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133 changes: 84 additions & 49 deletions README.rst
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Expand Up @@ -19,34 +19,40 @@ Introduction
============

This API is mainly for Terminal Emulator implementors -- any python program
that attempts to determine the printable width of a string on a Terminal.
that attempts to determine the printable width of a string on a Terminal. It
is implemented in python (no C library calls) and has no 3rd-party dependencies.

It is certainly possible to use your Operating System's ``wcwidth()`` and
``wcswidth()`` calls if it is POSIX-conforming, but this would not be possible
It is certainly possible to use your Operating System's ``wcwidth(3)`` and
``wcswidth(3)`` calls if it is POSIX-conforming, but this would not be possible
on non-POSIX platforms, such as Windows, or for alternative Python
implementations, such as jython.

Furthermore, testing (`wcwidth-libc-comparator.py`_) has shown that libc
wcwidth() is particularly out of date on most operating systems, reporting -1
for a great many characters that are actually a displayable width of 1 or 2.
implementations, such as jython. It is also commonly many releases older
than the most current Unicode Standard release files, which this project
aims to track.

The most current release of this API is based from Unicode Standard release
_7.0.0_, dated 2014-02-28, 23:15:00 GMT [KW, LI]
*7.0.0*, dated *2014-02-28, 23:15:00 GMT [KW, LI]* for table generated by
file ``EastAsianWidth-7.0.0.txt`` and *2014-02-07, 18:42:08 GMT [MD]* for
``DerivedCombiningClass-7.0.0.txt``.

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

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

pip install wcwidth

Problem
-------

You may have noticed some characters especially Chinese, Japanese, and
Korean (collectively known as the *CJK Unified Ideographs*) consume more
than 1 terminal cell.

In python, if you ask for the length of the string, ``u'コンニチハ'``
(Japanese: Hello), it is correctly determined to be a length of **5**.
than 1 terminal cell. If you ask for the length of the string, ``u'コンニチハ'``
(Japanese: Hello), it is correctly determined to be a length of **5** using
the ``len()`` built-in.

However, if you were to print this to a Terminal Emulator, such as xterm,
urxvt, Terminal.app, or PuTTY, it would consume **10** *cells* (columns) --
two for each symbol.

urxvt, Terminal.app, PuTTY, or iTerm2, it would consume **10** *cells* (columns).
This causes problems for many of the text-alignment functions, such as ``rjust()``.
On an 80-wide terminal, the following would wrap along the margin, instead
of displaying it right-aligned as desired::

Expand All @@ -65,17 +71,10 @@ that the length of ``wcwidth(u'コ')`` is reported as ``2``, and
This allows one to determine the printable effects of displaying *CJK*
characters on a terminal emulator.

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

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

pip install wcwidth

wcwidth, wcswidth
-----------------
Use ``wcwidth`` to determine the length of a single character,
and ``wcswidth`` to determine the length of a string of characters.
Use ``wcwidth`` to determine the length of a *single character*,
and ``wcswidth`` to determine the length of a *string of characters*.

To Display ``u'コンニチハ'`` right-adjusted on screen of 80 columns::

Expand All @@ -88,9 +87,9 @@ To Display ``u'コンニチハ'`` right-adjusted on screen of 80 columns::
Values
------

See the docstring for ``wcwidth()``, general overview of return values:
A general overview of return values:

- ``-1``: indeterminate, such as combining_ characters.
- ``-1``: indeterminate (see Todo_).

- ``0``: do not advance the cursor, such as NULL.

Expand All @@ -99,12 +98,37 @@ See the docstring for ``wcwidth()``, general overview of return values:
- ``1``: all others.

``wcswidth()`` simply returns the sum of all values along a string, or
``-1`` if it has occurred for any value returned by ``wcwidth()``.
``-1`` if it has occurred for any value returned by ``wcwidth()``. A more
exacting list of conditions and return values may be found in the docstring
for ``wcwidth()``.

Discrepacies
------------

There may be discrepancies with the determined printable width of of characters
by *wcwidth* and the results of any given terminal emulator -- most commonly,
emulators are using your Operating System's ``wcwidth(3)`` implementation which
is often based on tables much older than the most current Unicode Specification.
Python's determination of non-zero combining_ characters may also be based on an
older specification.

You may determine an exacting list of these discrepancies using files
`wcwidth-libc-comparator.py`_ and `wcwidth-combining-comparator.py`_

.. _`wcwidth-libc-comparator.py`: https://github.com/jquast/wcwidth/tree/master/bin/wcwidth-libc-comparator.py
.. _`wcwidth-combining-comparator.py`: https://github.com/jquast/wcwidth/tree/master/bin/wcwidth-combining-comparator.py


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

Execute the command ``python setup.py develop`` to prepare an environment
for running tests (``python setup.py test``), updating tables (
``python setup.py update``) or using any of the scripts in the ``bin/``
sub-folder. These files are only made available in the source repository.


Updating Tables
---------------

Expand All @@ -113,7 +137,10 @@ The command ``python setup.py update`` will fetch the following resources:
- http://www.unicode.org/Public/UNIDATA/EastAsianWidth.txt
- http://www.unicode.org/Public/UNIDATA/extracted/DerivedCombiningClass.txt

Generating the table files `wcwidth/table_wide.py`_ and `wcwidth/table_comb.py`_.
And generate the table files `wcwidth/table_wide.py`_ and `wcwidth/table_comb.py`_.

.. _`wcwidth/table_wide.py`: https://github.com/jquast/wcwidth/tree/master/wcwidth/table_wide.py
.. _`wcwidth/table_comb.py`: https://github.com/jquast/wcwidth/tree/master/wcwidth/table_comb.py

wcwidth.c
---------
Expand All @@ -122,9 +149,8 @@ This code was originally derived directly from C code of the same name,
whose latest version is available at: `wcwidth.c`_ And is authored by
Markus Kuhn -- 2007-05-26 (Unicode 5.0)

Any subsequent changes were done by directly testing against the various libc
implementations of POSIX-compliant Operating Systems, such as Mac OSX, Linux,
and OpenSolaris.
.. _`wcwidth.c`: http://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c


Examples
--------
Expand All @@ -133,17 +159,24 @@ This library is used in:

- `jquast/blessed`_, a simplified wrapper around curses.

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

Additional tools for displaying and testing wcwidth is found in the ``bin/``
folder of this project (github link: `wcwidth/bin`_). They are not distributed
as a script or part of the module.

.. _`jquast/blessed`: https://github.com/jquast/blessed
.. _`jonathanslenders/python-prompt-toolkit`: https://github.com/jonathanslenders/python-prompt-toolkit
.. _`wcwidth/bin`: https://github.com/jquast/wcwidth/tree/master/bin

Todo
----

It is my wish that `combining`_ characters are understood. Currently,
any string containing combining characters will always return ``-1``.
Though some of the most common ("zero-width") `combining`_ characters
are understood by wcswidth, there are still many edge cases that need
to be covered, especially certain kinds of sequences such as those
containing Control-Sequence-Inducer (CSI).


License
Expand Down Expand Up @@ -181,31 +214,33 @@ an OSI-approved license that appears most-alike has been chosen, the MIT license
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

.. _`jquast/blessed`: https://github.com/jquast/blessed
.. _`jonathanslenders/python-prompt-toolkit`: https://github.com/jonathanslenders/python-prompt-toolkit
.. _`wcwidth/bin`: https://github.com/jquast/wcwidth/tree/master/bin
.. _`wcwidth-libc-comparator.py`: https://github.com/jquast/wcwidth/tree/master/bin/wcwidth-libc-comparator.py
.. _`wcwidth/table_wide.py`: https://github.com/jquast/wcwidth/tree/master/wcwidth/table_wide.py
.. _`wcwidth/table_comb.py`: https://github.com/jquast/wcwidth/tree/master/wcwidth/table_comb.py
.. _`combining`: https://en.wikipedia.org/wiki/Combining_character
.. _`wcwidth.c`: http://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c

Changes
-------

0.1.4
* **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`_).
* added static analysis (prospector_) to testing framework.

0.1.3
* *Bugfix*: 2nd parameter of wcswidth was not honored.
(`thomasballinger`_ PR #4).
* **Bugfix**: 2nd parameter of wcswidth was not honored.
(`Thomas Ballinger`_, `PR #4`).

0.1.2
* Updated tables to Unicode Specification 7.0.0
(`thomasballinger`_ PR #3).
* **Updated** tables to Unicode Specification 7.0.0.
(`Thomas Ballinger`_, `PR #3`).

0.1.1
* Initial release to pypi, Based on Unicode Specification 6.3.0

.. _`thomasballinger`: https://github.com/thomasballinger
.. _`prospector`: https://github.com/landscapeio/prospector
.. _`combining`: https://en.wikipedia.org/wiki/Combining_character
.. _`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
.. _`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
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