Event Continuation Registry

ContinuationRegistry.lua

local ContinuationRegistry = Mixin(CreateFrame("Frame"), CallbackRegistryMixin);

local function ProcessContinuations(registry, event)
    ContinuationRegistry:UnregisterEvent(event);
    ContinuationRegistry:TriggerEvent(event);
end

local function InvokeContinuation(func, event)
    ContinuationRegistry:UnregisterCallback(event, func);
    func();  -- May error, this is fine.
end

function ContinueOnNextEvent(event, func, ...)
    ContinuationRegistry:RegisterCallback(event, InvokeContinuation, GenerateClosure(func, ...), event);
    ContinuationRegistry:RegisterEvent(event);
end

ContinuationRegistry:OnLoad();
ContinuationRegistry:SetUndefinedEventsAllowed(true);
ContinuationRegistry:SetScript("OnEvent", ProcessContinuations);

---

function ContinueWhenOutOfCombat(func, ...)
    if InCombatLockdown() then
        ContinueOnNextEvent("PLAYER_REGEN_ENABLED", func, ...);
    else
        func(...);
    end
end

ContinueWhenOutOfCombat(print, 1, 2, 3);