AutoTile: Allow transpose/flip bitmask with transposed/flipped tiles

[Aldlevine]

Describe the project you are working on:
A platformer using 3x3 autotiles to draw spikes on floor/ceiling/walls.

Describe the problem or limitation you are having in your project:
When rotating autotiles in a tilemap, the connections are determined based on the bitmask without rotation. Because of this, when drawing spikes on walls I either have to disable autotile and draw by hand, or create an additional set of rotated tiles (this could also be a problem for flipped tiles, but not in my specific case).

Describe the feature / enhancement and how it helps to overcome the problem or limitation:
Add a new option to autotiles such that the bitmask is flipped/transposed when the tiles are also flipped/transposed. This would save effort in building tilesets by removing the need to include rotated instances of certain tiles in the tileset or in manually placing flipped/transposed tiles in the tilemap.

Describe how your proposal will work, with code, pseudocode, mockups, and/or diagrams:

Bitmask setup

Behavior

If this enhancement will not be used often, can it be worked around with a few lines of script?:
It could possibly be handled with _forward_subtile_selection, but I have no experience with this function, so I'm not sure. One issue with this is that it would introduce a dependency on the TileMap from the TileSet (the TileSet would need to know if the specific cell is flipped/transposed which is defined in the TileMap, it would also need to know about adjacent cells).

Is there a reason why this should be core and not an add-on in the asset library?:
As far as I can tell, this would be difficult to build as an add-on in a generalized fashion. It seems like it would be useful in many cases, and would be intuitive.

[golddotasksquestions]

I think when using wang or autotiles, the general expectation is that you have to create the complete tileset (48 Tiles for 3x3 minimal). See here.

I don't know how autotiles would work logically, when you rotate the bitmask. That might be contrary to the whole idea of what an autotile is.

If you have a complete tileset, you certainly won't need to rotate. But I agree it kinda sucks that you have to do all this work upfront.

[SquiggelSquirrel]

Possibly this: godotengine/godot#39046

[SquiggelSquirrel]

On closer inspection, I can see that this is different from my proposed feature. I'm talking about using this:

To create this:

Whereas you're more about using something like this:

To create any/all of these:

Using these controls:

Correct?