TileMapTileDescriptor and building of tileset from them

nodes/TileMapObject.gd

@@ -1,17 +1,51 @@
 tool
 extends TileMap
 
+# todo: Give care about descriptor swaps being loseless / non introducing artifacts.
+
 ## Dictates whether tileset collision information should be exposed to game context.
 export var expose_collisions: bool = true
 
+var _descriptor_name_to_id: Dictionary # String to int
+
+func change_tile_texture(p_tile: String, p_texture: Texture) -> void:
+    if not p_tile in _descriptor_name_to_id:
+        push_error("Invalid tile name")
+        return
+    
+    var id := _descriptor_name_to_id[p_tile] as int
+    tile_set.tile_set_texture(id, p_texture)
+
 func _enter_tree() -> void:
+    tile_set = TileSet.new()
+
     # It's okay to fail here for non-grid contexts.
     if get_parent().connect("cell_size_changed", self, "_update_cell_size"):
         _update_cell_size(get_parent().cell_size, get_parent().cell_size)
 
+    if connect("child_entered_tree", self, "_on_child_entered_tree") != OK:
+        assert(false)
+
+    if connect("child_exiting_tree", self, "_on_child_exiting_tree") != OK:
+        assert(false)
+
 func _update_cell_size(_p_old_cell_size: Vector2, p_new_cell_size: Vector2) -> void:
     # We're assuming that all tile textures are of same dimensions.
     # todo: Diagnose mismatch by walking over all textures?
     var tileset_texture_size := tile_set.tile_get_texture(0).get_size()
     scale = p_new_cell_size / tileset_texture_size
     cell_size = p_new_cell_size / scale
+
+func _on_child_entered_tree(p_node: Node) -> void:
+    var id := tile_set.get_last_unused_tile_id()
+    _descriptor_name_to_id[p_node.name] = id
+    tile_set.create_tile(id)
+    tile_set.tile_set_texture(id, p_node.texture)
+
+func _on_child_exiting_tree(p_node: Node) -> void:
+    var id := _descriptor_name_to_id[p_node.name] as int
+    for cell in get_used_cells_by_id(id):
+        set_cell(cell.x, cell.y, -1)
+    tile_set.remove_tile(id)
+    if not _descriptor_name_to_id.erase(p_node.name):
+        assert(false)

nodes/TileMapTileDescriptor.gd

@@ -0,0 +1,13 @@
+tool
+extends Node
+class_name TK_TileMapTileDescriptor
+
+export var texture: Texture setget _set_texture
+
+# todo: More layer customizeability.
+export var is_solid: bool
+
+func _set_texture(p_texture: Texture) -> void:
+    texture = p_texture
+    if is_inside_tree():
+        get_parent().change_tile_texture(name, p_texture)