Fixed time step love.run

steady.lua

--MIT License
--Copyright (c) 2019 Arvid Gerstmann, Jake Besworth, Max Cahill, Pablo Mayobre, LÖVE Developers

--Original author: https://github.com/Leandros
--Max frame skip: https://github.com/jakebesworth
--Manual garbage collection: https://github.com/Geti
--Put it all together: https://github.com/Positive07
--Original love.run: LÖVE Developers

local conf = {
  --------- Update and Fixed update --------
  update_time = math.huge, --Max time spent updating the game

  ------ Fixed timestep configuration ------
  tick_rate = 1/60, --Fixed tick rate
  max_tick_skip = 25, --Max number of ticks before they are skipped

  ------------ GC configuration ------------
  gc_time = 1/600, --Max time dedicated to Garbage Collection per frame
  gc_steps = 1000, --Max number of Garbage Collection steps
  gc_safe_margin = 64, --When Garbage exceeds this number of MB, triggers a hard collection
}

if not love.event then
  require "love.event"
  love.createhandlers() --luacheck:ignore
end

if not love.timer then
  require "love.timer"
end

function love.run()
  if love.load then
    love.load(love.arg.parseGameArguments(arg), arg) --luacheck:ignore
  end

  -- We don't want the first frame's dt to include time taken by love.load.
  love.timer.step()

  local lag = 0.0
  local time = love.timer.getTime

  -- Main loop
  return function()
    love.event.pump() --Event handling
    for name, a,b,c,d,e,f in love.event.poll() do
      if name == "quit" then
        if not love.quit or not love.quit() then
          return a or 0
        end
      end
      love.handlers[name](a,b,c,d,e,f) --luacheck:ignore
    end

    do --Update and Fixed Update
      local startUpdate = time()
      local delta = love.timer.step()

      --Update
      if love.update then love.update(delta) end

      if love.fixedupdate then
        --Lag can't exceed the frame skip margin
        lag = math.min(lag + delta, conf.tick_rate * conf.max_tick_skip)

        --Number of fixed time frames based on the lag and tick rate
        local frames = math.floor(lag/conf.tick_rate)
        --Remaining lag is taken into account in the next frame
        lag = lag % conf.tick_rate

        for _=1, frames do
          --Don't exceed the allocated ammount of time for the update
          if startUpdate - time() > conf.update_time then break end

          --Fixed update
          love.fixedupdate(conf.tick_rate)
        end
      end
    end

    if love.graphics and love.graphics.isActive() then --Rendering
      love.graphics.origin()
      love.graphics.clear(love.graphics.getBackgroundColor())

      local w, h = love.graphics.getDimensions()
      if love.draw then love.draw(w, h, lag) end

      love.graphics.present()
    end

    do --Garbage collection
      local start = time()

      --Respect the max number of collection steps
      for _=1, conf.gc_steps do
        --Don't exceed the allocated time
        if time() - start > conf.gc_time then break end

        --Small step each time, prevents some big spikes during collection
        --Still may cause some spikes with big sets
        collectgarbage("step", 1)
      end

      --Safety net, hard collect when the safety margin is reached
      if collectgarbage("count")/1024 > conf.gc_safe_margin then
        collectgarbage("collect")
      end

      --Don't garbage collect outside of this
      collectgarbage("stop")
    end

    love.timer.sleep(0.001)
  end
end

return conf

Articles:

• Gaffer on Games - "Fix your timestep"
• Koonsolo - "deWiTTERS game loop"
• Game Programming Patterns - "Game Loop"

Base code

• Original Gist by @Leandros
• Modified Gist by @jakebesworth
• Manual garbage collection by @1bardesign
• love.run by LÖVE Developers

Posts

• Reddit post
• Forum post