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Backport #21642 Browsers introduce a opaque background on iframes if the iframe element's color-scheme does not match the document's color scheme which in case of a dark theme results in a mismatch and the browser adds a white background. Avoid this by specifying the same color scheme outside and inside the iframe. See https://fvsch.com/transparent-iframes for more info. My initial attempt was to make the iframe document the same color-scheme as the parent page (light or dark) but with that, there was a ugly background flash on load in Chrome because Chrome apparently always loads iframe in light scheme initially. Firefox still shows a background flash on load but this is not possible to get rid of and it's certainly a browser bug. Before: <img width="1147" alt="Screen Shot 2022-10-31 at 13 30 55" src="https://user-images.githubusercontent.com/115237/199017132-9828aace-bdd0-4ede-8118-359e72bcf2fe.png"> After: <img width="1152" alt="Screen Shot 2022-10-31 at 13 30 36" src="https://user-images.githubusercontent.com/115237/199017137-989a9e67-3fe0-445f-a191-df5bf290dabf.png">
68 lines
2.3 KiB
JavaScript
68 lines
2.3 KiB
JavaScript
import {isDarkTheme} from '../utils.js';
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const {mermaidMaxSourceCharacters} = window.config;
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const iframeCss = `
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:root {color-scheme: normal}
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body {margin: 0; padding: 0}
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#mermaid {display: block; margin: 0 auto}
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`;
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function displayError(el, err) {
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el.closest('pre').classList.remove('is-loading');
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const errorNode = document.createElement('div');
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errorNode.setAttribute('class', 'ui message error markup-block-error mono');
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errorNode.textContent = err.str || err.message || String(err);
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el.closest('pre').before(errorNode);
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}
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export async function renderMermaid() {
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const els = document.querySelectorAll('.markup code.language-mermaid');
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if (!els.length) return;
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const {default: mermaid} = await import(/* webpackChunkName: "mermaid" */'mermaid');
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mermaid.initialize({
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startOnLoad: false,
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theme: isDarkTheme() ? 'dark' : 'neutral',
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securityLevel: 'strict',
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});
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for (const el of els) {
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const source = el.textContent;
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if (mermaidMaxSourceCharacters >= 0 && source.length > mermaidMaxSourceCharacters) {
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displayError(el, new Error(`Mermaid source of ${source.length} characters exceeds the maximum allowed length of ${mermaidMaxSourceCharacters}.`));
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continue;
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}
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let valid;
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try {
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valid = mermaid.parse(source);
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} catch (err) {
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displayError(el, err);
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}
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if (!valid) {
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el.closest('pre').classList.remove('is-loading');
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continue;
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}
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try {
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// can't use bindFunctions here because we can't cross the iframe boundary. This
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// means js-based interactions won't work but they aren't intended to work either
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mermaid.mermaidAPI.render('mermaid', source, (svgStr) => {
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const heightStr = (svgStr.match(/viewBox="(.+?)"/) || ['', ''])[1].split(/\s+/)[3];
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if (!heightStr) return displayError(el, new Error('Could not determine chart height'));
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const iframe = document.createElement('iframe');
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iframe.classList.add('markup-render');
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iframe.sandbox = 'allow-scripts';
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iframe.style.height = `${Math.ceil(parseFloat(heightStr))}px`;
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iframe.srcdoc = `<html><head><style>${iframeCss}</style></head><body>${svgStr}</body></html>`;
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el.closest('pre').replaceWith(iframe);
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});
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} catch (err) {
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displayError(el, err);
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}
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}
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}
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