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

274 Part II ■ Programming in World of WarcraftAs mentioned in Chapter 8, each frame type has a number of widget scriptsthat can be set with a handler function. Table 14-1 describes the scripts you’reusing here (you can find more details about these scripts and the argumentsthey accept in Chapter 29, ‘‘Widget Reference’’).Table 14-1: Script Handlers Used in CombatTrackerSCRIPTUSEThe basic initialization function for CombatTracker willbe called CombatTracker_OnLoad(). It’s called fromthe handler on the frame when the framehas finished initializing. It works only for frames that aredefined in XML.The addon will respond to a number of events, so youmust define an OnEvent script to handle them. TheCombatTracker_OnEvent() function will beresponsible for each of the events. The handling functionwill need to know which event it’s being passed, soensure you are passing the frame self, the event nameevent, and the variable set of arguments ... to thefunction.When the player right-clicks CombatTrackerFrame,theOnClick script handler will call theCombatTracker_ReportDPS() function to print thecurrent combat status. The status message will be sentto party chat if the player is in a party, otherwise it will beprintedtothechatframe.The code for allowing a frame to be dragged and placedis very simple, so the code is written directly in the scripthandler rather than in a function defined inCombatTracker.lua. Later, if you wanted to addoptions to the addon, such as allowing the user to lockthe frame in place, you could move this code into theLua file to consolidate everything.Each frame that has the movable attribute set to truecan call the self:StartMoving() method, whichcauses the frame to follow the mouse. As a result, allthat’s required to set up frame movement when draggedis to call this function.Stopping the frame from moving is a matter of callingself:StopMovingOrSizing(). This function alsoflags the frame as user placed, meaning the next timethe addon loads, the frame will be put in the same placethe user dropped it. This is quite a handy side effect.