TCPDF::GetArrStringWidth()
Method: Returns the string length of an array of chars in user unit or an array of characters widths. A font must be selected.
Source: includes/lib/tcpdf/tcpdf.php:4071
TCPDF::GetCharWidth()
Method: Returns the length of the char in user unit for the current font considering current stretching and spacing (tracking).
Source: includes/lib/tcpdf/tcpdf.php:4110
TCPDF_FONTS::utf8Bidi()
Method: Reverse the RLT substrings using the Bidirectional Algorithm (http://unicode.org/reports/tr9/).
Source: includes/lib/tcpdf/include/tcpdf_fonts.php:2093