.. _Specification:

=============
Specification
=============

This document defines how the wcwidth library measures the printable width
of characters of a string.

Width of -1
-----------

The following have a column width of -1 for function :func:`wcwidth.wcwidth`

- ``C0`` control characters (`U+0001`_ through `U+001F`_).
- ``C1`` control characters and ``DEL`` (`U+007F`_ through `U+00A0`_).

If any character in sequence contains ``C0`` or ``C1`` control characters, the final
return value of of :func:`wcwidth.wcswidth` is -1.

Width of 0
----------

Any characters defined by category codes in `DerivedGeneralCategory.txt`_ files:

- 'Me': Enclosing Combining Mark, aprox. 13 characters.
- 'Mn': Nonspacing Combining Mark, aprox. 1,839 characters.
- 'Mc': Spacing Mark, aprox. 443 characters.
- 'Cf': Format control character, aprox. 161 characters.
- 'Zl': `U+2028`_ LINE SEPARATOR only
- 'Zp': `U+2029`_ PARAGRAPH SEPARATOR only
- 'Sk': Modifier Symbol, aprox. 4 characters of only those where phrase
  ``'EMOJI MODIFIER'`` is present in comment of unicode data file.

The NULL character (`U+0000`_).

Any character following ZWJ (`U+200D`_) when in sequence by
function :func:`wcwidth.wcswidth`.

Hangul Jamo Jungseong and "Extended-B" code blocks, `U+1160`_ through
`U+11FF`_ and `U+D7B0`_ through `U+D7FF`_.


Width of 1
----------

String characters are measured width of 1 when they are not
measured as `Width of 0`_ or `Width of 2`_.

Width of 2
----------

Any character defined by East Asian Fullwidth (``F``) or Wide (``W``)
properties in `EastAsianWidth.txt`_ files, except those that are defined by the
Category codes of Nonspacing Mark (``Mn``) and Spacing Mark (``Mc``).

Any characters of Modifier Symbol category, ``'Sk'`` where ``'FULLWIDTH'`` is
present in comment of unicode data file, aprox. 3 characters.

Any character in sequence with `U+FE0F`_ (Variation Selector 16) defined by
`emoji-variation-sequences.txt`_ as ``emoji style``.


.. _`U+0000`: https://codepoints.net/U+0000
.. _`U+0001`: https://codepoints.net/U+0001
.. _`U+001F`: https://codepoints.net/U+001F
.. _`U+007F`: https://codepoints.net/U+007F
.. _`U+00A0`: https://codepoints.net/U+00A0
.. _`U+1160`: https://codepoints.net/U+1160
.. _`U+11FF`: https://codepoints.net/U+11FF
.. _`U+200D`: https://codepoints.net/U+200D
.. _`U+2028`: https://codepoints.net/U+2028
.. _`U+2029`: https://codepoints.net/U+2029
.. _`U+D7B0`: https://codepoints.net/U+D7B0
.. _`U+D7FF`: https://codepoints.net/U+D7FF
.. _`U+FE0F`: https://codepoints.net/U+FE0F
.. _`DerivedGeneralCategory.txt`: https://www.unicode.org/Public/UCD/latest/ucd/extracted/DerivedGeneralCategory.txt
.. _`EastAsianWidth.txt`: https://www.unicode.org/Public/UCD/latest/ucd/EastAsianWidth.txt
.. _`emoji-variation-sequences.txt`: https://www.unicode.org/Public/UCD/latest/ucd/emoji/emoji-variation-sequences.txt