Adding onStart argument to LoadingManager constructor?

[takahirox]

Description of the problem

LoadingManager has four .on callback function properties, .onLoad, .onProgress, onError, and .onStart. It takes three of them as arguments of the constructor, onLoad, onProgress, and onError.

https://threejs.org/docs/#api/loaders/managers/LoadingManager

Why not adding the firth argument .onStart to the constructor? Any historical reasons?

If you folks agree with adding it, I'll make PR.

Three.js version

• Dev
• r95
• ...

Browser

• All of them
• Chrome
• Firefox
• Internet Explorer

OS

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

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

[Mugen87]

see #5689

@mrdoob mentioned in the PR that the order of the parameters would be unexpected when onStart() comes at the very end. There is definitely something to it.

[takahirox]

Oops, I've missed that thread. Hm, I can understand that..

[takahirox]

Hm, adding a note in the code so far? Other devs will think the same thing later.

[Mugen87]

Yeah, referring to #5689 in LoadingManager can't hurt. I would do it here:

three.js/src/loaders/LoadingManager.js

Line 14 in 32914a5

this.onStart = undefined;