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R Sig Mac Problem Loading Tcl Tk Interface On R For Mac Osx
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Tkx::Tutorial - How to use Tkx

You will also need to locate the Tcl/Tk libraries libtcl.a and libtk.a. These are usually located in /usr/local/lib. When locating the right header and libraries files, double check to make sure the files are the correct version and form a matching pair. SWIG works with the following Tcl/Tk releases. In this video, I'm going to briefly show how you can install R on the Mac. It's a very simple process, it only takes a few steps. So the first thing you need to do is open your web browser and go to CRAN, this is the Comprehensive R Archive Network, and you'll see that there are a number of options for you to download here for different platforms.

Tk is a toolkit that allows you to create applications with graphical interfaces for Windows, Mac OS X and X11. The Tk toolkit is native to the Tcl programming language, but its ease of use and cross-platform availability has made it the GUI toolkit of choice for many other dynamic languages as well.

Tkx is a Perl module that makes the Tk toolkit available to Perl programs. By loading the Tkx module Perl programs can create windows and fill them with text, images, buttons and other controls that make up the user interface of the application.

Hello World

Let's start with the mandatory exercise of creating an application that greats the world. Here we make the application window contain a single button which will shut down the application if clicked. The code to make this happen is:

Save this to a file called hello.pl and then run perl hello.pl to start up the application. A window with the text 'Hello, world' should appear on your screen.

After the Tkx module has been loaded by the use Tkx statement the application will show an empty window called '.'. We create a button with the name '.b' and tell the window to display the button with the call to Tkx::pack(). After the layout of the window has been set up we need to pass control back to Tk so that it can draw the window and invoke our callback if the button is clicked. This is achieved by the Tkx::MainLoop() call at the end. Clicking the button will invoke the subroutine registered with the -command option of the button. In this case the callback simply destroys the window, which in turn will terminate the application.

For reference this is how the same program would look in Tcl:

This program can be executed by the tclsh binary that comes with Tcl/Tk. As you can see the code is mostly identical, but with a slightly different syntax. The only real difference is that the call to MainLoop() is implicit in Tcl and does not have to be spelled out.

Tkx does not come with documentation that explain all the widgets (like 'button' above) that are available for use. Instead you will need to read the mostly excellent documentation that comes with Tcl/Tk and then figure out how this translates to Tkx yourself. As you can see this translation is straight forward. You basically only have add the prefix 'Tkx::' to all the functions and use the Perl way of passing arguments. Tcl is a very simple language, so it should not take long to understand enough of it to be able to read its documentation with ease.

A great place to look up the Tk documentation is http://aspn.activestate.com/ASPN/docs/ActiveTcl/at.pkg_index.html. This documents core Tk as well as all the useful add-on packages that are part of ActiveTcl. The ActiveTcl HTML documentation can also be downloaded from http://downloads.activestate.com/ActiveTcl/html/ and installed locally. The official Tcl/Tk docs are found at http://www.tcl.tk/doc/.

Hello World with objects

The windows and controls that make up a Tk interface are called widgets. The widgets are identified by path names of the form .foo.bar.baz. These names are hierarchical in the same way as file system names are, but '.' is used instead of '/' to separate levels. The name .foo.bar.baz is the name of a widget that is child of widget .foo.bar which in turn is a child of .foo. At the top of this hierarchy we have a widget called ., which is the main window of the application.

The Tkx module provide a class called Tkx::widget, that can be used to hide the details of Tk path names from Tkx applications. This provide a more 'perlish' way to create and manipulate Tk widgets.

Our 'Hello, world' program can be rewritten like this using the Tkx::widget class:

By loading the Tkx module we make the Tkx::widget class available and create the main window (the widget called .). Next we instantiate a new Tkx::widget object wrapping the main window. It is customary to name this object $mw.

To create a new button child widget we call $mw->new_button method. Constructor methods are always prefixed with new_. The rest of the method name is the name of the Tk widget to create; i.e. 'button' in this case. Arguments are passed as before.

Calling a 'g_' method will invoke the corresponding Tk command with the widget path as argument. In the code above we destroy the main window by calling $mw->g_destroy and we pack the button in the main window by invoking $b->g_pack.

In the end we need to invoke the MainLoop as before.

For trivial programs like the one above using Tkx::widget wrappers does not appear to be a win, but as the application grows and the Tk path names get longer it surely is.

Hello World expanded

In order to introduce a few more Tkx features, we now present a slightly expanded version of the previous Hello World program. This time we added line numbers to the program so that it is easier to reference back to its statements:

The first thing we added is the use strict statement, simply because that's a good idea in general.

In line 5 and 6 we set up some window manager attributes of the main application window. What is noteworthy here is that we use underscore in the g_ method names where Tcl would use space between words. Same rules apply to the function names in the Tkx:: namespace directly. We could alternatively have modified the window attributes with:

which in Tcl would have been:

The rule is: A single underscore on the Perl side turns into space on the Tcl side.

In line 11 to 16 we have expanded the button callback to change the text of button and then wait 1.5 seconds before we shut down the application. In addition to the 'g_' methods described in the previous section, Tkx::widget also provide 'm_' methods which are forwarded as Tcl subcommands of the current widget. The most commonly used subcommand is 'configure' that is used to change the attributes of a widget as we do in line 12. Since we now reference $b from the callback, we had to declare the variable upfront in line 8 instead of declaring it together with the assignment as we did previously. In line 15 we schedule for the window to be destroyed after a delay of 1500 ms. The delay is needed so that the new button text is actually show before the window goes away.

Btw, the 'm_' method prefix is actually optional, so you might prefer just to leave it out.

Padding around buttons is usually a good idea as we now do in line 18.

In line 23 we invoke the messageBox command to pop up a useful reminder to our user. But what's up with the 'tk___' prefix? In the Tcl docs you will find that the name of this command is actually 'tk_messageBox'. Remember the previous rule that an underscore in Tkx:: names turn into a space on the Tcl side? If you try to call Tkx::tk_messageBox() you will get an error telling you:

What happens is that Tkx invoked the 'tk messageBox' command, but the Tcl 'tk' command only take the subcommands listed in the error message above and refuse to do anything about 'messageBox'. In order to invoke Tcl commands with underscore their name, you need to t

R Sig Mac Problem Loading Tcl Tk Interface On R For Mac