Wiley-World.of.Warcraft.Programming.A.Guide.and.Reference.for.Creating.WoW.Addons

Chapter 18 ■ Responding to Graphic Updates with OnUpdate 357endendCombatTracker_UpdateText()counter = 0Finally, you should set the OnUpdate script when the player enters combat,and clear it when the player leaves combat. Under the PLAYER_REGEN_ENABLEDcondition in CombatTracker_OnEvent(), add the following:frame:SetScript(“OnUpdate“, nil)Within the PLAYER_REGEN_DISABLED condition, add this line:frame:SetScript(“OnUpdate“, CombatTracker_OnUpdate)Now as long as you are in combat the calculation will be updated everysecond.Considering Performance with OnUpdate ScriptsRemember that the code in your OnUpdate handler is called on every screenupdate. If the screen refreshes at 60 frames per second, then your script willbe called 60 times per second. As a result you should be sure to considerperformance when writing your functions. Don’t over-scrutinize your codeinto some monster, but be aware that a poorly written OnUpdate script can affectthe frame rate of the client. In particular you should consider the following:The game client runs code sequentially. As a result, all OnUpdate scripts arerun before the client continues to process events or update the graphics.If your function does not need to run every screen refresh, you can use athrottle to introduce a delay.Local variables are faster than global variables, so you can squeeze out abit of extra performance by using them.SummaryThis chapter discussed using OnUpdate scripts to introduce delays or run codeperiodically. You created a number of small addons that use OnUpdate scriptsto perform various tasks.The next chapter introduces you to function hooking, and using a combinationof an OnUpdate timer and function hooking to alter the default userinterface.