Finishing up some TODOs + cleanup.

Host apps can use it to help implement their own follow mode.

src/actions/actionCanvas.tsx

@@ -108,6 +108,9 @@ export const actionZoomIn = register({
           },
           appState,
         ),
+        userToFollow: appState.shouldDisconnectFollowModeOnCanvasInteraction
+          ? null
+          : appState.userToFollow,
       },
       commitToHistory: false,
     };
@@ -145,6 +148,9 @@ export const actionZoomOut = register({
           },
           appState,
         ),
+        userToFollow: appState.shouldDisconnectFollowModeOnCanvasInteraction
+          ? null
+          : appState.userToFollow,
       },
       commitToHistory: false,
     };
@@ -182,6 +188,9 @@ export const actionResetZoom = register({
           },
           appState,
         ),
+        userToFollow: appState.shouldDisconnectFollowModeOnCanvasInteraction
+          ? null
+          : appState.userToFollow,
       },
       commitToHistory: false,
     };
@@ -225,22 +234,20 @@ const zoomValueToFitBoundsOnViewport = (
   return clampedZoomValueToFitElements as NormalizedZoomValue;
 };
 
-export const zoomToFit = ({
-  targetElements,
+export const zoomToFitBounds = ({
+  bounds,
   appState,
   fitToViewport = false,
   viewportZoomFactor = 0.7,
 }: {
-  targetElements: readonly ExcalidrawElement[];
+  bounds: readonly [number, number, number, number];
   appState: Readonly<AppState>;
   /** whether to fit content to viewport (beyond >100%) */
   fitToViewport: boolean;
   /** zoom content to cover X of the viewport, when fitToViewport=true */
   viewportZoomFactor?: number;
 }) => {
-  const commonBounds = getCommonBounds(getNonDeletedElements(targetElements));
-
-  const [x1, y1, x2, y2] = commonBounds;
+  const [x1, y1, x2, y2] = bounds;
   const centerX = (x1 + x2) / 2;
   const centerY = (y1 + y2) / 2;
 
@@ -267,7 +274,7 @@ export const zoomToFit = ({
     scrollX = (appState.width / 2) * (1 / newZoomValue) - centerX;
     scrollY = (appState.height / 2) * (1 / newZoomValue) - centerY;
   } else {
-    newZoomValue = zoomValueToFitBoundsOnViewport(commonBounds, {
+    newZoomValue = zoomValueToFitBoundsOnViewport(bounds, {
       width: appState.width,
       height: appState.height,
     });
@@ -296,6 +303,29 @@ export const zoomToFit = ({
   };
 };
 
+export const zoomToFit = ({
+  targetElements,
+  appState,
+  fitToViewport,
+  viewportZoomFactor,
+}: {
+  targetElements: readonly ExcalidrawElement[];
+  appState: Readonly<AppState>;
+  /** whether to fit content to viewport (beyond >100%) */
+  fitToViewport: boolean;
+  /** zoom content to cover X of the viewport, when fitToViewport=true */
+  viewportZoomFactor?: number;
+}) => {
+  const commonBounds = getCommonBounds(getNonDeletedElements(targetElements));
+
+  return zoomToFitBounds({
+    bounds: commonBounds,
+    appState,
+    fitToViewport,
+    viewportZoomFactor,
+  });
+};
+
 // Note, this action differs from actionZoomToFitSelection in that it doesn't
 // zoom beyond 100%. In other words, if the content is smaller than viewport
 // size, it won't be zoomed in.
@@ -306,7 +336,12 @@ export const actionZoomToFitSelectionInViewport = register({
     const selectedElements = app.scene.getSelectedElements(appState);
     return zoomToFit({
       targetElements: selectedElements.length ? selectedElements : elements,
-      appState,
+      appState: {
+        ...appState,
+        userToFollow: appState.shouldDisconnectFollowModeOnCanvasInteraction
+          ? null
+          : appState.userToFollow,
+      },
       fitToViewport: false,
     });
   },
@@ -326,7 +361,12 @@ export const actionZoomToFitSelection = register({
     const selectedElements = app.scene.getSelectedElements(appState);
     return zoomToFit({
       targetElements: selectedElements.length ? selectedElements : elements,
-      appState,
+      appState: {
+        ...appState,
+        userToFollow: appState.shouldDisconnectFollowModeOnCanvasInteraction
+          ? null
+          : appState.userToFollow,
+      },
       fitToViewport: true,
     });
   },
@@ -343,7 +383,16 @@ export const actionZoomToFit = register({
   viewMode: true,
   trackEvent: { category: "canvas" },
   perform: (elements, appState) =>
-    zoomToFit({ targetElements: elements, appState, fitToViewport: false }),
+    zoomToFit({
+      targetElements: elements,
+      appState: {
+        ...appState,
+        userToFollow: appState.shouldDisconnectFollowModeOnCanvasInteraction
+          ? null
+          : appState.userToFollow,
+      },
+      fitToViewport: false,
+    }),
   keyTest: (event) =>
     event.code === CODES.ONE &&
     event.shiftKey &&

src/actions/actionNavigate.tsx

@@ -9,14 +9,30 @@ export const actionGoToCollaborator = register({
   viewMode: true,
   trackEvent: { category: "collab" },
   perform: (_elements, appState, value) => {
-    const point = value as Collaborator["pointer"];
+    const _value = value as Collaborator & { clientId: string };
+    const point = _value.pointer;
+
     if (!point) {
       return { appState, commitToHistory: false };
     }
 
+    if (appState.userToFollow?.clientId === _value.clientId) {
+      return {
+        appState: {
+          ...appState,
+          userToFollow: null,
+        },
+        commitToHistory: false,
+      };
+    }
+
     return {
       appState: {
         ...appState,
+        userToFollow: {
+          clientId: _value.clientId,
+          username: _value.username || "",
+        },
         ...centerScrollOn({
           scenePoint: point,
           viewportDimensions: {
@@ -31,17 +47,36 @@ export const actionGoToCollaborator = register({
       commitToHistory: false,
     };
   },
-  PanelComponent: ({ updateData, data }) => {
-    const [clientId, collaborator] = data as [string, Collaborator];
+  PanelComponent: ({ updateData, data, appState }) => {
+    const [clientId, collaborator, withName] = data as [
+      string,
+      Collaborator,
+      boolean,
+    ];
 
     const background = getClientColor(clientId);
 
-    return (
+    return withName ? (
+      <div
+        className="dropdown-menu-item dropdown-menu-item-base"
+        onClick={() => updateData({ ...collaborator, clientId })}
+      >
         <Avatar
           color={background}
-        onClick={() => updateData(collaborator.pointer)}
+          onClick={() => {}}
           name={collaborator.username || ""}
           src={collaborator.avatarUrl}
+          isBeingFollowed={appState.userToFollow?.clientId === clientId}
+        />
+        {collaborator.username}
+      </div>
+    ) : (
+      <Avatar
+        color={background}
+        onClick={() => updateData({ ...collaborator, clientId })}
+        name={collaborator.username || ""}
+        src={collaborator.avatarUrl}
+        isBeingFollowed={appState.userToFollow?.clientId === clientId}
       />
     );
   },

src/appState.ts

@@ -98,6 +98,9 @@ export const getDefaultAppState = (): Omit<
     pendingImageElementId: null,
     showHyperlinkPopup: false,
     selectedLinearElement: null,
+    userToFollow: null,
+    shouldDisconnectFollowModeOnCanvasInteraction: true,
+    amIBeingFollowed: false,
   };
 };
 
@@ -204,6 +207,13 @@ const APP_STATE_STORAGE_CONF = (<
   pendingImageElementId: { browser: false, export: false, server: false },
   showHyperlinkPopup: { browser: false, export: false, server: false },
   selectedLinearElement: { browser: true, export: false, server: false },
+  userToFollow: { browser: false, export: false, server: false },
+  shouldDisconnectFollowModeOnCanvasInteraction: {
+    browser: false,
+    export: false,
+    server: false,
+  },
+  amIBeingFollowed: { browser: false, export: false, server: false },
 });
 
 const _clearAppStateForStorage = <

src/components/App.tsx

@@ -331,6 +331,7 @@ import { actionWrapTextInContainer } from "../actions/actionBoundText";
 import BraveMeasureTextError from "./BraveMeasureTextError";
 import { activeEyeDropperAtom } from "./EyeDropper";
 import { isSidebarDockedAtom } from "./Sidebar/Sidebar";
+import FollowMode from "./FollowMode/FollowMode";
 
 const AppContext = React.createContext<AppClassProperties>(null!);
 const AppPropsContext = React.createContext<AppProps>(null!);
@@ -547,8 +548,19 @@ class App extends React.Component<AppProps, AppState> {
     } = this.state;
     const canvasWidth = canvasDOMWidth * canvasScale;
     const canvasHeight = canvasDOMHeight * canvasScale;
+
+    const userToFollow = this.state.userToFollow;
+
     if (viewModeEnabled) {
       return (
+        <FollowMode
+          width={canvasDOMWidth}
+          height={canvasDOMHeight}
+          userToFollow={userToFollow}
+          onDisconnect={() => {
+            this.setState({ userToFollow: null });
+          }}
+        >
           <canvas
             className="excalidraw__canvas"
             style={{
@@ -570,9 +582,18 @@ class App extends React.Component<AppProps, AppState> {
           >
             {t("labels.drawingCanvas")}
           </canvas>
+        </FollowMode>
       );
     }
     return (
+      <FollowMode
+        width={canvasDOMWidth}
+        height={canvasDOMHeight}
+        userToFollow={userToFollow}
+        onDisconnect={() => {
+          this.setState({ userToFollow: null });
+        }}
+      >
         <canvas
           className="excalidraw__canvas"
           style={{
@@ -594,6 +615,7 @@ class App extends React.Component<AppProps, AppState> {
         >
           {t("labels.drawingCanvas")}
         </canvas>
+      </FollowMode>
     );
   }
 
@@ -1500,13 +1522,37 @@ class App extends React.Component<AppProps, AppState> {
       this.refreshDeviceState(this.excalidrawContainerRef.current);
     }
 
-    if (
+    const hasScrollChanged =
       prevState.scrollX !== this.state.scrollX ||
-      prevState.scrollY !== this.state.scrollY
-    ) {
+      prevState.scrollY !== this.state.scrollY;
+
+    if (hasScrollChanged) {
       this.props?.onScrollChange?.(this.state.scrollX, this.state.scrollY);
     }
 
+    if (prevState.zoom.value !== this.state.zoom.value || hasScrollChanged) {
+      this.props?.onScrollAndZoomChange?.({
+        zoom: this.state.zoom,
+        scroll: { x: this.state.scrollX, y: this.state.scrollY },
+      });
+    }
+
+    if (prevState.userToFollow !== this.state.userToFollow) {
+      if (prevState.userToFollow) {
+        this.props?.onUserFollowed?.({
+          userToFollow: prevState.userToFollow,
+          action: "unfollow",
+        });
+      }
+
+      if (this.state.userToFollow) {
+        this.props?.onUserFollowed?.({
+          userToFollow: this.state.userToFollow,
+          action: "follow",
+        });
+      }
+    }
+
     if (
       Object.keys(this.state.selectedElementIds).length &&
       isEraserActive(this.state)
@@ -2365,7 +2411,14 @@ class App extends React.Component<AppProps, AppState> {
     state,
   ) => {
     this.cancelInProgresAnimation?.();
-    this.setState(state);
+
+    // potentially unfollow participant
+    this.setState((prevState, props) => ({
+      ...(typeof state === "function" ? state(prevState, props) : state),
+      userToFollow: prevState.shouldDisconnectFollowModeOnCanvasInteraction
+        ? null
+        : prevState.userToFollow,
+    }));
   };
 
   setToast = (
@@ -3980,6 +4033,12 @@ class App extends React.Component<AppProps, AppState> {
   private handleCanvasPointerDown = (
     event: React.PointerEvent<HTMLElement>,
   ) => {
+    this.setState((prevState) => ({
+      userToFollow: prevState.shouldDisconnectFollowModeOnCanvasInteraction
+        ? null
+        : prevState.userToFollow,
+    }));
+
     // since contextMenu options are potentially evaluated on each render,
     // and an contextMenu action may depend on selection state, we must
     // close the contextMenu before we update the selection on pointerDown

src/components/Avatar.scss

@@ -2,34 +2,6 @@
 
 .excalidraw {
   .Avatar {
-    width: 1.25rem;
-    height: 1.25rem;
-    position: relative;
-    border-radius: 100%;
-    outline-offset: 2px;
-    display: flex;
-    justify-content: center;
-    align-items: center;
-    cursor: pointer;
-    font-size: 0.75rem;
-    font-weight: 800;
-    line-height: 1;
-
-    &-img {
-      width: 100%;
-      height: 100%;
-      border-radius: 100%;
-    }
-
-    &::before {
-      content: "";
-      position: absolute;
-      top: -3px;
-      right: -3px;
-      bottom: -3px;
-      left: -3px;
-      border: 1px solid var(--avatar-border-color);
-      border-radius: 100%;
-    }
+    @include avatarStyles;
   }
 }

src/components/Avatar.tsx

@@ -2,21 +2,33 @@ import "./Avatar.scss";
 
 import React, { useState } from "react";
 import { getNameInitial } from "../clients";
+import clsx from "clsx";
 
 type AvatarProps = {
   onClick: (e: React.MouseEvent<HTMLDivElement, MouseEvent>) => void;
   color: string;
   name: string;
   src?: string;
+  isBeingFollowed?: boolean;
 };
 
-export const Avatar = ({ color, onClick, name, src }: AvatarProps) => {
+export const Avatar = ({
+  color,
+  onClick,
+  name,
+  src,
+  isBeingFollowed,
+}: AvatarProps) => {
   const shortName = getNameInitial(name);
   const [error, setError] = useState(false);
   const loadImg = !error && src;
   const style = loadImg ? undefined : { background: color };
   return (
-    <div className="Avatar" style={style} onClick={onClick}>
+    <div
+      className={clsx("Avatar", { "Avatar--is-followed": isBeingFollowed })}
+      style={style}
+      onClick={onClick}
+    >
       {loadImg ? (
         <img
           className="Avatar-img"

src/components/FollowMode/FollowMode.scss

@@ -0,0 +1,59 @@
+.excalidraw {
+  .follow-mode {
+    position: absolute;
+    box-sizing: border-box;
+    pointer-events: none;
+    border: 2px solid var(--color-primary-hover);
+    z-index: 9999;
+    display: flex;
+    align-items: flex-end;
+    justify-content: center;
+
+    &__badge {
+      background-color: var(--color-primary-hover);
+      color: var(--color-primary-light);
+      padding: 0.25rem 0.5rem;
+      margin-bottom: 0.5rem;
+      border-radius: 0.5rem;
+      pointer-events: all;
+      font-size: 0.75rem;
+      display: flex;
+      gap: 0.5rem;
+      align-items: center;
+
+      &__label {
+        display: flex;
+        white-space: pre-wrap;
+        line-height: 1;
+      }
+
+      &__username {
+        display: block;
+        white-space: nowrap;
+        overflow: hidden;
+        text-overflow: ellipsis;
+        max-width: 100px;
+      }
+    }
+
+    &__disconnect-btn {
+      all: unset;
+      cursor: pointer;
+      border-radius: 0.25rem;
+
+      &:hover {
+        background-color: var(--color-primary-darker);
+      }
+
+      &:active {
+        background-color: var(--color-primary-darkest);
+      }
+
+      svg {
+        display: block;
+        width: 1rem;
+        height: 1rem;
+      }
+    }
+  }
+}

src/components/FollowMode/FollowMode.tsx

@@ -0,0 +1,50 @@
+import { UserToFollow } from "../../types";
+import { CloseIcon } from "../icons";
+import "./FollowMode.scss";
+
+interface FollowModeProps {
+  width: number;
+  height: number;
+  children: React.ReactNode;
+  userToFollow?: UserToFollow | null;
+  onDisconnect: () => void;
+}
+
+const FollowMode = ({
+  children,
+  height,
+  width,
+  userToFollow,
+  onDisconnect,
+}: FollowModeProps) => {
+  if (!userToFollow) {
+    return <>{children}</>;
+  }
+
+  return (
+    <div style={{ position: "relative" }}>
+      <div className="follow-mode" style={{ width, height }}>
+        <div className="follow-mode__badge">
+          <div className="follow-mode__badge__label">
+            Following{" "}
+            <span
+              className="follow-mode__badge__username"
+              title={userToFollow.username}
+            >
+              {userToFollow.username}
+            </span>
+          </div>
+          <button
+            onClick={onDisconnect}
+            className="follow-mode__disconnect-btn"
+          >
+            {CloseIcon}
+          </button>
+        </div>
+      </div>
+      {children}
+    </div>
+  );
+};
+
+export default FollowMode;

src/components/Sidebar/SidebarTrigger.scss

@@ -22,6 +22,10 @@
       width: var(--lg-icon-size);
       height: var(--lg-icon-size);
     }
+
+    &__label-element {
+      align-self: flex-start;
+    }
   }
 
   .default-sidebar-trigger .sidebar-trigger__label {

src/components/Sidebar/SidebarTrigger.tsx

@@ -19,7 +19,7 @@ export const SidebarTrigger = ({
   const appState = useUIAppState();
 
   return (
-    <label title={title}>
+    <label title={title} className="sidebar-trigger__label-element">
       <input
         className="ToolIcon_type_checkbox"
         type="checkbox"

src/components/UserList.scss

@@ -1,3 +1,5 @@
+@import "../css/variables.module";
+
 .excalidraw {
   .UserList {
     pointer-events: none;
@@ -14,11 +16,13 @@
       display: none;
     }
 
-    // can fit max 5 avatars in a column
-    max-height: 140px;
+    box-sizing: border-box;
 
-    // can fit max 10 avatars in a row when there's enough space
-    max-width: 290px;
+    // can fit max 4 avatars (3 avatars + show more) in a column
+    max-height: 120px;
+
+    // can fit max 4 avatars (3 avatars + show more) when there's enough space
+    max-width: 120px;
 
     // Tweak in 30px increments to fit more/fewer avatars in a row/column ^^
 
@@ -33,5 +37,104 @@
     padding: 0;
     justify-content: normal;
     margin: 0.5rem 0;
+    max-width: none;
+    max-height: none;
+  }
+
+  .UserList__more {
+    @include avatarStyles;
+    background-color: var(--color-gray-20);
+    border: 0 !important;
+    font-size: 0.5rem;
+    font-weight: 400;
+    flex-shrink: 0;
+    color: var(--color-gray-70);
+  }
+
+  --userlist-hint-bg-color: var(--color-gray-10);
+  --userlist-hint-heading-color: var(--color-gray-80);
+  --userlist-hint-text-color: var(--color-gray-60);
+  --userlist-collaborators-border-color: var(--color-gray-20);
+
+  &.theme--dark {
+    --userlist-hint-bg-color: var(--color-gray-90);
+    --userlist-hint-heading-color: var(--color-gray-30);
+    --userlist-hint-text-color: var(--color-gray-40);
+    --userlist-collaborators-border-color: var(--color-gray-80);
+  }
+
+  .UserList__collaborators {
+    position: static;
+    top: auto;
+    margin-top: 0;
+    max-height: 12rem;
+    overflow-y: auto;
+    padding: 0.25rem 0.5rem;
+    border-top: 1px solid var(--userlist-collaborators-border-color);
+    border-bottom: 1px solid var(--userlist-collaborators-border-color);
+
+    &__empty {
+      color: var(--color-gray-60);
+      font-size: 0.75rem;
+      line-height: 150%;
+      padding: 0.5rem 0;
+    }
+  }
+
+  .UserList__hint {
+    background-color: var(--userlist-hint-bg-color);
+    padding: 0.5rem 0.75rem;
+    overflow: hidden;
+    border-radius: 0 0 var(--border-radius-lg) var(--border-radius-lg);
+
+    &-heading {
+      color: var(--userlist-hint-heading-color);
+      font-size: 0.875rem;
+      font-weight: 600;
+      line-height: 150%;
+    }
+
+    &-text {
+      color: var(--userlist-hint-text-color);
+      font-size: 0.75rem;
+      line-height: 150%;
+    }
+  }
+
+  .UserList__search-wrapper {
+    position: relative;
+    height: 2.5rem;
+
+    svg {
+      position: absolute;
+      top: 50%;
+      transform: translateY(-50%);
+      left: 0.75rem;
+      width: 1.25rem;
+      height: 1.25rem;
+      color: var(--color-gray-40);
+      z-index: 1;
+    }
+  }
+
+  .UserList__search {
+    position: absolute;
+    top: 0;
+    left: 0;
+    width: 100%;
+    box-sizing: border-box;
+    border: 0 !important;
+    border-radius: 0 !important;
+    font-size: 0.875rem;
+    padding-left: 2.5rem !important;
+    padding-right: 0.75rem !important;
+
+    &::placeholder {
+      color: var(--color-gray-40);
+    }
+
+    &:focus {
+      box-shadow: none !important;
+    }
   }
 }

src/components/UserList.tsx

@@ -5,48 +5,262 @@ import clsx from "clsx";
 import { AppState, Collaborator } from "../types";
 import { Tooltip } from "./Tooltip";
 import { useExcalidrawActionManager } from "./App";
+import { ActionManager } from "../actions/manager";
 
-export const UserList: React.FC<{
+import * as Popover from "@radix-ui/react-popover";
+import { Island } from "./Island";
+import { searchIcon } from "./icons";
+import { t } from "../i18n";
+
+// TODO follow-participant
+// can be used for debugging styling, filter, etc
+// don't forget to remove it before shipping
+const sampleCollaborators = new Map([
+  [
+    "client-id-1",
+    {
+      username: "John Doe",
+      color: "#1CA6FC",
+    },
+  ],
+  [
+    "client-id-2",
+    {
+      username: "Jane Doe",
+      color: "#FEA3AA",
+    },
+  ],
+  [
+    "client-id-3",
+    {
+      username: "Kate Doe",
+      color: "#B2F2BB",
+    },
+  ],
+  [
+    "client-id-4",
+    {
+      username: "Handsome Swan",
+      color: "#FFDBAB",
+    },
+  ],
+  [
+    "client-id-5",
+    {
+      username: "Brilliant Chameleon",
+      color: "#E2E2E2",
+    },
+  ],
+  [
+    "client-id-6",
+    {
+      username: "Jill Doe",
+      color: "#FCCB5F",
+    },
+  ],
+  [
+    "client-id-7",
+    {
+      username: "Jack Doe",
+      color: "#BCE784",
+    },
+  ],
+  [
+    "client-id-8",
+    {
+      username: "Jolly Doe",
+      color: "#5DD39E",
+    },
+  ],
+]) as any as Map<string, Collaborator>;
+
+const FIRST_N_AVATARS = 3;
+const SHOW_COLLABORATORS_FILTER_AT = 6;
+
+const ConditionalTooltipWrapper = ({
+  shouldWrap,
+  children,
+  clientId,
+  username,
+}: {
+  shouldWrap: boolean;
+  children: React.ReactNode;
+  username?: string | null;
+  clientId: string;
+}) =>
+  shouldWrap ? (
+    <Tooltip label={username || "Unknown user"} key={clientId}>
+      {children}
+    </Tooltip>
+  ) : (
+    <React.Fragment key={clientId}>{children}</React.Fragment>
+  );
+
+const renderCollaborator = ({
+  actionManager,
+  collaborator,
+  clientId,
+  withName = false,
+  shouldWrapWithTooltip = false,
+}: {
+  actionManager: ActionManager;
+  collaborator: Collaborator;
+  clientId: string;
+  withName?: boolean;
+  shouldWrapWithTooltip?: boolean;
+}) => {
+  const avatarJSX = actionManager.renderAction("goToCollaborator", [
+    clientId,
+    collaborator,
+    withName,
+  ]);
+
+  return (
+    <ConditionalTooltipWrapper
+      key={clientId}
+      clientId={clientId}
+      username={collaborator.username}
+      shouldWrap={shouldWrapWithTooltip}
+    >
+      {avatarJSX}
+    </ConditionalTooltipWrapper>
+  );
+};
+
+export const UserList = ({
+  className,
+  mobile,
+  collaborators,
+}: {
   className?: string;
   mobile?: boolean;
   collaborators: AppState["collaborators"];
-}> = ({ className, mobile, collaborators }) => {
+}) => {
   const actionManager = useExcalidrawActionManager();
 
-  const uniqueCollaborators = new Map<string, Collaborator>();
+  const uniqueCollaboratorsMap = React.useMemo(() => {
+    const map = new Map<string, Collaborator>();
     collaborators.forEach((collaborator, socketId) => {
-    uniqueCollaborators.set(
+      map.set(
         // filter on user id, else fall back on unique socketId
         collaborator.id || socketId,
         collaborator,
       );
     });
+    return map;
+  }, [collaborators]);
 
-  const avatars =
-    uniqueCollaborators.size > 0 &&
-    Array.from(uniqueCollaborators)
-      .filter(([_, client]) => Object.keys(client).length !== 0)
-      .map(([clientId, collaborator]) => {
-        const avatarJSX = actionManager.renderAction("goToCollaborator", [
-          clientId,
+  // const uniqueCollaboratorsMap = sampleCollaborators;
+  const uniqueCollaboratorsArray = React.useMemo(
+    () =>
+      Array.from(uniqueCollaboratorsMap).filter(
+        ([_, collaborator]) => Object.keys(collaborator).length !== 0,
+      ),
+    [uniqueCollaboratorsMap],
+  );
+
+  const [searchTerm, setSearchTerm] = React.useState("");
+
+  const filteredCollaborators = React.useMemo(
+    () =>
+      uniqueCollaboratorsArray.filter(([, collaborator]) =>
+        collaborator.username?.toLowerCase().includes(searchTerm.toLowerCase()),
+      ),
+    [uniqueCollaboratorsArray, searchTerm],
+  );
+
+  if (uniqueCollaboratorsArray.length === 0) {
+    return null;
+  }
+
+  const firstNCollaborators = uniqueCollaboratorsArray.slice(
+    0,
+    FIRST_N_AVATARS,
+  );
+
+  const firstNAvatarsJSX = firstNCollaborators.map(([clientId, collaborator]) =>
+    renderCollaborator({
+      actionManager,
       collaborator,
-        ]);
+      clientId,
+      shouldWrapWithTooltip: true,
+    }),
+  );
 
   return mobile ? (
-          <Tooltip
-            label={collaborator.username || "Unknown user"}
-            key={clientId}
-          >
-            {avatarJSX}
-          </Tooltip>
+    <div className={clsx("UserList UserList_mobile", className)}>
+      {uniqueCollaboratorsArray.map(([clientId, collaborator]) =>
+        renderCollaborator({
+          actionManager,
+          collaborator,
+          clientId,
+          shouldWrapWithTooltip: true,
+        }),
+      )}
+    </div>
   ) : (
-          <React.Fragment key={clientId}>{avatarJSX}</React.Fragment>
-        );
-      });
+    <div className={clsx("UserList", className)}>
+      {firstNAvatarsJSX}
 
-  return (
-    <div className={clsx("UserList", className, { UserList_mobile: mobile })}>
-      {avatars}
+      {uniqueCollaboratorsArray.length > FIRST_N_AVATARS && (
+        <Popover.Root
+          onOpenChange={(isOpen) => {
+            if (!isOpen) {
+              setSearchTerm("");
+            }
+          }}
+        >
+          <Popover.Trigger className="UserList__more">
+            +{uniqueCollaboratorsArray.length - FIRST_N_AVATARS}
+          </Popover.Trigger>
+          <Popover.Content
+            style={{ zIndex: 2, maxWidth: "14rem", textAlign: "left" }}
+            align="end"
+            sideOffset={10}
+          >
+            <Island style={{ overflow: "hidden" }}>
+              {SHOW_COLLABORATORS_FILTER_AT <=
+                uniqueCollaboratorsArray.length && (
+                <div className="UserList__search-wrapper">
+                  {searchIcon}
+                  <input
+                    className="UserList__search"
+                    type="text"
+                    placeholder={t("userList.search.placeholder")}
+                    value={searchTerm}
+                    onChange={(e) => {
+                      setSearchTerm(e.target.value);
+                    }}
+                  />
+                </div>
+              )}
+              <div className="dropdown-menu UserList__collaborators">
+                {filteredCollaborators.length === 0 && (
+                  <div className="UserList__collaborators__empty">
+                    {t("userList.search.empty")}
+                  </div>
+                )}
+                {filteredCollaborators.map(([clientId, collaborator]) =>
+                  renderCollaborator({
+                    actionManager,
+                    collaborator,
+                    clientId,
+                    withName: true,
+                  }),
+                )}
+              </div>
+              <div className="UserList__hint">
+                <div className="UserList__hint-heading">
+                  {t("userList.hint.heading")}
+                </div>
+                <div className="UserList__hint-text">
+                  {t("userList.hint.text")}
+                </div>
+              </div>
+            </Island>
+          </Popover.Content>
+        </Popover.Root>
+      )}
     </div>
   );
 };

src/components/icons.tsx

@@ -1647,3 +1647,12 @@ export const frameToolIcon = createIcon(
   </g>,
   tablerIconProps,
 );
+
+export const searchIcon = createIcon(
+  <g strokeWidth={1.5}>
+    <path stroke="none" d="M0 0h24v24H0z" fill="none" />
+    <path d="M10 10m-7 0a7 7 0 1 0 14 0a7 7 0 1 0 -14 0" />
+    <path d="M21 21l-6 -6" />
+  </g>,
+  tablerIconProps,
+);

src/css/theme.scss

@@ -81,6 +81,7 @@
   --color-primary-darkest: #4a47b1;
   --color-primary-light: #e3e2fe;
   --color-primary-light-darker: #d7d5ff;
+  --color-primary-hover: #5753d0;
 
   --color-gray-10: #f5f5f5;
   --color-gray-20: #ebebeb;
@@ -193,6 +194,7 @@
     --color-primary-darkest: #beb9ff;
     --color-primary-light: #4f4d6f;
     --color-primary-light-darker: #43415e;
+    --color-primary-hover: #bbb8ff;
 
     --color-text-warning: var(--color-gray-80);
 

src/css/variables.module.scss

@@ -104,6 +104,42 @@
   }
 }
 
+@mixin avatarStyles {
+  width: 1.25rem;
+  height: 1.25rem;
+  position: relative;
+  border-radius: 100%;
+  outline-offset: 2px;
+  display: flex;
+  justify-content: center;
+  align-items: center;
+  cursor: pointer;
+  font-size: 0.75rem;
+  font-weight: 800;
+  line-height: 1;
+
+  &-img {
+    width: 100%;
+    height: 100%;
+    border-radius: 100%;
+  }
+
+  &::before {
+    content: "";
+    position: absolute;
+    top: -3px;
+    right: -3px;
+    bottom: -3px;
+    left: -3px;
+    border: 1px solid var(--avatar-border-color);
+    border-radius: 100%;
+  }
+
+  &--is-followed::before {
+    border-color: var(--color-primary-hover);
+  }
+}
+
 $theme-filter: "invert(93%) hue-rotate(180deg)";
 $right-sidebar-width: "302px";
 

src/excalidraw-app/collab/Collab.tsx

@@ -1,6 +1,10 @@
 import throttle from "lodash.throttle";
 import { PureComponent } from "react";
-import { ExcalidrawImperativeAPI } from "../../types";
+import {
+  AppState,
+  ExcalidrawImperativeAPI,
+  OnUserFollowedPayload,
+} from "../../types";
 import { ErrorDialog } from "../../components/ErrorDialog";
 import { APP_NAME, ENV, EVENT } from "../../constants";
 import { ImportedDataState } from "../../data/types";
@@ -16,6 +20,7 @@ import { Collaborator, Gesture } from "../../types";
 import {
   preventUnload,
   resolvablePromise,
+  viewportCoordsToSceneCoords,
   withBatchedUpdates,
 } from "../../utils";
 import {
@@ -71,6 +76,7 @@ import { resetBrowserStateVersions } from "../data/tabSync";
 import { LocalData } from "../data/LocalData";
 import { atom, useAtom } from "jotai";
 import { appJotaiStore } from "../app-jotai";
+import { zoomToFitBounds } from "../../actions/actionCanvas";
 
 export const collabAPIAtom = atom<CollabAPI | null>(null);
 export const collabDialogShownAtom = atom(false);
@@ -89,6 +95,8 @@ export interface CollabAPI {
   /** function so that we can access the latest value from stale callbacks */
   isCollaborating: () => boolean;
   onPointerUpdate: CollabInstance["onPointerUpdate"];
+  onScrollAndZoomChange: CollabInstance["onScrollAndZoomChange"];
+  onUserFollowed: CollabInstance["onUserFollowed"];
   startCollaboration: CollabInstance["startCollaboration"];
   stopCollaboration: CollabInstance["stopCollaboration"];
   syncElements: CollabInstance["syncElements"];
@@ -162,6 +170,8 @@ class Collab extends PureComponent<Props, CollabState> {
     const collabAPI: CollabAPI = {
       isCollaborating: this.isCollaborating,
       onPointerUpdate: this.onPointerUpdate,
+      onScrollAndZoomChange: this.onScrollAndZoomChange,
+      onUserFollowed: this.onUserFollowed,
       startCollaboration: this.startCollaboration,
       syncElements: this.syncElements,
       fetchImageFilesFromFirebase: this.fetchImageFilesFromFirebase,
@@ -513,6 +523,7 @@ class Collab extends PureComponent<Props, CollabState> {
           case "MOUSE_LOCATION": {
             const { pointer, button, username, selectedElementIds } =
               decryptedData.payload;
+
             const socketId: SocketUpdateDataSource["MOUSE_LOCATION"]["payload"]["socketId"] =
               decryptedData.payload.socketId ||
               // @ts-ignore legacy, see #2094 (#2097)
@@ -530,6 +541,23 @@ class Collab extends PureComponent<Props, CollabState> {
             });
             break;
           }
+
+          case "SCROLL_AND_ZOOM": {
+            const { bounds } = decryptedData.payload;
+
+            const _appState = this.excalidrawAPI.getAppState();
+
+            const { appState } = zoomToFitBounds({
+              appState: _appState,
+              bounds,
+              fitToViewport: true,
+              viewportZoomFactor: 1,
+            });
+            this.excalidrawAPI.updateScene({ appState });
+
+            break;
+          }
+
           case "IDLE_STATUS": {
             const { userState, socketId, username } = decryptedData.payload;
             const collaborators = new Map(this.collaborators);
@@ -556,6 +584,18 @@ class Collab extends PureComponent<Props, CollabState> {
       scenePromise.resolve(sceneData);
     });
 
+    this.portal.socket.on("broadcast-follow", () => {
+      this.excalidrawAPI.updateScene({
+        appState: { amIBeingFollowed: true },
+      });
+    });
+
+    this.portal.socket.on("broadcast-unfollow", () => {
+      this.excalidrawAPI.updateScene({
+        appState: { amIBeingFollowed: false },
+      });
+    });
+
     this.initializeIdleDetector();
 
     this.setState({
@@ -763,6 +803,46 @@ class Collab extends PureComponent<Props, CollabState> {
     CURSOR_SYNC_TIMEOUT,
   );
 
+  onScrollAndZoomChange = throttle(
+    (payload: { zoom: AppState["zoom"]; scroll: { x: number; y: number } }) => {
+      const appState = this.excalidrawAPI.getAppState();
+
+      if (appState.amIBeingFollowed) {
+        const { x: x1, y: y1 } = viewportCoordsToSceneCoords(
+          { clientX: 0, clientY: 0 },
+          {
+            offsetLeft: appState.offsetLeft,
+            offsetTop: appState.offsetTop,
+            scrollX: payload.scroll.x,
+            scrollY: payload.scroll.y,
+            zoom: payload.zoom,
+          },
+        );
+
+        const { x: x2, y: y2 } = viewportCoordsToSceneCoords(
+          { clientX: appState.width, clientY: appState.height },
+          {
+            offsetLeft: appState.offsetLeft,
+            offsetTop: appState.offsetTop,
+            scrollX: payload.scroll.x,
+            scrollY: payload.scroll.y,
+            zoom: payload.zoom,
+          },
+        );
+
+        this.portal.socket &&
+          this.portal.broadcastScrollAndZoom(
+            { bounds: [x1, y1, x2, y2] },
+            `follow_${this.portal.socket.id}`,
+          );
+      }
+    },
+  );
+
+  onUserFollowed = (payload: OnUserFollowedPayload) => {
+    this.portal.socket && this.portal.broadcastUserFollowed(payload);
+  };
+
   onIdleStateChange = (userState: UserIdleState) => {
     this.portal.broadcastIdleChange(userState);
   };

src/excalidraw-app/collab/Portal.tsx

@@ -12,7 +12,7 @@ import {
   FILE_UPLOAD_TIMEOUT,
   WS_SCENE_EVENT_TYPES,
 } from "../app_constants";
-import { UserIdleState } from "../../types";
+import { OnUserFollowedPayload, UserIdleState } from "../../types";
 import { trackEvent } from "../../analytics";
 import throttle from "lodash.throttle";
 import { newElementWith } from "../../element/mutateElement";
@@ -83,6 +83,7 @@ class Portal {
   async _broadcastSocketData(
     data: SocketUpdateData,
     volatile: boolean = false,
+    roomId?: string,
   ) {
     if (this.isOpen()) {
       const json = JSON.stringify(data);
@@ -91,7 +92,7 @@ class Portal {
 
       this.socket?.emit(
         volatile ? WS_EVENTS.SERVER_VOLATILE : WS_EVENTS.SERVER,
-        this.roomId,
+        roomId ?? this.roomId,
         encryptedBuffer,
         iv,
       );
@@ -213,12 +214,43 @@ class Portal {
           username: this.collab.state.username,
         },
       };
+
       return this._broadcastSocketData(
         data as SocketUpdateData,
         true, // volatile
       );
     }
   };
+
+  broadcastScrollAndZoom = (
+    payload: {
+      bounds: [number, number, number, number];
+    },
+    roomId: string,
+  ) => {
+    if (this.socket?.id) {
+      const data: SocketUpdateDataSource["SCROLL_AND_ZOOM"] = {
+        type: "SCROLL_AND_ZOOM",
+        payload: {
+          socketId: this.socket.id,
+          username: this.collab.state.username,
+          bounds: payload.bounds,
+        },
+      };
+
+      return this._broadcastSocketData(
+        data as SocketUpdateData,
+        true, // volatile
+        roomId,
+      );
+    }
+  };
+
+  broadcastUserFollowed = (payload: OnUserFollowedPayload) => {
+    if (this.socket?.id) {
+      this.socket?.emit("on-user-follow", payload);
+    }
+  };
 }
 
 export default Portal;

src/excalidraw-app/data/index.ts

@@ -113,6 +113,14 @@ export type SocketUpdateDataSource = {
       username: string;
     };
   };
+  SCROLL_AND_ZOOM: {
+    type: "SCROLL_AND_ZOOM";
+    payload: {
+      socketId: string;
+      username: string;
+      bounds: [number, number, number, number];
+    };
+  };
   IDLE_STATUS: {
     type: "IDLE_STATUS";
     payload: {

src/excalidraw-app/index.tsx

@@ -649,6 +649,12 @@ const ExcalidrawWrapper = () => {
       })}
     >
       <Excalidraw
+        onScrollAndZoomChange={({ zoom, scroll }) => {
+          collabAPI?.onScrollAndZoomChange({ zoom, scroll });
+        }}
+        onUserFollowed={(userToFollow) => {
+          collabAPI?.onUserFollowed(userToFollow);
+        }}
         ref={excalidrawRefCallback}
         onChange={onChange}
         initialData={initialStatePromiseRef.current.promise}

src/locales/en.json

@@ -480,5 +480,15 @@
         "description": "Loading external drawing will <bold>replace your existing content</bold>.<br></br>You can back up your drawing first by using one of the options below."
       }
     }
+  },
+  "userList": {
+    "search": {
+      "placeholder": "Quick search",
+      "empty": "No users found"
+    },
+    "hint": {
+      "heading": "Follow mode",
+      "text": "You can click on a user to toggle follow mode. In follow mode, their canvas movements will be mirrored on your canvas."
+    }
   }
 }

src/packages/excalidraw/index.tsx

@@ -41,6 +41,8 @@ const ExcalidrawBase = (props: ExcalidrawProps) => {
     onLinkOpen,
     onPointerDown,
     onScrollChange,
+    onScrollAndZoomChange,
+    onUserFollowed,
     children,
   } = props;
 
@@ -115,6 +117,8 @@ const ExcalidrawBase = (props: ExcalidrawProps) => {
           onLinkOpen={onLinkOpen}
           onPointerDown={onPointerDown}
           onScrollChange={onScrollChange}
+          onScrollAndZoomChange={onScrollAndZoomChange}
+          onUserFollowed={onUserFollowed}
         >
           {children}
         </App>
@@ -249,3 +253,5 @@ export { LiveCollaborationTrigger };
 export { DefaultSidebar } from "../../components/DefaultSidebar";
 
 export { normalizeLink } from "../../data/url";
+
+export { zoomToFitBounds } from "../../actions/actionCanvas";

src/types.ts

@@ -98,6 +98,8 @@ export type LastActiveTool =
 export type SidebarName = string;
 export type SidebarTabName = string;
 
+export type UserToFollow = { clientId: string; username: string };
+
 export type AppState = {
   contextMenu: {
     items: ContextMenuItems;
@@ -223,6 +225,12 @@ export type AppState = {
   pendingImageElementId: ExcalidrawImageElement["id"] | null;
   showHyperlinkPopup: false | "info" | "editor";
   selectedLinearElement: LinearElementEditor | null;
+  /** the user's clientId who is being followed on the canvas */
+  userToFollow: UserToFollow | null;
+  /** whether follow mode should be disconnected when the non-remote user interacts with the canvas */
+  shouldDisconnectFollowModeOnCanvasInteraction: boolean;
+  /** whether the user is being followed on the canvas */
+  amIBeingFollowed: boolean;
 };
 
 export type UIAppState = Omit<
@@ -307,6 +315,11 @@ export type ExcalidrawInitialDataState = Merge<
   }
 >;
 
+export type OnUserFollowedPayload = {
+  userToFollow: UserToFollow;
+  action: "follow" | "unfollow";
+};
+
 export interface ExcalidrawProps {
   onChange?: (
     elements: readonly ExcalidrawElement[],
@@ -360,6 +373,14 @@ export interface ExcalidrawProps {
     pointerDownState: PointerDownState,
   ) => void;
   onScrollChange?: (scrollX: number, scrollY: number) => void;
+  onScrollAndZoomChange?: ({
+    zoom,
+    scroll,
+  }: {
+    zoom: Zoom;
+    scroll: { x: number; y: number };
+  }) => void;
+  onUserFollowed?: (payload: OnUserFollowedPayload) => void;
   children?: React.ReactNode;
 }