a.e.s.-decoblocks/utils.lua

function decoblocks.place_and_rotate(itemstack, placer, pointed_thing)
  local p0 = pointed_thing.under
  local p1 = pointed_thing.above
  local param2 = 0

  if placer then
    local placer_pos = placer:get_pos()
    if placer_pos then
      param2 = minetest.dir_to_facedir(vector.subtract(p1, placer_pos))
    end

    local finepos = minetest.pointed_thing_to_face_pos(placer, pointed_thing)
    local fpos = finepos.y % 1

    if p0.y - 1 == p1.y or (fpos > 0 and fpos < 0.5)
        or (fpos < -0.5 and fpos > -0.999999999) then
      param2 = param2 + 20
      if param2 == 21 then
        param2 = 23
      elseif param2 == 23 then
        param2 = 21
      end
    end
  end

  return minetest.item_place(itemstack, placer, pointed_thing, param2)
end