deprecated toBlob in Firefox 141.0.2 hangs to unresolved promise

[boggan]

Hi!

found a new issue with the latest Firefox version (141.0.2)

three.js/examples/jsm/exporters/GLTFExporter.js

Line 546 in 54ac263

if ( canvas.toBlob !== undefined ) {

this preventing the GLTFExporter to export GLB properly

I suggest changing the line to

if ( canvas.toBlob !== undefined && !canvas.convertToBlob ) {
...
}

Cheers!

[Mugen87]

When I understand the spec correctly, convertToBlob() should only be available with OffscreenCanvas. toBlob() is for HTMLCanvasElement.

I don't understand what you mean by "deprecated"? toBlob() seems a valid spec and there are no signs that Firefox deprecates the usage.

I have tested the export in https://threejs.org/examples/misc_exporter_gltf with the latest Firefox version and everything works as expected.

[boggan]

im my setup, the code ran inside a web worker, so it's using OffscreenCanvas, and since toBlob is still available in the class, it calls it, logs the deprecation warning, and never invokes the callback

if you want to repro:

let offscr = new OffscreenCanvas(1, 1);
offscr.toBlob(() => console.log("never called"));

from what I noticed, the toBlob already returns a promise now, but it no longer invokes the callback.

and since the THREEJS code is as follows:

function getToBlobPromise( canvas, mimeType ) {
        if ( canvas.toBlob !== undefined ) {
                return new Promise( ( resolve ) => canvas.toBlob( resolve, mimeType ) );
        }

        let quality;

        // Blink's implementation of convertToBlob seems to default to a quality level of 100%
        // Use the Blink default quality levels of toBlob instead so that file sizes are comparable.
        if ( mimeType === 'image/jpeg' ) {
                quality = 0.92;
        } else if ( mimeType === 'image/webp' ) {
                quality = 0.8;
        }

        return canvas.convertToBlob( {
                type: mimeType,
                quality: quality
        } );
}

the new Promise created when toBlob is invoked on canvas, will never resolve.

Cheers!

[Mugen87]

and since toBlob is still available in the class

To clarify, is that a bug in Firefox? At least in Chrome, toBlob() is not available in OffscreenCanvas.

[boggan]

yes, only in firefox 141.0.2, maybe a check for instanceof OffscreenCanvas or instanceof HTMLCanvasElement would be a better approach ?

[Mugen87]

That sounds good! Would be up for a PR?

[boggan]

sure thing, thanks for the quick replies!! :)