exdraw collaboration

frontend/src/pages/excalidraw-editor/collab/utils.js

@@ -0,0 +1,32 @@
+
+/**
+ * Transforms array of objects containing `id` attribute,
+ * or array of ids (strings), into a Map, keyd by `id`.
+ */
+export const arrayToMap = (items) => {
+  if (items instanceof Map) {
+    return items;
+  }
+  return items.reduce((acc, element) => {
+    acc.set(typeof element === 'string' ? element : element.id, element);
+    return acc;
+  }, new Map());
+};
+
+const DELETED_ELEMENT_TIMEOUT = 24 * 60 * 60 * 1000; // 1 day
+
+export const isSyncableElement = (element) => {
+  if (element.isDeleted) {
+    if (element.updated > Date.now() - DELETED_ELEMENT_TIMEOUT) {
+      return true; // 同步，在删除时间之内 1day
+    }
+    return false; // 不同步
+  }
+  return !isInvisiblySmallElement(element);
+};
+
+export const isInvisiblySmallElement = (
+  element
+) => {
+  return element.width === 0 && element.height === 0;
+};

frontend/src/pages/excalidraw-editor/index.js

@@ -7,10 +7,11 @@ import toaster from '../../components/toast';
 import { SAVE_INTERVAL_TIME } from './constants';
 import { Utils } from '../../utils/utils';
 import ExdrawServerApi from './collab/exdraw-server-api';
+import { io } from 'socket.io-client';
 
 import './index.css';
 
-const { docUuid, excalidrawServerUrl } = window.app.pageOptions;
+const { docUuid, excalidrawServerUrl, username } = window.app.pageOptions;
 
 const ExcaliEditor = () => {
   const [fileContent, setFileContent] = useState(null);
@@ -22,6 +23,11 @@ const ExcaliEditor = () => {
     exdrawUuid: '',
     accessToken: ''
   });
+  const exdrawClientConfigRef = useRef({
+    excalidrawServerUrl,
+    username
+  });
+  const exdrawClientRef = useRef(null);
 
   useEffect(() => {
     editorApi.getExdrawToken().then(res => {
@@ -35,6 +41,7 @@ const ExcaliEditor = () => {
         setFileContent(res.data);
         setIsFetching(false);
       });
+      exdrawClientRef.current = ExdrawClient(exdrawClientConfigRef.current);
     });
     onSetFavicon();
     // eslint-disable-next-line react-hooks/exhaustive-deps
@@ -44,7 +51,9 @@ const ExcaliEditor = () => {
     if (isChangedRef.current) {
       try {
         const exdrawServerApi = new ExdrawServerApi(exdrawServerConfigRef.current);
+        // socket emit event
         await exdrawServerApi.saveSceneContent(JSON.stringify(editorRef.current));
+        exdrawClientRef.current.emit('update-document', JSON.stringify(editorRef.current));
         isChangedRef.current = false;
         toaster.success(gettext('Successfully saved'), { duration: 2 });
       } catch {
@@ -95,7 +104,9 @@ const ExcaliEditor = () => {
   }, [saveSceneContent]);
 
   const onChangeContent = useCallback((elements) => {
-    editorRef.current = { elements };
+    editorRef.current = elements;
+    // socket emit event
+    exdrawClientRef.current.emit('update-document', JSON.stringify(editorRef.current));
     isChangedRef.current = true;
   }, []);
 
@@ -105,8 +116,28 @@ const ExcaliEditor = () => {
     document.getElementById('favicon').href = fileIcon;
   }, []);
 
+  const ExdrawClient = useCallback((options) => {
+    const socket = io(options.excalidrawServerUrl + '/exdraw');
+    socket.on('connect', () => {
+      const name = options.username;
+      const userInfo = { name };
+      socket.emit('join-room', userInfo);
+    });
+
+    socket.on('join-room', (userInfo) => {
+      console.log('join-room', userInfo);
+    });
+
+    socket.on('update-document', function (msg) {
+      setFileContent(JSON.parse(msg.msg));
+    });
+
+    return socket;
+  }, []);
+
   return (
     <SimpleEditor
+      exdrawClient={exdrawClientRef.current}
       isFetching={isFetching}
       sceneContent={fileContent}
       onSaveContent={onSaveContent}

frontend/src/pages/excalidraw-editor/simple-editor.js

@@ -1,8 +1,16 @@
 import React, { useEffect, useRef, useState } from 'react';
-import { Excalidraw, MainMenu } from '@excalidraw/excalidraw';
+import {
+  CaptureUpdateAction,
+  Excalidraw,
+  getSceneVersion,
+  MainMenu,
+  reconcileElements,
+  restoreElements
+} from '@excalidraw/excalidraw';
 import isHotkey from 'is-hotkey';
 import CodeMirrorLoading from '../../components/code-mirror-loading';
 import { langList } from './constants';
+import { isSyncableElement } from './collab/utils';
 
 import '@excalidraw/excalidraw/index.css';
 
@@ -10,25 +18,27 @@ const SimpleEditor = ({
   sceneContent = null,
   onChangeContent,
   onSaveContent,
-  isFetching
+  isFetching,
+  exdrawClient
 }) => {
   const [excalidrawAPI, setExcalidrawAPI] = useState(null);
-  const prevElementsRef = useRef([]);
   const UIOptions = {
     canvasActions: {
       saveToActiveFile: false,
-      LoadScene: false
+      LoadScene: true
     },
     tools: { image: false },
   };
-  const handleChange = () => {
-    const elements = excalidrawAPI.getSceneElements();
-    if (hasChanged(elements, prevElementsRef.current)) {
-      onChangeContent(elements);
-    }
-    prevElementsRef.current = elements;
+  const lastBroadcastedOrReceivedSceneVersion = useRef(-1);
+
+  const handleChange = (_elements) => {
+    broadcastElements(_elements);
   };
 
+  useEffect(() => {
+    handleRemoteSceneUpdate(_reconcileElements(sceneContent?.elements));
+  }, [sceneContent]);
+
   useEffect(() => {
     const handleHotkeySave = (event) => {
       if (isHotkey('mod+s', event)) {
@@ -43,12 +53,61 @@ const SimpleEditor = ({
     };
   }, [excalidrawAPI, onSaveContent]);
 
-  const hasChanged = (prev, current) => {
-    if (prev.length !== current.length) return true;
-
-    return current.some((element, index) => {
-      return element.version !== prev[index]?.version;
+  const handleRemoteSceneUpdate = (elements) => {
+    if (excalidrawAPI) {
+      excalidrawAPI.updateScene({
+        elements,
+        captureUpdate: CaptureUpdateAction.NEVER,
       });
+    }
+  };
+
+  const _reconcileElements = (remoteElements) => {
+    if (!remoteElements || !excalidrawAPI) return;
+    const localElements = getSceneElementsIncludingDeleted();
+    const appState = excalidrawAPI.getAppState();
+    const restoredRemoteElements = restoreElements(remoteElements, null);
+    const reconciledElements = reconcileElements(
+      localElements,
+      restoredRemoteElements,
+      appState
+    );
+
+    setLastBroadcastedOrReceivedSceneVersion(
+      getSceneVersion(reconciledElements)
+    );
+    return reconciledElements;
+  };
+
+  const broadcastElements = (elements) => {
+    if (
+      getSceneVersion(elements) >
+      lastBroadcastedOrReceivedSceneVersion.current
+    ) {
+      broadcastScene('SCENE_UPDATE', elements);
+      lastBroadcastedOrReceivedSceneVersion.current = getSceneVersion(elements);
+    }
+  };
+
+  const broadcastScene = (updateType, elements) => {
+    const data = {
+      type: updateType,
+      payload: {
+        elements: elements,
+      },
+    };
+    exdrawClient.emit('update-document', JSON.stringify(data.payload.elements));
+    onChangeContent({
+      elements: data.payload.elements,
+    });
+  };
+
+  const getSceneElementsIncludingDeleted = () => {
+    return excalidrawAPI?.getSceneElementsIncludingDeleted();
+  };
+
+  const setLastBroadcastedOrReceivedSceneVersion = (version) => {
+    lastBroadcastedOrReceivedSceneVersion.current = version;
   };
 
   if (isFetching) {