Panorama video viewer (copied from viewer)

[kyle-fitzp]

Same changes from OSH-Viewer: Botts-Innovative-Research/osh-viewer#284

[salsajeries]

Adding @Cardy2 as reviewer

[Cardy2]

Since this method wires itself into the permanent root window, we need to clean this up properly. Nothing calls back into the YUVCanvas/YUV360Canvas to detach its listeners

Store the bound handler refs to an array so they can be easily destroyed later:

	this._domListeners = [];
	const add = (target, type, handler, options) => {
		target.addEventListener(type, handler, options);
		this._domListeners.push({ target, type, handler, options });
	};

then below we can use add() instead of addEventListener() for each instance:
e.g.

		add(canvas, 'mousedown', (e) => onDragStart(e.clientX, e.clientY));
		add(window, 'mousemove', (e) => onDragMove(e.clientX, e.clientY));
		add(window, 'mouseup',   onDragEnd);

[Cardy2]

Add a dispose() method to be called in FFMPEG360View:

	dispose() {
		if (this._domListeners) {
			for (const { target, type, handler, options } of this._domListeners) {
				target.removeEventListener(type, handler, options);
			}
			this._domListeners = [];
		}

		const gl = this.contextGL;
		if (gl) {
			gl.getExtension('WEBGL_lose_context')?.loseContext();
			this.contextGL = null;
		}
	}

[Cardy2]

Add destroy() override so the existing VideoView.destroy() -> FFMPEGView.destroy() teardown chain reaches the 360canvas:

	destroy() {
		this.canvas360?.dispose();
		super.destroy();
	}

[Cardy2]

since we dont have a view that handles 360 mjpeg maybe the handling here should read:

-->      if (this.props360 != null && compression !== 'jpeg') {
            this.videoView = new FFMPEG360View({
                ...this.properties,
                codec: compression,
                layers: []
            });
        } else if(compression === 'jpeg') {
-->           if (this.props360 != null) {
                console.warn('VideoView: 360 display is not supported for MJPEG streams; falling back to standard MjpegView.');
            }
            // create MJPEG View
            this.videoView = new MjpegView({
                ...this.properties,
                layers: []
            });

[Cardy2]

Looks good. Mostly small fixes and need to add some cleanup detaching the event listeners in 360Canvas