1. Windowing Push-Pull Systems
Application
Events & Callbacks
Windowing System
Operating System
Device Drivers
Keyboard
Mouse
Video
Printer
Fall 2004
CS-321 Dr. Mark L. Hornick

2. Modern Windowing Systems
Program flow is NOT sequential
Order of execution is up to the user
When…
Buttons pressed
Keys typed
Mouse moved over a window
Timers
Etc.
Fall 2004
CS-321 Dr. Mark L. Hornick

3. Events and Callbacks GUI and mouse activity is registered
Actions are associated with functions
Events – user actions
Callbacks – registered functions that subscribe to event notifications
Each action can trigger a callback
Similar to interrupt service routines
Fall 2004
CS-321 Dr. Mark L. Hornick

4. Callback Features Should return in a reasonable period of time
Don’t wait for additional user input
Stalls application (<Windows 3.x would stall entire system)
Spy demo
Fall 2004
CS-321 Dr. Mark L. Hornick

5. Quiz tomorrow
Be able to compute line intersections using parametric equations.
Be able to describe and contrast the various polygon fill techniques discussed in the past few lectures
Be able to describe the various coordinate systems used in computer graphics
Be able to apply odd-even or NZW to determine inside/outside
Fall 2004
CS-321 Dr. Mark L. Hornick