How Many Non-printing Characters Are In Common Use?

When writing interpreters for PDF, HTML and other documents we need to deal with a variety of white-space characters and additional non-printing characters. The ANSI ones are well

Solution 1:

Unicode will be with us, in increasing quantity, for a long time. If an HTML or XML document is written in UTF-8 encoded Unicode, then you should expect any and all of these to appear.

In Unicode (Unicode Character Database) the following codepoints are defined as whitespace:

U+0009–U+000D (control characters, containing Tab, CR and LF)
U+0020 SPACE
U+0085 NEL (control character next line)
U+00A0 NBSP (NO-BREAK SPACE)
U+1680 OGHAM SPACE MARK
U+180E MONGOLIAN VOWEL SEPARATOR
U+2000–U+200A (different sorts of spaces)
U+2028 LS (LINE SEPARATOR)
U+2029 PS (PARAGRAPH SEPARATOR)
U+202F NNBSP (NARROW NO-BREAK SPACE)
U+205F MMSP (MEDIUM MATHEMATICAL SPACE)
U+3000 IDEOGRAPHIC SPACE

Solution 2:

In development world there's at least one more (most often used in web development)

   // non-breaking space

But the more you get to design world the more you see various space/invisible characters. Publishing software normally has

• space - the regular SPACE
• en space
• em space
• thin space
• hair space
• non-breaking space
• non-breaking fixed width space
• sixth space
• quarter space
• third space
• punctuation space
• flush space
• figure space
• ...