ObjectLoader: Ensure onLoad() is fired for DataTextures.

[Mugen87]

Related issue: Follow-up of #17745.

Description

During testing in the editor, I've overlooked a use case in #17745. When a JSON only contains data textures and no instances of HTMLImageElement, onLoad() is currently not fired. That happens because of this line:

if ( json.images === undefined || json.images.length === 0 ) {

The loader calls no onLoad() since it will be called when loading images via the internal ImageLoader. However, data textures don't use image loader which means ObjectLoader.parse() needs a different check.

[mrdoob]

I think this achieves the same?

	if ( onLoad !== undefined ) {

		for ( const uuid in images ) {

			if ( images[ uuid ] instanceof HTMLImageElement ) {

				onLoad( object );
				break;

			}

		}

	}

[Mugen87]

The loader should fire onLoad() at this place if there are no HTMLImageElements. It seems your code fires onLoad() as soon as an image element is in the images array.

[mrdoob]

Ah, I see... Then this?

	if ( onLoad !== undefined ) {

		let hasImages = false;

		for ( const uuid in images ) {

			if ( images[ uuid ] instanceof HTMLImageElement ) {

				hasImages = true;
				break;

			}

		}

		if ( hasImages === false ) onLoad( object );

	}

Basically trying to avoid doing any work if onLoad is not defined.

[Mugen87]

Basically trying to avoid doing any work if onLoad is not defined.

Makes sense! Yes, this approach works 👍 .

[Mugen87]

Okay, updated the PR!

[Mugen87]

The editor can now save/reload scenes with HDR textures 🎉 .

[mrdoob]

Thanks!