fix real cause of crash when falling back to wire mode

[micropolis] / src / tk / readme

The Tk Toolkit, Version 2.3

by John Ousterhout
University of California at Berkeley

1. Introduction
---------------

This directory contains the sources and documentation for Tk, which
is an X11 toolkit that provides the Motif look and feel and is
implemented using the Tcl command language.

For an introduction to Tcl and Tk you may wish to read two papers:
``Tcl:  An Embeddable Command Language'', in the Proceedings of the
1990 Winter USENIX Conference, and ``An X11 Toolkit Based on the Tcl
Language'', in the Proceedings of the 1991 Winter USENIX Conference.
A copy of the first paper is present in Postscript form in the file
"tcl/usenix.ps";  Postscript for the second paper is in "doc/usenix.ps".
Both Tcl and Tk have evolved quite a bit since these papers were
written so the papers are no longer complete or correct, but they will
give you an introduction to the systems.

The following things are present in this directory and its subdirectories:

    1. Tk, a toolkit for X11 windowing applications.
    2. Tcl, an embeddable command language on which Tk is based.
    3. Wish, a simple windowing shell that uses Tk and Tcl.
    4. A collection of demonstration scripts to illustrate the use
       of various features of Tk.

The enclosed code is known to run on most versions of SunOS and Ultrix
in combination with the X11R4 and X11R5 window servers from MIT.  It
should also run with few or no changes on H-P and IBM workstations.

2. What's New In This Release
-----------------------------

Tk 2.2 is a major new release with a number of new features relative
to the 2.1 release.  Here is a summary of some of the most significant
improvements:

- There is now a text widget.  It will display multiple lines of text
  and allows the text to be edited (but the set of bindings for
  editing isn't very rich yet).  It also includes a tagging mechanism
  that allows you to change the fonts, colors, etc. on a character-
  by-character basis, and you can associate bindings with tags to
  implement hypertext-like features.  It handles large texts
  efficiently.

- Canvases have been improved in many ways, including new item types
  (arcs, bitmaps, and subwindows), Bezier spline support for lines
  and polygons, "coords" and "bbox" widget commands, and many other
  improvements and bug fixes.

- There is a new "grab" command that can be used to create modal dialog
  boxes.

- There is a new "tkwait" command for waiting for particular events to
  occur (such as modal dialog box to complete its task).

- The menu bindings have been completely reworked to have better Motif
  compliance, such as keyboard traversal.

- Individual menu entries can now have their own colors and fonts.

- Most widgets (e.g. buttons, entries, text) now have a "-state" option
  that can be set to "disabled" to make the widget insensitive.

- A new "-disabledForeground" option allows you to request that disabled
  buttons and menu entries be displayed in a dimmer color rather than with
  a stippled version of the original color.

- Entries and messages can now be tied to a variable so that either is
  updated if the other changes.

A good way to try out the new features is to run the "widget" demo;
there are a number of new demonstrations to illustrate the new features.
This release also contains many bug fixes.  For a complete description
of the changes in this release, see the file "changes".  As far as I
know there should not be any compatibility problems with respect to the
2.1 release.

3. Documentation
----------------

Manual entries for Tk are in the "doc" subdirectory as a set of files
with ".man" extensions.  Man pages whose names start with capital letters
are for the procedures in Tk's C library.  All other man pages document Tcl
commands provided by Tk.  To print any of the man pages, cd to the "doc"
directory and invoke your favorite variant of troff using the normal
-man macros, for example

		ditroff -man <file>

where <file> is the name of the man page you'd like to print.  If you'd
like a complete set of hardcopy manual entries, send me a message with
your street address.

Manual entries for Tcl are available in the subdirectory "tcl/doc";
see the README file in the "tcl" directory for more information.

Unfortunately, there doesn't yet exist a tutorial-style introduction
to the facilities of Tcl and Tk.  The papers give a general introduction,
but it may be difficult to make the transition from the papers to the
manual entries.  If you are familiar with the Xt toolkit then the Tk
facilities will probably be easy to pick up from the manual entries.
If you have no experience with X or Xt, you may wish to wait another
6-12 months to use Tk, until a more gentle introduction is available.

4. Compiling Tk
---------------

Before attempting to compile Tk, personalize Makefile by following the
directions at the beginning of the file.  You should also configure
Tcl by following the directions in the file "tcl/README".  Then type
"make" in the top-level directory (the one that contains this file).
This will compile the Tk library and generate a simple windowing shell
called "wish".  It will also compile the Tcl library, which is in the
"tcl" subdirectory.

5. Installing Scripts
---------------------

Tk depends on a library of scripts that establish default behaviors
for Tk widgets and do many other things.  Tk normally expects the
scripts to be in /usr/local/lib/tk.  Create this directory and copy
everything in the "library" subdirectory to it, including both files
and subdirectories.  Or, if you don't want to create a subdirectory of
/usr/local/lib (or if you can't), you can either make a symbolic link
from there to the library subdirectory or you can add a "-DTK_LIBRARY"
switch to CFLAGS in Makefile;  this will allow you to put the script
library anywhere you like.

I also recommend installing the wish binary in /usr/local.  The demo
scripts all work best when it is installed there.

6. Getting Started
------------------

Once wish is compiled you can use it to play around with the Tk
facilities.  If you run wish with no arguments, it will open a small
window on the screen and read Tcl commands from standard input.
Or, you can play with some of the pre-canned scripts in the subdirectory
scripts/demos.  See the README file in the directory for a description
of what's available.  The file scripts/demos/widget is a script that
you can use to invoke many individual demostrations of Tk's facilities. 

If you want to start typing Tcl/Tk commands to wish, I'd suggest
starting with the "bind" command.  Then learn about a widget-creation
command like "button", and also learn about the "pack" and "place"
commands for geometry management.  Note:  when you create a widget,
it won't appear on the screen until you tell a geometry manager about
it.  The only geometry managers at present are the packer and the placer.
If you don't already know Tcl, read the Tcl paper and the Tcl.man manual
entry in the tcl subdirectory.

The easiest way to learn about writing new widgets is probably to look
at existing widget implementations.  The demos directory contains an
example of a trivial widget, which you might find useful as a starting
point for writing new widgets.  You might also take a look at main.c,
the main program for wish, to see how to write a main program that uses
the facilities of Tk and Tcl.

7. Newsgroup
------------

There is a network news group "comp.lang.tcl" intended for the exchange
of information about Tcl, Tk, and related applications.  Feel free to use
this newsgroup both for general information questions and for bug reports.
I read the newsgroup and will attempt to fix bugs and problems reported
to it.

8. Known Problems
-----------------

There are still many imperfections with the system.  Below is a list
of some of the more serious omissions and bugs:

    1. The widgets don't look very good on monochrome displays right now,
    because I haven't had a chance to figure out how to do the 3-D
    effects right without color.  The widgets should look pretty good in
    color.  The widgets aren't fully Motif-compliant yet. In particular,
    there is no keyboard navigation yet.  The widgets will eventually
    become fully Motif-compatible (assuming I can figure out how Motif
    widgets are supposed to look and feel).

    2. Tk doesn't work very well with virtual-root window managers such
    as tvtwm.

The file ToDo contains a list of various smaller bugs and mis-features
that haven't been fixed yet.
    
9. Feedback Wanted
------------------

I'm very interested in getting feedback from you both about bugs and about
overall design issues.  Send your comments to "ouster@sprite.berkeley.edu".
I'll do my best to fix show-stopping bugs quickly, but most other things
may not get fast turnaround, since I already have a zillion high-priority
things to fix or implement.  Before submitting requests for new features
you may wish to check the file ToDo, which has a list of things I already
know about and plan to implement soon.

7. The Future
-------------

Tk is still young.  I expect it to undergo substantial changes as I learn
more about its strengths and weaknesses.  Some of the changes will not be
backward compatible:  at this point I think it's more important to fix
problems and improve Tk's structure than to maintain compatibility.  At
some point in the next year or so there will be a new release with major
incompatibilities.  My plan is to save up as many as possible of the
incompatible changes that are needed and do them all at once.