Distance and Volume measuring tool for an OpenComputers Tablet (Minecraft)

measure.lua

local event = require("event")
local term = require("term")
local component = require("component")

gpu = component.gpu

local w, h = gpu.getResolution()
local prevX = nil
local prevY = nil
local prevZ = nil
local locked = false

function printStatic()
  term.clear()
  term.setCursor(2,h)
  print("Q: Quit R: Reset L: Lock first Coordinate")
end

function printfAt(x, y, s, ...)
  sf = string.format(s, ...)
  sfp = sf--text.padRight(sf, w-x)
  term.setCursor(x,y)
  print(sfp)
end

function tablet_use(_, data)
  if (prevX ~= nil) then
    X = data["posX"]
    Y = data["posY"]
    Z = data["posZ"]
    printfAt(2, 3, "Point B:      X=%d Z=%d Y=%d", X, Z, Y)

    diffX = X - prevX
    diffY = Y - prevY
    diffZ = Z - prevZ
    printfAt(2, 4, "Difference:   X=%d Z=%d Y=%d", diffX, diffZ, diffY)
    printfAt(2, 5, "Distance X-Z: %.2f", math.sqrt(diffX^2 + diffZ^2))
  
    dir = ""
    if (diffZ < 0) then
      dir = "North"
    elseif (diffZ > 0) then
      dir = "South"
    end

    if (diffZ ~= 0) then
      dir = dir .. "-"
    end

    if (diffX < 0) then
        dir = dir .. "West"
    elseif (diffX > 0) then
        dir = dir .. "East"
    end

    if (diffY ~= 0) then
      dir = dir .. " + "
      if (diffY < 0) then
        dir = dir .. "Down"
      else
        dir = dir .. "Up"
      end
    end

    printfAt(2, 6, "Direction:    %s", dir)

    printfAt(2, 7, "Distance 3D:  %.2f", math.sqrt(diffX^2 + diffY^2 + diffZ^2))
    printfAt(2, 8, "Volume:       %d", (math.abs(diffX) + 1) * (math.abs(diffY) + 1) * (math.abs(diffZ) + 1))

    if (locked == false) then
      prevX = nil
    end
    
  elseif (locked == false) then
    prevX = data["posX"]
    prevY = data["posY"]
    prevZ = data["posZ"]
    printStatic()
    printfAt(2, 2, "Point A:      X=%d Z=%d Y=%d", prevX, prevZ, prevY)
  end
end

function cleanExit()
  event.ignore("tablet_use", tablet_use)
  term.clear()
  os.exit()
end

function registerEvents()
  event.listen("tablet_use", tablet_use)
  event.listen("interrupted", cleanExit)
end

registerEvents()

while true do
  _, _, x, _, _ = event.pull("key_down")

  if (x ~= nil) then
    c = string.char(x)

    if (c == "Q") then
      cleanExit()

    elseif (c == "R") then
      term.clear()
      printStatic()
      prevX = nil
      locked = false

    elseif (c == "L" and prevX ~= nil) then
      printfAt(2, 2, "Point A:      X=%d Z=%d Y=%d (locked)", prevX, prevZ, prevY) 
      locked = true
    end
  end
end