Windowing PushPull Systems Application Events Callbacks Windowing System

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

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

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

Callback Features l Should return in a reasonable period of time l l l 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 4

Quiz tomorrow l l 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 5