Страницы справочника OS X

Эта страница руководства для  версии 10.9 Mac OS X

Читать страницы руководства

ntextWordBreak(n)             ntext Word Boundary Detection for the Text Widget            ntextWordBreak(n)



____________________________________________________________________________________________________________

NAME
       ntextWordBreak - ntext Word Boundary Detection for the Text Widget

SYNOPSIS
       package require Tcl  8.5

       package require Tk  8.5

       package require ntext  ?0.81?

____________________________________________________________________________________________________________

DESCRIPTION
       The  ntext package provides a binding tag named Ntext for use by text widgets in place of the default
       Text binding tag.

       Navigation and selection in a text widget require the detection of words and their  boundaries.   The
       word  boundary  detection  facilities  provided  by  Tcl/Tk  through the Text binding tag are limited
       because they define only one class of "word" characters and one class of "non-word" characters.   The
       Ntext  binding  tag  uses  more general rules for word boundary detection, that define two classes of
       "word" characters and one class of "non-word" characters.


CONFIGURATION OPTIONS
       The behaviour of Ntext may be configured application-wide by setting the values of a number of names-pace namespace
       pace variables.  One of these is relevant to word boundary detection:

       ::ntext::classicWordBreak

       •      0  -  (default  value) selects Ntext behaviour, i.e. platform-independent, two classes of word
              characters and one class of non-word characters.

       •      1 - selects classic Text behaviour, i.e. platform-dependent, one class of word characters  and
              one class of non-word characters

       •      After  changing  this  value,  Ntext  's regexp matching patterns should be recalculated.  See
              FUNCTIONS for details and advanced configuration options.



ADVANCED USE
VARIABLES (ADVANCED USE)
       ::ntext::tcl_match_wordBreakAfter

       ::ntext::tcl_match_wordBreakBefore

       ::ntext::tcl_match_endOfWord

       ::ntext::tcl_match_startOfNextWord

       ::ntext::tcl_match_startOfPreviousWord

       These variables hold the regexp patterns that are used by Ntext to search for  word  boundaries.   If
       they are changed, subsequent searches are immediately altered.  In many situations, it it unnecessary
       to alter the values of these variables directly: instead call one of the functions  ::ntext::initial-izeMatchPatterns, ::ntext::initializeMatchPatterns,
       izeMatchPatterns, ::ntext::createMatchPatterns.

       In  the  Text  binding tag one can change the search rules by changing the values of the global vari-ables variables
       ables tcl_wordchars and tcl_nonwordchars.  The equivalent operation in the Ntext binding  tag  is  to
       call ::ntext::createMatchPatterns with appropriate arguments.

FUNCTIONS (ADVANCED USE)
       If a simple regexp search should prove insufficient, the following functions (analogous to the Tcl/Tk
       core's tcl_wordBreakAfter etc) may be replaced by the developer:

       ntext::new_wordBreakAfter

       ntext::new_wordBreakBefore

       ntext::new_endOfWord

       ntext::new_startOfNextWord

       ntext::new_startOfPreviousWord


FUNCTIONS
       Each function calculates the five regexp search patterns that  define  the  word  boundary  searches.
       These values are stored in the namespace variables listed above.

       ::ntext::initializeMatchPatterns

       •      This  function  is  called  when Ntext is first used, and needs to be called again only if the
              script changes the value of either ::ntext::classicWordBreak or ::tcl_platform(platform).  The
              function  is  called with no arguments.  It is useful when the desired search patterns are the
              default patterns for either the Ntext or Text binding tag, and so are implicitly specified  by
              the values of ::ntext::classicWordBreak and ::tcl_platform(platform) alone.

       ::ntext::createMatchPatterns new_nonwordchars new_word1chars ?new_word2chars?

       •      This  function is useful in a wider range of situations than ::ntext::initializeMatchPatterns.
              It calculates the regexp search patterns for any case with one class of "non-word"  characters
              and one or two classes of "word" characters.

              Each  argument should be a regexp expression defining a class of characters.  An argument will
              usually be a bracket expression, but might alternatively be a  class-shorthand  escape,  or  a
              single  character.   The  third  argument  may be omitted, or supplied as the empty string, in
              which case it is unused.

              The first argument is interpreted as the class of non-word  characters;  the  second  argument
              (and  the  third,  if present) are classes of word characters.  The classes should include all
              possible characters and will normally be mutually exclusive: it is often convenient to  define
              one class as the negation of the other two.


WORD BOUNDARY MATCHING
       The  problem  of word boundary selection is a vexed one, because text is used to represent a universe
       of different types of information, and there are no simple rules that are useful for all  data  types
       or for all purposes.

       Ntext  attempts  to  improve  on the facilities available in classic Text by providing facilities for
       more complex definitions of words (with three classes of characters instead of two).

       What is a word?  Why two classes of word?

       When using the modified cursor keys <Control-Left> and <Control-Right> to navigate  through  a  Ntext
       widget,  the cursor is placed at the start of a word.  A word is defined as a sequence of one or more
       characters from only one of the two defined "word" classes; it may be preceded by  a  character  from
       the other "word" class or from the "non-word" class.

       The  double-click  of  mouse  button  1 selects a word of text, where in this case a "word" may be as
       defined above, or alternatively may be a sequence of one or more characters from the "non-word" class
       of characters.

       Traditionally  Tcl  has  defined only one word class and one non-word class: on Windows, the non-word
       class is whitespace, and so alphanumerics and punctuation belong to the same class.  On  other  plat-forms, platforms,
       forms,  punctuation is bundled with whitespace as "non-word" characters.  In either case, the naviga-tion navigation
       tion and selection of text are unnecessarily coarse-grained, and sometimes give unhelpful results.

       The use of three classes of characters might make selection too fine-grained; but in this case, hold-ing holding
       ing  down the Shift key and double-clicking another word is an excellent way to select a longer range
       of text (a useful binding that Tcl/Tk has long provided but which is missing in other systems).

       As well as its defaults, Ntext permits the developer to define their own classes of characters, or to
       revert to the classic Text definitions, or to specify their own regexp matching patterns.

EXAMPLE
       To use Ntext with Tcl/Tk's usual word-boundary detection rules:

       package require ntext
       text .t
       bindtags .t {.t Ntext . all}
       set ::ntext::classicWordBreak 1
       ::ntext::initializeMatchPatterns

       See bindtags for more information.

       To define a different set of word-boundary detection rules:

       package require ntext
       text .t
       bindtags .t {.t Ntext . all}
       ::ntext::createMatchPatterns \
         {[[:space:][:cntrl:]]} {[[:punct:]]} {[^[:punct:][:space:][:cntrl:]]}

       See regexp, re_syntax for more information.

SEE ALSO
       bindtags, ntext, re_syntax, regexp, text

KEYWORDS
       bindtags, re_syntax, regexp, text



ntext                                               0.81                                   ntextWordBreak(n)