Due:

This is a warmup exercise to introduce you to GUI programming - how to construct a display (GUI syntax - the composite design pattern) and how to program window actions (GUI semantics - the observer design pattern).

The relevant material is covered in Jia (Sections 2.2, 2.3.1, 8.3, 9.1 and 9.2).

Here's a partial solution.

1. Apply for a CS680 account on the Department's unix system.

2. Get the textbooks for the course. (You will need Jia right away.)

3. You will find the source code for version 1 of the scribble application in Chapter 9 of Jia in http://se.cs.depaul.edu/Java/chap09.html

   Get it, compile it, run it, understand it.

4. Modify the scribble application so that it puts up two canvases to scribble on, side by side. Each canvas should have a button beneath it labelled "clear". Clicking the button should clear that canvas. Here's a picture of what you might write. (You don't have to get the colors and sizes to match.)

   Your source code

   • must be well designed - if you simply add some lines of code to make the application work, look at what you've done and think "that's pretty ugly - not how I would have done it if I'd started from scratch" - them reorganize your code. Don't be afraid to design new classes.
   • must honor formatting conventions - either Jia's, or your own (note that I changed some of Jia's code when I retyped it).
   • should have no duplicated code (don't program by cutting a block of java, pasting it somewhere else and just changing a token or two).
   • should indicate clearly where you have modified Jia's code and where it is unchanged.

5. Write ta memo discussing your design and coding process. Where did you encounter problems? How did you solve them? What did you learn?

• memo.txt
• scribble.jar
• *.java