An ECS draw system I wrote.

drawSystem.lua

local tiny = require 'lib.tiny'
local spriteAtlas = require 'core.spriteAtlas'
local lume = require 'lib.lume'
local physicsSystem = require 'systems.physics'
local config = require 'gameConfig'

function drawSystem(groupName)
  groupName = groupName or 'default'
  local drawSystem = tiny.processingSystem({ isDraw = true })

  function drawSystem:filter(entity)
    if not entity.draw then return false end
    if entity.draw.group == groupName then
      return true
    elseif groupName == 'default' then
      return true
    end
    return false
  end

  function drawSystem:onAdd(e)
    e.draw = lume.extend({
      group = 'default',
      anchorX = 0.5,
      anchorY = 1,
      vflip = false,
      hflip = false,
      tint = { r = 255, g = 255, b = 255, a = 255 },
      sx = 1,
      sy = 1
    }, e.draw)
  end

  function drawSystem:process(entity, dt)
    if entity.draw.onDraw then
      entity.draw.onDraw(entity)
    end
    if config.debug and entity.body then
      physicsSystem:debugDraw(entity)
    end
  end

  return drawSystem
end

return drawSystem