Let's start with the obligatory ``hello world'' type of program:
(defun hello-1() (with-ltk () (let ((b (make-instance 'button :master nil :text "Press Me" :command (lambda () (format t "Hello World!~&"))))) (pack b))))
Let's go through it step-by-step. The whole code of
wrapped into the
with-ltk macro. It ensures that the GUI
library is properly set up and the communication with the Tk toolkit
is established. It runs the contained code which should initialize the
GUI and after that calls
mainloop to process the GUI events.
The next step is to create the button. This is done by
creating an instance of the class button.
The :text argument gives the text to display on the button
and :command is the function to call, whenever the button is pressed.
While the last two arguments should be obvious, the master needs
explanation. In Tk, all GUI elements are arranged in a tree. So
every GUI element has a parent node or ``master'' which designates
its position in the tree structure. So put there the object that
should be the parent for your button. Only for top level components
nil may be given instead of an object.
For displaying any ltk
object, a layout manager is used. There are two layout managers available,
which can be used to arrange widgets in its parent,
pack arranges widgets as a heap of boxes, which are horizontally or
grid arranges widgets in a table-like layout.
grid for the same container, unpredictable
behaviour may the result (or rather, the program will very predictably crash).