WebGL Minimap (#3510)

This PR replaces our current minimap implementation with one that uses
WebGL

### Change Type

<!-- ❗ Please select a 'Scope' label ❗️ -->

- [x] `sdk` — Changes the tldraw SDK
- [ ] `dotcom` — Changes the tldraw.com web app
- [ ] `docs` — Changes to the documentation, examples, or templates.
- [ ] `vs code` — Changes to the vscode plugin
- [ ] `internal` — Does not affect user-facing stuff

<!-- ❗ Please select a 'Type' label ❗️ -->

- [ ] `bugfix` — Bug fix
- [ ] `feature` — New feature
- [x] `improvement` — Improving existing features
- [ ] `chore` — Updating dependencies, other boring stuff
- [ ] `galaxy brain` — Architectural changes
- [ ] `tests` — Changes to any test code
- [ ] `tools` — Changes to infrastructure, CI, internal scripts,
debugging tools, etc.
- [ ] `dunno` — I don't know


### Test Plan

1. Add a step-by-step description of how to test your PR here.
2.

- [ ] Unit Tests
- [ ] End to end tests

### Release Notes

- Add a brief release note for your PR here.

---------

Co-authored-by: Steve Ruiz <steveruizok@gmail.com>

packages/editor/api-report.md

@@ -682,6 +682,8 @@ export class Editor extends EventEmitter<TLEventMap> {
     getCameraState(): "idle" | "moving";
     getCanRedo(): boolean;
     getCanUndo(): boolean;
+    getCollaborators(): TLInstancePresence[];
+    getCollaboratorsOnCurrentPage(): TLInstancePresence[];
     getContainer: () => HTMLElement;
     getContentFromCurrentPage(shapes: TLShape[] | TLShapeId[]): TLContent | undefined;
     // @internal
@@ -693,6 +695,8 @@ export class Editor extends EventEmitter<TLEventMap> {
     getCurrentPageId(): TLPageId;
     getCurrentPageRenderingShapesSorted(): TLShape[];
     getCurrentPageShapeIds(): Set<TLShapeId>;
+    // @internal (undocumented)
+    getCurrentPageShapeIdsSorted(): TLShapeId[];
     getCurrentPageShapes(): TLShape[];
     getCurrentPageShapesSorted(): TLShape[];
     getCurrentPageState(): TLInstancePageState;

packages/editor/api/api.json

@@ -10059,6 +10059,86 @@
               "isAbstract": false,
               "name": "getCanUndo"
             },
+            {
+              "kind": "Method",
+              "canonicalReference": "@tldraw/editor!Editor#getCollaborators:member(1)",
+              "docComment": "/**\n * Returns a list of presence records for all peer collaborators. This will return the latest presence record for each connected user.\n *\n * @public\n */\n",
+              "excerptTokens": [
+                {
+                  "kind": "Content",
+                  "text": "getCollaborators(): "
+                },
+                {
+                  "kind": "Content",
+                  "text": "import(\"@tldraw/tlschema\")."
+                },
+                {
+                  "kind": "Reference",
+                  "text": "TLInstancePresence",
+                  "canonicalReference": "@tldraw/tlschema!TLInstancePresence:interface"
+                },
+                {
+                  "kind": "Content",
+                  "text": "[]"
+                },
+                {
+                  "kind": "Content",
+                  "text": ";"
+                }
+              ],
+              "isStatic": false,
+              "returnTypeTokenRange": {
+                "startIndex": 1,
+                "endIndex": 4
+              },
+              "releaseTag": "Public",
+              "isProtected": false,
+              "overloadIndex": 1,
+              "parameters": [],
+              "isOptional": false,
+              "isAbstract": false,
+              "name": "getCollaborators"
+            },
+            {
+              "kind": "Method",
+              "canonicalReference": "@tldraw/editor!Editor#getCollaboratorsOnCurrentPage:member(1)",
+              "docComment": "/**\n * Returns a list of presence records for all peer collaborators on the current page. This will return the latest presence record for each connected user.\n *\n * @public\n */\n",
+              "excerptTokens": [
+                {
+                  "kind": "Content",
+                  "text": "getCollaboratorsOnCurrentPage(): "
+                },
+                {
+                  "kind": "Content",
+                  "text": "import(\"@tldraw/tlschema\")."
+                },
+                {
+                  "kind": "Reference",
+                  "text": "TLInstancePresence",
+                  "canonicalReference": "@tldraw/tlschema!TLInstancePresence:interface"
+                },
+                {
+                  "kind": "Content",
+                  "text": "[]"
+                },
+                {
+                  "kind": "Content",
+                  "text": ";"
+                }
+              ],
+              "isStatic": false,
+              "returnTypeTokenRange": {
+                "startIndex": 1,
+                "endIndex": 4
+              },
+              "releaseTag": "Public",
+              "isProtected": false,
+              "overloadIndex": 1,
+              "parameters": [],
+              "isOptional": false,
+              "isAbstract": false,
+              "name": "getCollaboratorsOnCurrentPage"
+            },
             {
               "kind": "Property",
               "canonicalReference": "@tldraw/editor!Editor#getContainer:member",

packages/editor/src/lib/editor/Editor.ts

@@ -2619,15 +2619,7 @@ export class Editor extends EventEmitter<TLEventMap> {
 	 * @public
 	 */
 	animateToUser(userId: string): this {
-		const presences = this.store.query.records('instance_presence', () => ({
+		const presence = this.getCollaborators().find((c) => c.userId === userId)
-			userId: { eq: userId },
-		}))
-
-		const presence = [...presences.get()]
-			.sort((a, b) => {
-				return a.lastActivityTimestamp - b.lastActivityTimestamp
-			})
-			.pop()
 
 		if (!presence) return this
 
@@ -2883,6 +2875,45 @@ export class Editor extends EventEmitter<TLEventMap> {
 			z: point.z ?? 0.5,
 		}
 	}
+	// Collaborators
+
+	@computed
+	private _getCollaboratorsQuery() {
+		return this.store.query.records('instance_presence', () => ({
+			userId: { neq: this.user.getId() },
+		}))
+	}
+
+	/**
+	 * Returns a list of presence records for all peer collaborators.
+	 * This will return the latest presence record for each connected user.
+	 *
+	 * @public
+	 */
+	@computed
+	getCollaborators() {
+		const allPresenceRecords = this._getCollaboratorsQuery().get()
+		if (!allPresenceRecords.length) return EMPTY_ARRAY
+		const userIds = [...new Set(allPresenceRecords.map((c) => c.userId))].sort()
+		return userIds.map((id) => {
+			const latestPresence = allPresenceRecords
+				.filter((c) => c.userId === id)
+				.sort((a, b) => b.lastActivityTimestamp - a.lastActivityTimestamp)[0]
+			return latestPresence
+		})
+	}
+
+	/**
+	 * Returns a list of presence records for all peer collaborators on the current page.
+	 * This will return the latest presence record for each connected user.
+	 *
+	 * @public
+	 */
+	@computed
+	getCollaboratorsOnCurrentPage() {
+		const currentPageId = this.getCurrentPageId()
+		return this.getCollaborators().filter((c) => c.currentPageId === currentPageId)
+	}
 
 	// Following
 
@@ -2894,9 +2925,9 @@ export class Editor extends EventEmitter<TLEventMap> {
 	 * @public
 	 */
 	startFollowingUser(userId: string): this {
-		const leaderPresences = this.store.query.records('instance_presence', () => ({
+		const leaderPresences = this._getCollaboratorsQuery()
-			userId: { eq: userId },
+			.get()
-		}))
+			.filter((p) => p.userId === userId)
 
 		const thisUserId = this.user.getId()
 
@@ -2905,7 +2936,7 @@ export class Editor extends EventEmitter<TLEventMap> {
 		}
 
 		// If the leader is following us, then we can't follow them
-		if (leaderPresences.get().some((p) => p.followingUserId === thisUserId)) {
+		if (leaderPresences.some((p) => p.followingUserId === thisUserId)) {
 			return this
 		}
 
@@ -2924,7 +2955,7 @@ export class Editor extends EventEmitter<TLEventMap> {
 
 		const moveTowardsUser = () => {
 			// Stop following if we can't find the user
-			const leaderPresence = [...leaderPresences.get()]
+			const leaderPresence = [...leaderPresences]
 				.sort((a, b) => {
 					return a.lastActivityTimestamp - b.lastActivityTimestamp
 				})
@@ -3281,6 +3312,14 @@ export class Editor extends EventEmitter<TLEventMap> {
 		return this._currentPageShapeIds.get()
 	}
 
+	/**
+	 * @internal
+	 */
+	@computed
+	getCurrentPageShapeIdsSorted() {
+		return Array.from(this.getCurrentPageShapeIds()).sort()
+	}
+
 	/**
 	 * Get the ids of shapes on a page.
 	 *
@@ -3893,7 +3932,7 @@ export class Editor extends EventEmitter<TLEventMap> {
 	 * @public
 	 */
 	getShapePageTransform(shape: TLShape | TLShapeId): Mat {
-		const id = typeof shape === 'string' ? shape : this.getShape(shape)!.id
+		const id = typeof shape === 'string' ? shape : shape.id
 		return this._getShapePageTransformCache().get(id) ?? Mat.Identity()
 	}
 
@@ -4227,7 +4266,7 @@ export class Editor extends EventEmitter<TLEventMap> {
 	@computed getCurrentPageBounds(): Box | undefined {
 		let commonBounds: Box | undefined
 
-		this.getCurrentPageShapeIds().forEach((shapeId) => {
+		this.getCurrentPageShapeIdsSorted().forEach((shapeId) => {
 			const bounds = this.getShapeMaskedPageBounds(shapeId)
 			if (!bounds) return
 			if (!commonBounds) {
@@ -8159,7 +8198,11 @@ export class Editor extends EventEmitter<TLEventMap> {
 		// it will be 0,0 when its actual screen position is equal
 		// to screenBounds.point. This is confusing!
 		currentScreenPoint.set(sx, sy)
-		currentPagePoint.set(sx / cz - cx, sy / cz - cy, sz)
+		const nx = sx / cz - cx
+		const ny = sy / cz - cy
+		if (isFinite(nx) && isFinite(ny)) {
+			currentPagePoint.set(nx, ny, sz)
+		}
 
 		this.inputs.isPen = info.type === 'pointer' && info.isPen
 

packages/editor/src/lib/hooks/usePeerIds.ts

@@ -1,5 +1,4 @@
 import { useComputed, useValue } from '@tldraw/state'
-import { useMemo } from 'react'
 import { uniq } from '../utils/uniq'
 import { useEditor } from './useEditor'
 
@@ -10,17 +9,12 @@ import { useEditor } from './useEditor'
  */
 export function usePeerIds() {
 	const editor = useEditor()
-	const $presences = useMemo(() => {
-		return editor.store.query.records('instance_presence', () => ({
-			userId: { neq: editor.user.getId() },
-		}))
-	}, [editor])
 
 	const $userIds = useComputed(
 		'userIds',
-		() => uniq($presences.get().map((p) => p.userId)).sort(),
+		() => uniq(editor.getCollaborators().map((p) => p.userId)).sort(),
 		{ isEqual: (a, b) => a.join(',') === b.join?.(',') },
-		[$presences]
+		[editor]
 	)
 
 	return useValue($userIds)

packages/editor/src/lib/hooks/usePresence.ts

@@ -1,6 +1,5 @@
 import { useValue } from '@tldraw/state'
 import { TLInstancePresence } from '@tldraw/tlschema'
-import { useMemo } from 'react'
 import { useEditor } from './useEditor'
 
 // TODO: maybe move this to a computed property on the App class?
@@ -11,21 +10,12 @@ import { useEditor } from './useEditor'
 export function usePresence(userId: string): TLInstancePresence | null {
 	const editor = useEditor()
 
-	const $presences = useMemo(() => {
-		return editor.store.query.records('instance_presence', () => ({
-			userId: { eq: userId },
-		}))
-	}, [editor, userId])
-
 	const latestPresence = useValue(
 		`latestPresence:${userId}`,
 		() => {
-			return $presences
+			return editor.getCollaborators().find((c) => c.userId === userId)
-				.get()
-				.slice()
-				.sort((a, b) => b.lastActivityTimestamp - a.lastActivityTimestamp)[0]
 		},
-		[]
+		[editor]
 	)
 
 	return latestPresence ?? null

packages/editor/src/lib/primitives/Mat.ts

@@ -39,12 +39,13 @@ export class Mat {
 
 	equals(m: Mat | MatModel) {
 		return (
-			this.a === m.a &&
+			this === m ||
+			(this.a === m.a &&
 				this.b === m.b &&
 				this.c === m.c &&
 				this.d === m.d &&
 				this.e === m.e &&
-			this.f === m.f
+				this.f === m.f)
 		)
 	}
 

packages/tldraw/src/lib/ui/components/Minimap/DefaultMinimap.tsx

@@ -1,18 +1,13 @@
 import {
 	ANIMATION_MEDIUM_MS,
-	Box,
 	TLPointerEventInfo,
-	TLShapeId,
 	Vec,
 	getPointerInfo,
-	intersectPolygonPolygon,
 	normalizeWheel,
 	releasePointerCapture,
 	setPointerCapture,
-	useComputed,
 	useEditor,
 	useIsDarkMode,
-	useQuickReactor,
 } from '@tldraw/editor'
 import * as React from 'react'
 import { MinimapManager } from './MinimapManager'
@@ -24,67 +19,78 @@ export function DefaultMinimap() {
 	const rCanvas = React.useRef<HTMLCanvasElement>(null!)
 	const rPointing = React.useRef(false)
 
-	const isDarkMode = useIsDarkMode()
+	const minimapRef = React.useRef<MinimapManager>()
-	const devicePixelRatio = useComputed('dpr', () => editor.getInstanceState().devicePixelRatio, [
-		editor,
-	])
-	const presences = React.useMemo(() => editor.store.query.records('instance_presence'), [editor])
-
-	const minimap = React.useMemo(() => new MinimapManager(editor), [editor])
 
 	React.useEffect(() => {
-		// Must check after render
+		const minimap = new MinimapManager(editor, rCanvas.current)
-		const raf = requestAnimationFrame(() => {
+		minimapRef.current = minimap
-			minimap.updateColors()
+		return minimapRef.current.close
-			minimap.render()
+	}, [editor])
-		})
-		return () => {
-			cancelAnimationFrame(raf)
-		}
-	}, [editor, minimap, isDarkMode])
 
 	const onDoubleClick = React.useCallback(
 		(e: React.MouseEvent<HTMLCanvasElement>) => {
 			if (!editor.getCurrentPageShapeIds().size) return
+			if (!minimapRef.current) return
 
-			const point = minimap.minimapScreenPointToPagePoint(e.clientX, e.clientY, false, false)
+			const point = minimapRef.current.minimapScreenPointToPagePoint(
+				e.clientX,
+				e.clientY,
+				false,
+				false
+			)
 
-			const clampedPoint = minimap.minimapScreenPointToPagePoint(e.clientX, e.clientY, false, true)
+			const clampedPoint = minimapRef.current.minimapScreenPointToPagePoint(
+				e.clientX,
+				e.clientY,
+				false,
+				true
+			)
 
-			minimap.originPagePoint.setTo(clampedPoint)
+			minimapRef.current.originPagePoint.setTo(clampedPoint)
-			minimap.originPageCenter.setTo(editor.getViewportPageBounds().center)
+			minimapRef.current.originPageCenter.setTo(editor.getViewportPageBounds().center)
 
 			editor.centerOnPoint(point, { duration: ANIMATION_MEDIUM_MS })
 		},
-		[editor, minimap]
+		[editor]
 	)
 
 	const onPointerDown = React.useCallback(
 		(e: React.PointerEvent<HTMLCanvasElement>) => {
+			if (!minimapRef.current) return
 			const elm = e.currentTarget
 			setPointerCapture(elm, e)
 			if (!editor.getCurrentPageShapeIds().size) return
 
 			rPointing.current = true
 
-			minimap.isInViewport = false
+			minimapRef.current.isInViewport = false
 
-			const point = minimap.minimapScreenPointToPagePoint(e.clientX, e.clientY, false, false)
+			const point = minimapRef.current.minimapScreenPointToPagePoint(
+				e.clientX,
+				e.clientY,
+				false,
+				false
+			)
 
-			const clampedPoint = minimap.minimapScreenPointToPagePoint(e.clientX, e.clientY, false, true)
+			const clampedPoint = minimapRef.current.minimapScreenPointToPagePoint(
+				e.clientX,
+				e.clientY,
+				false,
+				true
+			)
 
 			const _vpPageBounds = editor.getViewportPageBounds()
 
-			minimap.isInViewport = _vpPageBounds.containsPoint(clampedPoint)
+			minimapRef.current.isInViewport = _vpPageBounds.containsPoint(clampedPoint)
 
-			if (minimap.isInViewport) {
+			if (minimapRef.current.isInViewport) {
-				minimap.originPagePoint.setTo(clampedPoint)
+				minimapRef.current.originPagePoint.setTo(clampedPoint)
-				minimap.originPageCenter.setTo(_vpPageBounds.center)
+				minimapRef.current.originPageCenter.setTo(_vpPageBounds.center)
 			} else {
 				const delta = Vec.Sub(_vpPageBounds.center, _vpPageBounds.point)
 				const pagePoint = Vec.Add(point, delta)
-				minimap.originPagePoint.setTo(pagePoint)
+				minimapRef.current.originPagePoint.setTo(pagePoint)
-				minimap.originPageCenter.setTo(point)
+				minimapRef.current.originPageCenter.setTo(point)
 				editor.centerOnPoint(point, { duration: ANIMATION_MEDIUM_MS })
 			}
 
@@ -98,16 +104,24 @@ export function DefaultMinimap() {
 
 			document.body.addEventListener('pointerup', release)
 		},
-		[editor, minimap]
+		[editor]
 	)
 
 	const onPointerMove = React.useCallback(
 		(e: React.PointerEvent<HTMLCanvasElement>) => {
-			const point = minimap.minimapScreenPointToPagePoint(e.clientX, e.clientY, e.shiftKey, true)
+			if (!minimapRef.current) return
+			const point = minimapRef.current.minimapScreenPointToPagePoint(
+				e.clientX,
+				e.clientY,
+				e.shiftKey,
+				true
+			)
 
 			if (rPointing.current) {
-				if (minimap.isInViewport) {
+				if (minimapRef.current.isInViewport) {
-					const delta = minimap.originPagePoint.clone().sub(minimap.originPageCenter)
+					const delta = minimapRef.current.originPagePoint
+						.clone()
+						.sub(minimapRef.current.originPageCenter)
 					editor.centerOnPoint(Vec.Sub(point, delta))
 					return
 				}
@@ -115,7 +129,7 @@ export function DefaultMinimap() {
 				editor.centerOnPoint(point)
 			}
 
-			const pagePoint = minimap.getPagePoint(e.clientX, e.clientY)
+			const pagePoint = minimapRef.current.getPagePoint(e.clientX, e.clientY)
 
 			const screenPoint = editor.pageToScreen(pagePoint)
 
@@ -130,7 +144,7 @@ export function DefaultMinimap() {
 
 			editor.dispatch(info)
 		},
-		[editor, minimap]
+		[editor]
 	)
 
 	const onWheel = React.useCallback(
@@ -150,73 +164,16 @@ export function DefaultMinimap() {
 		[editor]
 	)
 
-	// Update the minimap's dpr when the dpr changes
+	const isDarkMode = useIsDarkMode()
-	useQuickReactor(
-		'update when dpr changes',
-		() => {
-			const dpr = devicePixelRatio.get()
-			minimap.setDpr(dpr)
 
-			const canvas = rCanvas.current as HTMLCanvasElement
+	React.useEffect(() => {
-			const rect = canvas.getBoundingClientRect()
+		// need to wait a tick for next theme css to be applied
-			const width = rect.width * dpr
+		// otherwise the minimap will render with the wrong colors
-			const height = rect.height * dpr
+		setTimeout(() => {
-
+			minimapRef.current?.updateColors()
-			// These must happen in order
+			minimapRef.current?.render()
-			canvas.width = width
-			canvas.height = height
-			minimap.canvasScreenBounds.set(rect.x, rect.y, width, height)
-
-			minimap.cvs = rCanvas.current
-		},
-		[devicePixelRatio, minimap]
-	)
-
-	useQuickReactor(
-		'minimap render when pagebounds or collaborators changes',
-		() => {
-			const shapeIdsOnCurrentPage = editor.getCurrentPageShapeIds()
-			const commonBoundsOfAllShapesOnCurrentPage = editor.getCurrentPageBounds()
-			const viewportPageBounds = editor.getViewportPageBounds()
-
-			const _dpr = devicePixelRatio.get() // dereference
-
-			minimap.contentPageBounds = commonBoundsOfAllShapesOnCurrentPage
-				? Box.Expand(commonBoundsOfAllShapesOnCurrentPage, viewportPageBounds)
-				: viewportPageBounds
-
-			minimap.updateContentScreenBounds()
-
-			// All shape bounds
-
-			const allShapeBounds = [] as (Box & { id: TLShapeId })[]
-
-			shapeIdsOnCurrentPage.forEach((id) => {
-				let pageBounds = editor.getShapePageBounds(id) as Box & { id: TLShapeId }
-				if (!pageBounds) return
-
-				const pageMask = editor.getShapeMask(id)
-
-				if (pageMask) {
-					const intersection = intersectPolygonPolygon(pageMask, pageBounds.corners)
-					if (!intersection) {
-						return
-					}
-					pageBounds = Box.FromPoints(intersection) as Box & { id: TLShapeId }
-				}
-
-				if (pageBounds) {
-					pageBounds.id = id // kinda dirty but we want to include the id here
-					allShapeBounds.push(pageBounds)
-				}
 		})
-
+	}, [isDarkMode])
-			minimap.pageBounds = allShapeBounds
-			minimap.collaborators = presences.get()
-			minimap.render()
-		},
-		[editor, minimap]
-	)
 
 	return (
 		<div className="tlui-minimap">

packages/tldraw/src/lib/ui/components/Minimap/MinimapManager.ts

@@ -1,114 +1,159 @@
 import {
 	Box,
+	ComputedCache,
 	Editor,
-	PI2,
+	TLShape,
-	TLInstancePresence,
-	TLShapeId,
 	Vec,
+	atom,
 	clamp,
+	computed,
+	react,
 	uniqueId,
 } from '@tldraw/editor'
+import { getRgba } from './getRgba'
+import { BufferStuff, appendVertices, setupWebGl } from './minimap-webgl-setup'
+import { pie, rectangle, roundedRectangle } from './minimap-webgl-shapes'
 
 export class MinimapManager {
-	constructor(public editor: Editor) {}
+	disposables = [] as (() => void)[]
-
+	close = () => this.disposables.forEach((d) => d())
-	dpr = 1
+	gl: ReturnType<typeof setupWebGl>
-
+	shapeGeometryCache: ComputedCache<Float32Array | null, TLShape>
-	colors = {
+	constructor(
-		shapeFill: 'rgba(144, 144, 144, .1)',
+		public editor: Editor,
-		selectFill: '#2f80ed',
+		public readonly elem: HTMLCanvasElement
-		viewportFill: 'rgba(144, 144, 144, .1)',
+	) {
+		this.gl = setupWebGl(elem)
+		this.shapeGeometryCache = editor.store.createComputedCache('webgl-geometry', (r: TLShape) => {
+			const bounds = editor.getShapeMaskedPageBounds(r.id)
+			if (!bounds) return null
+			const arr = new Float32Array(12)
+			rectangle(arr, 0, bounds.x, bounds.y, bounds.w, bounds.h)
+			return arr
+		})
+		this.colors = this._getColors()
+		this.disposables.push(this._listenForCanvasResize(), react('minimap render', this.render))
 	}
 
-	id = uniqueId()
+	private _getColors() {
-	cvs: HTMLCanvasElement | null = null
+		const style = getComputedStyle(this.editor.getContainer())
-	pageBounds: (Box & { id: TLShapeId })[] = []
-	collaborators: TLInstancePresence[] = []
 
-	canvasScreenBounds = new Box()
+		return {
-	canvasPageBounds = new Box()
+			shapeFill: getRgba(style.getPropertyValue('--color-text-3').trim()),
+			selectFill: getRgba(style.getPropertyValue('--color-selected').trim()),
+			viewportFill: getRgba(style.getPropertyValue('--color-muted-1').trim()),
+		}
+	}
 
-	contentPageBounds = new Box()
+	private colors: ReturnType<MinimapManager['_getColors']>
-	contentScreenBounds = new Box()
+	// this should be called after dark/light mode changes have propagated to the dom
+	updateColors() {
+		this.colors = this._getColors()
+	}
+
+	readonly id = uniqueId()
+	@computed
+	getDpr() {
+		return this.editor.getInstanceState().devicePixelRatio
+	}
+
+	@computed
+	getContentPageBounds() {
+		const viewportPageBounds = this.editor.getViewportPageBounds()
+		const commonShapeBounds = this.editor.getCurrentPageBounds()
+		return commonShapeBounds
+			? Box.Expand(commonShapeBounds, viewportPageBounds)
+			: viewportPageBounds
+	}
+
+	@computed
+	getContentScreenBounds() {
+		const contentPageBounds = this.getContentPageBounds()
+		const topLeft = this.editor.pageToScreen(contentPageBounds.point)
+		const bottomRight = this.editor.pageToScreen(
+			new Vec(contentPageBounds.maxX, contentPageBounds.maxY)
+		)
+		return new Box(topLeft.x, topLeft.y, bottomRight.x - topLeft.x, bottomRight.y - topLeft.y)
+	}
+
+	private _getCanvasBoundingRect() {
+		const { x, y, width, height } = this.elem.getBoundingClientRect()
+		return new Box(x, y, width, height)
+	}
+
+	private readonly canvasBoundingClientRect = atom('canvasBoundingClientRect', new Box())
+
+	getCanvasScreenBounds() {
+		return this.canvasBoundingClientRect.get()
+	}
+
+	private _listenForCanvasResize() {
+		const observer = new ResizeObserver(() => {
+			const rect = this._getCanvasBoundingRect()
+			this.canvasBoundingClientRect.set(rect)
+		})
+		observer.observe(this.elem)
+		return () => observer.disconnect()
+	}
+
+	@computed
+	getCanvasSize() {
+		const rect = this.canvasBoundingClientRect.get()
+		const dpr = this.getDpr()
+		return new Vec(rect.width * dpr, rect.height * dpr)
+	}
+
+	@computed
+	getCanvasClientPosition() {
+		return this.canvasBoundingClientRect.get().point
+	}
 
 	originPagePoint = new Vec()
 	originPageCenter = new Vec()
 
 	isInViewport = false
 
-	debug = false
-
-	setDpr(dpr: number) {
-		this.dpr = +dpr.toFixed(2)
-	}
-
-	updateContentScreenBounds = () => {
-		const { contentScreenBounds, contentPageBounds: content, canvasScreenBounds: canvas } = this
-
-		let { x, y, w, h } = contentScreenBounds
-
-		if (content.w > content.h) {
-			const sh = canvas.w / (content.w / content.h)
-			if (sh > canvas.h) {
-				x = (canvas.w - canvas.w * (canvas.h / sh)) / 2
-				y = 0
-				w = canvas.w * (canvas.h / sh)
-				h = canvas.h
-			} else {
-				x = 0
-				y = (canvas.h - sh) / 2
-				w = canvas.w
-				h = sh
-			}
-		} else if (content.w < content.h) {
-			const sw = canvas.h / (content.h / content.w)
-			x = (canvas.w - sw) / 2
-			y = 0
-			w = sw
-			h = canvas.h
-		} else {
-			x = canvas.h / 2
-			y = 0
-			w = canvas.h
-			h = canvas.h
-		}
-
-		contentScreenBounds.set(x, y, w, h)
-	}
-
 	/** Get the canvas's true bounds converted to page bounds. */
-	updateCanvasPageBounds = () => {
+	@computed getCanvasPageBounds() {
-		const { canvasPageBounds, canvasScreenBounds, contentPageBounds, contentScreenBounds } = this
+		const canvasScreenBounds = this.getCanvasScreenBounds()
+		const contentPageBounds = this.getContentPageBounds()
 
-		canvasPageBounds.set(
+		const aspectRatio = canvasScreenBounds.width / canvasScreenBounds.height
-			0,
-			0,
-			contentPageBounds.width / (contentScreenBounds.width / canvasScreenBounds.width),
-			contentPageBounds.height / (contentScreenBounds.height / canvasScreenBounds.height)
-		)
 
-		canvasPageBounds.center = contentPageBounds.center
+		let targetWidth = contentPageBounds.width
+		let targetHeight = targetWidth / aspectRatio
+		if (targetHeight < contentPageBounds.height) {
+			targetHeight = contentPageBounds.height
+			targetWidth = targetHeight * aspectRatio
 		}
 
-	getScreenPoint = (x: number, y: number) => {
+		const box = new Box(0, 0, targetWidth, targetHeight)
-		const { canvasScreenBounds } = this
+		box.center = contentPageBounds.center
-
+		return box
-		const screenX = (x - canvasScreenBounds.minX) * this.dpr
-		const screenY = (y - canvasScreenBounds.minY) * this.dpr
-
-		return { x: screenX, y: screenY }
 	}
 
-	getPagePoint = (x: number, y: number) => {
+	@computed getCanvasPageBoundsArray() {
-		const { contentPageBounds, contentScreenBounds, canvasPageBounds } = this
+		const { x, y, w, h } = this.getCanvasPageBounds()
+		return new Float32Array([x, y, w, h])
+	}
 
-		const { x: screenX, y: screenY } = this.getScreenPoint(x, y)
+	getPagePoint = (clientX: number, clientY: number) => {
+		const canvasPageBounds = this.getCanvasPageBounds()
+		const canvasScreenBounds = this.getCanvasScreenBounds()
 
-		return new Vec(
+		// first offset the canvas position
-			canvasPageBounds.minX + (screenX * contentPageBounds.width) / contentScreenBounds.width,
+		let x = clientX - canvasScreenBounds.x
-			canvasPageBounds.minY + (screenY * contentPageBounds.height) / contentScreenBounds.height,
+		let y = clientY - canvasScreenBounds.y
-			1
+
-		)
+		// then multiply by the ratio between the page and screen bounds
+		x *= canvasPageBounds.width / canvasScreenBounds.width
+		y *= canvasPageBounds.height / canvasScreenBounds.height
+
+		// then add the canvas page bounds' offset
+		x += canvasPageBounds.minX
+		y += canvasPageBounds.minY
+
+		return new Vec(x, y, 1)
 	}
 
 	minimapScreenPointToPagePoint = (
@@ -123,13 +168,13 @@ export class MinimapManager {
 		let { x: px, y: py } = this.getPagePoint(x, y)
 
 		if (clampToBounds) {
-			const shapesPageBounds = this.editor.getCurrentPageBounds()
+			const shapesPageBounds = this.editor.getCurrentPageBounds() ?? new Box()
 			const vpPageBounds = viewportPageBounds
 
-			const minX = (shapesPageBounds?.minX ?? 0) - vpPageBounds.width / 2
+			const minX = shapesPageBounds.minX - vpPageBounds.width / 2
-			const maxX = (shapesPageBounds?.maxX ?? 0) + vpPageBounds.width / 2
+			const maxX = shapesPageBounds.maxX + vpPageBounds.width / 2
-			const minY = (shapesPageBounds?.minY ?? 0) - vpPageBounds.height / 2
+			const minY = shapesPageBounds.minY - vpPageBounds.height / 2
-			const maxY = (shapesPageBounds?.maxY ?? 0) + vpPageBounds.height / 2
+			const maxY = shapesPageBounds.maxY + vpPageBounds.height / 2
 
 			const lx = Math.max(0, minX + vpPageBounds.width - px)
 			const rx = Math.max(0, -(maxX - vpPageBounds.width - px))
@@ -171,209 +216,110 @@ export class MinimapManager {
 		return new Vec(px, py)
 	}
 
-	updateColors = () => {
-		const style = getComputedStyle(this.editor.getContainer())
-
-		this.colors = {
-			shapeFill: style.getPropertyValue('--color-text-3').trim(),
-			selectFill: style.getPropertyValue('--color-selected').trim(),
-			viewportFill: style.getPropertyValue('--color-muted-1').trim(),
-		}
-	}
-
 	render = () => {
-		const { cvs, pageBounds } = this
+		// make sure we update when dark mode switches
-		this.updateCanvasPageBounds()
+		const context = this.gl.context
+		const canvasSize = this.getCanvasSize()
 
-		const { editor, canvasScreenBounds, canvasPageBounds, contentPageBounds, contentScreenBounds } =
+		this.gl.setCanvasPageBounds(this.getCanvasPageBoundsArray())
-			this
-		const { width: cw, height: ch } = canvasScreenBounds
 
-		const selectedShapeIds = new Set(editor.getSelectedShapeIds())
+		this.elem.width = canvasSize.x
-		const viewportPageBounds = editor.getViewportPageBounds()
+		this.elem.height = canvasSize.y
+		context.viewport(0, 0, canvasSize.x, canvasSize.y)
 
-		if (!cvs || !pageBounds) {
+		// this affects which color transparent shapes are blended with
-			return
+		// during rendering. If we were to invert this any shapes narrower
+		// than 1 px in screen space would have much lower contrast. e.g.
+		// draw shapes on a large canvas.
+		if (this.editor.user.getIsDarkMode()) {
+			context.clearColor(1, 1, 1, 0)
+		} else {
+			context.clearColor(0, 0, 0, 0)
 		}
 
-		const ctx = cvs.getContext('2d')!
+		context.clear(context.COLOR_BUFFER_BIT)
 
-		if (!ctx) {
+		const selectedShapes = new Set(this.editor.getSelectedShapeIds())
-			throw new Error('Minimap (shapes): Could not get context')
-		}
 
-		ctx.resetTransform()
+		const colors = this.colors
-		ctx.globalAlpha = 1
+		let selectedShapeOffset = 0
-		ctx.clearRect(0, 0, cw, ch)
+		let unselectedShapeOffset = 0
 
-		// Transform canvas
+		const ids = this.editor.getCurrentPageShapeIdsSorted()
 
-		const sx = contentScreenBounds.width / contentPageBounds.width
+		for (let i = 0, len = ids.length; i < len; i++) {
-		const sy = contentScreenBounds.height / contentPageBounds.height
+			const shapeId = ids[i]
+			const geometry = this.shapeGeometryCache.get(shapeId)
+			if (!geometry) continue
 
-		ctx.translate((cw - contentScreenBounds.width) / 2, (ch - contentScreenBounds.height) / 2)
+			const len = geometry.length
-		ctx.scale(sx, sy)
-		ctx.translate(-contentPageBounds.minX, -contentPageBounds.minY)
 
-		// shapes
+			if (selectedShapes.has(shapeId)) {
-		const shapesPath = new Path2D()
+				appendVertices(this.gl.selectedShapes, selectedShapeOffset, geometry)
-		const selectedPath = new Path2D()
+				selectedShapeOffset += len
-
+			} else {
-		const { shapeFill, selectFill, viewportFill } = this.colors
+				appendVertices(this.gl.unselectedShapes, unselectedShapeOffset, geometry)
-
+				unselectedShapeOffset += len
-		// When there are many shapes, don't draw rounded rectangles;
-		// consider using the shape's size instead.
-
-		let pb: Box & { id: TLShapeId }
-		for (let i = 0, n = pageBounds.length; i < n; i++) {
-			pb = pageBounds[i]
-			;(selectedShapeIds.has(pb.id) ? selectedPath : shapesPath).rect(
-				pb.minX,
-				pb.minY,
-				pb.width,
-				pb.height
-			)
-		}
-
-		// Fill the shapes paths
-		ctx.fillStyle = shapeFill
-		ctx.fill(shapesPath)
-
-		// Fill the selected paths
-		ctx.fillStyle = selectFill
-		ctx.fill(selectedPath)
-
-		if (this.debug) {
-			// Page bounds
-			const commonBounds = Box.Common(pageBounds)
-			const { minX, minY, width, height } = commonBounds
-			ctx.strokeStyle = 'green'
-			ctx.lineWidth = 2 / sx
-			ctx.strokeRect(minX + 1 / sx, minY + 1 / sy, width - 2 / sx, height - 2 / sy)
-		}
-
-		// Brush
-		{
-			const { brush } = editor.getInstanceState()
-			if (brush) {
-				const { x, y, w, h } = brush
-				ctx.beginPath()
-				MinimapManager.sharpRect(ctx, x, y, w, h)
-				ctx.closePath()
-				ctx.fillStyle = viewportFill
-				ctx.fill()
 			}
 		}
 
-		// Viewport
+		this.drawViewport()
-		{
+		this.drawShapes(this.gl.unselectedShapes, unselectedShapeOffset, colors.shapeFill)
-			const { minX, minY, width, height } = viewportPageBounds
+		this.drawShapes(this.gl.selectedShapes, selectedShapeOffset, colors.selectFill)
-
+		this.drawCollaborators()
-			ctx.beginPath()
-
-			const rx = 12 / sx
-			const ry = 12 / sx
-			MinimapManager.roundedRect(
-				ctx,
-				minX,
-				minY,
-				width,
-				height,
-				Math.min(width / 4, rx),
-				Math.min(height / 4, ry)
-			)
-			ctx.closePath()
-			ctx.fillStyle = viewportFill
-			ctx.fill()
-
-			if (this.debug) {
-				ctx.strokeStyle = 'orange'
-				ctx.strokeRect(minX + 1 / sx, minY + 1 / sy, width - 2 / sx, height - 2 / sy)
-			}
 	}
 
-		// Show collaborator cursors
+	private drawShapes(stuff: BufferStuff, len: number, color: Float32Array) {
-
+		this.gl.prepareTriangles(stuff, len)
-		// Padding for canvas bounds edges
+		this.gl.setFillColor(color)
-		const px = 2.5 / sx
+		this.gl.drawTriangles(len)
-		const py = 2.5 / sy
-
-		const currentPageId = editor.getCurrentPageId()
-
-		let collaborator: TLInstancePresence
-		for (let i = 0; i < this.collaborators.length; i++) {
-			collaborator = this.collaborators[i]
-			if (collaborator.currentPageId !== currentPageId) {
-				continue
 	}
 
-			ctx.beginPath()
+	private drawViewport() {
-			ctx.ellipse(
+		const viewport = this.editor.getViewportPageBounds()
-				clamp(collaborator.cursor.x, canvasPageBounds.minX + px, canvasPageBounds.maxX - px),
+		const zoom = this.getCanvasPageBounds().width / this.getCanvasScreenBounds().width
-				clamp(collaborator.cursor.y, canvasPageBounds.minY + py, canvasPageBounds.maxY - py),
+		const len = roundedRectangle(this.gl.viewport.vertices, viewport, 4 * zoom)
-				5 / sx,
+
-				5 / sy,
+		this.gl.prepareTriangles(this.gl.viewport, len)
-				0,
+		this.gl.setFillColor(this.colors.viewportFill)
-				0,
+		this.gl.drawTriangles(len)
-				PI2
-			)
-			ctx.fillStyle = collaborator.color
-			ctx.fill()
 	}
 
-		if (this.debug) {
+	drawCollaborators() {
-			ctx.lineWidth = 2 / sx
+		const collaborators = this.editor.getCollaboratorsOnCurrentPage()
+		if (!collaborators.length) return
 
-			{
+		const zoom = this.getCanvasPageBounds().width / this.getCanvasScreenBounds().width
-				// Minimap Bounds
+
-				const { minX, minY, width, height } = contentPageBounds
+		// just draw a little circle for each collaborator
-				ctx.strokeStyle = 'red'
+		const numSegmentsPerCircle = 20
-				ctx.strokeRect(minX + 1 / sx, minY + 1 / sy, width - 2 / sx, height - 2 / sy)
+		const dataSizePerCircle = numSegmentsPerCircle * 6
+		const totalSize = dataSizePerCircle * collaborators.length
+
+		// expand vertex array if needed
+		if (this.gl.collaborators.vertices.length < totalSize) {
+			this.gl.collaborators.vertices = new Float32Array(totalSize)
 		}
 
-			{
+		const vertices = this.gl.collaborators.vertices
-				// Canvas Bounds
+		let offset = 0
-				const { minX, minY, width, height } = canvasPageBounds
+		for (const { cursor } of collaborators) {
-				ctx.strokeStyle = 'blue'
+			pie(vertices, {
-				ctx.strokeRect(minX + 1 / sx, minY + 1 / sy, width - 2 / sx, height - 2 / sy)
+				center: Vec.From(cursor),
+				radius: 2 * zoom,
+				offset,
+				numArcSegments: numSegmentsPerCircle,
+			})
+			offset += dataSizePerCircle
+		}
+
+		this.gl.prepareTriangles(this.gl.collaborators, totalSize)
+
+		offset = 0
+		for (const { color } of collaborators) {
+			this.gl.setFillColor(getRgba(color))
+			this.gl.context.drawArrays(this.gl.context.TRIANGLES, offset / 2, dataSizePerCircle / 2)
+			offset += dataSizePerCircle
 		}
 	}
 }
-
-	static roundedRect(
-		ctx: CanvasRenderingContext2D | Path2D,
-		x: number,
-		y: number,
-		width: number,
-		height: number,
-		rx: number,
-		ry: number
-	) {
-		if (rx < 1 && ry < 1) {
-			ctx.rect(x, y, width, height)
-			return
-		}
-
-		ctx.moveTo(x + rx, y)
-		ctx.lineTo(x + width - rx, y)
-		ctx.quadraticCurveTo(x + width, y, x + width, y + ry)
-		ctx.lineTo(x + width, y + height - ry)
-		ctx.quadraticCurveTo(x + width, y + height, x + width - rx, y + height)
-		ctx.lineTo(x + rx, y + height)
-		ctx.quadraticCurveTo(x, y + height, x, y + height - ry)
-		ctx.lineTo(x, y + ry)
-		ctx.quadraticCurveTo(x, y, x + rx, y)
-	}
-
-	static sharpRect(
-		ctx: CanvasRenderingContext2D | Path2D,
-		x: number,
-		y: number,
-		width: number,
-		height: number,
-		_rx?: number,
-		_ry?: number
-	) {
-		ctx.rect(x, y, width, height)
-	}
-}

packages/tldraw/src/lib/ui/components/Minimap/getRgba.ts

@@ -0,0 +1,16 @@
+const memo = {} as Record<string, Float32Array>
+
+export function getRgba(colorString: string) {
+	if (memo[colorString]) {
+		return memo[colorString]
+	}
+	const canvas = document.createElement('canvas')
+	const context = canvas.getContext('2d')
+	context!.fillStyle = colorString
+	context!.fillRect(0, 0, 1, 1)
+	const [r, g, b, a] = context!.getImageData(0, 0, 1, 1).data
+	const result = new Float32Array([r / 255, g / 255, b / 255, a / 255])
+
+	memo[colorString] = result
+	return result
+}

packages/tldraw/src/lib/ui/components/Minimap/minimap-webgl-setup.ts

@@ -0,0 +1,148 @@
+import { roundedRectangleDataSize } from './minimap-webgl-shapes'
+
+export function setupWebGl(canvas: HTMLCanvasElement | null) {
+	if (!canvas) throw new Error('Canvas element not found')
+
+	const context = canvas.getContext('webgl2', {
+		premultipliedAlpha: false,
+	})
+	if (!context) throw new Error('Failed to get webgl2 context')
+
+	const vertexShaderSourceCode = `#version 300 es
+  precision mediump float;
+  
+  in vec2 shapeVertexPosition;
+
+	uniform vec4 canvasPageBounds;
+
+	// taken (with thanks) from
+	// https://webglfundamentals.org/webgl/lessons/webgl-2d-matrices.html
+  void main() {
+		// convert the position from pixels to 0.0 to 1.0
+		vec2 zeroToOne = (shapeVertexPosition - canvasPageBounds.xy) / canvasPageBounds.zw;
+	
+		// convert from 0->1 to 0->2
+		vec2 zeroToTwo = zeroToOne * 2.0;
+	
+		// convert from 0->2 to -1->+1 (clipspace)
+		vec2 clipSpace = zeroToTwo - 1.0;
+	
+		gl_Position = vec4(clipSpace * vec2(1, -1), 0, 1);
+  }`
+
+	const vertexShader = context.createShader(context.VERTEX_SHADER)
+	if (!vertexShader) {
+		throw new Error('Failed to create vertex shader')
+	}
+	context.shaderSource(vertexShader, vertexShaderSourceCode)
+	context.compileShader(vertexShader)
+	if (!context.getShaderParameter(vertexShader, context.COMPILE_STATUS)) {
+		throw new Error('Failed to compile vertex shader')
+	}
+
+	const fragmentShaderSourceCode = `#version 300 es
+  precision mediump float;
+  
+	uniform vec4 fillColor;
+  out vec4 outputColor;
+
+  void main() {
+	outputColor = fillColor;
+  }`
+
+	const fragmentShader = context.createShader(context.FRAGMENT_SHADER)
+	if (!fragmentShader) {
+		throw new Error('Failed to create fragment shader')
+	}
+	context.shaderSource(fragmentShader, fragmentShaderSourceCode)
+	context.compileShader(fragmentShader)
+	if (!context.getShaderParameter(fragmentShader, context.COMPILE_STATUS)) {
+		throw new Error('Failed to compile fragment shader')
+	}
+
+	const program = context.createProgram()
+	if (!program) {
+		throw new Error('Failed to create program')
+	}
+	context.attachShader(program, vertexShader)
+	context.attachShader(program, fragmentShader)
+	context.linkProgram(program)
+	if (!context.getProgramParameter(program, context.LINK_STATUS)) {
+		throw new Error('Failed to link program')
+	}
+	context.useProgram(program)
+
+	const shapeVertexPositionAttributeLocation = context.getAttribLocation(
+		program,
+		'shapeVertexPosition'
+	)
+	if (shapeVertexPositionAttributeLocation < 0) {
+		throw new Error('Failed to get shapeVertexPosition attribute location')
+	}
+	context.enableVertexAttribArray(shapeVertexPositionAttributeLocation)
+
+	const canvasPageBoundsLocation = context.getUniformLocation(program, 'canvasPageBounds')
+	const fillColorLocation = context.getUniformLocation(program, 'fillColor')
+
+	const selectedShapesBuffer = context.createBuffer()
+	if (!selectedShapesBuffer) throw new Error('Failed to create buffer')
+
+	const unselectedShapesBuffer = context.createBuffer()
+	if (!unselectedShapesBuffer) throw new Error('Failed to create buffer')
+
+	return {
+		context,
+		selectedShapes: allocateBuffer(context, 1024),
+		unselectedShapes: allocateBuffer(context, 4096),
+		viewport: allocateBuffer(context, roundedRectangleDataSize),
+		collaborators: allocateBuffer(context, 1024),
+
+		prepareTriangles(stuff: BufferStuff, len: number) {
+			context.bindBuffer(context.ARRAY_BUFFER, stuff.buffer)
+			context.bufferData(context.ARRAY_BUFFER, stuff.vertices, context.STATIC_DRAW, 0, len)
+			context.enableVertexAttribArray(shapeVertexPositionAttributeLocation)
+			context.vertexAttribPointer(
+				shapeVertexPositionAttributeLocation,
+				2,
+				context.FLOAT,
+				false,
+				0,
+				0
+			)
+		},
+
+		drawTriangles(len: number) {
+			context.drawArrays(context.TRIANGLES, 0, len / 2)
+		},
+
+		setFillColor(color: Float32Array) {
+			context.uniform4fv(fillColorLocation, color)
+		},
+
+		setCanvasPageBounds(bounds: Float32Array) {
+			context.uniform4fv(canvasPageBoundsLocation, bounds)
+		},
+	}
+}
+
+export type BufferStuff = ReturnType<typeof allocateBuffer>
+
+function allocateBuffer(context: WebGL2RenderingContext, size: number) {
+	const buffer = context.createBuffer()
+	if (!buffer) throw new Error('Failed to create buffer')
+	return { buffer, vertices: new Float32Array(size) }
+}
+
+export function appendVertices(bufferStuff: BufferStuff, offset: number, data: Float32Array) {
+	let len = bufferStuff.vertices.length
+	while (len < offset + data.length) {
+		len *= 2
+	}
+	if (len != bufferStuff.vertices.length) {
+		const newVertices = new Float32Array(len)
+		newVertices.set(bufferStuff.vertices)
+		bufferStuff.vertices = newVertices
+	}
+
+	bufferStuff.vertices.set(data, offset)
+}

packages/tldraw/src/lib/ui/components/Minimap/minimap-webgl-shapes.ts

@@ -0,0 +1,144 @@
+import { Box, HALF_PI, PI, PI2, Vec } from '@tldraw/editor'
+
+export const numArcSegmentsPerCorner = 10
+
+export const roundedRectangleDataSize =
+	// num triangles in corners
+	4 * 6 * numArcSegmentsPerCorner +
+	// num triangles in center rect
+	12 +
+	// num triangles in outer rects
+	4 * 12
+
+export function pie(
+	array: Float32Array,
+	{
+		center,
+		radius,
+		numArcSegments = 20,
+		startAngle = 0,
+		endAngle = PI2,
+		offset = 0,
+	}: {
+		center: Vec
+		radius: number
+		numArcSegments?: number
+		startAngle?: number
+		endAngle?: number
+		offset?: number
+	}
+) {
+	const angle = (endAngle - startAngle) / numArcSegments
+	let i = offset
+	for (let a = startAngle; a < endAngle; a += angle) {
+		array[i++] = center.x
+		array[i++] = center.y
+		array[i++] = center.x + Math.cos(a) * radius
+		array[i++] = center.y + Math.sin(a) * radius
+		array[i++] = center.x + Math.cos(a + angle) * radius
+		array[i++] = center.y + Math.sin(a + angle) * radius
+	}
+	return array
+}
+
+/** @internal **/
+export function rectangle(
+	array: Float32Array,
+	offset: number,
+	x: number,
+	y: number,
+	w: number,
+	h: number
+) {
+	array[offset++] = x
+	array[offset++] = y
+	array[offset++] = x
+	array[offset++] = y + h
+	array[offset++] = x + w
+	array[offset++] = y
+
+	array[offset++] = x + w
+	array[offset++] = y
+	array[offset++] = x
+	array[offset++] = y + h
+	array[offset++] = x + w
+	array[offset++] = y + h
+}
+
+export function roundedRectangle(data: Float32Array, box: Box, radius: number): number {
+	const numArcSegments = numArcSegmentsPerCorner
+	radius = Math.min(radius, Math.min(box.w, box.h) / 2)
+	// first draw the inner box
+	const innerBox = Box.ExpandBy(box, -radius)
+	if (innerBox.w <= 0 || innerBox.h <= 0) {
+		// just draw a circle
+		pie(data, { center: box.center, radius: radius, numArcSegments: numArcSegmentsPerCorner * 4 })
+		return numArcSegmentsPerCorner * 4 * 6
+	}
+	let offset = 0
+	// draw center rect first
+	rectangle(data, offset, innerBox.minX, innerBox.minY, innerBox.w, innerBox.h)
+	offset += 12
+	// then top rect
+	rectangle(data, offset, innerBox.minX, box.minY, innerBox.w, radius)
+	offset += 12
+	// then right rect
+	rectangle(data, offset, innerBox.maxX, innerBox.minY, radius, innerBox.h)
+	offset += 12
+	// then bottom rect
+	rectangle(data, offset, innerBox.minX, innerBox.maxY, innerBox.w, radius)
+	offset += 12
+	// then left rect
+	rectangle(data, offset, box.minX, innerBox.minY, radius, innerBox.h)
+	offset += 12
+
+	// draw the corners
+
+	// top left
+	pie(data, {
+		numArcSegments,
+		offset,
+		center: innerBox.point,
+		radius,
+		startAngle: PI,
+		endAngle: PI * 1.5,
+	})
+
+	offset += numArcSegments * 6
+
+	// top right
+	pie(data, {
+		numArcSegments,
+		offset,
+		center: Vec.Add(innerBox.point, new Vec(innerBox.w, 0)),
+		radius,
+		startAngle: PI * 1.5,
+		endAngle: PI2,
+	})
+
+	offset += numArcSegments * 6
+
+	// bottom right
+	pie(data, {
+		numArcSegments,
+		offset,
+		center: Vec.Add(innerBox.point, innerBox.size),
+		radius,
+		startAngle: 0,
+		endAngle: HALF_PI,
+	})
+
+	offset += numArcSegments * 6
+
+	// bottom left
+	pie(data, {
+		numArcSegments,
+		offset,
+		center: Vec.Add(innerBox.point, new Vec(0, innerBox.h)),
+		radius,
+		startAngle: HALF_PI,
+		endAngle: PI,
+	})
+
+	return roundedRectangleDataSize
+}