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Improve iframe dark mode sync and prevent duplicate listeners #1365

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114 changes: 66 additions & 48 deletions docs/iframe-theme.js
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Original file line number Diff line number Diff line change
@@ -1,67 +1,85 @@
(function () {
function updateIframesForDarkMode() {
const isDark = document.documentElement.classList.contains("dark");
const IFRAME_SELECTOR = 'iframe[src*="chromatic.com/iframe.html"]';
const MESSAGE_TYPE = "THEME_CHANGE";

document.querySelectorAll('iframe[src*="chromatic.com/iframe.html"]').forEach((iframe) => {
iframe.style.background = "transparent";
iframe.allowTransparency = true;
function getIsDark() {
return document.documentElement.classList.contains("dark");
}

function sendThemeMessage(iframe, isDark) {
try {
if (!iframe.contentWindow) return;

iframe.contentWindow.postMessage(
{
type: MESSAGE_TYPE,
isDark,
styles: {
background: isDark ? "#0b0d0f" : "transparent",
},
},
"*" // consider restricting origin if possible
);
} catch (e) {
console.warn("Could not send message to iframe:", e);
}
}

function setupIframe(iframe) {
const isDark = getIsDark();

iframe.style.background = "transparent";
iframe.setAttribute("allowTransparency", "true");

// prevent duplicate listeners
if (iframe.dataset.themeListenerAttached === "true") return;
iframe.dataset.themeListenerAttached = "true";

// Use postMessage to communicate with the iframe since we can't access contentDocument due to CORS
const sendThemeMessage = () => {
try {
const message = {
type: 'THEME_CHANGE',
isDark: isDark,
styles: {
background: isDark ? '#0b0d0f' : 'transparent' // transparent for light mode
}
};
iframe.contentWindow.postMessage(message, '*');
} catch (e) {
console.warn("Could not send message to iframe:", e);
}
};
const onLoad = () => {
setTimeout(() => sendThemeMessage(iframe, getIsDark()), 100);
};

// Send message immediately if iframe might be loaded
sendThemeMessage();
iframe.addEventListener("load", onLoad);

// Also send message when iframe loads
iframe.addEventListener("load", () => {
// Add a small delay to ensure iframe is ready
setTimeout(sendThemeMessage, 100);
});
});
// initial attempt
sendThemeMessage(iframe, isDark);
}

// Listen for theme changes on the parent document
function updateIframes() {
const iframes = document.querySelectorAll(IFRAME_SELECTOR);
iframes.forEach(setupIframe);
}

// Observe class changes on <html>
const observer = new MutationObserver((mutations) => {
mutations.forEach((mutation) => {
if (mutation.type === 'attributes' &&
mutation.attributeName === 'class' &&
mutation.target === document.documentElement) {
updateIframesForDarkMode();
for (const mutation of mutations) {
if (
mutation.type === "attributes" &&
mutation.attributeName === "class"
) {
updateIframes();
break;
}
});
}
});

observer.observe(document.documentElement, {
attributes: true,
attributeFilter: ['class']
attributeFilter: ["class"],
});

function init() {
updateIframes();
}

if (document.readyState === "loading") {
document.addEventListener("DOMContentLoaded", updateIframesForDarkMode);
document.addEventListener("DOMContentLoaded", init, { once: true });
} else {
setTimeout(updateIframesForDarkMode, 100);
// TODO: add Storybook with Darkmode enabled
let themeChangeCount = 0;
const themeChangeInterval = setInterval(() => {
if (themeChangeCount < 2) {
updateIframesForDarkMode();
themeChangeCount++;
} else {
clearInterval(themeChangeInterval);
}
}, 1000);
init();
}

// optional: cleanup on page unload (good practice)
window.addEventListener("beforeunload", () => {
observer.disconnect();
});
})();