WP_Customize_Widgets::enqueue_scripts()

	public function enqueue_scripts() {
		global $wp_scripts, $wp_registered_sidebars, $wp_registered_widgets;

		wp_enqueue_style( 'customize-widgets' );
		wp_enqueue_script( 'customize-widgets' );

		/** This action is documented in wp-admin/admin-header.php */
		do_action( 'admin_enqueue_scripts', 'widgets.php' );

		/*
		 * Export available widgets with control_tpl removed from model
		 * since plugins need templates to be in the DOM.
		 */
		$available_widgets = array();

		foreach ( $this->get_available_widgets() as $available_widget ) {
			unset( $available_widget['control_tpl'] );
			$available_widgets[] = $available_widget;
		}

		$widget_reorder_nav_tpl = sprintf(
			'<div class="widget-reorder-nav"><span class="move-widget" tabindex="0">%1$s</span><span class="move-widget-down" tabindex="0">%2$s</span><span class="move-widget-up" tabindex="0">%3$s</span></div>',
			__( 'Move to another area&hellip;' ),
			__( 'Move down' ),
			__( 'Move up' )
		);

		$move_widget_area_tpl = str_replace(
			array( '{description}', '{btn}' ),
			array(
				__( 'Select an area to move this widget into:' ),
				_x( 'Move', 'Move widget' ),
			),
			'<div class="move-widget-area">
				<p class="description">{description}</p>
				<ul class="widget-area-select">
					<% _.each( sidebars, function ( sidebar ){ %>
						<li class="" data-id="<%- sidebar.id %>" title="<%- sidebar.description %>" tabindex="0"><%- sidebar.name %></li>
					<% }); %>
				</ul>
				<div class="move-widget-actions">
					<button class="move-widget-btn button" type="button">{btn}</button>
				</div>
			</div>'
		);

		/*
		 * Gather all strings in PHP that may be needed by JS on the client.
		 * Once JS i18n is implemented (in https://core.trac.wordpress.org/ticket/20491), this can be removed.
		 */
		$some_non_rendered_areas_messages = array();
		$some_non_rendered_areas_messages[1] = html_entity_decode(
			__( 'Your theme has 1 other widget area, but this particular page doesn&#8217;t display it.' ),
			ENT_QUOTES,
			get_bloginfo( 'charset' )
		);
		$registered_sidebar_count = count( $wp_registered_sidebars );
		for ( $non_rendered_count = 2; $non_rendered_count < $registered_sidebar_count; $non_rendered_count++ ) {
			$some_non_rendered_areas_messages[ $non_rendered_count ] = html_entity_decode( sprintf(
				/* translators: %s: the number of other widget areas registered but not rendered */
				_n(
					'Your theme has %s other widget area, but this particular page doesn&#8217;t display it.',
					'Your theme has %s other widget areas, but this particular page doesn&#8217;t display them.',
					$non_rendered_count
				),
				number_format_i18n( $non_rendered_count )
			), ENT_QUOTES, get_bloginfo( 'charset' ) );
		}

		if ( 1 === $registered_sidebar_count ) {
			$no_areas_shown_message = html_entity_decode( sprintf(
				__( 'Your theme has 1 widget area, but this particular page doesn&#8217;t display it.' )
			), ENT_QUOTES, get_bloginfo( 'charset' ) );
		} else {
			$no_areas_shown_message = html_entity_decode( sprintf(
				/* translators: %s: the total number of widget areas registered */
				_n(
					'Your theme has %s widget area, but this particular page doesn&#8217;t display it.',
					'Your theme has %s widget areas, but this particular page doesn&#8217;t display them.',
					$registered_sidebar_count
				),
				number_format_i18n( $registered_sidebar_count )
			), ENT_QUOTES, get_bloginfo( 'charset' ) );
		}

		$settings = array(
			'registeredSidebars'   => array_values( $wp_registered_sidebars ),
			'registeredWidgets'    => $wp_registered_widgets,
			'availableWidgets'     => $available_widgets, // @todo Merge this with registered_widgets
			'l10n' => array(
				'saveBtnLabel'     => __( 'Apply' ),
				'saveBtnTooltip'   => __( 'Save and preview changes before publishing them.' ),
				'removeBtnLabel'   => __( 'Remove' ),
				'removeBtnTooltip' => __( 'Trash widget by moving it to the inactive widgets sidebar.' ),
				'error'            => __( 'An error has occurred. Please reload the page and try again.' ),
				'widgetMovedUp'    => __( 'Widget moved up' ),
				'widgetMovedDown'  => __( 'Widget moved down' ),
				'navigatePreview'  => __( 'You can navigate to other pages on your site while using the Customizer to view and edit the widgets displayed on those pages.' ),
				'someAreasShown'   => $some_non_rendered_areas_messages,
				'noAreasShown'     => $no_areas_shown_message,
				'reorderModeOn'    => __( 'Reorder mode enabled' ),
				'reorderModeOff'   => __( 'Reorder mode closed' ),
				'reorderLabelOn'   => esc_attr__( 'Reorder widgets' ),
				/* translators: %d: the number of widgets found */
				'widgetsFound'     => __( 'Number of widgets found: %d' ),
				'noWidgetsFound'   => __( 'No widgets found.' ),
			),
			'tpl' => array(
				'widgetReorderNav' => $widget_reorder_nav_tpl,
				'moveWidgetArea'   => $move_widget_area_tpl,
			),
			'selectiveRefreshableWidgets' => $this->get_selective_refreshable_widgets(),
		);

		foreach ( $settings['registeredWidgets'] as &$registered_widget ) {
			unset( $registered_widget['callback'] ); // may not be JSON-serializeable
		}

		$wp_scripts->add_data(
			'customize-widgets',
			'data',
			sprintf( 'var _wpCustomizeWidgetsSettings = %s;', wp_json_encode( $settings ) )
		);
	}