How to make a Object Oriented and Graphical Operating System

local _w, _h = term.getSize()

CCInterfaceEntities = {
    List = {},

   Add = function(_entity)
      table.insert(CCInterfaceEntities.List, _entity)
   end
}

CCDrawing = {

	Screen = {
		Width = _w,
		Height = _h
	},

	DrawCharacters = function (_x, _y, _string, _textColour, _backgroundColour)
		term.setBackgroundColour(_backgroundColour)
		term.setTextColour(_textColour)
		term.setCursorPos(_x, _y)
		term.write(_string)
	end,

	DrawArea = function (_x, _y, _w, _h, _character, _textColour, _bgColour)
		--width and height must be greater than 1, other wise we get a stack overflow
		if _w < 0 then
			_w = _w * -1
		elseif _w == 0 then
			_w = 1
		end

		if _h < 0 then
			_h = _h * -1
		elseif _h == 0 then
			_h = 1
		end

		local sRow = ""
		for ix = 1, _w do
			sRow = sRow .. _character
		end

		for iy = 1, _h do
			local currY = _y + iy - 1
			CCDrawing.DrawCharacters(_x, currY, sRow, _textColour, _bgColour)
		end
	end

}

OSObject = {
    Type = "OSObject",
    ID = 0
}

CCEntity = {
    __index = OSObject,

    X = 0,
    Y = 0,
    Width = 0,
    Height =  0,
    Title = "",
}

CCControl = {
    __index = CCEntity,
    Action = nil,
    Enabled = true
}

CCButton = {
    __index = CCControl,
    Type = "CCButton",
    TextColour = colours.white,
    BackgroundColour = colours.grey,
    Height = 1,
    New = function(self, _x, _y, _title, _action)
      local new = {}    -- the new instance
      setmetatable( new, {__index = CCButton} )
      new.Width = string.len(_title)+2
      new.X = _x
      new.Y = _y
      new.Title = _title
      new.Action = _action
      new.Enabled = true
      return new
    end,
    Draw = function(self)
        CCDrawing.DrawCharacters(self.X,self.Y, " "..self.Title.." ", self.TextColour, self.BackgroundColour)
    end
}

function DrawScreen()
	for _,entity in ipairs(CCInterfaceEntities.List) do
		entity:Draw()
	end
end

function EventHandler()
	while true do
		local event, arg, x, y = os.pullEventRaw()

		if event == "mouse_click" then
			for _,entity in pairs(CCInterfaceEntities.List) do
				--check if the click overlaps an entities
				if x >= entity.X and x <=entity.X + entity.Width - 1 and y >= entity.Y and y <=entity.Y + entity.Height then
					if entity.Action then
						entity:Action()
						break
					end
				end
			end
		end
	end
end

function init()
	CCDrawing.DrawArea(1, 1, CCDrawing.Screen.Width, CCDrawing.Screen.Height, " ", colours.white, colours.lightGrey)
	local ourButton = CCButton:New(19, 10, "Hello Again!", function() print("hi") end)
	CCInterfaceEntities.Add(ourButton)
	DrawScreen()
	EventHandler()
end