current_theme_supports( string $feature, mixed $args )

function current_theme_supports( $feature ) {
	global $_wp_theme_features;

	if ( 'custom-header-uploads' == $feature )
		return current_theme_supports( 'custom-header', 'uploads' );

	if ( !isset( $_wp_theme_features[$feature] ) )
		return false;

	// If no args passed then no extra checks need be performed
	if ( func_num_args() <= 1 )
		return true;

	$args = array_slice( func_get_args(), 1 );

	switch ( $feature ) {
		case 'post-thumbnails':
			// post-thumbnails can be registered for only certain content/post types by passing
			// an array of types to add_theme_support(). If no array was passed, then
			// any type is accepted
			if ( true === $_wp_theme_features[$feature] )  // Registered for all types
				return true;
			$content_type = $args[0];
			return in_array( $content_type, $_wp_theme_features[$feature][0] );

		case 'html5':
		case 'post-formats':
			// specific post formats can be registered by passing an array of types to
			// add_theme_support()

			// Specific areas of HTML5 support *must* be passed via an array to add_theme_support()

			$type = $args[0];
			return in_array( $type, $_wp_theme_features[$feature][0] );

		case 'custom-logo':
		case 'custom-header':
		case 'custom-background':
			// Specific capabilities can be registered by passing an array to add_theme_support().
			return ( isset( $_wp_theme_features[ $feature ][0][ $args[0] ] ) && $_wp_theme_features[ $feature ][0][ $args[0] ] );
	}

	/**
	 * Filters whether the current theme supports a specific feature.
	 *
	 * The dynamic portion of the hook name, `$feature`, refers to the specific theme
	 * feature. Possible values include 'post-formats', 'post-thumbnails', 'custom-background',
	 * 'custom-header', 'menus', 'automatic-feed-links', 'html5',
	 * 'starter-content', and 'customize-selective-refresh-widgets'.
	 *
	 * @since WP-3.4.0
	 *
	 * @param bool   true     Whether the current theme supports the given feature. Default true.
	 * @param array  $args    Array of arguments for the feature.
	 * @param string $feature The theme feature.
	 */
	return apply_filters( "current_theme_supports-{$feature}", true, $args, $_wp_theme_features[$feature] );
}