ui/src/public/workspace.ts - third_party/perfetto - Git at Google

 // Copyright (C) 2024 The Android Open Source Project
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //      http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.

 import {assertTrue} from '../base/logging';

 export interface WorkspaceManager {
   // This is the same of ctx.workspace, exposed for consistency also here.
   readonly currentWorkspace: Workspace;
   readonly all: ReadonlyArray<Workspace>;
   createEmptyWorkspace(displayName: string): Workspace;
   switchWorkspace(workspace: Workspace): void;
 }

 let sessionUniqueIdCounter = 0;

 /**
  * Creates a short ID which is unique to this instance of the UI.
  *
  * The advantage of using this over uuidv4() is that the ids produced are
  * significantly shorter, saving memory and making them more human
  * read/write-able which helps when debugging.
  *
  * Note: The ID range will reset every time the UI is restarted, so be careful
  * not rely on these IDs in any medium that can survive between UI instances.
  *
  * TODO(stevegolton): We could possibly move this into its own module and use it
  * everywhere where session-unique ids are required.
  */
 function createSessionUniqueId(): string {
   // Return the counter in base36 (0-z) to keep the string as short as possible
   // but still human readable.
   return (sessionUniqueIdCounter++).toString(36);
 }

 /**
  * Describes generic parent track node functionality - i.e. any entity that can
  * contain child TrackNodes, providing methods to add, remove, and access child
  * nodes.
  *
  * This class is abstract because, while it can technically be instantiated on
  * its own (no abstract methods/properties), it can't and shouldn't be
  * instantiated anywhere in practice - all APIs require either a TrackNode or a
  * Workspace.
  *
  * Thus, it serves two purposes:
  * 1. Avoiding duplication between Workspace and TrackNode, which is an internal
  *    implementation detail of this module.
  * 2. Providing a typescript interface for a generic TrackNode container class,
  *    which otherwise you might have to achieve using `Workspace | TrackNode`
  *    which is uglier.
  *
  * If you find yourself using this as a Javascript class in external code, e.g.
  * `instance of TrackNodeContainer`, you're probably doing something wrong.
  */
 export abstract class TrackNodeContainer {
   protected _children: Array<TrackNode> = [];
   protected readonly tracksById = new Map<string, TrackNode>();
   protected abstract fireOnChangeListener(): void;

   /**
    * True if this node has children, false otherwise.
    */
   get hasChildren(): boolean {
     return this._children.length > 0;
   }

   /**
    * The ordered list of children belonging to this node.
    */
   get children(): ReadonlyArray<TrackNode> {
     return this._children;
   }

   /**
    * Inserts a new child node considering it's sortOrder.
    *
    * The child will be added before the first child whose |sortOrder| is greater
    * than the child node's sort order, or at the end if one does not exist. If
    * |sortOrder| is omitted on either node in the comparison it is assumed to be
    * 0.
    *
    * @param child - The child node to add.
    */
   addChildInOrder(child: TrackNode): void {
     const insertPoint = this._children.find(
       (n) => (n.sortOrder ?? 0) > (child.sortOrder ?? 0),
     );
     if (insertPoint) {
       this.addChildBefore(child, insertPoint);
     } else {
       this.addChildLast(child);
     }
   }

   /**
    * Add a new child node at the start of the list of children.
    *
    * @param child The new child node to add.
    */
   addChildLast(child: TrackNode): void {
     this.adopt(child);
     this._children.push(child);
     this.fireOnChangeListener();
   }

   /**
    * Add a new child node at the end of the list of children.
    *
    * @param child The child node to add.
    */
   addChildFirst(child: TrackNode): void {
     this.adopt(child);
     this._children.unshift(child);
     this.fireOnChangeListener();
   }

   /**
    * Add a new child node before an existing child node.
    *
    * @param child The child node to add.
    * @param referenceNode An existing child node. The new node will be added
    * before this node.
    */
   addChildBefore(child: TrackNode, referenceNode: TrackNode): void {
     if (child === referenceNode) return;

     assertTrue(this.children.includes(referenceNode));

     this.adopt(child);

     const indexOfReference = this.children.indexOf(referenceNode);
     this._children.splice(indexOfReference, 0, child);
     this.fireOnChangeListener();
   }

   /**
    * Add a new child node after an existing child node.
    *
    * @param child The child node to add.
    * @param referenceNode An existing child node. The new node will be added
    * after this node.
    */
   addChildAfter(child: TrackNode, referenceNode: TrackNode): void {
     if (child === referenceNode) return;

     assertTrue(this.children.includes(referenceNode));

     this.adopt(child);

     const indexOfReference = this.children.indexOf(referenceNode);
     this._children.splice(indexOfReference + 1, 0, child);
     this.fireOnChangeListener();
   }

   /**
    * Remove a child node from this node.
    *
    * @param child The child node to remove.
    */
   removeChild(child: TrackNode): void {
     this._children = this.children.filter((x) => child !== x);
     child.parent = undefined;
     child.id && this.tracksById.delete(child.id);
     this.fireOnChangeListener();
   }

   /**
    * The flattened list of all descendent nodes.
    */
   get flatTracks(): ReadonlyArray<TrackNode> {
     return this.children.flatMap((node) => {
       return [node, ...node.flatTracks];
     });
   }

   /**
    * Remove all children from this node.
    */
   clear(): void {
     this._children = [];
     this.tracksById.clear();
     this.fireOnChangeListener();
   }

   /**
    * Find a track node by its id.
    *
    * Node: This is an O(N) operation where N is the depth of the target node.
    * I.e. this is more efficient than findTrackByURI().
    *
    * @param id The id of the node we want to find.
    * @returns The node or undefined if no such node exists.
    */
   getTrackById(id: string): TrackNode | undefined {
     const foundNode = this.tracksById.get(id);
     if (foundNode) {
       return foundNode;
     } else {
       // Recurse our children
       for (const child of this._children) {
         const foundNode = child.getTrackById(id);
         if (foundNode) return foundNode;
       }
     }
     return undefined;
   }

   private adopt(child: TrackNode): void {
     if (child.parent) {
       child.parent.removeChild(child);
     }
     child.parent = this;
     child.id && this.tracksById.set(child.id, child);
   }
 }

 export interface TrackNodeArgs {
   title: string;
   id: string;
   uri: string;
   headless: boolean;
   sortOrder: number;
   collapsed: boolean;
   isSummary: boolean;
   removable: boolean;
 }

 /**
  * A base class for any node with children (i.e. a group or a workspace).
  */
 export class TrackNode extends TrackNodeContainer {
   // Immutable unique (within the workspace) ID of this track node. Used for
   // efficiently retrieving this node object from a workspace. Note: This is
   // different to |uri| which is used to reference a track to render on the
   // track. If this means nothing to you, don't bother using it.
   public readonly id: string;

   // Parent node - could be the workspace or another node.
   public parent?: TrackNodeContainer;

   // A human readable string for this track - displayed in the track shell.
   // TODO(stevegolton): Make this optional, so that if we implement a string for
   // this track then we can implement it here as well.
   public title: string;

   // The URI of the track content to display here.
   public uri?: string;

   // Optional sort order, which workspaces may or may not take advantage of for
   // sorting when displaying the workspace.
   public sortOrder?: number;

   // Don't show the header at all for this track, just show its un-nested
   // children. This is helpful to group together tracks that logically belong to
   // the same group (e.g. all ftrace cpu tracks) and ease the job of
   // sorting/grouping plugins.
   public headless: boolean;

   // If true, this track is to be used as a summary for its children. When the
   // group is expanded the track will become sticky to the top of the viewport
   // to provide context for the tracks within, and the content of this track
   // shall be omitted. It will also be squashed down to a smaller height to save
   // vertical space.
   public isSummary: boolean;

   // If true, this node will be removable by the user. It will show a little
   // close button in the track shell which the user can press to remove the
   // track from the workspace.
   public removable: boolean;

   protected _collapsed = true;

   constructor(args?: Partial<TrackNodeArgs>) {
     super();

     const {
       title = '',
       id = createSessionUniqueId(),
       uri,
       headless = false,
       sortOrder,
       collapsed = true,
       isSummary = false,
       removable = false,
     } = args ?? {};

     this.id = id;
     this.uri = uri;
     this.headless = headless;
     this.title = title;
     this.sortOrder = sortOrder;
     this.isSummary = isSummary;
     this._collapsed = collapsed;
     this.removable = removable;
   }

   /**
    * Remove this track from it's parent & unpin from the workspace if pinned.
    */
   remove(): void {
     this.workspace?.unpinTrack(this);
     this.parent?.removeChild(this);
   }

   /**
    * Add this track to the list of pinned tracks in its parent workspace.
    *
    * Has no effect if this track is not added to a workspace.
    */
   pin(): void {
     this.workspace?.pinTrack(this);
   }

   /**
    * Remove this track from the list of pinned tracks in its parent workspace.
    *
    * Has no effect if this track is not added to a workspace.
    */
   unpin(): void {
     this.workspace?.unpinTrack(this);
   }

   /**
    * Returns true if this node is added to a workspace as is in the pinned track
    * list of that workspace.
    */
   get isPinned(): boolean {
     return Boolean(this.workspace?.hasPinnedTrack(this));
   }

   /**
    * Find the closest visible ancestor TrackNode.
    *
    * Given the path from the root workspace to this node, find the fist one,
    * starting from the root, which is collapsed. This will be, from the user's
    * point of view, the closest ancestor of this node.
    *
    * Returns undefined if this node is actually visible.
    *
    * TODO(stevegolton): Should it return itself in this case?
    */
   findClosestVisibleAncestor(): TrackNode {
     // Build a path from the root workspace to this node
     const path: TrackNode[] = [];
     let node = this.parent;
     while (node && node instanceof TrackNode) {
       path.unshift(node);
       node = node.parent;
     }

     // Find the first collapsed track in the path starting from the root. This
     // is effectively the closest we can get to this node without expanding any
     // groups.
     return path.find((node) => node.collapsed) ?? this;
   }

   /**
    * Expand all ancestor nodes.
    */
   reveal(): void {
     let parent = this.parent;
     while (parent && parent instanceof TrackNode) {
       parent.expand();
       parent = parent.parent;
     }
   }

   /**
    * Find this node's root node - this may be a workspace or another node.
    */
   get rootNode(): TrackNodeContainer | undefined {
     // Travel upwards through the tree to find the root node.
     let parent: TrackNodeContainer | undefined = this;
     while (parent && parent instanceof TrackNode) {
       parent = parent.parent;
     }
     return parent;
   }

   /**
    * Find this node's parent workspace if it is attached to one.
    */
   get workspace(): Workspace | undefined {
     // Find the root node and return it if it's a Workspace instance
     const rootNode = this.rootNode;
     if (rootNode instanceof Workspace) {
       return rootNode;
     }
     return undefined;
   }

   /**
    * Mark this node as un-collapsed, indicating its children should be rendered.
    */
   expand(): void {
     this._collapsed = false;
     this.fireOnChangeListener();
   }

   /**
    * Mark this node as collapsed, indicating its children should not be
    * rendered.
    */
   collapse(): void {
     this._collapsed = true;
     this.fireOnChangeListener();
   }

   /**
    * Toggle the collapsed state.
    */
   toggleCollapsed(): void {
     this._collapsed = !this._collapsed;
     this.fireOnChangeListener();
   }

   /**
    * Whether this node is collapsed, indicating its children should be rendered.
    */
   get collapsed(): boolean {
     return this._collapsed;
   }

   /**
    * Whether this node is expanded - i.e. not collapsed, indicating its children
    * should be rendered.
    */
   get expanded(): boolean {
     return !this._collapsed;
   }

   /**
    * Returns the list of titles representing the full path from the root node to
    * the current node. This path consists only of node titles, workspaces are
    * omitted.
    */
   get fullPath(): ReadonlyArray<string> {
     let fullPath = [this.title];
     let parent = this.parent;
     while (parent && parent instanceof TrackNode) {
       // Ignore headless containers as they don't appear in the tree...
       if (!parent.headless) {
         fullPath = [parent.title, ...fullPath];
       }
       parent = parent.parent;
     }
     return fullPath;
   }

   protected override fireOnChangeListener(): void {
     this.workspace?.onchange(this.workspace);
   }
 }

 /**
  * Defines a workspace containing a track tree and a pinned area.
  */
 export class Workspace extends TrackNodeContainer {
   public title = '<untitled-workspace>';
   public readonly id: string;
   onchange: (w: Workspace) => void = () => {};

   // Dummy node to contain the pinned tracks
   public readonly pinnedRoot = new TrackNode();

   get pinnedTracks(): ReadonlyArray<TrackNode> {
     return this.pinnedRoot.children;
   }

   constructor() {
     super();
     this.id = createSessionUniqueId();
     this.pinnedRoot.parent = this;
   }

   /**
    * Reset the entire workspace including the pinned tracks.
    */
   override clear(): void {
     super.clear();
     this.pinnedRoot.clear();
   }

   /**
    * Adds a track node to this workspace's pinned area.
    */
   pinTrack(track: TrackNode): void {
     // Make a lightweight clone of this track - just the uri and the title.
     const cloned = new TrackNode({
       uri: track.uri,
       title: track.title,
       removable: track.removable,
     });
     this.pinnedRoot.addChildLast(cloned);
   }

   /**
    * Removes a track node from this workspace's pinned area.
    */
   unpinTrack(track: TrackNode): void {
     const foundNode = this.pinnedRoot.children.find((t) => t.uri === track.uri);
     if (foundNode) {
       this.pinnedRoot.removeChild(foundNode);
     }
   }

   /**
    * Check if this workspace has a pinned track with the same URI as |track|.
    */
   hasPinnedTrack(track: TrackNode): boolean {
     return this.pinnedTracks.some((p) => p.uri === track.uri);
   }

   /**
    * Find a track node via its URI.
    *
    * Note: This in an O(N) operation where N is the number of nodes in the
    * workspace.
    *
    * @param uri The uri of the track to find.
    * @returns A reference to the track node if it exists in this workspace,
    * otherwise undefined.
    */
   findTrackByUri(uri: string): TrackNode | undefined {
     return this.flatTracks.find((t) => t.uri === uri);
   }

   /**
    * Find a track by ID, also searching pinned tracks.
    */
   override getTrackById(id: string): TrackNode | undefined {
     // Also search the pinned tracks
     return this.pinnedRoot.getTrackById(id) || super.getTrackById(id);
   }

   protected override fireOnChangeListener(): void {
     this.onchange(this);
   }
 }
	// Copyright (C) 2024 The Android Open Source Project
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.

	import {assertTrue} from '../base/logging';

	export interface WorkspaceManager {
	// This is the same of ctx.workspace, exposed for consistency also here.
	readonly currentWorkspace: Workspace;
	readonly all: ReadonlyArray<Workspace>;
	createEmptyWorkspace(displayName: string): Workspace;
	switchWorkspace(workspace: Workspace): void;
	}

	let sessionUniqueIdCounter = 0;

	/**
	* Creates a short ID which is unique to this instance of the UI.
	*
	* The advantage of using this over uuidv4() is that the ids produced are
	* significantly shorter, saving memory and making them more human
	* read/write-able which helps when debugging.
	*
	* Note: The ID range will reset every time the UI is restarted, so be careful
	* not rely on these IDs in any medium that can survive between UI instances.
	*
	* TODO(stevegolton): We could possibly move this into its own module and use it
	* everywhere where session-unique ids are required.
	*/
	function createSessionUniqueId(): string {
	// Return the counter in base36 (0-z) to keep the string as short as possible
	// but still human readable.
	return (sessionUniqueIdCounter++).toString(36);
	}

	/**
	* Describes generic parent track node functionality - i.e. any entity that can
	* contain child TrackNodes, providing methods to add, remove, and access child
	* nodes.
	*
	* This class is abstract because, while it can technically be instantiated on
	* its own (no abstract methods/properties), it can't and shouldn't be
	* instantiated anywhere in practice - all APIs require either a TrackNode or a
	* Workspace.
	*
	* Thus, it serves two purposes:
	* 1. Avoiding duplication between Workspace and TrackNode, which is an internal
	* implementation detail of this module.
	* 2. Providing a typescript interface for a generic TrackNode container class,
	* which otherwise you might have to achieve using `Workspace \| TrackNode`
	* which is uglier.
	*
	* If you find yourself using this as a Javascript class in external code, e.g.
	* `instance of TrackNodeContainer`, you're probably doing something wrong.
	*/
	export abstract class TrackNodeContainer {
	protected _children: Array<TrackNode> = [];
	protected readonly tracksById = new Map<string, TrackNode>();
	protected abstract fireOnChangeListener(): void;

	/**
	* True if this node has children, false otherwise.
	*/
	get hasChildren(): boolean {
	return this._children.length > 0;
	}

	/**
	* The ordered list of children belonging to this node.
	*/
	get children(): ReadonlyArray<TrackNode> {
	return this._children;
	}

	/**
	* Inserts a new child node considering it's sortOrder.
	*
	* The child will be added before the first child whose \|sortOrder\| is greater
	* than the child node's sort order, or at the end if one does not exist. If
	* \|sortOrder\| is omitted on either node in the comparison it is assumed to be
	* 0.
	*
	* @param child - The child node to add.
	*/
	addChildInOrder(child: TrackNode): void {
	const insertPoint = this._children.find(
	(n) => (n.sortOrder ?? 0) > (child.sortOrder ?? 0),
	);
	if (insertPoint) {
	this.addChildBefore(child, insertPoint);
	} else {
	this.addChildLast(child);
	}
	}

	/**
	* Add a new child node at the start of the list of children.
	*
	* @param child The new child node to add.
	*/
	addChildLast(child: TrackNode): void {
	this.adopt(child);
	this._children.push(child);
	this.fireOnChangeListener();
	}

	/**
	* Add a new child node at the end of the list of children.
	*
	* @param child The child node to add.
	*/
	addChildFirst(child: TrackNode): void {
	this.adopt(child);
	this._children.unshift(child);
	this.fireOnChangeListener();
	}

	/**
	* Add a new child node before an existing child node.
	*
	* @param child The child node to add.
	* @param referenceNode An existing child node. The new node will be added
	* before this node.
	*/
	addChildBefore(child: TrackNode, referenceNode: TrackNode): void {
	if (child === referenceNode) return;

	assertTrue(this.children.includes(referenceNode));

	this.adopt(child);

	const indexOfReference = this.children.indexOf(referenceNode);
	this._children.splice(indexOfReference, 0, child);
	this.fireOnChangeListener();
	}

	/**
	* Add a new child node after an existing child node.
	*
	* @param child The child node to add.
	* @param referenceNode An existing child node. The new node will be added
	* after this node.
	*/
	addChildAfter(child: TrackNode, referenceNode: TrackNode): void {
	if (child === referenceNode) return;

	assertTrue(this.children.includes(referenceNode));

	this.adopt(child);

	const indexOfReference = this.children.indexOf(referenceNode);
	this._children.splice(indexOfReference + 1, 0, child);
	this.fireOnChangeListener();
	}

	/**
	* Remove a child node from this node.
	*
	* @param child The child node to remove.
	*/
	removeChild(child: TrackNode): void {
	this._children = this.children.filter((x) => child !== x);
	child.parent = undefined;
	child.id && this.tracksById.delete(child.id);
	this.fireOnChangeListener();
	}

	/**
	* The flattened list of all descendent nodes.
	*/
	get flatTracks(): ReadonlyArray<TrackNode> {
	return this.children.flatMap((node) => {
	return [node, ...node.flatTracks];
	});
	}

	/**
	* Remove all children from this node.
	*/
	clear(): void {
	this._children = [];
	this.tracksById.clear();
	this.fireOnChangeListener();
	}

	/**
	* Find a track node by its id.
	*
	* Node: This is an O(N) operation where N is the depth of the target node.
	* I.e. this is more efficient than findTrackByURI().
	*
	* @param id The id of the node we want to find.
	* @returns The node or undefined if no such node exists.
	*/
	getTrackById(id: string): TrackNode \| undefined {
	const foundNode = this.tracksById.get(id);
	if (foundNode) {
	return foundNode;
	} else {
	// Recurse our children
	for (const child of this._children) {
	const foundNode = child.getTrackById(id);
	if (foundNode) return foundNode;
	}
	}
	return undefined;
	}

	private adopt(child: TrackNode): void {
	if (child.parent) {
	child.parent.removeChild(child);
	}
	child.parent = this;
	child.id && this.tracksById.set(child.id, child);
	}
	}

	export interface TrackNodeArgs {
	title: string;
	id: string;
	uri: string;
	headless: boolean;
	sortOrder: number;
	collapsed: boolean;
	isSummary: boolean;
	removable: boolean;
	}

	/**
	* A base class for any node with children (i.e. a group or a workspace).
	*/
	export class TrackNode extends TrackNodeContainer {
	// Immutable unique (within the workspace) ID of this track node. Used for
	// efficiently retrieving this node object from a workspace. Note: This is
	// different to \|uri\| which is used to reference a track to render on the
	// track. If this means nothing to you, don't bother using it.
	public readonly id: string;

	// Parent node - could be the workspace or another node.
	public parent?: TrackNodeContainer;

	// A human readable string for this track - displayed in the track shell.
	// TODO(stevegolton): Make this optional, so that if we implement a string for
	// this track then we can implement it here as well.
	public title: string;

	// The URI of the track content to display here.
	public uri?: string;

	// Optional sort order, which workspaces may or may not take advantage of for
	// sorting when displaying the workspace.
	public sortOrder?: number;

	// Don't show the header at all for this track, just show its un-nested
	// children. This is helpful to group together tracks that logically belong to
	// the same group (e.g. all ftrace cpu tracks) and ease the job of
	// sorting/grouping plugins.
	public headless: boolean;

	// If true, this track is to be used as a summary for its children. When the
	// group is expanded the track will become sticky to the top of the viewport
	// to provide context for the tracks within, and the content of this track
	// shall be omitted. It will also be squashed down to a smaller height to save
	// vertical space.
	public isSummary: boolean;

	// If true, this node will be removable by the user. It will show a little
	// close button in the track shell which the user can press to remove the
	// track from the workspace.
	public removable: boolean;

	protected _collapsed = true;

	constructor(args?: Partial<TrackNodeArgs>) {
	super();

	const {
	title = '',
	id = createSessionUniqueId(),
	uri,
	headless = false,
	sortOrder,
	collapsed = true,
	isSummary = false,
	removable = false,
	} = args ?? {};

	this.id = id;
	this.uri = uri;
	this.headless = headless;
	this.title = title;
	this.sortOrder = sortOrder;
	this.isSummary = isSummary;
	this._collapsed = collapsed;
	this.removable = removable;
	}

	/**
	* Remove this track from it's parent & unpin from the workspace if pinned.
	*/
	remove(): void {
	this.workspace?.unpinTrack(this);
	this.parent?.removeChild(this);
	}

	/**
	* Add this track to the list of pinned tracks in its parent workspace.
	*
	* Has no effect if this track is not added to a workspace.
	*/
	pin(): void {
	this.workspace?.pinTrack(this);
	}

	/**
	* Remove this track from the list of pinned tracks in its parent workspace.
	*
	* Has no effect if this track is not added to a workspace.
	*/
	unpin(): void {
	this.workspace?.unpinTrack(this);
	}

	/**
	* Returns true if this node is added to a workspace as is in the pinned track
	* list of that workspace.
	*/
	get isPinned(): boolean {
	return Boolean(this.workspace?.hasPinnedTrack(this));
	}

	/**
	* Find the closest visible ancestor TrackNode.
	*
	* Given the path from the root workspace to this node, find the fist one,
	* starting from the root, which is collapsed. This will be, from the user's
	* point of view, the closest ancestor of this node.
	*
	* Returns undefined if this node is actually visible.
	*
	* TODO(stevegolton): Should it return itself in this case?
	*/
	findClosestVisibleAncestor(): TrackNode {
	// Build a path from the root workspace to this node
	const path: TrackNode[] = [];
	let node = this.parent;
	while (node && node instanceof TrackNode) {
	path.unshift(node);
	node = node.parent;
	}

	// Find the first collapsed track in the path starting from the root. This
	// is effectively the closest we can get to this node without expanding any
	// groups.
	return path.find((node) => node.collapsed) ?? this;
	}

	/**
	* Expand all ancestor nodes.
	*/
	reveal(): void {
	let parent = this.parent;
	while (parent && parent instanceof TrackNode) {
	parent.expand();
	parent = parent.parent;
	}
	}

	/**
	* Find this node's root node - this may be a workspace or another node.
	*/
	get rootNode(): TrackNodeContainer \| undefined {
	// Travel upwards through the tree to find the root node.
	let parent: TrackNodeContainer \| undefined = this;
	while (parent && parent instanceof TrackNode) {
	parent = parent.parent;
	}
	return parent;
	}

	/**
	* Find this node's parent workspace if it is attached to one.
	*/
	get workspace(): Workspace \| undefined {
	// Find the root node and return it if it's a Workspace instance
	const rootNode = this.rootNode;
	if (rootNode instanceof Workspace) {
	return rootNode;
	}
	return undefined;
	}

	/**
	* Mark this node as un-collapsed, indicating its children should be rendered.
	*/
	expand(): void {
	this._collapsed = false;
	this.fireOnChangeListener();
	}

	/**
	* Mark this node as collapsed, indicating its children should not be
	* rendered.
	*/
	collapse(): void {
	this._collapsed = true;
	this.fireOnChangeListener();
	}

	/**
	* Toggle the collapsed state.
	*/
	toggleCollapsed(): void {
	this._collapsed = !this._collapsed;
	this.fireOnChangeListener();
	}

	/**
	* Whether this node is collapsed, indicating its children should be rendered.
	*/
	get collapsed(): boolean {
	return this._collapsed;
	}

	/**
	* Whether this node is expanded - i.e. not collapsed, indicating its children
	* should be rendered.
	*/
	get expanded(): boolean {
	return !this._collapsed;
	}

	/**
	* Returns the list of titles representing the full path from the root node to
	* the current node. This path consists only of node titles, workspaces are
	* omitted.
	*/
	get fullPath(): ReadonlyArray<string> {
	let fullPath = [this.title];
	let parent = this.parent;
	while (parent && parent instanceof TrackNode) {
	// Ignore headless containers as they don't appear in the tree...
	if (!parent.headless) {
	fullPath = [parent.title, ...fullPath];
	}
	parent = parent.parent;
	}
	return fullPath;
	}

	protected override fireOnChangeListener(): void {
	this.workspace?.onchange(this.workspace);
	}
	}

	/**
	* Defines a workspace containing a track tree and a pinned area.
	*/
	export class Workspace extends TrackNodeContainer {
	public title = '<untitled-workspace>';
	public readonly id: string;
	onchange: (w: Workspace) => void = () => {};

	// Dummy node to contain the pinned tracks
	public readonly pinnedRoot = new TrackNode();

	get pinnedTracks(): ReadonlyArray<TrackNode> {
	return this.pinnedRoot.children;
	}

	constructor() {
	super();
	this.id = createSessionUniqueId();
	this.pinnedRoot.parent = this;
	}

	/**
	* Reset the entire workspace including the pinned tracks.
	*/
	override clear(): void {
	super.clear();
	this.pinnedRoot.clear();
	}

	/**
	* Adds a track node to this workspace's pinned area.
	*/
	pinTrack(track: TrackNode): void {
	// Make a lightweight clone of this track - just the uri and the title.
	const cloned = new TrackNode({
	uri: track.uri,
	title: track.title,
	removable: track.removable,
	});
	this.pinnedRoot.addChildLast(cloned);
	}

	/**
	* Removes a track node from this workspace's pinned area.
	*/
	unpinTrack(track: TrackNode): void {
	const foundNode = this.pinnedRoot.children.find((t) => t.uri === track.uri);
	if (foundNode) {
	this.pinnedRoot.removeChild(foundNode);
	}
	}

	/**
	* Check if this workspace has a pinned track with the same URI as \|track\|.
	*/
	hasPinnedTrack(track: TrackNode): boolean {
	return this.pinnedTracks.some((p) => p.uri === track.uri);
	}

	/**
	* Find a track node via its URI.
	*
	* Note: This in an O(N) operation where N is the number of nodes in the
	* workspace.
	*
	* @param uri The uri of the track to find.
	* @returns A reference to the track node if it exists in this workspace,
	* otherwise undefined.
	*/
	findTrackByUri(uri: string): TrackNode \| undefined {
	return this.flatTracks.find((t) => t.uri === uri);
	}

	/**
	* Find a track by ID, also searching pinned tracks.
	*/
	override getTrackById(id: string): TrackNode \| undefined {
	// Also search the pinned tracks
	return this.pinnedRoot.getTrackById(id) \|\| super.getTrackById(id);
	}

	protected override fireOnChangeListener(): void {
	this.onchange(this);
	}
	}