ntextIndent - ntext Indentation for the Text Widget

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ntextIndent(n) 0.81 "ntext Indentation for the Text Widget"


ntextIndent - ntext Indentation for the Text Widget


  • package require Tcl 8.5
  • package require Tk 8.5
  • package require ntext ?0.81?


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

Tk's text widget may be configured to wrap lines of text that are longer than the width of the text area, a feature that is familiar from text editors and word processors. A complete line of text (delimited by newlines, or by the beginning or end of the document) is called a "logical line". When a logical line is wrapped onto more than one line of the display area, these fragments of the logical line are called "display lines".

If a logical line begins with whitespace, then wrapped display lines begin further to the left than the first display line, which can make the text layout untidy and difficult to read. The Ntext binding tag provides facilities so that a text widget in -wrap word mode will automatically indent display lines (other than the first) to match the initial whitespace of the first display line.

This indentation is available to text widgets only in -wrap word mode.


The behavior of Ntext may be configured application-wide by setting the values of a number of namespace variables:


  • 0 - selects Ntext behaviour, i.e. display lines are indented to match the initial whitespace of the first display line of a logical line.

    No other action is required if this option, and the text widget's -wrap option, are set before any text is entered in the widget, and if text is entered and edited only by the mouse and keyboard. If, instead, text is manipulated by the script, or if the text widget's -wrap option or the value of ::ntext::classicWrap are changed while the widget holds text, then calls to ntext functions are needed to alter the indentation. See the section INDENTING DISPLAY LINES for detailed instructions.

  • 1 - (default value) selects classic Text behaviour, i.e. no indentation.

Advanced Use


  • the value is a regexp pattern that determines the character of a logical line to which display lines other than the first will be aligned. The default value, [^[:space:]], ensures alignment with the first non-whitespace character.


To use Ntext 's display line indentation:

  1. Set the variable ::ntext::classicWrap to 0 (default value is 1). This enables bindings that will preserve indentation whenever the user modifies the widget contents using the keyboard and mouse. If the widget already holds text, call ::ntext::wrapIndent to initialise indentation.

    Further instructions apply if the program changes the widget's contents, wrap configuration, or indent configuration.

  2. The program can change the text contents, e.g. by the .text insert command. Such a change does not trigger a window binding, so the program should explicitly call function ::ntext::wrapIndent after inserting text.

  3. Auto-indentation occurs only if the widget is in -wrap word mode. If the program changes to or from -wrap word when the widget is not empty, it should call ::ntext::wrapIndent to format the widget's text.

  4. If indentation is used, and then switched off by setting ::ntext::classicWrap to 1, call ::ntext::wrapIndent to remove indentation.


::ntext::wrapIndent textWidget ?index1? ?index2?

  • Adjust the indentation of a text widget. Different cases are discussed below.

::ntext::wrapIndent textWidget

  • Adjust the indentation of all the text in text widget textWidget.

::ntext::wrapIndent textWidget index1

  • Adjust the indentation of a single logical line of a text widget - the line of textWidget that contains the index index1.

::ntext::wrapIndent textWidget index1 index2

  • Adjust the indentation of a range of logical lines of a text widget - the lines of textWidget that contain indices index1 to index2.


  • ::ntext::wrapIndent should be called only if the script changes the widget's contents or display properties. If the contents of the widget have been modified by the keyboard or mouse, it is not necessary for the script to call ::ntext::wrapIndent because the appropriate calls are made automatically by the Ntext bindings.

  • The script should normally call ::ntext::wrapIndent if, for example, the script changes one of the following when the widget is not empty: the value of ::ntext::classicWrap, or the widget's -wrap status, or the widget's tab spacing, or the font size, or the widget's contents.

  • A call of the form ::ntext::wrapIndent textWidget will always suffice, but if changes are needed only to certain lines, it is more efficient to specify those lines with the optional arguments ?index1?, ?index2?.

  • If the widget is in -word wrap mode, and if ::ntext::classicWrap is set to 0, ::ntext::wrapIndent will apply indentation to the logical lines within the range specified by the function's arguments.

  • In other cases, i.e. if the widget is in -word char or -word none mode, or if ::ntext::classicWrap is set to 1, ::ntext::wrapIndent will remove the indentation of the logical lines within the range specified by the function's arguments.


To switch on Ntext 's indentation and use it in widget .t:

package require ntext
set ::ntext::classicWrap 0
text .t -wrap word
bindtags .t {.t Ntext . all}

To decide later to switch off Ntext 's indentation:

set ::ntext::classicWrap 1
::ntext::wrapIndent .t

To decide later to switch Ntext 's indentation back on:

set ::ntext::classicWrap 0
::ntext::wrapIndent .t 1.0 end

To inject some text into the widget:

set foo [.t index end]
.t insert end {This line was added by the script, not the keyboard!}
::ntext::wrapIndent .t $foo end

To switch to -wrap char mode:

.t configure -wrap char
::ntext::wrapIndent .t

Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category ntext of the Tklib Trackers. Please also report any ideas for enhancements you may have for either package and/or documentation.

Copyright © 2015 for compilation: ActiveState