local pairs, wipe, select, pcall = pairs, wipe, select, pcall
local GetFramesRegisteredForEvent = GetFramesRegisteredForEvent
local enteredOnce, listenForUnreg

local occured = {}
local events = {
    SPELLS_CHANGED = {},
    USE_GLYPH = {},
    PET_TALENT_UPDATE = {},
    WORLD_MAP_UPDATE = {},
    UPDATE_WORLD_STATES = {},
    CRITERIA_UPDATE = {},
    RECEIVED_ACHIEVEMENT_LIST = {},
    ACTIONBAR_SLOT_CHANGED = {},
}

local t = {GetFramesRegisteredForEvent("PLAYER_ENTERING_WORLD")}
for i, frame in ipairs(t) do
    frame:UnregisterEvent("PLAYER_ENTERING_WORLD")
end

local f = CreateFrame("Frame")
f:RegisterEvent("PLAYER_ENTERING_WORLD")

for i, frame in ipairs(t) do
    frame:RegisterEvent("PLAYER_ENTERING_WORLD")
end
wipe(t)
t = nil

local function unregister(event, ...)
    for i = 1, select("#", ...) do
        local frame = select(i, ...)
        frame:UnregisterEvent(event)
        events[event][frame] = 1
    end
end

if PetStableFrame then
    PetStableFrame:UnregisterEvent("SPELLS_CHANGED")
end

f:SetScript("OnEvent", function(self, event)
        if event == "PLAYER_ENTERING_WORLD" then
        collectgarbage("restart")
            if not enteredOnce then
                f:RegisterEvent("PLAYER_LEAVING_WORLD")

                hooksecurefunc(getmetatable(f).__index, "UnregisterEvent", function(frame, event)
                        if listenForUnreg then
                            local frames = events[event]
                            if frames then
                                frames[frame] = nil
                            end
                        end
                end)
                enteredOnce = 1
            else
                listenForUnreg = nil
                for event, frames in pairs(events) do
                    for frame in pairs(frames) do
                        frame:RegisterEvent(event)
                        local OnEvent = occured[event] and frame:GetScript("OnEvent")
                        if OnEvent then
                            local arg1
                            if event == "ACTIONBAR_SLOT_CHANGED" then
                                arg1 = 0
                            end
                            local success, err = pcall(OnEvent, frame, event, arg1)
                            if not success then
                                geterrorhandler()(err, 1)
                            end
                        end
                        frames[frame] = nil
                    end
                end
                wipe(occured)
            end
        elseif event == "PLAYER_LEAVING_WORLD" then
            wipe(occured)
            for event in pairs(events) do
                unregister(event, GetFramesRegisteredForEvent(event))
                f:RegisterEvent(event)
            end
            listenForUnreg = 1
            collectgarbage("stop")
        else
            occured[event] = 1
            f:UnregisterEvent(event)
        end
end)

-- Improves loading time by 40-70%
-- stops garbage collection during loading screens & tweaks events