Software Design Lecture Notes
Fall 2004

For Thursday you should:

1) finish your project proposal

   ok if it is preliminary, but turn it in on time!

2) prepare for a quiz

Exam 2 will be Thursday 28 October

Leftover: Homework 7 suggestions


A quick intro to GUI programming
--------------------------------

Try this:

wget http://wb/sd/code/HelloGui.py
python HelloGui.py

from World import *

class Hello(Gui):
    def __init__(self):
        Gui.__init__(self)
        self.ca_width = 400
        self.ca_height = 400
        self.transforms = [ CanvasTransform(self.ca_width, self.ca_height) ]

    def setup(self):
    # setup creates the GUI elements (called widgets)
        
        # left frame
        self.fr(LEFT)
        self.canvas = self.ca(width=self.ca_width, height=self.ca_height,
                              bg='white')
        self.endfr()

        # right frame
        self.fr(LEFT, fill=BOTH, expand=1)

        self.fr()
        self.bu(LEFT, text='Hello', command=self.hello)
        self.bu(LEFT, text='Quit', command=self.quit)
        self.endfr()

        self.endfr()

    def hello(self):
        self.create_text([0, 0], 'Hello')

if __name__ == '__main__':

    # create the GUI
    h = Hello()
    h.setup()

    # wait for user events
    h.mainloop()


Key ideas in HelloGui:

1) event-driven programming

   create a GUI, then enter an infinite loop, waiting for
   user events and then processing them


2) GUIs are made up of a hierarchy of elements called WIDGETS

   The widgets in this example include

   Frame: container that holds other widgets

   Button: widget that invokes a command when pressed

   Canvas: big blank widget for drawing graphics


3) I have written methods that are wrappers on tkinter methods.
   The following are Gui methods inherited by HelloGui

   fr returns a Frame object
   bu returns a Button object
   ca returns a Canvas object
   ...

Documentation of the tkinter objects is available from

http://www.python.org/topics/tkinter/

But to understand widget options, you may want to look at
the Tcl/Tk documentation at

http://dev.scriptics.com/man/tcl8.5/TkCmd/contents.htm

You should also look at the examples I have provided in
World.py and Gui.py.


4) Next time... callbacks and event bindings!