|pypi_downloads| |codecov| |license|

============
Introduction
============

This library is mainly for CLI programs that carefully produce output for
Terminals, or make pretend to be an emulator.

**Problem Statement**: The printable length of *most* strings are equal to the
number of cells they occupy on the screen ``1 charater : 1 cell``.  However,
there are categories of characters that *occupy 2 cells* (full-wide), and
others that *occupy 0* cells (zero-width).

**Solution**: POSIX.1-2001 and POSIX.1-2008 conforming systems provide
`wcwidth(3)`_ and `wcswidth(3)`_ C functions of which this python module's
functions precisely copy.  *These functions return the number of cells a
unicode string is expected to occupy.*

Installation
------------

The stable version of this package is maintained on pypi, install using pip::

    pip install wcwidth

Example
-------

**Problem**: given the following phrase (Japanese),

   >>>  text = u'コンニチハ'

Python **incorrectly** uses the *string length* of 5 codepoints rather than the
*printible length* of 10 cells, so that when using the `rjust` function, the
output length is wrong::

    >>> print(len('コンニチハ'))
    5

    >>> print('コンニチハ'.rjust(20, '_'))
    _____コンニチハ

By defining our own "rjust" function that uses wcwidth, we can correct this::

   >>> def wc_rjust(text, length, padding=' '):
   ...    from wcwidth import wcswidth
   ...    return padding * max(0, (length - wcswidth(text))) + text
   ...

Our **Solution** uses wcswidth to determine the string length correctly::

   >>> from wcwidth import wcswidth
   >>> print(wcswidth('コンニチハ'))
   10

   >>> print(wc_rjust('コンニチハ', 20, '_'))
   __________コンニチハ


Choosing a Version
------------------

Export an environment variable, ``UNICODE_VERSION``. This should be done by
*terminal emulators* or those developers experimenting with authoring one of
their own, from shell::

   $ export UNICODE_VERSION=13.0

If unspecified, the latest version is used. If your Terminal Emulator does not
export this variable, you can use the `jquast/ucs-detect`_ utility to
automatically detect and export it to your shell.

wcwidth, wcswidth
-----------------
Use function ``wcwidth()`` to determine the length of a *single unicode
character*, and ``wcswidth()`` to determine the length of many, a *string
of unicode characters*.

Briefly, return values of function ``wcwidth()`` are:

``-1``
  Indeterminate (not printable).

``0``
  Does not advance the cursor, such as NULL or Combining.

``2``
  Characters of category East Asian Wide (W) or East Asian
  Full-width (F) which are displayed using two terminal cells.

``1``
  All others.

Function ``wcswidth()`` simply returns the sum of all values for each character
along a string, or ``-1`` when it occurs anywhere along a string.

Full API Documentation at http://wcwidth.readthedocs.org

==========
Developing
==========

Install wcwidth in editable mode::

   pip install -e.

Execute unit tests using tox_::

   tox

Regenerate python code tables from latest Unicode Specification data files::

   tox -eupdate

Supplementary tools for browsing and testing terminals for wide unicode
characters are found in the `bin/`_ of this project's source code.  Just ensure
to first ``pip install -erequirements-develop.txt`` from this projects main
folder. For example, an interactive browser for testing::

  ./bin/wcwidth-browser.py

Uses
----

This library is used in:

- `jquast/blessed`_: a thin, practical wrapper around terminal capabilities in
  Python.

- `jonathanslenders/python-prompt-toolkit`_: a Library for building powerful
  interactive command lines in Python.

- `dbcli/pgcli`_: Postgres CLI with autocompletion and syntax highlighting.

- `thomasballinger/curtsies`_: a Curses-like terminal wrapper with a display
  based on compositing 2d arrays of text.

- `selectel/pyte`_: Simple VTXXX-compatible linux terminal emulator.

- `astanin/python-tabulate`_: Pretty-print tabular data in Python, a library
  and a command-line utility.

- `LuminosoInsight/python-ftfy`_: Fixes mojibake and other glitches in Unicode
  text.

- `nbedos/termtosvg`_: Terminal recorder that renders sessions as SVG
  animations.

- `peterbrittain/asciimatics`_: Package to help people create full-screen text
  UIs.

Other Languages
---------------

- `timoxley/wcwidth`_: JavaScript
- `janlelis/unicode-display_width`_: Ruby
- `alecrabbit/php-wcwidth`_: PHP
- `Text::CharWidth`_: Perl
- `bluebear94/Terminal-WCWidth`: Perl 6
- `mattn/go-runewidth`_: Go
- `emugel/wcwidth`_: Haxe
- `aperezdc/lua-wcwidth`: Lua
- `joachimschmidt557/zig-wcwidth`: Zig
- `fumiyas/wcwidth-cjk`: `LD_PRELOAD` override
- `joshuarubin/wcwidth9`: Unicode version 9 in C

History
-------

0.2.0 *2020-06-01*
  * **Enhancement**: Unicode version may be selected by exporting the
    Environment variable ``UNICODE_VERSION``, such as ``13.0``, or ``6.3.0``.
    See the `jquast/ucs-detect`_ CLI utility for automatic detection.
  * **Enhancement**:
    API Documentation is published to readthedocs.org.
  * **Updated** tables for *all* Unicode Specifications with files
    published in a programmatically consumable format, versions 4.1.0
    through 13.0
    that are published
    , versions

0.1.9 *2020-03-22*
  * **Performance** optimization by `Avram Lubkin`_, `PR #35`_.
  * **Updated** tables to Unicode Specification 13.0.0.

0.1.8 *2020-01-01*
  * **Updated** tables to Unicode Specification 12.0.0. (`PR #30`_).

0.1.7 *2016-07-01*
  * **Updated** tables to Unicode Specification 9.0.0. (`PR #18`_).

0.1.6 *2016-01-08 Production/Stable*
  * ``LICENSE`` file now included with distribution.

0.1.5 *2015-09-13 Alpha*
  * **Bugfix**:
    Resolution of "combining_ character width" issue, most especially
    those that previously returned -1 now often (correctly) return 0.
    resolved by `Philip Craig`_ via `PR #11`_.
  * **Deprecated**:
    The module path ``wcwidth.table_comb`` is no longer available,
    it has been superseded by module path ``wcwidth.table_zero``.

0.1.4 *2014-11-20 Pre-Alpha*
  * **Feature**: ``wcswidth()`` now determines printable length
    for (most) combining_ characters.  The developer's tool
    `bin/wcwidth-browser.py`_ is improved to display combining_
    characters when provided the ``--combining`` option
    (`Thomas Ballinger`_ and `Leta Montopoli`_ `PR #5`_).
  * **Feature**: added static analysis (prospector_) to testing
    framework.

0.1.3 *2014-10-29 Pre-Alpha*
  * **Bugfix**: 2nd parameter of wcswidth was not honored.
    (`Thomas Ballinger`_, `PR #4`_).

0.1.2 *2014-10-28 Pre-Alpha*
  * **Updated** tables to Unicode Specification 7.0.0.
    (`Thomas Ballinger`_, `PR #3`_).

0.1.1 *2014-05-14 Pre-Alpha*
  * Initial release to pypi, Based on Unicode Specification 6.3.0

This code was originally derived directly from C code of the same name,
whose latest version is available at
http://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c::

 * Markus Kuhn -- 2007-05-26 (Unicode 5.0)
 *
 * Permission to use, copy, modify, and distribute this software
 * for any purpose and without fee is hereby granted. The author
 * disclaims all warranties with regard to this software.

.. _`tox`: https://testrun.org/tox/latest/install.html
.. _`prospector`: https://github.com/landscapeio/prospector
.. _`combining`: https://en.wikipedia.org/wiki/Combining_character
.. _`bin/`: https://github.com/jquast/wcwidth/tree/master/bin
.. _`bin/wcwidth-browser.py`: https://github.com/jquast/wcwidth/tree/master/bin/wcwidth-browser.py
.. _`Thomas Ballinger`: https://github.com/thomasballinger
.. _`Leta Montopoli`: https://github.com/lmontopo
.. _`Philip Craig`: https://github.com/philipc
.. _`PR #3`: https://github.com/jquast/wcwidth/pull/3
.. _`PR #4`: https://github.com/jquast/wcwidth/pull/4
.. _`PR #5`: https://github.com/jquast/wcwidth/pull/5
.. _`PR #11`: https://github.com/jquast/wcwidth/pull/11
.. _`PR #18`: https://github.com/jquast/wcwidth/pull/18
.. _`PR #30`: https://github.com/jquast/wcwidth/pull/30
.. _`PR #35`: https://github.com/jquast/wcwidth/pull/35
.. _`jquast/blessed`: https://github.com/jquast/blessed
.. _`selectel/pyte`: https://github.com/selectel/pyte
.. _`thomasballinger/curtsies`: https://github.com/thomasballinger/curtsies
.. _`dbcli/pgcli`: https://github.com/dbcli/pgcli
.. _`jonathanslenders/python-prompt-toolkit`: https://github.com/jonathanslenders/python-prompt-toolkit
.. _`timoxley/wcwidth`: https://github.com/timoxley/wcwidth
.. _`wcwidth(3)`:  http://man7.org/linux/man-pages/man3/wcwidth.3.html
.. _`wcswidth(3)`: http://man7.org/linux/man-pages/man3/wcswidth.3.html
.. _`astanin/python-tabulate`: https://github.com/astanin/python-tabulate
.. _`janlelis/unicode-display_width`: https://github.com/janlelis/unicode-display_width
.. _`LuminosoInsight/python-ftfy`: https://github.com/LuminosoInsight/python-ftfy
.. _`alecrabbit/php-wcwidth`: https://github.com/alecrabbit/php-wcwidth
.. _`Text::CharWidth`: https://metacpan.org/pod/Text::CharWidth
.. _`bluebear94/Terminal-WCWidth`: https://github.com/bluebear94/Terminal-WCWidth
.. _`mattn/go-runewidth`: https://github.com/mattn/go-runewidth
.. _`emugel/wcwidth`: https://github.com/emugel/wcwidth
.. _`jquast/ucs-detect`: https://github.com/jquast/ucs-detect
.. _`Avram Lubkin`: https://github.com/avylove
.. _`nbedos/termtosvg`: https://github.com/nbedos/termtosvg
.. _`peterbrittain/asciimatics`: https://github.com/peterbrittain/asciimatics
.. _`aperezdc/lua-wcwidth`: https://github.com/aperezdc/lua-wcwidth
.. _`fumiyas/wcwidth-cjk`: https://github.com/fumiyas/wcwidth-cjk
.. |pypi_downloads| image:: https://img.shields.io/pypi/dm/wcwidth.svg?logo=pypi
    :alt: Downloads
    :target: https://pypi.org/project/wcwidth/
.. |codecov| image:: https://codecov.io/gh/jquast/wcwidth/branch/master/graph/badge.svg
    :alt: codecov.io Code Coverage
    :target: https://codecov.io/gh/jquast/wcwidth/
.. |license| image:: https://img.shields.io/github/license/jquast/wcwidth.svg
    :target: https://pypi.python.org/pypi/wcwidth/
    :alt: MIT License
