Editor: Add SelectionHelper for Viewport.

[linbingquan]

Related issue: #23464

Description

I'm not sure this is the best implementation of the SelectionHelper component.

Other plugin can receive raycaster.intersectObjects in #viewport with Signal intersects function like:

editor.signals.intersects.add( ( intersects ) => {
    // do some thing.

    // stop SelectionHelper
    return false;
} , null, 1 );

If there is no problem, I will continue to implement plugin register API.

Please provide feedback.

Todo List

• Add Signal intersects function in Editor.js.
• Extract SelectionHelper component.
• Implement plugin register API for editor.
• Provide the method to prevent execute SelectionHelper logic, like DOM event's preventDefault().

[Mugen87]

https://raw.githack.com/linbingquan/three.js/dev-editor-plugins/editor/index.html

[Mugen87]

Looking good! The only thing I have noticed is that SelectionHelper needs to be added to sw.js right here:

three.js/editor/sw.js

Lines 188 to 192 in f9d1f84

	'./js/Viewport.js',
	'./js/Viewport.Camera.js',
	'./js/Viewport.Info.js',
	'./js/Viewport.ViewHelper.js',
	'./js/Viewport.VR.js',

[linbingquan]

Looking good! The only thing I have noticed is that SelectionHelper needs to be added to sw.js right here:

Good job. Thank you for your advice. I wasn't aware of sw.js.

[mrdoob]

Thanks!

[mrdoob]

Renamed SelectionHelper to Selector: 909350e

[mrdoob]

The editor broke because there is a lot of references to editor.selected. Here's my fix: 4e0930a