OC Stop Watch

local component = require "component"
local event = require "event"
local term = require "term"
local computer = require "computer"
local gpu = component.gpu

local key_space = require("keyboard").keys.space
local running = true
local x, y, width, height
local outputWidth = 9 -- 00:00.000 == 9 chars
local startTime, timerEvent

local events = setmetatable({}, {__index = function() return function() end end})
function events.key_up(keyboard, char, code, player)
  if (code == key_space) then
    running = false
  end
end

function events.screen_resized(screenAddress, newWidth, newHeight)
  width, height = newWidth, newHeight
  x = math.max(1, math.floor((width - outputWidth) / 2))
  y = math.max(1, math.floor(height / 2))

  term.clear()
  clockTimer(true)
end

function events.touch(adr, x, y, button, player)
  if (timerEvent) then
    event.cancel(timerEvent)
    timerEvent = nil
  else
    startTime = computer.uptime()
    timerEvent = event.timer(1/20, clockTimer, math.huge)
  end
end

function clockTimer(reset)
  if (reset) then
    gpu.set(x, y, "00:00.000")
  else
    local m, s, ms
    local t = math.floor((computer.uptime() - startTime) * 1000)
    ms = t % 1000
    t = math.floor(t / 1000)
    s = t % 60
    t = math.floor(t / 60)
    m = t % 60
    gpu.set(x, y, string.format("%02d:%02d.%03d", m, s, ms))
  end
end

function handleEvent(event, ...)
  if (event) then
    events[event](...)
  end
end

local prevWidth, prevHeight = gpu.getResolution()
if (not gpu.setResolution(outputWidth, 1)) then
  events.screen_resized(false, prevWidth, prevHeight)
end

while running do
  handleEvent(event.pull())
end

if (timerEvent) then event.cancel(timerEvent) end
gpu.setResolution(prevWidth, prevHeight)