent
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}
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}
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