39 lines
2.0 KiB
TypeScript
39 lines
2.0 KiB
TypeScript
/** Mirror changed language labels without rescanning every code block on each DOM mutation. */
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export function installCodeBlockLabels(root: HTMLElement): () => void {
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const sync = (block: HTMLElement) => {
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const label = block.querySelector('.language-button')?.textContent?.trim() || 'Plain text'
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if (block.dataset.languageLabel !== label) block.dataset.languageLabel = label
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}
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const discover = (node: Node, blocks: Set<HTMLElement>) => {
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if (!(node instanceof HTMLElement)) return
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if (node.matches('.milkdown-code-block')) blocks.add(node)
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node.querySelectorAll<HTMLElement>('.milkdown-code-block').forEach(block => blocks.add(block))
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}
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const observer = new MutationObserver(records => {
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const changed = new Set<HTMLElement>()
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for (const record of records) {
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const element = record.target instanceof Element ? record.target : record.target.parentElement
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// CodeMirror viewport/text changes do not change the footer's language.
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const label = element?.closest('.language-button')
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const block = label?.closest<HTMLElement>('.milkdown-code-block')
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if (block) changed.add(block)
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if ([...record.removedNodes].some(node => node instanceof Element &&
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(node.matches('.language-button') || node.querySelector('.language-button')))) {
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const owner = element?.closest<HTMLElement>('.milkdown-code-block')
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if (owner) changed.add(owner)
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}
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for (const node of record.addedNodes) {
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discover(node, changed)
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if (node instanceof Element && (node.matches('.language-button') || node.querySelector('.language-button'))) {
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const owner = node.closest<HTMLElement>('.milkdown-code-block')
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if (owner) changed.add(owner)
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}
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}
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}
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changed.forEach(block => { if (root.contains(block)) sync(block) })
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})
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root.querySelectorAll<HTMLElement>('.milkdown-code-block').forEach(sync)
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observer.observe(root, { subtree: true, childList: true, characterData: true })
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return () => observer.disconnect()
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}
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