path2d-polyfill

path2d-polyfill

Polyfills Path2D api and roundRect for CanvasRenderingContext2D

Usage

Add this script tag to your page to enable the feature.

<script lang="javascript" src="https://unpkg.com/path2d-polyfill"></script>

or install from npm

npm install --save path2d-polyfill

and import with module bundler e.g. webpack before using the feature

import "path2d-polyfill";

This will polyfill the browser's window object with Path2D features and it will also polyfill roundRect if they are missing in both CanvasRenderingContexst and Path2D.

Example of usage

ctx.fill(new Path2D("M 80 80 A 45 45 0 0 0 125 125 L 125 80 Z"));
ctx.stroke(new Path2D("M 80 80 A 45 45 0 0 0 125 125 L 125 80 Z"));

Usage in a node environment

It is possible to use this library in a node environment as well. The package exports a few functions that can be used:

• Path2D - class to create Path2D objects used by the polyfill methods
• polyfillPath2D - function that adds Path2D to a "window like" object and polyfills CanvasRenderingContext2D to use Path2D
• polyfillRoundRect - polyfills roundRect function on Path2D and CanvasRenderingContext2D (missing in firefox)
• parsePath - function for parsing an SVG path string into canvas commands

use any of these functions like:

const { polyfillRoundRect } = require "path2d-polyfill";

const windowlike = { CanvasRenderingContext2D, Path2D };

polyfillRoundRect(windowLike);
// roundRect functions has now been added if they were missing

usage with node-canvas

To get Path2D features with the node-canvas library use the following pattern:

const { createCanvas, CanvasRenderingContext2D } = require("canvas");
const { polyfillPath2D } = require("path2d-polyfill/path2d");

global.CanvasRenderingContext2D = CanvasRenderingContext2D;
polyfillPath2D(global);
// Path2D has now been added to global object

const canvas = createCanvas(200, 200);
const ctx = canvas.getContext("2d");

const p = new Path2D("M10 10 l 20 0 l 0 20 Z");
ctx.fillStyle = "green";
ctx.fill(p);

A working example of a node express server that serves an image drawn with canvas can be seen here

Support table

Method	Supported
constructor(SVGPath)	Yes
addPath()	Yes
closePath()	Yes
moveTo()	Yes
lineTo()	Yes
bezierCurveTo()	Yes
quadraticCurveTo()	Yes
arc()	Yes
ellipse()	Yes
rect()	Yes
roundRect()	Yes

See it in action

Clone this repo and run the following

yarn
yarn start

open http://localhost:10001 to see the example page.

Contributing

Recommended to use vscode with the prettier extension to keep formatting intact.