Add SCENE_INIT broadcast type for new user (#1095)

src/components/App.tsx

@@ -502,7 +502,7 @@ export class App extends React.Component<any, AppState> {
       getDrawingVersion(globalSceneState.getAllElements()) >
       this.lastBroadcastedOrReceivedSceneVersion
     ) {
-      this.broadcastSceneUpdate();
+      this.broadcastScene("SCENE_UPDATE");
     }
 
     history.record(this.state, globalSceneState.getAllElements());
@@ -708,28 +708,9 @@ export class App extends React.Component<any, AppState> {
       //  initial SCENE_UPDATE message
       const initializationTimer = setTimeout(initialize, 5000);
 
-      this.socket = socketIOClient(SOCKET_SERVER);
-      this.roomID = roomMatch[1];
-      this.roomKey = roomMatch[2];
-      this.socket.on("init-room", () => {
-        this.socket && this.socket.emit("join-room", this.roomID);
-      });
-      this.socket.on(
-        "client-broadcast",
-        async (encryptedData: ArrayBuffer, iv: Uint8Array) => {
-          if (!this.roomKey) {
-            return;
-          }
-          const decryptedData = await decryptAESGEM(
-            encryptedData,
-            this.roomKey,
-            iv,
-          );
-
-          switch (decryptedData.type) {
-            case "INVALID_RESPONSE":
-              return;
-            case "SCENE_UPDATE": {
+      const updateScene = (
+        decryptedData: SocketUpdateDataSource["SCENE_INIT" | "SCENE_UPDATE"],
+      ) => {
         const { elements: remoteElements } = decryptedData.payload;
         const restoredState = restore(remoteElements || [], null, {
           scrollToContent: true,
@@ -772,8 +753,7 @@ export class App extends React.Component<any, AppState> {
                   delete localElementMap[element.id];
                 } else if (
                   localElementMap.hasOwnProperty(element.id) &&
-                        localElementMap[element.id].version ===
-                          element.version &&
+                  localElementMap[element.id].version === element.version &&
                   localElementMap[element.id].versionNonce !==
                     element.versionNonce
                 ) {
@@ -803,6 +783,7 @@ export class App extends React.Component<any, AppState> {
         this.lastBroadcastedOrReceivedSceneVersion = getDrawingVersion(
           globalSceneState.getAllElements(),
         );
+
         // We haven't yet implemented multiplayer undo functionality, so we clear the undo stack
         // when we receive any messages from another peer. This UX can be pretty rough -- if you
         // undo, a user makes a change, and then try to redo, your element(s) will be lost. However,
@@ -811,8 +792,38 @@ export class App extends React.Component<any, AppState> {
         if (this.socketInitialized === false) {
           initialize();
         }
+      };
+
+      this.socket = socketIOClient(SOCKET_SERVER);
+      this.roomID = roomMatch[1];
+      this.roomKey = roomMatch[2];
+      this.socket.on("init-room", () => {
+        this.socket && this.socket.emit("join-room", this.roomID);
+      });
+      this.socket.on(
+        "client-broadcast",
+        async (encryptedData: ArrayBuffer, iv: Uint8Array) => {
+          if (!this.roomKey) {
+            return;
+          }
+          const decryptedData = await decryptAESGEM(
+            encryptedData,
+            this.roomKey,
+            iv,
+          );
+
+          switch (decryptedData.type) {
+            case "INVALID_RESPONSE":
+              return;
+            case "SCENE_INIT": {
+              if (!this.socketInitialized) {
+                updateScene(decryptedData);
+              }
               break;
             }
+            case "SCENE_UPDATE":
+              updateScene(decryptedData);
+              break;
             case "MOUSE_LOCATION": {
               const { socketID, pointerCoords } = decryptedData.payload;
               this.setState((state) => {
@@ -852,7 +863,7 @@ export class App extends React.Component<any, AppState> {
         });
       });
       this.socket.on("new-user", async (socketID: string) => {
-        this.broadcastSceneUpdate();
+        this.broadcastScene("SCENE_INIT");
       });
 
       this.setState({
@@ -879,9 +890,9 @@ export class App extends React.Component<any, AppState> {
     }
   };
 
-  private broadcastSceneUpdate = () => {
-    const data: SocketUpdateDataSource["SCENE_UPDATE"] = {
-      type: "SCENE_UPDATE",
+  private broadcastScene = (sceneType: "SCENE_INIT" | "SCENE_UPDATE") => {
+    const data: SocketUpdateDataSource[typeof sceneType] = {
+      type: sceneType,
       payload: {
         elements: getSyncableElements(globalSceneState.getAllElements()),
       },

src/data/index.ts

@@ -32,6 +32,12 @@ export type EncryptedData = {
 };
 
 export type SocketUpdateDataSource = {
+  SCENE_INIT: {
+    type: "SCENE_INIT";
+    payload: {
+      elements: readonly ExcalidrawElement[];
+    };
+  };
   SCENE_UPDATE: {
     type: "SCENE_UPDATE";
     payload: {