uē-tôo

Appearance

@ue-too/board / Board

Class: Board ​

Defined in: packages/board/src/boardify/index.ts:199

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

typescript
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

typescript
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

typescript
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

typescript
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

typescript
const board = new Board();

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

See ​

Accessors ​

alignCoordinateSystem ​

Get Signature ​

get alignCoordinateSystem(): boolean

Defined in: packages/board/src/boardify/index.ts:525

Returns ​

boolean

Set Signature ​

set alignCoordinateSystem(align): void

Defined in: packages/board/src/boardify/index.ts:519

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:614

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:618

Parameters ​
camera ​

ObservableBoardCamera

Returns ​

void

cameraMux ​

Get Signature ​

get cameraMux(): CameraMux

Defined in: packages/board/src/boardify/index.ts:628

Returns ​

CameraMux

Set Signature ​

set cameraMux(cameraMux): void

Defined in: packages/board/src/boardify/index.ts:632

Parameters ​
cameraMux ​

CameraMux

Returns ​

void

canvasDimensions ​

Get Signature ​

get canvasDimensions(): CanvasDimensions

Defined in: packages/board/src/boardify/index.ts:941

Returns ​

CanvasDimensions

clampRotation ​

Get Signature ​

get clampRotation(): boolean

Defined in: packages/board/src/boardify/index.ts:921

Returns ​

boolean

Set Signature ​

set clampRotation(value): void

Defined in: packages/board/src/boardify/index.ts:925

Parameters ​
value ​

boolean

Returns ​

void

clampTranslation ​

Get Signature ​

get clampTranslation(): boolean

Defined in: packages/board/src/boardify/index.ts:905

Returns ​

boolean

Set Signature ​

set clampTranslation(value): void

Defined in: packages/board/src/boardify/index.ts:909

Parameters ​
value ​

boolean

Returns ​

void

clampZoom ​

Get Signature ​

get clampZoom(): boolean

Defined in: packages/board/src/boardify/index.ts:913

Returns ​

boolean

Set Signature ​

set clampZoom(value): void

Defined in: packages/board/src/boardify/index.ts:917

Parameters ​
value ​

boolean

Returns ​

void

context ​

Get Signature ​

get context(): CanvasRenderingContext2D | undefined

Defined in: packages/board/src/boardify/index.ts:549

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:533

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:537

Parameters ​
value ​

boolean

Returns ​

void

height ​

Get Signature ​

get height(): number

Defined in: packages/board/src/boardify/index.ts:510

Returns ​

number

inputOrchestrator ​

Get Signature ​

get inputOrchestrator(): InputOrchestrator

Defined in: packages/board/src/boardify/index.ts:485

Returns ​

InputOrchestrator

kmtParser ​

Get Signature ​

get kmtParser(): KMTEventParser

Defined in: packages/board/src/boardify/index.ts:588

Returns ​

KMTEventParser

Set Signature ​

set kmtParser(parser): void

Defined in: packages/board/src/boardify/index.ts:578

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:570

Returns ​

boolean

Set Signature ​

set limitEntireViewPort(value): void

Defined in: packages/board/src/boardify/index.ts:560

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:756

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:763

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:857

Returns ​

boolean

Set Signature ​

set restrictRelativeXTranslation(value): void

Defined in: packages/board/src/boardify/index.ts:873

Parameters ​
value ​

boolean

Returns ​

void

restrictRelativeYTranslation ​

Get Signature ​

get restrictRelativeYTranslation(): boolean

Defined in: packages/board/src/boardify/index.ts:861

Returns ​

boolean

Set Signature ​

set restrictRelativeYTranslation(value): void

Defined in: packages/board/src/boardify/index.ts:877

Parameters ​
value ​

boolean

Returns ​

void

restrictRotation ​

Get Signature ​

get restrictRotation(): boolean

Defined in: packages/board/src/boardify/index.ts:897

Returns ​

boolean

Set Signature ​

set restrictRotation(value): void

Defined in: packages/board/src/boardify/index.ts:901

Parameters ​
value ​

boolean

Returns ​

void

restrictXTranslation ​

Get Signature ​

get restrictXTranslation(): boolean

Defined in: packages/board/src/boardify/index.ts:865

Returns ​

boolean

Set Signature ​

set restrictXTranslation(value): void

Defined in: packages/board/src/boardify/index.ts:881

Parameters ​
value ​

boolean

Returns ​

void

restrictYTranslation ​

Get Signature ​

get restrictYTranslation(): boolean

Defined in: packages/board/src/boardify/index.ts:869

Returns ​

boolean

Set Signature ​

set restrictYTranslation(value): void

Defined in: packages/board/src/boardify/index.ts:885

Parameters ​
value ​

boolean

Returns ​

void

restrictZoom ​

Get Signature ​

get restrictZoom(): boolean

Defined in: packages/board/src/boardify/index.ts:889

Returns ​

boolean

Set Signature ​

set restrictZoom(value): void

Defined in: packages/board/src/boardify/index.ts:893

Parameters ​
value ​

boolean

Returns ​

void

touchParser ​

Get Signature ​

get touchParser(): TouchEventParser

Defined in: packages/board/src/boardify/index.ts:606

Returns ​

TouchEventParser

Set Signature ​

set touchParser(parser): void

Defined in: packages/board/src/boardify/index.ts:596

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:506

Returns ​

number

Methods ​

convertWindowPoint2WorldCoord() ​

convertWindowPoint2WorldCoord(clickPointInWindow): Point

Defined in: packages/board/src/boardify/index.ts:708

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:475

Returns ​

void

enableEventListeners() ​

enableEventListeners(): void

Defined in: packages/board/src/boardify/index.ts:480

Returns ​

void

getCameraRig() ​

getCameraRig(): CameraRig

Defined in: packages/board/src/boardify/index.ts:929

Returns ​

CameraRig

on() ​

on<K>(eventName, callback): UnSubscribe

Defined in: packages/board/src/boardify/index.ts:731

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:937

Parameters ​

callback ​

(dimensions) => void

Returns ​

(): void

Returns ​

void

onInput() ​

onInput<K>(eventName, callback): UnsubscribeToUserRawInput

Defined in: packages/board/src/boardify/index.ts:746

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:933

Parameters ​

mode ​

"kmt" | "trackpad"

Returns ​

void

step() ​

step(timestamp): void

Defined in: packages/board/src/boardify/index.ts:645

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.

Helper Methods ​

setMaxTransWidthWithFixedMaxBoundary() ​

setMaxTransWidthWithFixedMaxBoundary(value): void

Defined in: packages/board/src/boardify/index.ts:826

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:791

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:303

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

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

Create board without canvas, attach later

typescript
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

typescript
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:454

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

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

Attach canvas after construction

typescript
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

typescript
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:493

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.