Determines the monospace display width of a string in Ruby. Implementation based on EastAsianWidth.txt and other data, 100% in Ruby. Other than wcwidth(), which fulfills a similar purpose, it does not rely on the OS vendor to provide an up-to-date method for measuring string width. Guesing the correct space a character will consume on terminals is not easy. There is no single standard. Most implementations combine data from East Asian Width, some General Categories, and hand-picked adjustments.