useTexture(..., onLoad) callback receives incorrect values

[jwueller]

• three version: 0.164.1
• @react-three/fiber version: 8.16.6
• @react-three/drei version: 9.105.6
• node version: v22.2.0
• npm (or yarn) version: 1.22.22

Problem description:

The types declare that the callback receives the same type that's returned from the hook itself. However, that's not the case, and it will never receive a record object.

Relevant code:

const returnedTextures = useTexture(
    {map: 'color.jpg', normalMap: 'normal.png'},
    (callbackTextures) => {
        // callbackTextures can never be an object here, and always produces and
        // array, as opposed to returnedTextures, which correctly adheres to the
        // declared type.
    },
);

Suggested solution:

Fix the callback to adhere to the declared type. I will provide a PR for this.