src/vs/base/browser/ui/splitview/splitview.ts/ViewItem/setVisible
class ViewItem:	setVisible(visible: boolean, size?: number): void {
		if (visible === this.visible) {
			return;
		}

		if (visible) {
			this.size = clamp(this._cachedVisibleSize!, this.viewMinimumSize, this.viewMaximumSize);
			this._cachedVisibleSize = undefined;
		} else {
			this._cachedVisibleSize = typeof size === 'number' ? size : this.size;
			this.size = 0;
		}

		this.container.classList.toggle('visible', visible);

		this.view.setVisible?.(visible);
	}