Show tiles for members we're trying to connect to

This should help give more context on what's going wrong in
splitbrain scenarios.

If users leave calls uncleanly, their tile will remain in until
their member event times out, which will be an hour from when they
joined the call. See https://github.com/vector-im/element-call/issues/639.

Part of https://github.com/vector-im/element-call/issues/616

src/room/InCallView.tsx

@@ -70,6 +70,7 @@ const isSafari = /^((?!chrome|android).)*safari/i.test(navigator.userAgent);
 interface Props {
   client: MatrixClient;
   groupCall: GroupCall;
+  participants: RoomMember[];
   roomName: string;
   avatarUrl: string;
   microphoneMuted: boolean;
@@ -82,14 +83,16 @@ interface Props {
   onLeave: () => void;
   isScreensharing: boolean;
   screenshareFeeds: CallFeed[];
-  localScreenshareFeed: CallFeed;
   roomIdOrAlias: string;
   unencryptedEventsFromUsers: Set<string>;
   hideHeader: boolean;
 }
 
-export interface Participant {
+// Represents something that should get a tile on the layout,
+// ie. a user's video feed or a screen share feed.
+export interface TileDescriptor {
   id: string;
+  member: RoomMember;
   focused: boolean;
   presenter: boolean;
   callFeed?: CallFeed;
@@ -99,6 +102,7 @@ export interface Participant {
 export function InCallView({
   client,
   groupCall,
+  participants,
   roomName,
   avatarUrl,
   microphoneMuted,
@@ -111,7 +115,6 @@ export function InCallView({
   toggleScreensharing,
   isScreensharing,
   screenshareFeeds,
-  localScreenshareFeed,
   roomIdOrAlias,
   unencryptedEventsFromUsers,
   hideHeader,
@@ -185,39 +188,48 @@ export function InCallView({
   }, [setLayout]);
 
   const items = useMemo(() => {
-    const participants: Participant[] = [];
+    const tileDescriptors: TileDescriptor[] = [];
 
-    for (const callFeed of userMediaFeeds) {
-      participants.push({
-        id: callFeed.stream.id,
-        callFeed,
-        focused:
-          screenshareFeeds.length === 0 && callFeed.userId === activeSpeaker,
-        isLocal: callFeed.isLocal(),
+    // one tile for each participants, to start with (we want a tile for everyone we
+    // think should be in the call, even if we don't have a media feed for them yet)
+    for (const p of participants) {
+      const userMediaFeed = userMediaFeeds.find((f) => f.userId === p.userId);
+
+      // NB. this assumes that the same user can't join more than once from multiple
+      // devices, but the participants are just RoomMembers, so this assumption is baked
+      // into GroupCall itself.
+      tileDescriptors.push({
+        id: p.userId,
+        member: p,
+        callFeed: userMediaFeed,
+        focused: screenshareFeeds.length === 0 && p.userId === activeSpeaker,
+        isLocal: p.userId === client.getUserId(),
         presenter: false,
       });
     }
 
-    for (const callFeed of screenshareFeeds) {
-      const userMediaItem = participants.find(
-        (item) => item.callFeed.userId === callFeed.userId
+    // add the screenshares too
+    for (const screenshareFeed of screenshareFeeds) {
+      const userMediaItem = tileDescriptors.find(
+        (item) => item.member.userId === screenshareFeed.userId
       );
 
       if (userMediaItem) {
         userMediaItem.presenter = true;
       }
 
-      participants.push({
-        id: callFeed.stream.id,
-        callFeed,
+      tileDescriptors.push({
+        id: screenshareFeed.stream.id,
+        member: userMediaItem?.member,
+        callFeed: screenshareFeed,
         focused: true,
-        isLocal: callFeed.isLocal(),
+        isLocal: screenshareFeed.isLocal(),
         presenter: false,
       });
     }
 
-    return participants;
-  }, [userMediaFeeds, activeSpeaker, screenshareFeeds]);
+    return tileDescriptors;
+  }, [client, participants, userMediaFeeds, activeSpeaker, screenshareFeeds]);
 
   // The maximised participant: either the participant that the user has
   // manually put in fullscreen, or the focused (active) participant if the
@@ -281,7 +293,13 @@ export function InCallView({
 
     return (
       <VideoGrid items={items} layout={layout} disableAnimations={isSafari}>
-        {({ item, ...rest }: { item: Participant; [x: string]: unknown }) => (
+        {({
+          item,
+          ...rest
+        }: {
+          item: TileDescriptor;
+          [x: string]: unknown;
+        }) => (
           <VideoTileContainer
             key={item.id}
             item={item}