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factor reconcilation out of `updateScene` & remove `replaceAll` (#2266)

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Co-authored-by: dwelle <luzar.david@gmail.com>
pull/2271/head
Aakansha Doshi 4 years ago committed by GitHub
parent 1034ec91b8
commit 499a60309f
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 83 additions and 87 deletions
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111
src/components/App.tsx
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@ -15,7 +15,6 @@ import {
getCursorForResizingElement,
getPerfectElementSize,
getNormalizedDimensions,
getElementMap,
getSceneVersion,
getSyncableElements,
newLinearElement,
@ -1285,8 +1284,15 @@ class App extends React.Component<ExcalidrawProps, AppState> {
if (init || initFromSnapshot) {
this.setScrollToCenter(elements);
}
const newElements = this.portal.reconcileElements(elements);
this.updateScene({ elements });
// Avoid broadcasting to the rest of the collaborators the scene
// we just received!
// Note: this needs to be set before updating the scene as it
// syncronously calls render.
this.setLastBroadcastedOrReceivedSceneVersion(getSceneVersion(newElements));
this.updateScene({ elements: newElements });
if (!this.portal.socketInitialized && !initFromSnapshot) {
this.initializeSocket();
@ -1301,94 +1307,27 @@ class App extends React.Component<ExcalidrawProps, AppState> {
this.portal.close();
};
public updateScene = (
sceneData: {
public updateScene = withBatchedUpdates(
(sceneData: {
elements: readonly ExcalidrawElement[];
appState?: AppState;
},
{ replaceAll = false }: { replaceAll?: boolean } = {},
) => {
// currently we only support syncing background color
if (sceneData.appState?.viewBackgroundColor) {
this.setState({
viewBackgroundColor: sceneData.appState.viewBackgroundColor,
});
}
// Perform reconciliation - in collaboration, if we encounter
// elements with more staler versions than ours, ignore them
// and keep ours.
const currentElements = this.scene.getElementsIncludingDeleted();
if (replaceAll || !currentElements.length) {
this.scene.replaceAllElements(sceneData.elements);
} else {
// create a map of ids so we don't have to iterate
// over the array more than once.
const localElementMap = getElementMap(currentElements);
// Reconcile
const newElements = sceneData.elements
.reduce((elements, element) => {
// if the remote element references one that's currently
// edited on local, skip it (it'll be added in the next
// step)
if (
element.id === this.state.editingElement?.id ||
element.id === this.state.resizingElement?.id ||
element.id === this.state.draggingElement?.id
) {
return elements;
}
if (
localElementMap.hasOwnProperty(element.id) &&
localElementMap[element.id].version > element.version
) {
elements.push(localElementMap[element.id]);
delete localElementMap[element.id];
} else if (
localElementMap.hasOwnProperty(element.id) &&
localElementMap[element.id].version === element.version &&
localElementMap[element.id].versionNonce !== element.versionNonce
) {
// resolve conflicting edits deterministically by taking the one with the lowest versionNonce
if (
localElementMap[element.id].versionNonce < element.versionNonce
) {
elements.push(localElementMap[element.id]);
} else {
// it should be highly unlikely that the two versionNonces are the same. if we are
// really worried about this, we can replace the versionNonce with the socket id.
elements.push(element);
}
delete localElementMap[element.id];
} else {
elements.push(element);
delete localElementMap[element.id];
}
return elements;
}, [] as Mutable<typeof sceneData.elements>)
// add local elements that weren't deleted or on remote
.concat(...Object.values(localElementMap));
// Avoid broadcasting to the rest of the collaborators the scene
// we just received!
// Note: this needs to be set before replaceAllElements as it
// syncronously calls render.
this.setLastBroadcastedOrReceivedSceneVersion(
getSceneVersion(newElements),
);
}) => {
// currently we only support syncing background color
if (sceneData.appState?.viewBackgroundColor) {
this.setState({
viewBackgroundColor: sceneData.appState.viewBackgroundColor,
});
}
this.scene.replaceAllElements(newElements);
}
this.scene.replaceAllElements(sceneData.elements);
// 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,
// right now we think this is the right tradeoff.
history.clear();
};
// 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,
// right now we think this is the right tradeoff.
history.clear();
},
);
private initializeSocket = () => {
this.portal.socketInitialized = true;

59
src/components/Portal.tsx
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@ -3,7 +3,12 @@ import { encryptAESGEM, SocketUpdateDataSource } from "../data";
import { SocketUpdateData } from "../types";
import { BROADCAST, SCENE } from "../constants";
import App from "./App";
import { getSceneVersion, getSyncableElements } from "../element";
import {
getElementMap,
getSceneVersion,
getSyncableElements,
} from "../element";
import { ExcalidrawElement } from "../element/types";
class Portal {
app: App;
@ -151,6 +156,58 @@ class Portal {
);
}
};
reconcileElements = (sceneElements: readonly ExcalidrawElement[]) => {
const currentElements = this.app.getSceneElementsIncludingDeleted();
// create a map of ids so we don't have to iterate
// over the array more than once.
const localElementMap = getElementMap(currentElements);
// Reconcile
const newElements = sceneElements
.reduce((elements, element) => {
// if the remote element references one that's currently
// edited on local, skip it (it'll be added in the next
// step)
if (
element.id === this.app.state.editingElement?.id ||
element.id === this.app.state.resizingElement?.id ||
element.id === this.app.state.draggingElement?.id
) {
return elements;
}
if (
localElementMap.hasOwnProperty(element.id) &&
localElementMap[element.id].version > element.version
) {
elements.push(localElementMap[element.id]);
delete localElementMap[element.id];
} else if (
localElementMap.hasOwnProperty(element.id) &&
localElementMap[element.id].version === element.version &&
localElementMap[element.id].versionNonce !== element.versionNonce
) {
// resolve conflicting edits deterministically by taking the one with the lowest versionNonce
if (localElementMap[element.id].versionNonce < element.versionNonce) {
elements.push(localElementMap[element.id]);
} else {
// it should be highly unlikely that the two versionNonces are the same. if we are
// really worried about this, we can replace the versionNonce with the socket id.
elements.push(element);
}
delete localElementMap[element.id];
} else {
elements.push(element);
delete localElementMap[element.id];
}
return elements;
}, [] as Mutable<typeof sceneElements>)
// add local elements that weren't deleted or on remote
.concat(...Object.values(localElementMap));
return newElements;
};
}
export default Portal;

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