What is `set_grid_shape_hull` message?

Questions
1

Hi!

I noticed, that when I set tiles on a tilemap the script there receives messages like this:

message_id:

hash: [set_grid_shape_hull]

message:

{ --[[0x7420934a3520]]
  hull = 42,
  flip_horizontal = 0,
  flip_vertical = 0,
  shape = 1,
  rotate90 = 0,
  row = 7,
  column = 12
}

I can’t find any documentation on this, only this issue (Tilemap.set_tile error "SetGridShapHull" (SOLVED) - #14 by britzl)

I’m just wondering what it is and why it is send? Beside “hull” field, with which I don’t know what to do, everything is as I actually set, so it’s some kind of confirmation of a change?

There’s second message as well:

hash: [enable_grid_shape_layer],
{ --[[0x7eab78d41f50]]
  enable = 0,
  shape = 0
}