fix(web): keep title in sync with iframe

web/src/components/IFrame.tsx

@@ -4,25 +4,30 @@ import { uniqueId } from 'lodash'
 import styles from '../style/components/IFrame.module.css'
 interface Props {
   src: string
-  onPageChanged: (page: string, hash: string) => void
+  onPageChanged: (page: string, hash: string, title?: string) => void
   onHashChanged: (hash: string) => void
+  onTitleChanged: (title: string) => void
   onNotFound: () => void
 }
 
 export default function IFrame(props: Props): JSX.Element {
   const iFrameRef = useRef<HTMLIFrameElement>(null)
 
   const onIframeLoad = (): void => {
-    if (iFrameRef.current == null) {
+    if (iFrameRef.current === null) {
       console.error('iFrameRef is null')
       return
     }
 
-    // remove the hashchange event listener to prevent memory leaks
+    // remove the event listeners to prevent memory leaks
     iFrameRef.current.contentWindow?.removeEventListener(
       'hashchange',
       hashChangeEventListener
     )
+    iFrameRef.current.contentWindow?.removeEventListener(
+      'titlechange',
+      titleChangeEventListener
+    )
 
     const url = iFrameRef.current?.contentDocument?.location.href
     if (url == null) {
@@ -69,6 +74,10 @@ export default function IFrame(props: Props): JSX.Element {
       'hashchange',
       hashChangeEventListener
     )
+    iFrameRef.current.contentWindow?.addEventListener(
+      'titlechange',
+      titleChangeEventListener
+    )
 
     const parts = url.split('/doc/').slice(1).join('/doc/').split('/')
     const urlPageAndHash = parts.slice(2).join('/')
@@ -77,12 +86,13 @@ export default function IFrame(props: Props): JSX.Element {
       : urlPageAndHash.length
     const urlPage = urlPageAndHash.slice(0, hashIndex)
     const urlHash = urlPageAndHash.slice(hashIndex)
+    const title = iFrameRef.current?.contentDocument?.title
 
-    props.onPageChanged(urlPage, urlHash)
+    props.onPageChanged(urlPage, urlHash, title)
   }
 
   const hashChangeEventListener = (): void => {
-    if (iFrameRef.current == null) {
+    if (iFrameRef.current === null) {
       console.error('hashChangeEvent from iframe but iFrameRef is null')
       return
     }
@@ -102,6 +112,20 @@ export default function IFrame(props: Props): JSX.Element {
     props.onHashChanged(hash)
   }
 
+  const titleChangeEventListener = (): void => {
+    if (iFrameRef.current === null) {
+      console.error('titleChangeEvent from iframe but iFrameRef is null')
+      return
+    }
+
+    const title = iFrameRef.current?.contentDocument?.title
+    if (title == null) {
+      return
+    }
+
+    props.onTitleChanged(title)
+  }
+
   return (
     <iframe
       ref={iFrameRef}

web/src/pages/Docs.tsx

@@ -117,7 +117,14 @@ export default function Docs(): JSX.Element {
     window.history.pushState(null, '', url)
   }
 
-  const iFramePageChanged = (urlPage: string, urlHash: string): void => {
+  const updateTitle = (newTitle: string): void => {
+    document.title = newTitle
+  }
+
+  const iFramePageChanged = (urlPage: string, urlHash: string, title?: string): void => {
+    if (title != null && title !== document.title) {
+      updateTitle(title)
+    }
     if (urlPage === page.current) {
       return
     }
@@ -225,6 +232,7 @@ export default function Docs(): JSX.Element {
         src={iFrameSrc}
         onPageChanged={iFramePageChanged}
         onHashChanged={iFrameHashChanged}
+        onTitleChanged={updateTitle}
         onNotFound={iFrameNotFound}
       />
       {!hideUi && (