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Tcl/Tk 8.6.0

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Tcl/Tk 8.6.0 Release Announcement
December 20, 2012

The Tcl Core Team is pleased to announce the 8.6.0 releases of the Tcl
dynamic language and the Tk toolkit. This is the first stable release
of Tcl/Tk 8.6. More details can be found below. We would like to
express our gratitude to all those who submit bug reports and patches.
This information is invaluable in enabling us to identify and eliminate
problems in the core.

Where to get the new releases:

Tcl/Tk 8.6.0 sources are freely available as open source from the Tcl
Developer Xchange web site at:

This web page also contains additional information about the releases,
including a summary of new features. Sources are always available from
the Tcl SourceForge project's file distribution area:

For additional information:

Please visit the Tcl Developer Xchange web site:

This site contains a variety of information about Tcl/Tk in general, the
core Tcl and Tk distributions, Tcl development tools, and much more.

Summary of Changes since Tcl/Tk 8.6b3:

A complete list can be found in the changes file at the root of the
source tree. The more complete ChangeLog is also included with each
source release.

The short list of key changes since the Tcl/Tk 8.6b3 release follows.
For those who have not been following alpha and beta development,
read on to the next sections for pointers to information on the changes
since Tcl/Tk 8.5. All bug fixes in Tcl/Tk 8.5.13 are included, plus:

* [TIP 405] New commands [lmap] and [dict map].

* [TIP 416] New [load] options -global and -lazy.

* [TIP 413] Default [string trim*] trimset changed to Unicode.

* [TIP 400] New [zlib] options to set gzip compression dictionary.

* Bytecode compiled: [array exists|set|unset] [format] [yield]
[dict create|exists|merge|unset] [string first|last|map|range]
[namespace current|code|qualifiers|tail|which] [tailcall]
[info commands|coroutine|level|object] [regsub] [self].

* Fixed crashes when some attempts to write to a variable in
a namespace that does not exist fail.

* Fixed paths returned from [tk_getOpenFile -multiple] on Windows.

* Corrected decoding of base64 with trailing whitespace.

* Updated packages:
- dde 1.4.0 : Full Unicode support.
- http 2.8.5 : keep-alive multiple callback bug fix.
- tcltest 2.3.5 : legacy $argv support bug fix.
- TclOO 1.0 : Stable interface built into Tcl.
- Itcl 4.0.0 : Stable release.
- tdbc + driver packages, 1.0.0 : Stable releases.
- Thread 2.7.0 : Stable release.
- Sqlite 3.7.15 : New release.

* Threads inherit floating point setting from master on Windows.

* [text] handle images and windows with names looking like indices.

* Compile-time control over where [file tempfile] creates files.

* Legacy Carbon sources removed. For support, get Tk 8.5.12.

Summary of new features since Tcl/Tk 8.5:

Development of Tcl/Tk 8.6 began in March 2008, shortly after the release
of Tcl/Tk 8.5.2. The number of new features, bug fixes, and changes
since then is quite large. New features in Tcl are recorded as Tcl
Improvement Proposals (TIPs) at:

Highlights of the new Tcl features include:

Object Oriented Programming

The commands of the TclOO package are now part of Tcl itself. This gives
Tcl a built-in object system that is fully dynamic, class-based, and
includes advanced features such as meta-classes, filters, and mixins.

New version 4 of the popular package Itcl (aka [incr Tcl]) is also
included, now built on a TclOO foundation, granting support for some
traditional OO Tcl programming out of the box as well.

Stackless Evaluation

The evaluation of many levels of nested proc calls are no longer
implemented as a stack of nested C routine calls. This revision in the
internal implementation of Tcl evaluation makes deep recursion in Tcl
scripts safe to do. But there's more...

This new implementation enables a collection of new commands,
[coroutine], [tailcall], [yield], and [yieldto] that provide profound
new capabilities and models of concurrency to Tcl scripts.

Enhanced Exceptions

New commands [try] and [throw] and a wealth of new -errorcode values
enable far more precise trapping and handling of exceptions using a
familiar construct.

Batteries Included

Tcl delivers in the pkgs subdirectory a bundled collection of
third-party packages built and installed along with Tcl.

Thread-enabled Operations

A thread-enabled default build, a bundled Thread package, and new
command [interp cancel] make Tcl 8.6 ready for your multi-threaded
programming tasks.

SQL Database Powered

The bundled Tcl DataBase Connectivity (tdbc) interface package makes it
possible to write your SQL database-powered scripts decoupled from any
particular database engine. The bundled sqlite3 and tdbc::sqlite3
packages supply a powerful and popular SQL database engine ready to use.

IPv6 Networking

Both client and server [socket]s support IPv6 where platform support

Built-in Zlib Compression

New command [zlib] provides utilities to handle compression of data and

List Processing

New commands [lmap] and [dict map] enable the elegant expression of
transformations over Tcl containers.

Stacked Channels by Script

New commands [chan push] and [chan pop] expose the power of stacked
channels without the need to write C code.

Additional New Features

Temporary file creation, enhancements to list sorting and setting, dict
filtering, half-close of bidirectional channels, encoding and decoding
of binary sequences, finer control over load, and many many more.

Highlights of the new Tk features include:

Built-in PNG Image Support

Photo images now support read/write in the PNG format, with the ability
to set the alpha channel.

Busy Windows

New command [tk busy] is a variant of [blt::busy] that lets the
interactivity of windows be suspended and restored as required by the
needs of the program.

New Font Selection Dialog Interface

New command [tk fontchooser] provides a portable interface to the
standard font selector of the platform, whether that is modal or not.

Angled Text

New option "-angle $degrees" to [$canvas create text] for rotating
displayed text.

Moving Things on a Canvas

New commands [$canvas moveto], [$canvas imove] and [$canvas rchars]
for moving and manipulating canvas items.

Additional New Features

Text widget cursor control, more window manager hints, and a collection
of modernizations in appearance and function.

The complete summary of new features visible to Tcl scripts in the
Tcl/Tk 8.6 releases is:

Each item includes links to the TIP(s) that approved the change.

There have also been changes to the C API for the Tcl and Tk libraries
that are not visible to Tcl scripts, but are important to those who
create extensions and applications that use Tcl/Tk. The relevant TIPs

TIP #265: A Convenient C-side Command Option Parser for Tcl
TIP #307: Make TclTransferResult() Public
TIP #316: Portable Access Functions for Stat Buffers
TIP #322: Publish the NRE API
TIP #330: Eliminate interp->result from the Public Headers
TIP #335: An API for Detecting Active Interpreters
TIP #336: Supported Access To interp->errorline
TIP #337: Make TclBackgroundException() Public
TIP #338: Embedder Access to Startup Scripts of *_Main()
TIP #353: NR-enabled Expressions for Extensions
TIP #356: NR-enabled Substitutions for Extensions
TIP #357: Export TclLoadFile

These lists of feature changes are starting points for exploring the
new capabilities of Tcl/Tk 8.6.0. As more developers become familiar
with the new tools, expect more guides to effective use of the new
features to appear online.

Building and installing Tcl will also build and install a set of
packages bundled with it in source code distribution form under the
pkgs subdirectory. These packages are Itcl, Thread, sqlite3, tdbc,
and several tdbc driver packages.

Compatibility issues:
The Tcl/Tk 8.6.0 releases are highly compatible with prior releases
of Tcl/Tk since 8.1. There are a handful of changes that may cause
programs and scripts written for prior releases to behave differently
with Tcl/Tk 8.6.0. Here we summarize the known things to watch out for.

Build and platform support issues:

* Default build configuration for Tcl is now --enable-threads. Use
the configure option --disable-threads if your use of Tcl is
incompatible with a thread-enabled build.

* The --enable-aqua build for Tk on Mac OS X is a Cocoa implementation.
Tk 8.6 no longer supports Carbon, even as a compile-time option.
This implies dropping support for pre-Leopard (10.5) releases of
Mac OS X. See Tk 8.5.12 for last Carbon-supporting release.

* Attempts to run on Win9x systems will panic.

* Support for pre-ANSI compilers via _ANSI_ARGS_ removed.

* The included support for Xcode builds on Mac OS X requires at least
Tiger (10.4).

Script-visible issues:

* As a general comment, any scripts that rely on the precise text of
an error message or error code (a common issue in test suites) may
need revision. Tcl/Tk 8.6 includes many revisions to the text of
many error messages for the sake of clarity or readability, and a
large collection of new error code values useful for the new [try]

* On exit, Tcl will no longer flush open non-blocking channels. Scripts
relying on open non-blocking channels being flushed on exit will have
to be modified to explicitly flush or close those channels.

* Tk color names have been redefined to match Web color standards.

* Tk defines many more virtual events that control the built-in widget
set. These can override virtual events created in your scripts with
the [event add] command, changing program behavior.

* The default bindings have changed.

* On Unix-like platforms, [load] is implemented as a call to dlopen(),
with the flags (RTLD_NOW|RTLD_LOCAL) passed by default. If your use
of [load] requires otherwise, use the new -global or -lazy options to
[load] to set the RTLD_GLOBAL or RTLD_LAZY flags respectively.

* The default set of whitespace characters trimmed by the
[string trim*] commands was changed to add more Unicode whitespace

* When a channel gets std channel status on creation, it now gets the
appropriate name matching std*, and no other.

* A workaround built in to the default [unknown] command allowed
programs to make errors with [namespace code]. Scripts are now
expected to use [namespace code] correctly.

Issues for users of the public C API:

* C code compiled with USE_TCL_STUBS now must be linked against a
stub library. The Tcl shared library no longer exports variables
used in the stub interface. Analogous changes also made to Tk.

* The Tcl_Interp no longer contains the fields "result" or "errorline".
Update your programs to use the supported interfaces
Tcl_GetStringResult(), Tcl_(Get|Set)ErrorLine(), and
Tcl_Set(Obj)Result(). While working on that update, use temporary
workarounds of
to keep existing code working until the update is complete.

* Tcl_Exit() no longer calls Tcl_Finalize() to do a complete orderly
teardown of Tcl. It calls handlers registered by
Tcl_CreateExitHandler() and little else. Most of the tasks skipped
will be accomplished by the OS anyway, freeing memory and such.
This avoids many tricky finalization bugs, especially in
multi-threaded operation. Callers of Tcl_Exit() that want to keep
a full teardown may call Tcl_Finalize() themselves, or set the
environment variable TCL_FINALIZE_ON_EXIT to non-zero.

* System encoding during Tcl library initialization now iso8859-1,
not identity.

* A [load]able extension is no longer [unload]able unless it signals
its ability to be [unload]ed by exporting suitable _Unload()
and _SafeUnload() routines.

* Tcl_GetObjType(), Tcl_GetChannelType(), Tcl_FSGetFileSystemForPath()
now return const (read-only) pointers.

* Tcl_SetMainLoop() can now only influence Tcl_Main() if it is called
from the same thread as Tcl_Main().

* Providers of a Tcl_Filesystem will need to update their
Tcl_FSFileAttrStringProc entry to match the prototype

typedef const char * CONST86 *Tcl_FSFileAttrStringsProc(
Tcl_Obj *pathPtr, Tcl_Obj **objPtrRef);

where CONST86 indicates a new const on the return value in Tcl 8.6.

* The Tcl_ObjType "option" is no longer registered. Callers of
Tcl_GetObjType("option") must be prepared to accept NULL as a result.

Issues for users of the private interfaces:

* Callers of the Tcl*Startup*() routines should convert to using the
corresponding (now public) Tcl_*Startup*() routines.

* Callers of TclFindElement() must adapt to its revised specification
for its final argument.

* TclpGetUserHome() and TclSetPreInitScript() now return const
(read-only) pointers.