The tkdock package is a small, Cocoa-based Tcl extension that allows a
Tcl/Tk application to change its icon on the OS X Dock while running.
This can be useful for indicating changes in application state, for
instance that the application is executing a long-running process,
connecting to a server, or similar activities.

Using the Tkdock Package

Tkdock is invoked by calling package require tkdock. It implements two
commands:

::tkdock::switchIcon /path/to/icon: This command switches the
application's Dock icon while the application is running, and takes a
path to an image as an argument. Any image format supported on Mac OS X
should work, but Apple's native "icns" icon format (at 128x128 pixels)
appears to provide the sharpest results.

::tkdock::origIcon: This command restores the original application icon.

Installing Tkdock

Because it calls into the Mac's native Cocoa frameworks, tkdock is a
binary extension (shipped as a .dylib). The universal binary package was
built against Tcl/Tk 8.5.3 on Mac OS X 10.5.6 and should run on both
Intel and PPC systems. The source code comes with a makefile if you want
to build the extension yourself. Tkdock is available under the standard
Tcl/Tk BSD-style license.

Tkdock can be downloaded at http://www.codebykevin.com/opensource/oss.html.