Display call member speaking status on bottom bar (#2742)

* add mutation observer hok

* add hook to read speaking member by observing iframe content

* display speaking member name in call status bar and improve layout

* fix shrining

src/app/hooks/useCallSpeakers.ts

@@ -0,0 +1,60 @@
+import { useCallback, useEffect, useMemo, useState } from 'react';
+import { CallEmbed } from '../plugins/call';
+import { useMutationObserver } from './useMutationObserver';
+import { isUserId } from '../utils/matrix';
+import { useCallMembers, useCallSession } from './useCall';
+import { useCallJoined } from './useCallEmbed';
+
+export const useCallSpeakers = (callEmbed: CallEmbed): Set<string> => {
+  const [speakers, setSpeakers] = useState(new Set<string>());
+  const callSession = useCallSession(callEmbed.room);
+  const callMembers = useCallMembers(callEmbed.room, callSession);
+  const joined = useCallJoined(callEmbed);
+
+  const videoContainers = useMemo(() => {
+    if (callMembers && joined) return callEmbed.document?.querySelectorAll('[data-video-fit]');
+    return undefined;
+  }, [callEmbed, callMembers, joined]);
+
+  const mutationObserver = useMutationObserver(
+    useCallback(
+      (mutations) => {
+        const s = new Set<string>();
+
+        mutations.forEach((mutation) => {
+          if (mutation.type !== 'attributes') return;
+          const el = mutation.target as HTMLElement;
+
+          const style = callEmbed.iframe.contentWindow?.getComputedStyle(el, '::before');
+          if (!style) return;
+          const tileBackgroundImage = style.getPropertyValue('background-image');
+          const speaking = tileBackgroundImage !== 'none';
+          if (!speaking) return;
+
+          const speakerId = el.querySelector('[aria-label]')?.getAttribute('aria-label');
+          if (speakerId && isUserId(speakerId)) {
+            s.add(speakerId);
+          }
+        });
+
+        setSpeakers(s);
+      },
+      [callEmbed]
+    )
+  );
+
+  useEffect(() => {
+    videoContainers?.forEach((element) => {
+      mutationObserver.observe(element, {
+        attributes: true,
+        attributeFilter: ['class', 'style'],
+      });
+    });
+
+    return () => {
+      mutationObserver.disconnect();
+    };
+  }, [videoContainers, mutationObserver]);
+
+  return speakers;
+};