Crazy Idea for Web Worker Extension

Posted in: javascript , web standards


This article describes an extension to Web Workers by enabling the use of a subset of the Shading Language 1.0 – as defined by the WebGL and OpenGL ES specifications – on a Web Worker.

The Shading Language is already present in web applications that use WebGL or CSS Shaders. Web Workers are implemented and exposed by the major browsers Opera Software, Google Chrome, Apple Safari and Mozilla Firefox. The idea is to combine these two things to enable Web Workers to execute Shading Language code.


This would enable (depending on the inner implementation) faster code execution, but more important graphics programmers or developers in need for more clever idioms for mathematics or computational geometry operations could use this language to perform these operations easily. Much of the Web today depends on graphics, as can be seen by the numerous languages and APIs designed to render content on the screen (HTML/CSS, WebGL, 2D Canvas and SVG) and although JavaScript is suitable for prototyping, it doesn’t provide features that are friendly to graphic developers such as operator overloading, static typing, advanced built-int math and geometry functions and matrix and vector classes.

How it works

The main idea of the api extension would be to define an extra option argument to the Web Worker constructor that would specify the type of the file to be executed. By default the file type would be JavaScript:

var worker = new Worker('myworker.glsl', { type: 'glsl' });

Then the worker api would remain the same, with onmessage and postMessage operations. If used with GLSL, the postMessage operation would be restricted to send transferable objects, in particular ArrayBuffers or TypedArrays. Continuing the example we would have:

//create array of floats
    var floats = new Float32Array([1, 2, 3]);
    //send this data over transferable objects to the worker
    //add a listener to get back the data
    worker.onmessage = function(e) {
        //print the resulting typed array

The shader file would require a main function which can have an in transferable object argument and out transferable object argument. For example, we could have inside myworker.glsl:

void main(in float numbersIn[3], out float numbersOut[3]) {
    numbersOut[0] = numbersIn[0] * numbersIn[0];
    numbersOut[1] = numbersIn[1] * numbersIn[1];
    numbersOut[2] = numbersIn[2] * numbersIn[2];

Once main returns, the out parameter will be set as the data property of the event object and sent in the onmessage callback.

Implementation notes

I don’t think that in this case GLSL would be run in the GPU (that would be crazy!), but I do think that GLSL is a language that could be safely executed or safely transpiled into any language in the ANSI C family. As opposed to the WebCL/OpenCL 1.0 language, GLSL does not have pointers and seems safer enough that it’s currently being used in CSS Shaders and WebGL.

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