API hooksecurefunc

Securely posthooks the specified function. The hook will be called with the same arguments after the original call is performed.
 hooksecurefunc([table,] functionName, hookfunc)
==Arguments==
:;table:Optional Table - Table to hook the functionName key in; if omitted, defaults to the global table (_G).
:;functionName: - name of the function being hooked.
:;hookfunc: - your hook function.
==Example==
The following calls hook and without compromising their secure status. When those functions are called, the hook prints their argument list into the default chat frame.
 hooksecurefunc("CastSpellByName", print); -- Hooks the global CastSpellByName
 hooksecurefunc(GameTooltip, "SetUnitBuff", print); -- Hooks GameTooltip.SetUnitBuff
==Details==
* This is the only safe way to hook functions that execute protected functionality.
* hookfunc is invoked after the original function, and receives the same parameters; return values from hookfunc are discarded. 
* After this function is used on a function, setfenv() throws an error when attempted on that function
* You cannot "unhook" a function that is hooked with this function except by a UI reload. Calling hooksecurefunc() multiple times only adds more hooks to be called.
* Also note that using hooksecurefunc() may not always produce the expected result. Keep in mind that it actually replaces the original function with a new one (the function reference changes). For example, if you try to hook the global function "MacroFrame_OnHide" (after the macro frame has been displayed), your function will not be called when the macro frame is closed. It's simply because in Blizzard_MacroUI.xml the OnHide function call is registered like this:
 <OnHide function="MacroFrame_OnHide"/>
: The function ID called when the frame is hidden is the former one, before you hooked "MacroFrame_OnHide". The workaround is to hook a function called by "MacroFrame_OnHide":
 hooksecurefunc(MacroPopupFrame, "Hide", MyFunction)
* If you want to securely hook a frame's script handler, use :
 MacroPopupFrame:HookScript("OnHide", MyFunction)