OffscreenCanvasRenderingContext2D.md

OffscreenCanvasRenderingContext2D

Namespace: SpawnDev.SpawnJS.JSObjects
Inherits: CanvasRenderingContext2D
Source: JSObjects/OffscreenCanvasRenderingContext2D.cs
MDN Reference: OffscreenCanvasRenderingContext2D on MDN

The OffscreenCanvasRenderingContext2D interface is a CanvasRenderingContext2D rendering context for drawing to the bitmap of an OffscreenCanvas object. It is similar to the CanvasRenderingContext2D object, with the following differences: https://developer.mozilla.org/en-US/docs/Web/API/OffscreenCanvasRenderingContext2D

Constructors

Signature	Description
OffscreenCanvasRenderingContext2D(SpawnJSObjectReference _ref)	Deserialization constructor

Methods

Method	Return Type	Description
Commit()	void	Pushes the rendered image to the context's OffscreenCanvas object's placeholder canvas element. ⚠ Deprecated - Not for use in new websites

Examples

SpawnDev.SpawnJS Mapping Note: The JavaScript examples below show the standard Web API usage. In SpawnDev.SpawnJS, the same API is available with C# conventions:

• Properties and methods use PascalCase (e.g., readyState becomes ReadyState)
• Events use ActionEvent with +=/-= (e.g., addEventListener("click", fn) becomes OnClick += handler)
• Async methods return Task<T> instead of Promise<T>
• Objects should be disposed with using statements
• Access via JS.Get<OffscreenCanvasRenderingContext2D>(...) or constructor new OffscreenCanvasRenderingContext2D(...)

const canvas = document.getElementById("canvas");
const offscreen = canvas.transferControlToOffscreen();
const worker = new Worker("worker.js");
worker.postMessage({ canvas: offscreen }, [offscreen]);

onmessage = (event) => {
  const canvas = event.data.canvas;
  const offCtx = canvas.getContext("2d");
  // draw to the offscreen canvas context
  offCtx.fillStyle = "red";
  offCtx.fillRect(0, 0, 100, 100);
};

See full example on MDN