src/vs/workbench/browser/parts/compositePart.ts/CompositePart/hideActiveComposite
class CompositePart:	protected hideActiveComposite(): Composite | undefined {
		if (!this.activeComposite) {
			return undefined; // Nothing to do
		}

		const composite = this.activeComposite;
		this.activeComposite = undefined;

		const compositeContainer = this.mapCompositeToCompositeContainer.get(composite.getId());

		// Indicate to Composite
		composite.setVisible(false);

		// Take Container Off-DOM and hide
		if (compositeContainer) {
			compositeContainer.remove();
			hide(compositeContainer);
		}

		// Clear any running Progress
		if (this.progressBar) {
			this.progressBar.stop().hide();
		}

		// Empty Actions
		if (this.toolBar) {
			this.collectCompositeActions()();
		}
		this.onDidCompositeClose.fire(composite);

		return composite;
	}