GLTFLoader ImageBitmapLoader overrides loaders for types it can't handle

[JohannesDeml]

Description of the problem

Due to the recently added usage of BitmapLoader in GLFTLoader (#19518), using handlers for specific file formats will be overwritten from the BitmapLoader.

In r117 to support basis textures for gltf files you would just need to add

var basisLoader = new BasisTextureLoader();
basisLoader.setTranscoderPath( 'js/libs/basis/' );
basisLoader.detectSupport( renderer );
THREE.DefaultLoadingManager.addHandler( /\.basis$/, basisLoader );

This is not possible anymore, since the resolve will be overwritten here:

three.js/examples/jsm/loaders/GLTFLoader.js

Lines 2077 to 2093 in 7df06a0

	return new Promise( function ( resolve, reject ) {
	var onLoad = resolve;
	if ( useImageBitmap ) {
	onLoad = function ( imageBitmap ) {
	resolve( new CanvasTexture( imageBitmap ) );
	};
	}
	loader.load( resolveURL( sourceURI, options.path ), onLoad, undefined, reject );
	} );

I'm getting the following error:

THREE.WebGLState: TypeError: Failed to execute 'texImage2D' on 'WebGL2RenderingContext': No function was found that matched the signature provided.
    at Object.texImage2D (three.module.js:21828)
    at uploadTexture (three.module.js:22749)
    at setTexture2D (three.module.js:22274)
    at WebGLTextures.safeSetTexture2D (three.module.js:23169)
    at SingleUniform.setValueT1 [as setValue] (three.module.js:17755)
    at Function.WebGLUniforms.upload (three.module.js:18260)
    at setProgram (three.module.js:26406)
    at WebGLRenderer.renderBufferDirect (three.module.js:25441)
    at renderObject (three.module.js:25994)
    at renderObjects (three.module.js:25966)

• demo
• code

Three.js version

• Dev
• r118
• r117

Browser

• All of them
• Chrome
• Firefox
• Edge

OS

• All of them
• Windows
• macOS
• Linux
• Android
• iOS

Hardware Requirements (graphics card, VR Device, ...)

[Mugen87]

Same error occurs with one of the official examples when using the glTF-dds extension:

https://threejs.org/examples/webgl_loader_gltf_extensions

[Mugen87]

@JohannesDeml Can you please check if the linked PR solves your issue? At least I could fix the DDS example with it^^.

[JohannesDeml]

@Mugen87 Yes, that does fix the problem for me. Thanks a lot taking care of the bug so fast!