working keyboard and plugin for better tilemaps

addons/TileMapDual/AtlasWatcher.gd

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+##[br] Watches a TileSetAtlasSource for changes.
+##[br] Causes its 'parent' TileSetWatcher to emit terrains_changed when the atlas changes.
+##[br] Also emits parent.atlas_autotiled when it thinks the user auto-generated atlas tiles.
+class_name AtlasWatcher
+
+## Prevents the number of seen atlases from extending to infinity.
+const UNDO_LIMIT = 1024
+## Stores all of the atlas instance id's that have been seen before, to prevent autogen on redo.
+static var _registered_atlases := []
+
+## The TileSetWatcher that created this AtlasWatcher. Used to send signals back.
+var parent: TileSetWatcher
+
+## The Source ID of `self.atlas`.
+var sid: int
+
+## The atlas to be watched for changes.
+var atlas: TileSetAtlasSource
+
+func _init(parent: TileSetWatcher, sid: int, atlas: TileSetAtlasSource) -> void:
+	self.parent = parent
+	self.sid = sid
+	self.atlas = atlas
+	atlas.changed.connect(_atlas_changed, ConnectFlags.CONNECT_DEFERRED)
+	var id := atlas.get_instance_id()
+	# should not autogen if atlas was created through redo, i.e. its instance id already existed
+	if _atlas_is_empty() and id not in _registered_atlases:
+		_registered_atlases.push_back(id)
+		if _registered_atlases.size() > UNDO_LIMIT:
+			_registered_atlases.pop_front()
+		atlas.changed.connect(_detect_autogen, ConnectFlags.CONNECT_DEFERRED | ConnectFlags.CONNECT_ONE_SHOT)
+
+
+func _atlas_is_empty() -> bool:
+	return atlas.get_tiles_count() == 0
+
+
+## Returns true if the texture has any opaque pixels in the specified tile coordinates.
+func _is_opaque_tile(image: Image, tile: Vector2i, p_threshold: float = 0.1) -> bool:
+	# We cannot use atlas.get_tile_texture_region(tile) as it fails on unregistered tiles.
+	var region := Rect2i(tile * atlas.texture_region_size, atlas.texture_region_size)
+	var sprite := image.get_region(region)
+	if sprite.is_invisible():
+		return false
+	# We're still not sure if the tile is empty or not.
+	# Godot's auto-gen considers 0.1 opacity as "transparent" but not "invisible".
+	for y in range(region.position.y, region.end.y):
+		for x in range(region.position.x, region.end.x):
+			if image.get_pixel(x, y).a > p_threshold:
+				return true
+	return false
+
+
+##[br] HACK: literally just tries to guess which tiles the terrain autogen system would make
+##[br] Called once, and only once, at the end of the first frame that a texture is created.
+func _detect_autogen() -> void:
+	var size := Vector2i(atlas.texture.get_size()) / atlas.texture_region_size
+	var image := atlas.texture.get_image()
+	var expected_tiles := []
+	for y in size.y:
+		for x in size.x:
+			var tile := Vector2i(x, y)
+			if atlas.has_tile(tile) != _is_opaque_tile(image, tile):
+				return
+	parent.atlas_autotiled.emit(sid, atlas)
+
+
+## Called every time the atlas changes. Simply flags that terrains have changed.
+func _atlas_changed() -> void:
+	parent._flag_terrains_changed = true