musescore-downloader/src/mscore.ts

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import { fetchMscz } from './mscz'
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import { fetchData } from './utils'
const WEBMSCORE_URL = 'https://cdn.jsdelivr.net/npm/webmscore@0.10/webmscore.js'
// fonts for Chinese characters (CN) and Korean hangul (KR)
// JP characters are included in the CN font
const FONT_URLS = ['CN', 'KR'].map(l => `https://cdn.jsdelivr.net/npm/@librescore/fonts/SourceHanSans${l}-Regular.woff2`)
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const SF3_URL = 'https://cdn.jsdelivr.net/npm/@librescore/sf3/FluidR3Mono_GM.sf3'
const SOUND_FONT_LOADED = Symbol('SoundFont loaded')
export type WebMscore = import('webmscore').default
const initMscore = async (w: Window) => {
if (!w['WebMscore']) {
// init webmscore (https://github.com/LibreScore/webmscore)
const script = w.document.createElement('script')
script.src = WEBMSCORE_URL
w.document.body.append(script)
await new Promise(resolve => { script.onload = resolve })
}
}
let fonts: Promise<Uint8Array[]> | undefined
const initFonts = () => {
// load CJK fonts
// CJK (East Asian) characters will be rendered as "tofu" if there is no font
if (!fonts) {
fonts = Promise.all(
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FONT_URLS.map(url => fetchData(url)),
)
}
}
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export const loadSoundFont = (score: WebMscore): Promise<void> => {
if (!score[SOUND_FONT_LOADED]) {
const loadPromise = (async () => {
await score.setSoundFont(
await fetchData(SF3_URL),
)
})()
score[SOUND_FONT_LOADED] = loadPromise
}
return score[SOUND_FONT_LOADED] as Promise<void>
}
export const loadMscore = async (w: Window): Promise<WebMscore> => {
initFonts()
await initMscore(w)
const WebMscore: typeof import('webmscore').default = w['WebMscore']
// parse mscz data
const data = new Uint8Array(
new Uint8Array(await fetchMscz()), // copy its ArrayBuffer
)
const score = await WebMscore.load('mscz', data, await fonts)
await score.generateExcerpts()
return score
}