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

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

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

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

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