@ue-too/board / index / Board

Class: Board

Defined in: packages/board/src/boardify/index.ts:233

Main user-facing API class that provides an infinite canvas with pan, zoom, and rotate capabilities.

The Board class is the primary entry point for using the board package. It integrates all subsystems including camera management, input handling, and state machines into a simple, unified API for creating interactive 2D canvases with advanced camera controls.

Remarks

Architecture Overview

The Board class orchestrates several subsystems:

• Camera System: Manages viewport transformations (pan/zoom/rotate) through ObservableBoardCamera. The camera can be configured with boundaries, zoom limits, and various movement constraints.

• Input System: Processes user input through state machines for both mouse/keyboard/trackpad (KMT) and touch events. Input is parsed, interpreted, and translated into camera movements.

• Camera Rig: Enforces constraints and restrictions on camera movement (boundaries, zoom limits, clamping behavior). See CameraRig for details.

• Camera Multiplexer: Coordinates between different camera control sources (user input, animations, programmatic control) to ensure smooth transitions. See CameraMux for details.

Coordinate Systems

The Board supports three coordinate systems:

1. World Coordinates: The infinite canvas space where your content lives. When the camera is at position (0, 0) with no zoom or rotation, world coordinates map directly to viewport coordinates.

2. Viewport Coordinates: The visible area of the canvas relative to the camera center. The camera center is at (0, 0) in viewport space, with coordinates extending in both directions based on the canvas size.

3. Window/Canvas Coordinates: The browser's coordinate system, with (0, 0) at the top-left corner of the canvas element. Use convertWindowPoint2WorldCoord to convert from window to world space.

By default, alignCoordinateSystem is true, which means the Y-axis points down (standard HTML canvas orientation). Set it to false to use a mathematical coordinate system where Y points up.

Main Features

• Camera Control: Pan, zoom, and rotate the viewport through user input or programmatic API
• Boundaries: Define world-space boundaries to constrain camera movement
• Zoom Limits: Set minimum and maximum zoom levels
• Input Modes: Support for mouse/keyboard/trackpad and touch input with customizable parsers
• Event System: Subscribe to camera events (pan, zoom, rotate) and input events
• Coordinate Conversion: Convert between window and world coordinates
• Flexible Configuration: Extensive options for restricting/clamping camera movement

Examples

Basic setup with drawing

const canvasElement = document.querySelector("canvas") as HTMLCanvasElement;
const board = new Board(canvasElement);

function draw(timestamp: number) {
  board.step(timestamp);

  // Because board can be initialized without a canvas element,
  // the context can be undefined until the canvas is attached
  if(board.context == undefined) {
    return;
  }

  // Draw after the board has stepped
  // The coordinate system has (0, 0) at the center of the canvas when camera position is at (0, 0)
  board.context.beginPath();
  board.context.rect(0, 0, 100, 100);
  board.context.fill();

  requestAnimationFrame(draw);
}

requestAnimationFrame(draw);

Handling camera and input events

const board = new Board(canvasElement);

// Listen to camera pan events
board.on('pan', (event, cameraState) => {
  console.log('Camera panned to:', cameraState.position);
});

// Listen to camera zoom events
board.on('zoom', (event, cameraState) => {
  console.log('Camera zoom level:', cameraState.zoomLevel);
});

// Listen to raw input events (before camera movement)
board.onInput('pan', (event) => {
  console.log('User is panning');
});

Configuring boundaries and zoom limits

const board = new Board(canvasElement);

// Set world boundaries
board.camera.boundaries = {
  min: { x: -1000, y: -1000 },
  max: { x: 1000, y: 1000 }
};

// Set zoom limits
board.camera.setMinZoomLevel(0.1);
board.camera.setMaxZoomLevel(5.0);

// Ensure entire viewport stays within boundaries
board.limitEntireViewPort = true;

// Clamp camera position to boundaries
board.clampTranslation = true;
board.clampZoom = true;

Converting window coordinates to world coordinates

const board = new Board(canvasElement);

canvasElement.addEventListener('click', (event) => {
  const windowPoint = { x: event.clientX, y: event.clientY };
  const worldPoint = board.convertWindowPoint2WorldCoord(windowPoint);
  console.log('Clicked at world position:', worldPoint);
});

Initialize board without canvas, attach canvas later

const board = new Board();

// Attach canvas later
const canvasElement = document.createElement('canvas');
document.body.appendChild(canvasElement);
board.attach(canvasElement);

See

• ObservableBoardCamera for camera API details
• CameraRig for camera constraint configuration
• CameraMux for camera control coordination

Accessors

alignCoordinateSystem

Get Signature

get alignCoordinateSystem(): boolean

Defined in: packages/board/src/boardify/index.ts:558

Returns

boolean

Set Signature

set alignCoordinateSystem(align): void

Defined in: packages/board/src/boardify/index.ts:552

Description

This is an attribute that determines if the coordinate system should be aligned with the one of the HTML canvas element. The default is true. If you set this to true, the coordinate system will be aligned with the one of the HTML canvas element. If you change this value during runtime, you should update the context to be aligned with the new coordinate system. (just call board.context again)

Parameters

align

boolean

Returns

void

---

camera

Get Signature

get camera(): ObservableBoardCamera

Defined in: packages/board/src/boardify/index.ts:707

Description

The underlying camera of the board. The camera of the board can be switched. The boundaries are based on camera meaning you can have cameras with different boundaries, and you can switch between them during runtime.

Returns

ObservableBoardCamera

Set Signature

set camera(camera): void

Defined in: packages/board/src/boardify/index.ts:711

Parameters

camera

ObservableBoardCamera

Returns

void

---

cameraMux

Get Signature

get cameraMux(): CameraMux

Defined in: packages/board/src/boardify/index.ts:721

Returns

CameraMux

Set Signature

set cameraMux(cameraMux): void

Defined in: packages/board/src/boardify/index.ts:725

Parameters

cameraMux

CameraMux

Returns

void

---

canvasDimensions

Get Signature

get canvasDimensions(): CanvasDimensions

Defined in: packages/board/src/boardify/index.ts:1069

Returns

CanvasDimensions

---

clampRotation

Get Signature

get clampRotation(): boolean

Defined in: packages/board/src/boardify/index.ts:1014

Returns

boolean

Set Signature

set clampRotation(value): void

Defined in: packages/board/src/boardify/index.ts:1018

Parameters

value

boolean

Returns

void

---

clampTranslation

Get Signature

get clampTranslation(): boolean

Defined in: packages/board/src/boardify/index.ts:998

Returns

boolean

Set Signature

set clampTranslation(value): void

Defined in: packages/board/src/boardify/index.ts:1002

Parameters

value

boolean

Returns

void

---

clampZoom

Get Signature

get clampZoom(): boolean

Defined in: packages/board/src/boardify/index.ts:1006

Returns

boolean

Set Signature

set clampZoom(value): void

Defined in: packages/board/src/boardify/index.ts:1010

Parameters

value

boolean

Returns

void

---

context

Get Signature

get context(): CanvasRenderingContext2D | undefined

Defined in: packages/board/src/boardify/index.ts:582

Description

The context used to draw on the canvas. If alignCoordinateSystem is false, this returns a proxy that automatically negates y-coordinates for relevant drawing methods.

Returns

CanvasRenderingContext2D | undefined

---

fullScreen

Get Signature

get fullScreen(): boolean

Defined in: packages/board/src/boardify/index.ts:566

Description

Determines if the board should be full screen. If this is set to true, the width and height of the board will be set to the window's inner width and inner height respectively, and the width and height of the board will resize with the window.

Returns

boolean

Set Signature

set fullScreen(value): void

Defined in: packages/board/src/boardify/index.ts:570

Parameters

value

boolean

Returns

void

---

height

Get Signature

get height(): number

Defined in: packages/board/src/boardify/index.ts:543

Returns

number

---

inputMode

Get Signature

get inputMode(): "kmt" | "trackpad" | "TBD"

Defined in: packages/board/src/boardify/index.ts:1036

The current input modality.

Returns

"kmt" | "trackpad" | "TBD"

'kmt' (keyboard-mouse), 'trackpad', or 'TBD' when auto-detection is active and has not yet committed to a mode.

---

inputOrchestrator

Get Signature

get inputOrchestrator(): InputOrchestrator

Defined in: packages/board/src/boardify/index.ts:518

Returns

InputOrchestrator

---

kmtInputStateMachine

Get Signature

get kmtInputStateMachine(): KmtInputStateMachine | undefined

Defined in: packages/board/src/boardify/index.ts:648

The keyboard/mouse/trackpad input state machine currently driving the board, read from the active parser so it stays correct after a kmtParser swap.

Remarks

Intended for tooling/introspection — a visualizer reading currentState and context, for instance. Drive the board through real input or through the parser, not by dispatching here, and never call wrapup() on it: that parks the machine in TERMINAL and the board stops responding to all input.

KMTEventParser.stateMachine is only typed for the minimal { happens } contract the parser itself needs, so a custom parser can install a stateMachine that satisfies that contract without being a real being state machine. This getter structurally checks for the being StateMachine surface and returns undefined rather than handing back something that doesn't actually have currentState or onStateChange.

Returns

KmtInputStateMachine | undefined

The machine, or undefined when a custom parser does not expose one.

---

kmtParser

Get Signature

get kmtParser(): KMTEventParser

Defined in: packages/board/src/boardify/index.ts:621

Returns

KMTEventParser

Set Signature

set kmtParser(parser): void

Defined in: packages/board/src/boardify/index.ts:611

Description

The strategy used to handle the keyboard, mouse events. The default strategy is the DefaultBoardKMTStrategy. You can implement your own strategy by implementing the BoardKMTStrategy interface.

Parameters

parser

KMTEventParser

Returns

void

---

limitEntireViewPort

Get Signature

get limitEntireViewPort(): boolean

Defined in: packages/board/src/boardify/index.ts:603

Returns

boolean

Set Signature

set limitEntireViewPort(value): void

Defined in: packages/board/src/boardify/index.ts:593

Description

Determines the behavior of the camera when the camera is at the edge of the boundaries. If set to true, the entire view port would not move beyond the boundaries. If set to false, only the center of the camera is bounded by the boundaries.

Parameters

value

boolean

Returns

void

---

maxHalfTransHeight

Get Signature

get maxHalfTransHeight(): number | undefined

Defined in: packages/board/src/boardify/index.ts:849

Description

The max translation height of the camera. This is the maximum distance the camera can move in the vertical direction.

Returns

number | undefined

---

maxHalfTransWidth

Get Signature

get maxHalfTransWidth(): number | undefined

Defined in: packages/board/src/boardify/index.ts:856

Description

The max translation width of the camera. This is the maximum distance the camera can move in the horizontal direction.

Returns

number | undefined

---

restrictRelativeXTranslation

Get Signature

get restrictRelativeXTranslation(): boolean

Defined in: packages/board/src/boardify/index.ts:950

Returns

boolean

Set Signature

set restrictRelativeXTranslation(value): void

Defined in: packages/board/src/boardify/index.ts:966

Parameters

value

boolean

Returns

void

---

restrictRelativeYTranslation

Get Signature

get restrictRelativeYTranslation(): boolean

Defined in: packages/board/src/boardify/index.ts:954

Returns

boolean

Set Signature

set restrictRelativeYTranslation(value): void

Defined in: packages/board/src/boardify/index.ts:970

Parameters

value

boolean

Returns

void

---

restrictRotation

Get Signature

get restrictRotation(): boolean

Defined in: packages/board/src/boardify/index.ts:990

Returns

boolean

Set Signature

set restrictRotation(value): void

Defined in: packages/board/src/boardify/index.ts:994

Parameters

value

boolean

Returns

void

---

restrictXTranslation

Get Signature

get restrictXTranslation(): boolean

Defined in: packages/board/src/boardify/index.ts:958

Returns

boolean

Set Signature

set restrictXTranslation(value): void

Defined in: packages/board/src/boardify/index.ts:974

Parameters

value

boolean

Returns

void

---

restrictYTranslation

Get Signature

get restrictYTranslation(): boolean

Defined in: packages/board/src/boardify/index.ts:962

Returns

boolean

Set Signature

set restrictYTranslation(value): void

Defined in: packages/board/src/boardify/index.ts:978

Parameters

value

boolean

Returns

void

---

restrictZoom

Get Signature

get restrictZoom(): boolean

Defined in: packages/board/src/boardify/index.ts:982

Returns

boolean

Set Signature

set restrictZoom(value): void

Defined in: packages/board/src/boardify/index.ts:986

Parameters

value

boolean

Returns

void

---

touchInputStateMachine

Get Signature

get touchInputStateMachine(): TouchInputStateMachine | undefined

Defined in: packages/board/src/boardify/index.ts:696

The touch input state machine currently driving the board, read from the active parser so it stays correct after a touchParser swap.

Remarks

Intended for tooling/introspection — a visualizer reading currentState and context, for instance. Drive the board through real input or through the parser, not by dispatching here, and never call wrapup() on it: that parks the machine in TERMINAL and the board stops responding to all input.

TouchEventParser.stateMachine is typed to the full TouchInputStateMachine, but a custom parser could still install a value that satisfies that type shape without behaving like a real being state machine at runtime (e.g. across a duck-typed adapter). This getter applies the same structural check as kmtInputStateMachine and returns undefined rather than handing back something that doesn't actually have currentState or onStateChange.

Returns

TouchInputStateMachine | undefined

The machine, or undefined when a custom parser does not expose one.

---

touchParser

Get Signature

get touchParser(): TouchEventParser

Defined in: packages/board/src/boardify/index.ts:669

Returns

TouchEventParser

Set Signature

set touchParser(parser): void

Defined in: packages/board/src/boardify/index.ts:659

Description

The parser used to handle touch events. The default parser is the DefaultTouchParser. You can have your own parser by implementing the BoardTouchParser interface.

Parameters

parser

TouchEventParser

Returns

void

---

width

Get Signature

get width(): number

Defined in: packages/board/src/boardify/index.ts:539

Returns

number

Methods

convertWindowPoint2WorldCoord()

convertWindowPoint2WorldCoord(clickPointInWindow): Point

Defined in: packages/board/src/boardify/index.ts:801

TODO add the option to make the camera position to be at the top left corner of the canvas; or better yet any point in the viewport (within the viewport boundaries)

Parameters

clickPointInWindow

Point

The point in window coordinates to convert.

Returns

Point

The converted point in world coordinates.

Description

Converts a point from window coordinates to world coordinates.

---

disableEventListeners()

disableEventListeners(): void

Defined in: packages/board/src/boardify/index.ts:508

Returns

void

---

enableAutoInputMode()

enableAutoInputMode(): void

Defined in: packages/board/src/boardify/index.ts:1061

Returns the board to auto-detection of input modality after a manual lock set via setInputMode or toggleInputMode.

The mode reverts to 'TBD' until auto-detection commits to a mode.

Returns

void

---

enableEventListeners()

enableEventListeners(): void

Defined in: packages/board/src/boardify/index.ts:513

Returns

void

---

getCameraRig()

getCameraRig(): CameraRig

Defined in: packages/board/src/boardify/index.ts:1022

Returns

CameraRig

---

on()

on<K>(eventName, callback): UnSubscribe

Defined in: packages/board/src/boardify/index.ts:824

Type Parameters

K

K extends keyof CameraEventMap

Parameters

eventName

K

The event name to listen for. The events are "pan", "zoom", and "rotate".

callback

(event, cameraState) => void

The callback function to call when the event is triggered. The event provided to the callback is different for the different events.

Returns

UnSubscribe

The converted point in world coordinates.

Description

Add an camera movement event listener. The events are "pan", "zoom", and "rotate". There's also an "all" event that will be triggered when any of the above events are triggered.

---

onCanvasDimensionChange()

onCanvasDimensionChange(callback): () => void

Defined in: packages/board/src/boardify/index.ts:1065

Parameters

callback

(dimensions) => void

Returns

(): void

Returns

void

---

onInput()

onInput<K>(eventName, callback): UnsubscribeToUserRawInput

Defined in: packages/board/src/boardify/index.ts:839

Type Parameters

K

K extends keyof RawUserInputEventMap

Parameters

eventName

K

callback

(event) => void

Returns

UnsubscribeToUserRawInput

Description

Add an input event listener. The events are "pan", "zoom", and "rotate". This is different from the camera event listener as this is for input events. There's also an "all" event that will be triggered when any of the above events are triggered. Input event does not necesarily mean that the camera will move. The input events are the events triggered when the user interacts with the board.

---

setInputMode()

setInputMode(mode): void

Defined in: packages/board/src/boardify/index.ts:1026

Parameters

mode

"kmt" | "trackpad"

Returns

void

---

step()

step(timestamp): void

Defined in: packages/board/src/boardify/index.ts:738

Parameters

timestamp

number

Returns

void

Description

This is the step function that is called in the animation frame. This function is responsible for updating the canvas context and the camera state.

---

toggleInputMode()

toggleInputMode(): void

Defined in: packages/board/src/boardify/index.ts:1051

Flips the input mode between keyboard-mouse and trackpad and locks it, disabling auto-detection.

From 'kmt' this switches to 'trackpad'; from 'trackpad' or 'TBD' it switches to 'kmt'. ('TBD' already behaves like trackpad, so the natural "other" mode to toggle into is 'kmt'.)

Returns

void

See

setInputMode to set a specific mode, and enableAutoInputMode to return to auto-detection.

Helper Methods

setMaxTransWidthWithFixedMaxBoundary()

setMaxTransWidthWithFixedMaxBoundary(value): void

Defined in: packages/board/src/boardify/index.ts:919

Parameters

value

number

Returns

void

Description

This function sets the max translation width of the camera while fixing the minimum x boundary.

---

setMaxTransWidthWithFixedMinBoundary()

setMaxTransWidthWithFixedMinBoundary(value): void

Defined in: packages/board/src/boardify/index.ts:884

Parameters

value

number

Returns

void

Description

This function sets the max translation width of the camera while fixing the minimum x boundary.

LifeCycle

Constructor

new Board(canvas?, debug?): Board

Defined in: packages/board/src/boardify/index.ts:337

Creates a new Board instance with an optional canvas element.

The constructor initializes all subsystems including the camera, input parsers, state machines, and event publishers. The board can be created with or without a canvas element - if no canvas is provided, you can attach one later using attach.

Parameters

canvas?

HTMLCanvasElement

Optional HTMLCanvasElement to attach to the board. If provided, the board will immediately initialize with this canvas. If omitted, you must call attach before the board can be used.

debug?

boolean = false

Optional debug flag that enables willReadFrequently hint on the canvas context, which optimizes the canvas for frequent readback operations. Default is false. Only use this if you need to frequently read pixel data from the canvas.

Returns

Board

Remarks

Initialization Sequence

When the constructor is called, it performs the following initialization:

1. Camera Setup: Creates a DefaultBoardCamera with default boundaries of ±50,000 units in both X and Y directions. This provides a large working area for most use cases.

2. Canvas Proxy: Initializes a CanvasProxy that observes canvas dimension changes and automatically updates the camera's viewport dimensions.

3. Camera Rig: Creates a CameraRig with default configuration:

   • limitEntireViewPort: true - Entire viewport is constrained within boundaries
   • clampTranslation: true - Camera position is clamped to boundaries
   • clampZoom: true - Zoom level is clamped to min/max limits
   • All translation restrictions are disabled by default

4. Input System: Initializes both keyboard/mouse/trackpad (KMT) and touch input parsers, state machines, and the input orchestrator that coordinates camera control.

5. Canvas Attachment (if canvas provided): If a canvas element is provided, it's immediately attached and the viewport dimensions are synchronized with the canvas size.

Default Configuration

The board is created with sensible defaults:

• World boundaries: (-50000, -50000) to (50000, 50000)
• Coordinate system: Aligned with HTML canvas (Y-axis points down)
• Camera position: (0, 0)
• Zoom level: 1.0
• Rotation: 0 radians
• Full screen: disabled

You can customize these defaults after construction by setting properties on the board or camera.

Examples

Create board with canvas element

const canvas = document.querySelector('canvas') as HTMLCanvasElement;
const board = new Board(canvas);
// Board is ready to use immediately

Create board without canvas, attach later

const board = new Board();
// ... later, when canvas is ready
const canvas = document.createElement('canvas');
document.body.appendChild(canvas);
board.attach(canvas);

Enable debug mode for pixel readback

const board = new Board(canvas, true);
// Now getImageData() and similar operations will be optimized

See

• attach for attaching a canvas after construction
• tearDown for cleanup when done with the board

---

attach()

attach(canvas, debug): void

Defined in: packages/board/src/boardify/index.ts:487

Attaches a canvas element to the board, enabling rendering and input handling.

This method connects a canvas element to the board's rendering and input systems. It must be called before the board can be used if no canvas was provided to the constructor. If a canvas was already attached, this method will replace it with the new canvas.

Parameters

canvas

HTMLCanvasElement

The HTMLCanvasElement to attach to the board. This canvas will be used for rendering and will receive all input events.

debug

boolean = false

Optional debug flag that enables willReadFrequently hint on the canvas context. Default is false. Set to true if you need to frequently read pixel data from the canvas, which will optimize the context for readback operations.

Returns

void

Remarks

When a canvas is attached, the following happens:

1. Context Creation: A 2D rendering context is obtained from the canvas with the specified debug settings.

2. Input Parser Attachment: Both KMT (keyboard/mouse/trackpad) and touch input parsers are attached to the canvas to begin receiving input events.

3. Canvas Proxy Attachment: The canvas proxy begins observing the canvas for dimension changes, automatically updating the camera's viewport dimensions when the canvas is resized.

4. Zoom Level Synchronization: If limitEntireViewPort is enabled, the minimum zoom level is calculated and set to ensure the entire viewport can fit within the camera boundaries.

5. Coordinate System Setup: Both standard and Y-reversed rendering contexts are created to support both coordinate system modes (see alignCoordinateSystem).

Examples

Attach canvas during construction

const canvas = document.querySelector('canvas') as HTMLCanvasElement;
const board = new Board(canvas);
// No need to call attach() - already attached

Attach canvas after construction

const board = new Board();

// Later, when canvas is ready...
const canvas = document.createElement('canvas');
canvas.width = 800;
canvas.height = 600;
document.body.appendChild(canvas);

board.attach(canvas);
// Board is now ready to use

Switch to a different canvas

const board = new Board(canvas1);

// Later, switch to a different canvas
const canvas2 = document.querySelector('#other-canvas') as HTMLCanvasElement;
board.attach(canvas2);
// Board is now rendering to canvas2

See

• tearDown for detaching and cleaning up
• context for accessing the rendering context

---

tearDown()

tearDown(): void

Defined in: packages/board/src/boardify/index.ts:526

Returns

void

Description

This function is used to clean up the board. It removes all the event listeners and disconnects the resize observer and the attribute observer.