Methods for retrieving widget instances.

americanaura-widget-classes.php

<?php
function americanaura_widget_classes( $params ) {
	if ( 'pinboard' != $params[0]['id'] ) {
		return $params;
	}

	// If a track has a file add a '.js-playable' class to the widget container
	if ( 'audiotheme-track' == $widget_id_base ) {
		$instance = americanaura_get_widget_instance( $params[0]['widget_id'], $params[1]['number'] );
		if ( isset( $instance['post_id'] ) && get_audiotheme_track_file_url( $instance['post_id'] ) ) {
			$params[0]['before_widget'] = str_replace( '">', ' js-playable">', $params[0]['before_widget'] );
		}
	}

	return $params;
}
add_filter( 'dynamic_sidebar_params', 'americanaura_widget_classes' );

/**
 * Retrieve a widget instance.
 *
 * A helper function for retrieving a specific widget instance. The widget ID
 * and instance number must be known.
 *
 * @param string $widget_id Widget identifier.
 * @param int $number Widget number.
 * @return array
 */
function americanaura_get_widget_instance( $widget_id, $number ) {
	global $wp_registered_widgets;

	$widget_instance = null;
	if ( isset( $wp_registered_widgets[ $widget_id ] ) ) {
		$widget = $wp_registered_widgets[ $widget_id ];

		$widget_instances = get_option( $widget['callback'][0]->option_name );
		$widget_instance = $widget_instances[ $number ];
	}

	return $widget_instance;
}

tortilla-widget-api.php

<?php
/**
 * Retrieve a widget instance.
 *
 * A helper function for retrieving a specific widget instance. The widget ID
 * and instance number must be known.
 *
 * Inspect the $wp_registered_widgets global for widget ids and numbers.
 *
 * @since 1.0.0
 * @uses $wp_registered_widgets
 *
 * @param string $widget_id
 * @param int $number
 * @return array
 */
function tortilla_get_widget_instance( $widget_id, $number ) {
	global $wp_registered_widgets;

	$widget_instance = null;
	if ( isset( $wp_registered_widgets[ $widget_id ] ) ) {
		$widget = $wp_registered_widgets[ $widget_id ];

		$widget_instances = get_option( $widget['callback'][0]->option_name );
		$widget_instance = $widget_instances[ $number ];
	}

	return $widget_instance;
}

/**
 * Retrieve a list of widget instances for a given widget area.
 *
 * @since 1.0.0
 * @see dynamic_sidebar()
 * @uses tortilla_is_valid_sidebar()
 * @uses tortilla_get_widget_instance()
 *
 * @param int|string $index Widget area id.
 * @return array
 */
function tortilla_get_widget_instances( $index = 1 ) {
	global $wp_registered_sidebars, $wp_registered_widgets;

	$index = tortilla_is_valid_sidebar( $index );
	if ( ! $index ) {
		return false;
	}

	$widgets = array();
	$sidebar = $wp_registered_sidebars[ $index ];
	$sidebars_widgets = wp_get_sidebars_widgets();

	foreach( $sidebars_widgets[ $index ] as $id ) {
		if ( ! isset( $wp_registered_widgets[ $id ] ) ) {
			continue;
		}

		$widget = $wp_registered_widgets[ $id ];
		$class = get_class( $widget['callback'][0] );
		$instance = tortilla_get_widget_instance( $id, $widget['params'][0]['number'] );

		// Add some extra args to indicate the type of widget.
		$instance['widget_id_base'] = $widget['callback'][0]->id_base;
		$instance['widget_classname'] = $widget['classname'];

		$widgets[] = $instance;
	}

	return ( empty( $widgets ) ) ? false : $widgets;
}

/**
 * Determine if a given identifier is a valid sidebar and retrieve it's id.
 *
 * Converts sidebar names and integers to ids.
 *
 * @since 1.0.0
 * @see dynamic_sidebar()
 *
 * @param string|int $index A sidebar identifier (id|name|numeric index).
 * @return string|bool The sidebar id if found or false if not.
 */
function tortilla_is_valid_sidebar( $index ) {
	global $wp_registered_sidebars;

	if ( is_int( $index ) ) {
		$index = 'sidebar-' . $index;
	} else {
		$index = sanitize_title( $index );
		foreach ( (array) $wp_registered_sidebars as $key => $value ) {
			if ( sanitize_title( $value['name'] ) == $index ) {
				$index = $key;
				break;
			}
		}
	}

	$sidebars_widgets = wp_get_sidebars_widgets();
	if ( empty( $sidebars_widgets ) ) {
		return false;
	}

	if ( empty( $wp_registered_sidebars[ $index ] ) || ! array_key_exists( $index, $sidebars_widgets ) || ! is_array( $sidebars_widgets[ $index ] ) || empty( $sidebars_widgets[ $index ] ) ) {
		return false;
	}

	return $index;
}