DN581955744

Subject: ANNOUNCE: Widget callback package Wcb 2.1 - DN [1]

Csaba Nemethi <csaba.nemethi@t-online.de> - 05 Feb 2000 - comp.lang.tcl

 I am pleased to announce Version 2.1 of the widget callback package Wcb.

 What is new in Wcb 2.1?
 -----------------------

 1. Fixed a bug in the procedure "cbprepend", introduced in version 2.0.

 2. Included a new demo script using an activate callback for a listbox.
    This new example is also discussed in the manual file "wcb.html".

 3. Minor improvements in the code and documentation.

 What is Wcb?
 ------------

 Wcb is a library package for Tcl/Tk version 8.0 or higher, written in
 pure Tcl/Tk code.  It contains a few commands providing a simple and
 GENERAL solution to problems like the following:

   - How to restrict the set of characters that the user can type or
     paste into an entry or text widget?
   - How to manipulate the user input characters before they are
     inserted into an entry or text widget?  In the case of a text
     widget:  How to change the font, colors, or other attributes of
     the input characters?
   - How to set a limit for the number of characters that can be typed
     or pasted into an entry widget?
   - How to protect some parts of the text contained in an entry or text
     widget from being changed by the user?
   - How to define notifications to be triggered automatically after
     text is inserted into or deleted from an entry or text widget?
   - How to define some actions to be invoked automatically whenever the
     insertion cursor in an entry or text widget is moved?
   - How to define a command to be called automatically when selecting a
     listbox element?
   - How to disable any or all items of a listbox, i.e., how to protect
     them from being selected?

 In most books, FAQs, newsgroup articles, and widget sets, you can find
 INDIVIDUAL solutions to some of the above problems by means of widget
 bindings.  This approach quite often proves to be incomplete.

 The Tk core addresses just a few of the above problems:  In Tk 8.1 the
 <<ListboxSelect>> virtual event for listbox widgets was introduced, and
 Tk 8.3 supports widget options for entry validation.  Also these
 improvements are of INDIVIDUAL nature.

 The package Wcb goes a completely different way:  Based on redefining
 the Tcl command corresponding to a widget, the main Wcb procedure
 "callback" enables you to associate arbitrary commands with some entry,
 listbox, and text widget operations.  These commands will be invoked
 automatically in the global scope whenever the respective widget
 operation is executed.  You can request that these commands be called
 either before or after executing the respective widget operation, i.e.,
 you can define both before- and after-callbacks.  From within a before-
 callback, you can cancel the respective widget command by invoking the
 procedure "cancel", or modify its arguments by calling "extend" or
 "replace".

 Besides these (and three other) general-purpose commands, the Wcb
 package exports three utility procedures for entry widgets, as well as
 some before-insert callbacks for entry and text widgets, which you can
 use directly or modify to suit your needs.

 How to get it?
 --------------

 Wcb is available for free download from the Web page

     http://www.nemethi.de

 The distribution file is "wcb2.1.tar.gz" for UNIX and "wcb2_1.zip" for
 Windows 95/98/NT.  These files contain the same information, except for
 the additional carriage return character preceding the linefeed at the
 end of each line in the text files for Windows.

 How to install it?
 ------------------

 Install the package as a subdirectory of one of the directories given
 by the "auto_path" variable.  For example, you can install it as a
 directory at the same level as the Tcl and Tk script libraries.  The
 locations of these library directories are given by the "tcl_library"
 and "tk_library" variables, respectively.

 To install Wcb on UNIX, "cd" to the desired directory and unpack the
 distribution file "wcb2.1.tar.gz":

     gunzip -c wcb2.1.tar.gz | tar -xf -

 This command will create a directory named "wcb2.1", with the
 subdirectories "demos", "doc", and "scripts".

 On Windows 95/98/NT, use WinZip or some other program capable of
 unpacking the distribution file "wcb2_1.zip" into the directory
 "wcb2.1", with the subdirectories "demos", "doc", and "scripts".

 How to use it?
 --------------

 To be able to use the commands and variables implemented in the package
 Wcb, your scripts must contain one of the lines

     package require Wcb
     package require wcb

 Since the package Wcb is implemented in its own namespace called "wcb",
 you must either import the procedures you need, or use qualified names
 like "wcb::callback".

 For a detailed description of the commands and variables provided by Wcb
 and of the examples contained in the "demos" directory, see the manual
 file "wcb.html" in the "doc" directory.

 --
 Csaba Nemethi   http://www.nemethi.de   mailto:csaba.nemethi@t-online.de