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27 lines
1.1 KiB
TypeScript
27 lines
1.1 KiB
TypeScript
/**
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* Whether a mail paints a full-bleed background canvas: a table, div or body
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* that is 100% wide and carries a background colour. The reader drops its
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* own gutter around such mail, since the gutter would show as a frame around
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* the mail's background.
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*
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* Each start tag is looked at on its own and each condition tested on its
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* attribute text separately. The former single regex ran two unbounded
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* `[^>]*` scans over one tag and backtracked between them, which made a tag
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* with many `width:100%` declarations and no background cost quadratic time:
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* a 1 MB style attribute held the UI thread for well over a minute, on
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* every open of the message.
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*/
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const START_TAG = /<(?:table|div|body)\b([^<>]{0,8192})/gi;
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const FULL_WIDTH = /\bwidth\s*=\s*["']?\s*100%|width\s*:\s*100%/i;
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const BACKGROUND = /\bbgcolor\s*=|background(?:-color)?\s*:/i;
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export function hasFullBleedCanvas(html: string): boolean {
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START_TAG.lastIndex = 0;
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for (const match of html.matchAll(START_TAG)) {
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const attributes = match[1];
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if (FULL_WIDTH.test(attributes) && BACKGROUND.test(attributes)) return true;
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}
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return false;
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}
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