Metatables. Add functionality into metamethod without overriding

[Koji6ac9H]

Hello.
Is there way to extend Panel's metatable methods like:

PANEL:OnCursorEntered
PANEL:OnCursorExited

Without loosing initial functionality. (Kinda like adding event listeners in JS)

For example I have a panel that highlights on CursorEntered.

But I want to create custom tooltip meta method like:

local meta = FindMetaTable("Panel")

function meta:CustomTip(str)
	self.OnCursorEntered = function() -- Here we override the method and it loses it's functionality and panel no more highlights itself :(
		-- Show custom tooltip
	end
	self.OnCursorExited = function()
		-- Hife custom tooltip
	end
end

[aStonedPenguin]

Detours.

mt._Function = mt.Function
function mt:Function() 
    -- code here 
    mt:_function()
end

[Koji6ac9H]

[QUOTE=StonedPenguin;51094837]Detours.

mt._Function = mt.Functionfunction mt:Function() -- code here mt:_function()end[/QUOTE]

Yes, but it's a little bit hacky way.

[Vioxtar]

[QUOTE=StonedPenguin;51094837]Detours.

mt._Function = mt.Function
function mt:Function() 
    -- code here 
    mt:_function()
end

[/QUOTE]

Popping out of the blue here a little bit, but what is the nature of detours? I've never used them and have no idea what that code does, it seems really useful.

[bigdogmat]

[QUOTE=VIoxtar;51094955]Popping out of the blue here a little bit, but what are detours? I've never used them and have no idea what that code does, it seems really useful.[/QUOTE]

The code does exactly what it looks like it does, it saves the current function and then overwrites it.

Just like if I want to know whenever something printed shit

local old_print = print

function print(...)
  -- Print was called, do our stuff here

  old_print(...) -- Call old print to retain functionality
end

[crazyscouter]

ninja'd

[UselessGhost]

[QUOTE=Koji6ac9H;51094845]Yes, but it's a little bit hacky way.[/QUOTE]

vanilla gmod code does this in quite a few spots, i wouldn't worry too much about it being hacky. if you really must have a cleaner syntax, you'd have to implement a hooking system for your panel yourself.