Tilemap's set_cell function for scene instances bigger than one tile size

[mguldner]

I'm creating a 2D isometric tile-based city builder.

When creating a building, I want to make a "shadow building" follow the mouse on tilemap's coordinates and, on click, have the building created.
The buildings are scene instances imported in the Tileset of the Tilemap. Their sizes are bigger than 1*1 --> 2 * 2, 4 * 3, etc !
When the buidling can't be created (another building already there), the "shadow building" turns to red.

I manage making this work, but I have to call Tilemap's add_child myself, set global_position according to mouse position on the map, turn to red when there is an Area2D overlapping.
But because of the fact it's a scene instance, the _ready function is already called in the step of the "shadow building".
That's why I have to create another function to call when the building is effectively created --> let's call it the create function.

I discovered the method set_cell of Tilemap (which would be cleaner).
Use it would enable to follow the "right path" and surely simplify the code.

But if I want to use it, I must get the created instance when set_cell is called in order to call the create function.
This limitation is here because I have to manage the red color on bad positionning (did by script).

Another way would be to only display a Sprite2D as "shadow building".
Via the Tilemap, I could check if the "shadow building" is overlapping another building and create it if not.
The code in the create function would then be moved in the _ready function.

That's why I was thinking about these features:

• Add the possibility to set the size of an instance scene in the Tileset in terms of cell size.

https://user-images.githubusercontent.com/11960112/234028201-35aacec0-ed59-4c0f-80a0-af48e9c26d16.png

• Add new parameters to method set_cell: length and width.
  This enable to set the different cells in the area described and link to the scene instance.

The method get_cell would then return the same value for the multiple cells under the same scene instance.

[mguldner]

Re-reading my message, perhaps my description was too big, sorry for that.
In a nutshell :

The aim is to set different cells of a Tilemap with the same instance of an instanced scene (when this scene is bigger than 1*1).
The method set_cell only enables to set one cell, not a bunch of them.