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import type { CanvasRenderingContext2D } from './CanvasRenderingContext2D'
import * as _ from './utils'
import { __createCanvasRenderingContext2D } from './CanvasRenderingContext2D'
export class OffscreenCanvas extends EventTarget {
constructor(width: number, height: number) {
super()
if (arguments.length < 2) throw new TypeError(`Failed to construct 'OffscreenCanvas': 2 arguments required.`)
width = Number(width) || 0
height = Number(height) || 0
_.INTERNALS.set(this, { width, height } as OffscreenCanvasInternals)
}
get height(): number {
return _.internalsOf(this, 'OffscreenCanvas', 'height').height
}
set height(value) {
_.internalsOf(this, 'OffscreenCanvas', 'height').height = Number(value) || 0
}
get width(): number {
return _.internalsOf(this, 'OffscreenCanvas', 'width').width
}
set width(value) {
_.internalsOf(this, 'OffscreenCanvas', 'width').width = Number(value) || 0
}
getContext(contextType: PredefinedContextId): CanvasRenderingContext2D | null {
const internals = _.internalsOf<OffscreenCanvasInternals>(this, 'HTMLCanvasElement', 'getContext')
switch (contextType) {
case '2d':
if (internals.renderingContext2D) return internals.renderingContext2D
internals.renderingContext2D = __createCanvasRenderingContext2D(this)
return internals.renderingContext2D
default:
return null
}
}
convertToBlob(options: Partial<ConvertToBlobOptions>) {
options = Object(options)
const quality = Number(options.quality) || 0
const type = getImageType(String(options.type).trim().toLowerCase())
void quality
return Promise.resolve(
new Blob([], { type })
)
}
}
_.allowStringTag(OffscreenCanvas)
const getImageType = (type: string): PredefinedImageType => type === 'image/avif' || type === 'image/jpeg' || type === 'image/png' || type === 'image/webp' ? type : 'image/png'
interface OffscreenCanvasInternals {
height: number
renderingContext2D: CanvasRenderingContext2D
width: number
}
interface ConvertToBlobOptions {
quality: number
type: PredefinedImageType
}
type PredefinedContextId = '2d' | 'bitmaprenderer' | 'webgl' | 'webgl2' | 'webgpu'
type PredefinedImageType = 'image/avif' | 'image/jpeg' | 'image/png' | 'image/webp'
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