Touchscreen Problems

--Monitor Setup
local mon = peripheral.wrap("top")
mon.setTextScale(1)
mon.setTextColor(colors.white)
local button={}
mon.setBackgroundColor(colors.black)

--Functions

function setTable(name, func, xmin, xmax, ymin, ymax)
   button[name] = {}
   button[name]["func"] = func
   button[name]["active"] = true
   button[name]["xmin"] = xmin
   button[name]["ymin"] = ymin
   button[name]["xmax"] = xmax
   button[name]["ymax"] = ymax
end

function fill(text, color, bData)
   mon.setBackgroundColor(color)
   local yspot = math.floor((bData["ymin"] + bData["ymax"]) /2)
   local xspot = math.floor((bData["xmax"] - bData["xmin"] - string.len(text)) /2) +1
   for j = bData["ymin"], bData["ymax"] do
	  mon.setCursorPos(bData["xmin"], j)
	  if j == yspot then
		 for k = 0, bData["xmax"] - bData["xmin"] - string.len(text) +1 do
			if k == xspot then
			   mon.write(text)
			else
			   mon.write(" ")
			end
		 end
	  else
		 for i = bData["xmin"], bData["xmax"] do
			mon.write(" ")
		 end
	  end
   end
   mon.setBackgroundColor(colors.black)
end
	
function screen()
   local currColor
   for name,data in pairs(button) do
	  local on = data["active"]
	  if on == true then currColor = colors.lime else currColor = colors.red end
	  fill(name, currColor, data)
   end
end
	
function checkxy(x, y)
   for name, data in pairs(button) do
	  if y>=data["ymin"] and  y <= data["ymax"] then
		 if x>=data["xmin"] and x<= data["xmax"] then
			data["func"]()
			data["active"] = not data["active"]
			print(name)
		 end
	  end
   end
end
	
function heading(text)
   w, h = mon.getSize()
   mon.setCursorPos((w-string.len(text))/2+1, 1)
   mon.write(text)
end
function next()
local nextScreen = not nextScreen
end
--Program
local nextScreen = false
	
setTable("Begin", next, 5, 35, 20, 25)
while nextScreen == false do
   mon.clear()
   heading("Dummy Test Screen")
   screen()
   local e,side,x,y = os.pullEvent("monitor_touch")
   print(x..":"..y)
   checkxy(x,y)
   sleep(.1)
end
next()
heading("Success!!")