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gitea/web_src/js/markup/mermaid.ts
william-allspice 88f5d33ab2
Fix race condition in mermaid observer (#32599)
This Pull Request addresses a race condition in the updateIframeHeight
function where it is sometimes called when the iframe is not fully
loaded or accessible resulting in an alarming error message for the
user.

To address this we:
1. Add defensive programming within the updateIframeHeight function
2. Delay instantiating the intersection observer until the iframe has
loaded

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
2024-11-26 06:37:24 +00:00

90 lines
3.2 KiB
TypeScript

import {isDarkTheme} from '../utils.ts';
import {makeCodeCopyButton} from './codecopy.ts';
import {displayError} from './common.ts';
const {mermaidMaxSourceCharacters} = window.config;
// margin removal is for https://github.com/mermaid-js/mermaid/issues/4907
const iframeCss = `:root {color-scheme: normal}
body {margin: 0; padding: 0; overflow: hidden}
#mermaid {display: block; margin: 0 auto}
blockquote, dd, dl, figure, h1, h2, h3, h4, h5, h6, hr, p, pre {margin: 0}`;
export async function renderMermaid(): Promise<void> {
const els = document.querySelectorAll('.markup code.language-mermaid');
if (!els.length) return;
const {default: mermaid} = await import(/* webpackChunkName: "mermaid" */'mermaid');
mermaid.initialize({
startOnLoad: false,
theme: isDarkTheme() ? 'dark' : 'neutral',
securityLevel: 'strict',
suppressErrorRendering: true,
});
for (const el of els) {
const pre = el.closest('pre');
if (pre.hasAttribute('data-render-done')) continue;
const source = el.textContent;
if (mermaidMaxSourceCharacters >= 0 && source.length > mermaidMaxSourceCharacters) {
displayError(pre, new Error(`Mermaid source of ${source.length} characters exceeds the maximum allowed length of ${mermaidMaxSourceCharacters}.`));
continue;
}
try {
await mermaid.parse(source);
} catch (err) {
displayError(pre, err);
continue;
}
try {
// can't use bindFunctions here because we can't cross the iframe boundary. This
// means js-based interactions won't work but they aren't intended to work either
const {svg} = await mermaid.render('mermaid', source);
const iframe = document.createElement('iframe');
iframe.classList.add('markup-render', 'tw-invisible');
iframe.srcdoc = `<html><head><style>${iframeCss}</style></head><body>${svg}</body></html>`;
const mermaidBlock = document.createElement('div');
mermaidBlock.classList.add('mermaid-block', 'is-loading', 'tw-hidden');
mermaidBlock.append(iframe);
const btn = makeCodeCopyButton();
btn.setAttribute('data-clipboard-text', source);
mermaidBlock.append(btn);
const updateIframeHeight = () => {
const body = iframe.contentWindow?.document?.body;
if (body) {
iframe.style.height = `${body.clientHeight}px`;
}
};
iframe.addEventListener('load', () => {
pre.replaceWith(mermaidBlock);
mermaidBlock.classList.remove('tw-hidden');
updateIframeHeight();
setTimeout(() => { // avoid flash of iframe background
mermaidBlock.classList.remove('is-loading');
iframe.classList.remove('tw-invisible');
}, 0);
// update height when element's visibility state changes, for example when the diagram is inside
// a <details> + <summary> block and the <details> block becomes visible upon user interaction, it
// would initially set a incorrect height and the correct height is set during this callback.
(new IntersectionObserver(() => {
updateIframeHeight();
}, {root: document.documentElement})).observe(iframe);
});
document.body.append(mermaidBlock);
} catch (err) {
displayError(pre, err);
}
}
}