WP_Customize_Widgets::render_widget_partial( WP_Customize_Partial $partial, array $context )

	public function render_widget_partial( $partial, $context ) {
		$id_data   = $partial->id_data();
		$widget_id = array_shift( $id_data['keys'] );

		if ( ! is_array( $context )
			|| empty( $context['sidebar_id'] )
			|| ! is_registered_sidebar( $context['sidebar_id'] )
		) {
			return false;
		}

		$this->rendering_sidebar_id = $context['sidebar_id'];

		if ( isset( $context['sidebar_instance_number'] ) ) {
			$this->context_sidebar_instance_number = intval( $context['sidebar_instance_number'] );
		}

		// Filter sidebars_widgets so that only the queried widget is in the sidebar.
		$this->rendering_widget_id = $widget_id;

		$filter_callback = array( $this, 'filter_sidebars_widgets_for_rendering_widget' );
		add_filter( 'sidebars_widgets', $filter_callback, 1000 );

		// Render the widget.
		ob_start();
		dynamic_sidebar( $this->rendering_sidebar_id = $context['sidebar_id'] );
		$container = ob_get_clean();

		// Reset variables for next partial render.
		remove_filter( 'sidebars_widgets', $filter_callback, 1000 );

		$this->context_sidebar_instance_number = null;
		$this->rendering_sidebar_id = null;
		$this->rendering_widget_id = null;

		return $container;
	}