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Polypad API Docs

Setup

Our JavaScript API allows you to add interactive Polypad canvases to any website. You simply need to include our JS source file, create a parent element for Polypad, and then call Polypad.create():

<script src="https://static.mathigon.org/api/polypad-v1.3.js"></script>
<div id="polypad" style="width: 800px; height: 500px;"></div>
<script>Polypad.create(document.querySelector('#polypad'), {apiKey: 'test'})</script>

Polypad requires Custom Web Components and the Web Animations API. If you want to use browsers that don’t support these APIs, you have to include a polyfill, e.g. mathigon.org/polyfill.js.

Our goal is to support the latest version of Chrome, Firefox, Opera and Edge on all mobile and desktop devices.

Note: the polypad-v1.3.js script needs to be included in the <body>, not the <head> of your HTML document.

JSON Schema

Every Polypad canvas consists of a collection of tiles and strokes. The state of a Polypad can be serialised as JSON, with the following schema:

interface TileData {
  name: string,       // The tile type (since 'type' is a reserved field in many databases)
  options?: string,   // Parameters for this tile
  id?: string;        // Unique identifier
  x?: number,         // X-position
  y?: number,         // Y-position
  rot?: number,       // Rotation (in degrees)
  size?: number;      // Used for some resizable tiles like images or text boxes
  colour?: string;    // HEX colour (e.g. "#ff0044")
  flipped?: boolean;
  locked?: boolean;
}

interface StrokeData {
  id?: string;         // Unique identifier
  points: string;      // SVG path
  colour?: string;     // HEX colour
  brush: 'pen'|'marker'|'highlighter'
}

type GridType = 'none'|'square2-grid'|'square-dots'|'square-grid'|'tri-dots'|'tri-grid'|'tri2-dots'|'tri2-grid';

interface PolypadData {
  title: string;         // Polypad title
  grid: GridType;
  noLabels: boolean;
  tiles: TileData[];
  strokes: StrokeData[];
}

Please that the maximum length of the tiles and strokes array is 2000. With more items on the same page, you might see performance issues on some devices.

Methods

The Polypad.create() function takes an options argument with many ways to customise Polypad:

interface Polypad {
  create: ({
    apiKey?: string;        // Mathigon-issued API key
    userKey?: string;       // Unique identifier for the current user

    sidebar?: boolean;      // Whether to show the sidebar
    toolbar?: boolean;      // Whether to show the toolbar
    settings?: boolean;     // Whether to show the settings bar

    initial?: PolypadData;  // Initial data to show

    // Override the default theme colours 'red', 'blue', 'green', ...
    themeColours?: Record<string, string>;

    // Whether to bind keyboard events for undo/redo and cut/copy/paste. Default is false.
    bindKeyboardEvents?: boolean;

    // Provide a way to upload image files: you need to upload the file object to a storage
    // backend and return a promise that resolves with the URL of the uploaded file.
    imageUpload?: (file: File) => Promise<string>;
  }) => PolypadInstance;
}

Polypad.create() then returns a PolypadInstance object with additional methods for manipulating the canvas. Please note that most of these methods don’t type-check their input arguments. If you pass in incorrect data, the behaviour is undefined.

interface PolypadInstance {
  // Bind or unbind event listeners. See below for all supported events.
  on: (event: string, callback: (e: unknown) => void) => void;
  off: (event: string, callback: (e: unknown) => void) => void;

  // Serialize or un-serialize a polypad state from JSON data. See above for types.
  serialize: () => PolypadData;
  unSerialize: (data: PolypadData) => void;

  // Create a PNG image of a given size. This asynchronous function returns a Data URI string.
  pngImage: (width: number, height: number) => Promise<string>;

  // Add, update or delete a tile or stroke. .add() returns the ID of the new item. Note that
  // you cannot update strokes, or update the 'name' property of a tile once created.
  add: (data: TileData|StrokeData) => string;
  update: (id: string, properties: TileData) => void;
  delete: (...ids: string[]) => void;

  // Get the current user selection, or programmatically select multiple existing tiles.
  getSelection: () => string[];
  selectTiles: (...tileIds: string[]) => void;

  // Undo or redo the latest changes to the canvas.
  undo: () => void;
  redo: () => void;

  // Set the background grid of the canvas.
  setGrid: (string: GridType) => void;

  // Clear all tiles on the current canvas. Unline .unSerialize({}), this action can be undone.
  clear: () => void;

  // Get or update the visible viewport of the canvas, or reset it to its initia position.
  getViewport: () => {x: number; y: number; zoom: number};
  setViewport: (x: number, y: number, zoom: number) => void;
  resetViewport: () => void;
}

Events

Using the .on() and .off() methods on PolypadInstance, you can bind and unbind many different event listeners. The following events are supported:

.on('change')

This event is triggered whenever the state of the Polypad changes because the user has added, updated or deleted a stroke or tile. Note that multiple different tiles can change at once, but the event is only triggered once at the end of a move or rotate action.

Callback Options: {added: (TileData|StrokeData)[], changed: TileData[], deleted: (TileData|StrokeData)[]}

.on('viewport')

Triggered whenever the position of the visible viewport changes, for example because the user pans or zooms. Note that the viewport is not part of the “state” of a polypad. When calling .unSerialize() or .resetViewport(), we update the viewport so that all tiles and strokes are visible and centered.

Callback Options: {x: number, y: number, zoom: number}

.on('undo'), .on('redo')

Triggered on undo and redo: both from a user input (e.g. clicking the undo button or CTRL + Z on the keyboard), or programatically (e.g. calling .undo() above),

.on('grid')

Triggered whenever the user changes the grid background of the canvas.

Callback Options: {grid: GridType}

.on('move')

This event is triggered continuously while users are moving one or more tiles. It is throttled to be triggered at most once per second. The Callback argument contains the ID and the current position of all currently selected tiles.

Callback Options: {tiles: {id: string, x: number, y: number}[]}

Tile Types

Polypad supports a large number of different tile types.

Tile Name Options String
Polygons polygon Either a named polygon like square, reg-hexagon or kite, or a string of vertex coordinates, e.g. 0 0,1 0,1 1,0 1
Custom Polygons custom-polygon Same as for Polygon
Polyominoes pentomino Index from 0 to 11 for pentominoes and 12 to 16 for tetrominoes
Tangram tangram Index from 0 to 6
Tangram Egg egg Index from 0 to 8
Ruler ruler Width, e.g. 400
Protractor protractor Width, e.g. 200
Penrose Tiles penrose Either 0 or 1
Penrose Nature garden Index from 0 to 7
Kolam Tiles kolam Index from 0 to 5
Fractals fractal Index from 0 (large) to 4 (small)
Tantrix Tiles tantrix Index from 0 to 13
Number Tiles number-tile ${width}:${count}, e.g. 10:100 for a 10x10 block of tiles
Number Bars number-bar Width from 1 to 10
Number Line number-line TODO…
Prime Circle prime-disk TODO…
Number Card number-card TODO…
Decimal Grid decimal-grid TODO…
Dot Machine dot-machine TODO…
Exploding Dot dot TODO…
Fraction Bars fraction-bar TODO…
Fraction Circles fraction-circle TODO…
Algebra Tiles algebra-tile TODO…
Algebra Grid grid TODO…
Balance Scale balance TODO…
Balance Tokens token TODO…
Coordinate Axes axes TODO…
Dice dice TODO…
Coin coin TODO…
Spinner spinner TODO…
Custom Spinner custom-spinner TODO…
Image image The URL of the image, which should be returned by the imageUpload() config function.
Text text The text body of the string
Geometry geo A geometric expression, e.g. a=point(10,20) or c=segment(a,b)

Future Features

  • Expose additional, internal methods and events
  • Customise the maximum zoom/pan limits
  • Animate the drawing of strokes in .add().
  • Animate the position of tiles in .update(), rather than changing the position instantly.
  • Switch colour scheme (light/dark)
  • Customisation options for which items to show in the sidebar, toolbar and settings menu
  • Support non-English languages
  • Support including the script in the <head>. Currently, it accesses document.body, so it needs to be included in the <body>.

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