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

484 Part III ■ Advanced Addon Techniquesthings like frame attributes or previously stored information, as well ascurrent API checks of approved information, such as whether you have atarget, or other legitimate macro conditions.Notice that the SecureHandlerWrapScript call refers to BuffCycler twice.When you call SecureHandlerWrapScript, you have to give it two frames,which can be the same or different frames. The first one is the frame whosescript handler you will actually wrap. The second one (the third argument) isthe ‘‘owner’’ of the script; any private variable references (explained in moredetail a little later in the chapter) are associated with that frame. All scriptsowned by a frame have access to all private variables created by any scriptowned by that frame.To prevent exploits, only an explicitly protected frame (one inheriting fromatemplatewiththeprotected=“true“ tag attribute) can be designated as ascript owner. Moreover, snippets wrapping a frame script will not be run ifthe wrapped frame becomes unprotected, such as by having all its protectedchildren re-parented to other frames. Its original script will be run withoutmodification, and its wrappers will resume functioning if it becomes protectedagain.WARNING At the time of this writing, implicit protection is not sufficient toallow script wrappers to run on a frame; any script wrappers on a frame that is notexplicitly protected will be created successfully, but will be silently ignored. It ispossible that a future version of the secure handlers will lift this restriction, butuntil such a change is made, you can make protected proxy frames with suitablescripts and have them manipulate references to the frames you want to control.It is also possible to unwrap a script, so that it returns to its originalbehavior. SecureHandlerUnwrapScript(wrappedFrame, scriptName) willsecurely restore the original handler, and return the prebody snippet, owningheader frame, and postbody snippet, allowing you to put the wrapper backon if needed.Using a Post-HookIf two strings are supplied to SecureHandlerWrapScript, the second one is apost-hook snippet called after the original handler completes. Most pre-hookscan include a message as an additional return value; if this message is non-nil,the post-hook is called and receives the message as an additional argument.Post-hooks are commonly used to perform clean-up or change an addon’sstate information after an action completes, setting it up for the next action.You can use this to make the menu frames created by BlessedMenus actmore like conventional popup menus, closing after a choice is made fromthem. Open up the BlessedMenus.xml file and find the first template,BlessedMenusSpellButtonTemplate. LocateitsOnLoad handler and add thefollowing statement at the end of the handler: