The window manager was one of the most important parts of the user interface toolbox and the ultimate showcase for QuickDraw's "region clipping" technology. The window manager had to calculate various regions for windows as they were created, moved, and resized, and objects drawn inside the windows were automatically clipped as necessary.
The Macintosh window manager was based on the one Bill Atkinson wrote for the Lisa, which was written in Pascal. My job was to rewrite it in 68000 assembly language and adapt it to the Macintosh environment. The first step was to port Bill's Pascal version. I wrote a small program to test the port, which I called "Window Manager Demo," that generated windows and put the window manager through its paces.
A year earlier, I had written a fast "ball bouncing" routine using custom 16x16 pixel graphics routines that could animate hundreds of balls simultaneously—a fun way to show off the Mac's raw graphical horsepower. I decided to animate a few dozen balls in each window in the Window Manager Demo using QuickDraw, as their continuous movement would eventually cover every area inside a window and expose any flaws in the underlying clipping.
After Susan started in January 1983, I asked her to draw some tiny 16-by-16 bitmaps to use in the Window Manager Demo instead of the now-monotonous ball shapes. Soon, we had a variety of little objects bouncing around in the windows—tiny Macintoshes, apples, insects, and alligators. I thought the Window Manager Demo was finished, but I was wrong.
Steve Jobs came by the software area one evening a couple of months later, excited about someone he had recently met in New York City. "Hey, I want you to do a demo next week for this guy I met yesterday—John Sculley, the president of Pepsi. He's really smart—you wouldn't believe how smart he is. If we impress him, we can get Pepsi to buy thousands of Macs. Maybe even five thousand. Why don't you come up with something special to show him?"
It sounded a little fishy to me, since we rarely demoed for potential customers at that point. But I asked Susan to draw some Pepsi imagery, and she came up with tiny Pepsi caps as well as Pepsi cans in his honor. I added them to the Window Manager Demo.
The next week, Mike Murray led John Sculley around the engineering area, since Steve was out of town. He brought him by my cubicle to see the modified Window Manager Demo. I opened the windows one at a time, saving the Pepsi caps and cans for last. He seemed genuinely excited to see the Pepsi elements but oddly cold for most of the demo. He asked a few questions but didn't seem all that interested in the answers.
A few weeks later, we found out the real story: the purpose of John's visit was to interview for CEO of Apple—and he got the job, convinced by Steve's famous line: "Would you rather sell sugar water to kids for the rest of your life, or would you like a chance to change the world?