Lua coroutines in obslua https://obsproject.com/forum/threads/tips-and-tricks-for-lua-scripts.132256/#post-491713

concurrent.lua

local obs = obslua
local coroutine = require 'coroutine'
local math = require 'math'

local Timer = {}
function Timer:init(o)
  o = o or {}
  setmetatable(o,self)
  self.__index = self
  return o
end

function Timer:update(dt)
  self.current_time = self.current_time + dt
  if self.current_time >= self.delay then
    self.finished = true
  end
end

function Timer:enter()
  self.finished = false
  self.current_time = 0
end

function Timer:exit()
  --print('on exit')
end

function Timer:launch()
  self:enter()
  while not self.finished do
    local dt = coroutine.yield()
    self:update(dt)
  end
  self:exit()
end

function time_sleep(s)
  local action = Timer:init{delay=s}
  action:launch()
end

---[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]

function current_scene()
  print('start current scene')
  time_sleep(1)
  print('end waiting one second / starting to wait again')
  time_sleep(4)
  print('end waiting [current] for four seconds')
end

function infinity_scene()
  while true do
    n = math.random(1,3)
    print('random sleep [' .. n .. '] seconds')
    time_sleep(n)
  end
end


local scene_item 
local source_name = 'c2c2'

function find_scene_item()
  local source = obs.obs_frontend_get_current_scene()
  if not source then
    print('there is no current scene')
    return
  end
  scene_width = obs.obs_source_get_width(source)
  scene_height = obs.obs_source_get_height(source)
  local scene = obs.obs_scene_from_source(source)
  obs.obs_source_release(source)
  scene_item = obs.obs_scene_find_source(scene, source_name)
  if scene_item then
    original_pos = get_scene_item_pos(scene_item)
    return true
  end
  print(source_name..' not found')
  return false
end

function get_scene_item_pos(scene_item)
  local pos = obs.vec2()
  obs.obs_sceneitem_get_pos(scene_item, pos)
  return pos
end

local x,y = 0,0

function move_scene_item(scene_item,absolute_progress)
  absolute_progress = absolute_progress or false
  if not scene_item then return end
  local next_pos = obs.vec2()
  if not absolute_progress then
    x = x + 30
    y = y + 30
  else
    x = absolute_progress
    y = absolute_progress
  end
  next_pos.x,next_pos.y = x,y
  obs.obs_sceneitem_set_pos(scene_item, next_pos)
end

function second_scene()
  local tries = 15 
  --print('start second scene')
  repeat
    time_sleep(0.3)
    move_scene_item(scene_item) 
    tries = tries - 1
  until tries == 0
  --print('end second')
end

local pow = math.pow
-- https://github.com/EmmanuelOga/easing/blob/master/lib/easing.lua
function inOutExpo(t, b, c, d)
  if t == 0 then return b end
  if t == d then return b + c end
  t = t / d * 2
  if t < 1 then
    return c / 2 * pow(2, 10 * (t - 1)) + b - c * 0.0005
  else
    t = t - 1
    return c / 2 * 1.0005 * (-pow(2, -10 * t) + 2) + b
  end
end

function inOutQuart(t, b, c, d)
  t = t / d * 2
  if t < 1 then
    return c / 2 * pow(t, 4) + b
  else
    t = t - 2
    return -c / 2 * (pow(t, 4) - 2) + b
  end
end

function easing_scene_item_movement(begin,end_val,duration)
  local begin = begin or 500
  local end_val = end_val or 0
  local duration = duration or 0.6
  local current = 0
  local interval = 0.02
  local change = end_val - begin
  repeat
    --local absolute_progress = inOutExpo(current,begin,change,duration)
    local absolute_progress = inOutQuart(current,begin,change,duration)
    move_scene_item(scene_item,absolute_progress)
    time_sleep(interval)
    current = current + interval
  until current >= duration
end

function easing_scene_loop()
  while true do
    easing_scene_item_movement(900,0,0.16)
    easing_scene_item_movement(0,300)
    time_sleep(0.1)
    easing_scene_item_movement(300,600,0.8)
    time_sleep(0.3)
    easing_scene_item_movement(600,900,0.23)
  end
end

local c1 = coroutine.create(current_scene)
--local c2 = coroutine.create(second_scene) -- move some source on scene with name c2c2
local c2 = coroutine.create(easing_scene_loop)
local c3 = coroutine.create(infinity_scene)
local c4 = coroutine.create(function() coroutine.yield() end)


function delayed_print_logic()
  print('hello')
  time_sleep(3)
  print('world')
end

function delayed_print()
  if coroutine.status(c4) == 'dead' then
    c4 = coroutine.create(delayed_print_logic)
  end
end

function cancel_delayed_print()
  print('abort printing')
  c4 = nil
  c4 = coroutine.create(function() coroutine.yield() end)
end

---[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]
function script_tick(dt)
  -- set c2c2 as source name within current scene
  if not scene_item then find_scene_item() end 
  coroutine.resume(c1,dt)
  coroutine.resume(c2,dt)
  coroutine.resume(c3,dt)
  coroutine.resume(c4,dt)
end
---[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]-[]

function htk_1_cb(pressed)
  if pressed then
    delayed_print()
  end
end

function htk_2_cb(pressed)
  if pressed then
    cancel_delayed_print()
  end
end

key_1 = '{"htk_1": [ { "key": "OBS_KEY_1" } ],'
key_2 = '"htk_2": [ { "key": "OBS_KEY_2" } ]}'
json_s = key_1 .. key_2
default_hotkeys = {
  {id='htk_1',des='print with delay',callback=htk_1_cb},
  {id='htk_2',des='cancel delayed print',callback=htk_2_cb},
}

function script_load(settings)

  s = obs.obs_data_create_from_json(json_s)
  for _,v in pairs(default_hotkeys) do
    local a = obs.obs_data_get_array(s,v.id)
    h = obs.obs_hotkey_register_frontend(v.id,v.des,v.callback)
    obs.obs_hotkey_load(h,a)
    obs.obs_data_array_release(a)
  end
  obs.obs_data_release(s)
end