if drawing.y == nil then
    -- something invalidated all the y's; just wait for a draw
    return
  end

    if love.timer then dt = love.timer.step() end

    if App.update then App.update(dt) end -- will pass 0 if love.timer is disabled

    -- perform draw before update to give it a chance to mutate state

    if love.timer then dt = love.timer.step() end
    if App.update then App.update(dt) end -- will pass 0 if love.timer is disabled