Default custom background callback.

function _custom_background_cb() {
	// $background is the saved custom image, or the default image.
	$background = set_url_scheme( get_background_image() );

	// $color is the saved custom color.
	// A default has to be specified in style.css. It will not be printed here.
	$color = get_background_color();

	if ( get_theme_support( 'custom-background', 'default-color' ) === $color ) {
		$color = false;
	}

	$type_attr = current_theme_supports( 'html5', 'style' ) ? '' : ' type="text/css"';

	if ( ! $background && ! $color ) {
		if ( is_customize_preview() ) {
			printf( '', $type_attr );
		}
		return;
	}

	$style = $color ? "background-color: #$color;" : '';

	if ( $background ) {
		$image = ' background-image: url("' . sanitize_url( $background ) . '");';

		// Background Position.
		$position_x = get_theme_mod( 'background_position_x', get_theme_support( 'custom-background', 'default-position-x' ) );
		$position_y = get_theme_mod( 'background_position_y', get_theme_support( 'custom-background', 'default-position-y' ) );

		if ( ! in_array( $position_x, array( 'left', 'center', 'right' ), true ) ) {
			$position_x = 'left';
		}

		if ( ! in_array( $position_y, array( 'top', 'center', 'bottom' ), true ) ) {
			$position_y = 'top';
		}

		$position = " background-position: $position_x $position_y;";

		// Background Size.
		$size = get_theme_mod( 'background_size', get_theme_support( 'custom-background', 'default-size' ) );

		if ( ! in_array( $size, array( 'auto', 'contain', 'cover' ), true ) ) {
			$size = 'auto';
		}

		$size = " background-size: $size;";

		// Background Repeat.
		$repeat = get_theme_mod( 'background_repeat', get_theme_support( 'custom-background', 'default-repeat' ) );

		if ( ! in_array( $repeat, array( 'repeat-x', 'repeat-y', 'repeat', 'no-repeat' ), true ) ) {
			$repeat = 'repeat';
		}

		$repeat = " background-repeat: $repeat;";

		// Background Scroll.
		$attachment = get_theme_mod( 'background_attachment', get_theme_support( 'custom-background', 'default-attachment' ) );

		if ( 'fixed' !== $attachment ) {
			$attachment = 'scroll';
		}

		$attachment = " background-attachment: $attachment;";

		$style .= $image . $position . $size . $repeat . $attachment;
	}
	?>