[Saiket]

Your original code creates at least three garbage tables every time one of the hooked functions is called. Some of those hooked functions, like ActionButton_UpdateUsable, get called a lot: once per visible action button for each action that becomes usable/unusable. Every action button is registered for ACTIONBAR_UPDATE_USABLE, and each one responds by calling ActionButton_UpdateUsable separately.



Imagine you have 20 action buttons visible, and 10 of them become unusable when you unstealth. If you unstealth, ACTIONBAR_UPDATE_USABLE fires 10 times, and ActionButton_UpdateUsable gets called 10*20 = 200 times. Then, your hook creates one garbage table each call:

hooksecurefunc("ActionButton_UpdateUsable", function(self)
                for i, v in pairs({"ActionButton", "MultiBarBottomLeftButton", "MultiBarBottomRightButton", "MultiBarLeftButton", "MultiBarRightButton", "MultiCastActionButton", "MultiCastSummonSpellButton", "MultiCastRecallSpellButton"}) do

Then, BorderBeautification gets called for each of those 8 object types, totaling 200*8 = 1600 calls. Each of those calls creates two more garbage tables for top and bottom color:

local BorderBeautification = function(object)
       
                if IsAddOnLoaded("FacePaint") and FacePaint then
                        tc = {r = topcolor.r, g = topcolor.g, b = topcolor.b, a = topalpha}
                        bc = {r = bottomcolor.r, g = bottomcolor.g, b = bottomcolor.b, a = bottomalpha}
                else
                        tc = {r = BorderColors.top.r, g = BorderColors.top.g, b = BorderColors.top.b, a = BorderColors.top.a}
                        bc = {r = BorderColors.bot.r, g = BorderColors.bot.g, b = BorderColors.bot.b, a = BorderColors.bot.a}
                end

In total, 3400 garbage tables created by unstealthing in this case--200 object list tables plus 1600*2 color tables.

That explains why your memory usage ballooned when you spammed stealth/unstealth. The other technique in your second version is more efficient because it doesn't recolor the same button multiple times per event like the first did. It still would still create a fair number of garbage color tables though.



I suggest using the preexisting topcolor/bottomcolor and BorderColors tables instead of copying them each time. Using the second version of your code, here's an updated colorit function that doesn't create any new tables:

local colorit = function(object)
    local tc, bc, ta, ba;
    if IsAddOnLoaded("FacePaint") and FacePaint.enable and not FacePaint.invert then
        tc, ta = topcolor, topalpha;
        bc, ba = bottomcolor, bottomalpha;
    elseif IsAddOnLoaded("FacePaint") and FacePaint.enable and FacePaint.invert then
        tc, ta = bottomcolor, bottomalpha;
        bc, ba = topcolor, topalpha;
    else
        tc, bc = bordercolor.top, bordercolor.bot;
        ta, ba = tc.a, bc.a;
    end
    object:SetGradientAlpha("VERTICAL", bc.r, bc.g, bc.b, ba, tc.r, tc.g, tc.b, ta)
end