WebGPU: not able to use the alphaMode member of GPUCanvasConfiguration

[chirsz-ever]

Version: Deno 1.42.4

Example code

import { WindowBuilder } from "jsr:@divy/sdl2@0.10.5";

const adapter = await navigator.gpu.requestAdapter();
if (!adapter) {
    console.error("init WebGPU failed: adapter is", adapter);
    Deno.exit(1);
}
const device = await adapter.requestDevice();

const WIDTH = 800;
const HEIGHT = 600;

const surfaceFormat = navigator.gpu.getPreferredCanvasFormat();

const win = new WindowBuilder("demo", WIDTH, HEIGHT).build();
const surface = win.windowSurface();
const context = surface.getContext("webgpu")
context.configure({
    device,
    format: surfaceFormat,
    width: WIDTH,
    height: HEIGHT,
    alphaMode: "premultiplied"
})

Run it with deno run --unstable-ffi --unstable-webgpu -A alphamode-test.ts. This would cause:

error: Uncaught (in promise) TypeError: [object Object]: The provided value 'preMultiplied' is not a valid enum value of type GPUCanvasAlphaMode.
context.configure({
        ^
    at ext:deno_webidl/00_webidl.js:817:13
    at Array.GPUCanvasConfiguration (ext:deno_webidl/00_webidl.js:788:32)
    at GPUCanvasContext.configure (ext:deno_webgpu/02_surface.js:53:39)
    at file://xxx/alphamode-test.ts:18:9

But if we replace alphaMode: "premultiplied" with alphaMode: "preMultiplied", there would be another error:

error: Uncaught (in promise) TypeError: [object Object]: The provided value 'preMultiplied' is not a valid enum value of type GPUCanvasAlphaMode.
context.configure({
        ^
    at ext:deno_webidl/00_webidl.js:817:13
    at Array.GPUCanvasConfiguration (ext:deno_webidl/00_webidl.js:788:32)
    at GPUCanvasContext.configure (ext:deno_webgpu/02_surface.js:53:39)
    at file://xxx/alphamode-test.ts:18:9