207 lines
7.2 KiB
Python
207 lines
7.2 KiB
Python
"""
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This is an implementation of wcwidth() and wcswidth().
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Defined in IEEE Std 1002.1-2001.
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https://github.com/jquast/wcwidth
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from Markus Kuhn's C code at:
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http://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c
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This is an implementation of wcwidth() and wcswidth() (defined in
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IEEE Std 1002.1-2001) for Unicode.
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http://www.opengroup.org/onlinepubs/007904975/functions/wcwidth.html
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http://www.opengroup.org/onlinepubs/007904975/functions/wcswidth.html
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In fixed-width output devices, Latin characters all occupy a single
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"cell" position of equal width, whereas ideographic CJK characters
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occupy two such cells. Interoperability between terminal-line
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applications and (teletype-style) character terminals using the
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UTF-8 encoding requires agreement on which character should advance
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the cursor by how many cell positions. No established formal
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standards exist at present on which Unicode character shall occupy
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how many cell positions on character terminals. These routines are
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a first attempt of defining such behavior based on simple rules
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applied to data provided by the Unicode Consortium.
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For some graphical characters, the Unicode standard explicitly
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defines a character-cell width via the definition of the East Asian
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FullWidth (F), Wide (W), Half-width (H), and Narrow (Na) classes.
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In all these cases, there is no ambiguity about which width a
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terminal shall use. For characters in the East Asian Ambiguous (A)
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class, the width choice depends purely on a preference of backward
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compatibility with either historic CJK or Western practice.
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Choosing single-width for these characters is easy to justify as
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the appropriate long-term solution, as the CJK practice of
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displaying these characters as double-width comes from historic
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implementation simplicity (8-bit encoded characters were displayed
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single-width and 16-bit ones double-width, even for Greek,
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Cyrillic, etc.) and not any typographic considerations.
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Much less clear is the choice of width for the Not East Asian
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(Neutral) class. Existing practice does not dictate a width for any
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of these characters. It would nevertheless make sense
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typographically to allocate two character cells to characters such
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as for instance EM SPACE or VOLUME INTEGRAL, which cannot be
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represented adequately with a single-width glyph. The following
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routines at present merely assign a single-cell width to all
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neutral characters, in the interest of simplicity. This is not
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entirely satisfactory and should be reconsidered before
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establishing a formal standard in this area. At the moment, the
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decision which Not East Asian (Neutral) characters should be
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represented by double-width glyphs cannot yet be answered by
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applying a simple rule from the Unicode database content. Setting
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up a proper standard for the behavior of UTF-8 character terminals
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will require a careful analysis not only of each Unicode character,
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but also of each presentation form, something the author of these
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routines has avoided to do so far.
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http://www.unicode.org/unicode/reports/tr11/
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Markus Kuhn -- 2007-05-26 (Unicode 5.0)
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Permission to use, copy, modify, and distribute this software
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for any purpose and without fee is hereby granted. The author
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disclaims all warranties with regard to this software.
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Latest version: http://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c
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"""
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from __future__ import division
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from .table_wide import WIDE_EASTASIAN
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from .table_zero import ZERO_WIDTH
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def _bisearch(ucs, table):
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"""
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Auxiliary function for binary search in interval table.
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:arg int ucs: Ordinal value of unicode character.
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:arg list table: List of starting and ending ranges of ordinal values,
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in form of ``[(start, end), ...]``.
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:rtype: int
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:returns: 1 if ordinal value ucs is found within lookup table, else 0.
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"""
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lbound = 0
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ubound = len(table) - 1
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if ucs < table[0][0] or ucs > table[ubound][1]:
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return 0
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while ubound >= lbound:
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mid = (lbound + ubound) // 2
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if ucs > table[mid][1]:
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lbound = mid + 1
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elif ucs < table[mid][0]:
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ubound = mid - 1
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else:
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return 1
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return 0
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def wcwidth(wc):
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r"""
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Given one unicode character, return its printable length on a terminal.
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The wcwidth() function returns 0 if the wc argument has no printable effect
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on a terminal (such as NUL '\0'), -1 if wc is not printable, or has an
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indeterminate effect on the terminal, such as a control character.
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Otherwise, the number of column positions the character occupies on a
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graphic terminal (1 or 2) is returned.
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The following have a column width of -1:
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- C0 control characters (U+001 through U+01F).
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- C1 control characters and DEL (U+07F through U+0A0).
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The following have a column width of 0:
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- Non-spacing and enclosing combining characters (general
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category code Mn or Me in the Unicode database).
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- NULL (U+0000, 0).
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- COMBINING GRAPHEME JOINER (U+034F).
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- ZERO WIDTH SPACE (U+200B) through
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RIGHT-TO-LEFT MARK (U+200F).
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- LINE SEPERATOR (U+2028) and
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PARAGRAPH SEPERATOR (U+2029).
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- LEFT-TO-RIGHT EMBEDDING (U+202A) through
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RIGHT-TO-LEFT OVERRIDE (U+202E).
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- WORD JOINER (U+2060) through
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INVISIBLE SEPARATOR (U+2063).
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The following have a column width of 1:
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- SOFT HYPHEN (U+00AD) has a column width of 1.
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- All remaining characters (including all printable
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ISO 8859-1 and WGL4 characters, Unicode control characters,
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etc.) have a column width of 1.
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The following have a column width of 2:
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- Spacing characters in the East Asian Wide (W) or East Asian
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Full-width (F) category as defined in Unicode Technical
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Report #11 have a column width of 2.
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"""
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# pylint: disable=C0103
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# Invalid argument name "wc"
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ucs = ord(wc)
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# NOTE: created by hand, there isn't anything identifiable other than
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# general Cf category code to identify these, and some characters in Cf
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# category code are of non-zero width.
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# pylint: disable=too-many-boolean-expressions
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# Too many boolean expressions in if statement (7/5)
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if (ucs == 0 or
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ucs == 0x034F or
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0x200B <= ucs <= 0x200F or
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ucs == 0x2028 or
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ucs == 0x2029 or
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0x202A <= ucs <= 0x202E or
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0x2060 <= ucs <= 0x2063):
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return 0
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# C0/C1 control characters
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if ucs < 32 or 0x07F <= ucs < 0x0A0:
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return -1
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# combining characters with zero width
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if _bisearch(ucs, ZERO_WIDTH):
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return 0
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return 1 + _bisearch(ucs, WIDE_EASTASIAN)
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def wcswidth(pwcs, n=None):
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"""
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Given a unicode string, return its printable length on a terminal.
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Return the width, in cells, necessary to display the first ``n``
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characters of the unicode string ``pwcs``. When ``n`` is None (default),
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return the length of the entire string.
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Returns ``-1`` if a non-printable character is encountered.
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"""
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# pylint: disable=C0103
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# Invalid argument name "n"
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end = len(pwcs) if n is None else n
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idx = slice(0, end)
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width = 0
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for char in pwcs[idx]:
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wcw = wcwidth(char)
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if wcw < 0:
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return -1
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else:
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width += wcw
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return width
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