Tcl/Tk 8.6.6 主要是修复 bug 的版本，但令人惊讶的是，该版本中包括了诸多新功能，其中最受期待的当属更新的 Unicode 支持。
* [TIP 443] More configuration options for text tags.
* [TIP 446] [$text edit (canundo|canredo)].
* Update to Unicode 9.0.
*** POTENTIAL INCOMPATIBILITY ***
* Final newline in [text] handling restored compat with 8.6.4 and
before.
*** POTENTIAL INCOMPATIBILITY ***
* [file] support for more Windows filesystem conventions.
[5d7ca0,ae61a6]
*** POTENTIAL INCOMPATIBILITY ***
* [namespace upvar $ns] now ignores custom resolvers in $ns.
*** POTENTIAL INCOMPATIBILITY ***
* Tcl_WrongNumArgs() now uses proper list formatting in error message.
Matters when parameter names contain spaces, etc.
*** POTENTIAL INCOMPATIBILITY ***
* Fixed crashes or hangs in...
- [apply {{} {foreach x y {if 1 break else}}}]
- compiled [string replace]
- notifier finalization
- server socket creation on Win
- [glob -path a]
- Tcl_DString appends to self
- mouse pointer warping
- Aqua geometry calculations on new toplevel
- zlib-8.17, zlib-8.18
- apply {{} {lassign {} item; dict update item item item two two {}}}
- [vwait] after namespace delete destroys variable waited on.
* Fix: Safe handling of widget destruction during callbacks.
* Fix: compiled [lreplace $list end ...].
*** POTENTIAL INCOMPATIBILITY ***
* Fix: circumstances of command callbacks from [scale].
* Fix: Stop
