next: Tk items
This is one of the simplest Tk programs you can write. First, you have to
create a main window (a big thing with border). Each call for MainWindow
creates a new one. You can create more than one for one application, and they
can reside on different screens... only on UNIX, of course.
Not before the
MainLoop the window will appear. On the moment
your program reaches the MainLoop statement, the whole interface must be
built. The program will never return from the MainLoop: the rest must be
done (user-)event driven.
To show an object, like a button, you require two things: first you have
to create the object to be displayed on a window. Then you give the object
a place in the window.
The list of parameters looks like a hash, which is almost true: within the
object creation routines it is tranformed into a hash. The labels start with a
dash which is (happily) accepted by Perl as part of a string left from the
=>'. The names are usually equivalent to the option-names
which can be used with other X11 client programs. Even X-resource files can