Practical Programming in TCL and Tk

This is the most comprehensive, practical guide to Tcl and Tk available -- with coverage of the latest released versions, Tcl 7.6 and Tk 4.2. Beginners will get a complete introduction to Tcl and Tk, and experts will gain insight from the book's extensive programming tips and examples. The book's CD-ROM includes Tcl/Tk implementations for all versions of Windows and key UNIX platforms, plus all code samples. Practical Programming in Tcl and Tk presents both basic and advanced coding techniques, describes Tcl's interface to the operating system, and the script library facility. It introduces Tk and the relevant aspects of the X Window system, presenting examples and sample widgets. There is extensive coverage of user interface development, including techniques for creating user interfaces that run on all major desktop platforms. The book describes Tcl's improved network support, as well as Safe Tcl. It also covers advanced topics such as C programming with the Tk toolkit. It even previews the Tcl 8.0 compiler and the Tcl/Tk plug-in for both Netscape Navigator and Microsoft Explorer.

Features:

• All-new chapters on network socket programming, multiplatform programming, HTML support, and creating new Tcl widgets with the Tk metawidget facility.
• Learn to use Tcl as an Internet scripting language.
• Includes CD-ROM with Tcl/Tk implementations for all versions of Windows and key UNIX platforms, plus all code samples.

Table of contents

List of Examples

List of Tables

Preface

I. Tcl Basics

1. Tcl Fundamentals

Tcl Commands

Hello, World!

Variables

Command Substitution

Math Expressions

Backslash Substitution

Grouping with Braces and Double Quotes

Square Brackets Do Not Group

Grouping before Substitution

Procedures

A Factorial Example

More about Variables

Funny Variable Names

The unset Command

Using info to Find Out about Variables

More about Math Expressions

Comments

Substitution and Grouping Summary

Fine Points

Reference

Backslash Sequences

Arithmetlc Operators

Built-in Math Functions

Core Tcl Commands

2. Getting Started

The source Command

UNIX Tcl Scripts

Windows 95 Start Menu

The Macintosh and ResEdit

The console Command

Command-Line Arguments

Command-Line Options to Wish

Predefined Variables

3. The Guestbook CGI Application A Quick Introduction to HTML

CGI for Dynamic Pages

The guestbook.cgi Script

Beginning the HTML Page

Simple Tags and Hypertext Links

Using a Tcl Array for the Database

Sample Output

Defining Forms and Processing Form Data

4. String Processing in Tcl

The string Command

Strings and Expressions

The append Command

The format Command

The scan Command

String Matching

The binary Command

Format Templates

Examples

Related Chapters

5. Tcl Lists

Tcl Lists

Constructing Lists

The list command

The lappend Command

The concat Command

Getting List Elements: llength, lindex, and lrange

Seacrching Lists: linsert and lreplace

Sorting Lists: lsort

The split Command

The join Command

Related Chapters

6. Control Structure

Commands

If then E1se

Switch

Comments in switch Commands

While

Foreach

Multiple Loop Variables

Multiple Value Lists

For

Break and Continue

Catch

Catching More Than Errors

Error

Return

7. Procedures and Scope

The proc Command

Changing Command Names with rename

Scope

The global Command

Call by Name Using upvar

Variable Aliases with upvar

Associating State with Data

Commands That Take Variable Names

8. Tcl Arrays

Array Syntax

Complex Indices

Array Variables

The array Command

Converting Arrays to Lists

Passing Arrays by Name

Building Data Structures with Arrays

Simple Records

A Stack

A List of Arrays

9. Working With Files and Programs

Running Programs with exec

The auto_noexec Variable

Limitations of exec on Windows

Limitations of exec on Macintosh

The fi1e Command

Cross-Platform File Naming

Building up Pathnames: file join

Chopping Pathnames: split, dirname, tail

Manipulating Files and Directories

Copying Files

Creating Directories

Deleting Files

Renaming Files and Directories

File Attributes

Input/Output Command Summary

Opening Files for I/O

Opening a Process Pipeline

Reading and Writing

The puts and gets Commands

The read Command

Platform-Specific End of Line Characters

Random Access I/O

Closing I/O channels

The Current Directory -- cd and pwd

Matching File Names with global

Expanding Tilde in File Names

The exit and pid Commands

Environment Variables

II. Advanced Tcl

10. Eval

Construct Commands with list

Exploiting the concat inside eval

Double Quotes and eval

More Examples

The uplevel Command

Commands That Concatenate Their Arguments

The subset Command

String Processing with subset

11. Regular Expressions

Regular Expression Syntax

A Pattern to Match URLs

The regexp Command

Useful Regular Expressions

The regsub Command

Transforming Data to Tcl with regsub

URL Decoding

CGI Argument Parsing

Decoding HTML Entities

A Simple HTML Parser

Stripping HTML Comments

Other Commands That Use Regular Expressions

12. Script Libraries and Packages

Locating Packages: The auto_path Variable

Using Packages

Loading Packages Automatically

Packages Implemented in C Code

The package Command

Libaries Based on the tclIndex File

The unkown Command

How Auto Loading Works 1

Disabling the Library Facility:

auto_noload

Interactive Conveniences

Auto Execute

History

Abbreviations

Tcl Shell Library Environment

Coding Style

A Module Prefix for Procedure Names

A Global Array for State Variables

13. Reflection and Debugging

The clock Command

The info Command

Variables

Procedures

The Call Stack

Command Evaluation

Scripts and the Library

Version Numbers

Execution Environment

Cross-Platform Support

Tracing Variable Values

Interactive Command History

History Syntax

A Comparison to C Shell History Syntax

Debugging

Don Libes' Debugger

Breakpoints by Pattern

Matching

Deleting Break Points

Debugging Tk Scripts

The tkinspect Program

The tdebug Program

The bgerror Command

The tkerror Command

Performance Tuning

Time stamps in a Log

Tcl 8.0

14. Namespaces

Using Namespaces

Qualified Names

Command Lookup

Nested Namespaces

Importing Procedures

Other Namespaces

Callbacks and Namespaces

Introspection

The namespace Command

Wrapping Existing Packages

[incr Tcl] Object System

Notes

AutoLoading

Namespaces and uplevel

Naming Quirks

Miscellaneous

15. Event-Driven Programming

The Tcl Event Loop

The after Command

The fileevent Command

The vwait Command

The fconfigure Command

Non-Blocking I/O

The fblocked Command

Buffering End of Line Translations

End of File Character

Serial Devices

Configuring Read-Write Channels

16. Socket Programming

Client Sockets

Client Socket Options

Server Sockets

Server Socket Options

The Echo Service

Fetching a URL with HTTP

Proxy Servers

The HEAD Request

The GET and POST Requests

The unsupported0 Command

The fcopy Command

The http Package

http_config

http_get

http_formatQuery

http_reset

17. Multiple Interpreters and

The interp Command

Creating Interpreters

The Interpreter Hierachy

The Interpreter Name as a Command

Use list with interp eval

Safe Interpreters

Command Aliases

Alias Introspection

Hidden Commands

Substitutions

I/O from Safe Interpreters

The Safe Base

Security Policies

Limited Socket Access

Limited Temporary Files

Safe after Command

III. Tk Basics

18. Tk Fundamentals

Hello, World! in Tk

Naming Tk Widgets

Conflgunng Tk Widgets

Tk Widget Attributes and the Resource Database

The Tk Manual Pages

Summary of the Tk

Commands

19. Tk by Example

ExecLog

Window Title

A Frame for Buttons

Command Buttons

A Label and an Entry

Key Bindings and Focus

A Resizable Text and Scrollbar

The Run Procedure

The Log Procedure

The Stop Procedure

Cross-Platform Issues

The Example Browser

More about Resizing Windows

Managing Global State

Searching through Files

Cascaded Menus

A Read-Only Text Widget

A Tcl Shell

Text Marks, Tags, and Bindings

Multiple Interpreters

Native Look and Feel

20. The Pack Geometry Manager

Packing toward a Side

Shrinking Frames and pack propagate

Horizontal and Vertical Stacking

The Cavity Model

Packing Space and Display Space

The -fill Option

Internal Padding with -ipadx and -ipady

External Padding with -padx and -pady

Resizing and -expand

Anchoring

Packing Order

Introspection

Pack the Scrollbar First

Choosing the Parent for Packing

Unpacking a Widget

Packer Summary

The pack Command

Window Stacking Order

21. The Grid Geometry

Manager

A Basic Grid

The -sticky Setting

External Padding with -padx and -pady

Internal Padding with -ipadx and -ipady

Multiple Widgets in a Cell

Spanning Rows and Columns

Row and Column Constraints

Row and Column Padding

Minimum Size

Managing Resize Behavior

The grid Command

22. The Place Geometry Manager

place Basics

The Pane Manager

Parsing Arguments and Maintaining State

Sticky Geometry Settings

Event Bindings

Managing the Layout

The place Command

23. Binding Commands to Events

The bind Command

The bindtags Command

Focus and Key Events

Using break and continue in Bindings

Defining New Binding Tags

Binding Precedence in Tk 3.6

Event Syntax

Keyboard Events

Detecting Modifiers in Tk 3.6 Mouse Events

Other Events

Bindings on Top-level Windows

Modifers

Modifiers in Tk 3.6

Event Sequences

Virtual Events

Event Keywords

IV. Tk Widgets

24. Buttons and Menus

Button Commands and Scope Issues

Butttons Associated with Tcl Variables

Button Attributes

Button Operations

Menus and Menubuttons

A Menu Bar

System Menus

Pop-up Menus

Option Menus

Multicolumn Palette Menus

Keyboard Traversal

Manipulating Menus and Menu Entries

Menu Attributes

A Menu by Name Package

Menu Accelerators

25. The Resource Database

Introduction to Resources

Resource Patterns

Loading Option Database Files

Adding Individual Database Entries

Accessing the Database

User-Defined Buttons

User-Defined Menus

Application and User Resources

Expanding Variables

26. Simple Tk Widgets

Frames and Toplevel Windows

Attributes for Frames and Toplevels

Embedding Other Applications

Toplevel Window Styles

The Label Widget

Label Width and Wrap Length

Label Attributes

The Message Widget

Message Attributes

Arranging Labels and Messages

The Scale Widget

Scale Bindings

Scale Attributes

Programming Scales

The be11 Command

27. Scrollbars

Using Scrollbars

The Scrollbar Protocol

The Scrollbar set Operation

The xview and yview Operations

The Tk 3.6 Protocol

The Scrollbar Widget

Scrollbar Bindings

Scrollbar Attributes

Programming Scrollbars

28. The Entry Widget

Using Entry Widgets

Tips for Using Entry Widgets

The Entry Widget

Entry Attributes

Programming Entry Widgets

29. The Listbox Widget

Using Listboxes

Programming Listboxes

Listbox Bindings

Browse Select Mode

Single Select Mode

Extended Select Mode

Multiple Select Mode

Scroll Bindings

Listbox Attributes

Geometry Gridding

30. The Text Widget

Text Indices

Inserting and Deleting Text

Index Arithmetic

Comparing Indices

Text Marks

Mark Gravity

Text Tags

Tag Attributes

Mixing Attributes from Different Tags

Line Spacing and Justification

Tab stops

The Selection

Tag Bindings

Searching Text

Embedded Widgets

Embedded Images

Looking inside the Text Widget

Looking at Tags

Looking at Marks

Dumping the Contents

Text Bindings

Text Operations

Text Attributes

31. The Canvas Widget

Canvas Coordinates

Hello, World!

Canvas Tags

The Min Max Scale Example

Canvas Objects

Arc Items

Bitmap Items

Image Items

Line Items

Oval Items

Polygon Items

Rectangle Items

Text Items

Window Items

Canvas Operations

Hints

Screen Coordinates vs Canvas Coordinates

Large Coordinate Spaces

Scaling and Rotation

Resources

Objects with Many Points

Selecting Canvas Items

V. Tk Details

32. Selections and the Clipboard

The Selection Model

The selection Command

The clipboard Command

Selection Handlers

A Canvas Selection Handler

33. Focus, Grabs, and Dialogs

Standard Dialogs

Message Box

File Dialogs

Color Dialog

Custom Dialogs

Input Focus

The focus Command

Keyboard Focus Traversal

Grabbing the Focus

The tkwait Command

Destroying Widgets

The focus, grab, tkwait sequence

Prompter Dialog

Keyboard Shortcuts and Focus

Animation with the update Command

34. Tk Widget Attributes

Configuring Attributes

Size

Borders and Relief

The Focus Highlight

Padding and Anchors

Putting It All Together

35. Color, Images, and Cursors

Colors

Color Palettes

Color Values

Colormaps and Visuals

Bitmaps and Images

The image Command

Bitmap Images

The bitmap Attribute

Photo Images

The Text Insert Cursor

The Mouse Cursor

36. Fonts and Text Attributes

Naming a Font

Named Fonts

System Fonts

X Font Names

Font Failures before Tk 80

Font Metrics

The font Command

Text Attributes

Layout

Selection Attributes

Gridding, Resizing, and Geometry

A Font Selection Application

37. Send

The send Command

Send and X Authority

The Sender Script

Communicating Processes

Remote eval through

Sockets

38. Window Managers and Window Information The wm Command

Size, Placement, and Decoration

Icons

Session State

Miscellaneous

The winfo Command

Sending Commands between

Applications

Family Relationships

Size

Location

Virtual Root Window

Atoms and IDs

Colormaps and Visuals

The tk Command

39. Managing User Preferences

App-Defaults Files

Defining Preferences

The Preferences User Interface

Managing the Preference File

Tracing Changes to Preference Variables

Improving the Package

40. A User Interface to Bindings

A Pair of Listboxes Working Together

The Editing Interface

Saving and Loading Bindings

VI. C Programming

41. C Programming and Tcl

Using the Tcl C Library

Application Structure

Creating a Loadable Package

The load Command

Using Tcl_PkgProvide

A C Command Procedure

The String Command

Interface

Managing String Result

The Object Command Interface

Managing Object Reference Counts

Tcl_Main and

Tcl_AppInit

The Event Loop

Invoking Scripts from C

Bypassing Tcl_Eval

Expect's Tcl Debugger

The Dbg C Interface

Handling SIGINT

Putting a Tcl Program Together

A Simple UNIX Example

Autoconf

Windows

Macintosh

42. C Librarv Overview

An Overview of the Tcl C Library

Application Initialization

Creating and Deleting Interpreters

Creating and Deleting Commands

Dynamic Loading and Packages

Managing the Result String

Memory Allocation

Lists and Command Parsing

Command Pipelines

Tracing the Actions of the Tcl

Interpreter

Evaluating Tcl Commands

Reporting Script Errors

Manipulating Tcl Variables

Evaluating Expressions

Converting Numbers

Tcl Objects

Primitive Object Types

String Keys for Data Structures

Option Processing

Hash Tables

Dynamic Strings

Regular Expressions and String Matching

Event Loop Interface

Handling Window Events

File Handlers

Timer Events

Idle Callbacks

Sleeping

Event Loop Implementation

Input/Output

I/O Channel Drivers

Manipulating File Names

Working with Signals

Exit Handlers

An Overwew of the Tk C Library

Parsing Command-Line Arguments

The Standard Application Setup

Creating Windows

Application Name for Send

Configuring Windows

Window Coordinates

Window Stacking Order

Window Information

Configuring Widget Attributes

Safe Handling of the Widget Data Structure

The Selection and Clipboard

Event Bindings

Handling Graphic Protocol Errors

Using the Resource

Database

Managing Bitmaps

Creating New Image Types

Using an Image in a Widget

Photo Image Types

Canvas Object Support

Geometry management

String Identifiers (UIDS)

Colors, Colormaps, and Visuals

3D Borders

Mouse Cursors

Fonts and Text Display

Graphics Contexts

Allocate a Pixmap

Screen Measurements

Relief Style

Text Anchor Positions

Line Cap Styles

Line Join Styles

Text Justification Styles

Atoms

X Resource ID Management

43. Writing a Tk Widget in C

The Widget Data Structure

The Widget Class Command

The Widget Instance Command

Configuring and Reconfiguring Attributes

Specifying Widget Attributes

Displaying the Clock

The Window Event Procedure

Final Cleanup

VIII. Changes

44. Tcl 7.4/Tk 4.0

wish

Obsolete Features

The cget Operation

Input Focus Highlight

Bindings

Scrollbar Interface

pack info

Focus

The send Command

Internal Button Padding

Radiobutton Value

Entry Widget

Menus

Listboxes

No geometry Attribute

Text Widget

Color Attributes

Color Allocation and tk colormodel

Canvas scrollincrement

The Selection

The bell Command

45. Tcl 7.5/Tk 4.1

File Name Manipulation

Newline Translations

The tcl_platform Variable

The console Command

The clock Command

The load Command

The package Command

Multiple foreach loop variables

Event Loop Moves from Tk to Tcl

Network Sockets

info hostname

The fconfigure Command

Multiple Interpreters and Safe-Tcl

The grid Geometry Manager

The Text Widget

The Entry Widget

46. Tcl 7.6/Tk 4.2

More file Operations

Virtual Events

Standard Dialogs

New grid Geometry Manager

Macintosh unsupported1 Command

47. Tcl/Tk 8.0

The Tcl Compiler

Compile-Time Errors

Binary String Support

Namespaces

Safe-Tcl

New lsort

No tcl_precision Variable

Year 2000 Convention

Http Package

Serial Line I/O

Platform-Independent Fonts

The tk scale Command

Application Embedding

Native Menus and Menubars

CDE Border Width

Native Buttons and Scrollbars

Images in Text Widgets

No Errors from destroy

grid rowconfigure Late Breaking News

48. Safe-Tk and the Browser Plug-In

Tk in Child Interpreters

Embedding Tk Windows

Safe-Tk Restrictions

The Browser Plug-In

Setting Up the Plug-In

UNIX Configuration

Windows Configuration

Macintosh Configuration

Security Policies and Browser Plug-in

The Browser Policy

Notes