private static function getProgressbarWidth( $prefix ) {
		$width = self::$_progressWidth;
		if ( $width === false ) {
			return 0;
		}
		$screenSize = static::getScreenSize( true );
		if ( $screenSize === false && $width < 1 ) {
			return 0;
		}
		if ( $width === null ) {
			$width = $screenSize[0];
		} else if ( $width > 0 && $width < 1 ) {
			$width = floor( $screenSize[0] * $width );
		}
		$width -= static::ansiStrlen( $prefix );

		return $width;
	}