Serialization: Reuse serialized resources

Add a resource property to blocks. The resource will be updated before
building the tree.

This mitigates having a huge diff in scenes with blocks for minimum
changes like moving a block in the canvas.

Author: manuq

addons/block_code/ui/block_canvas/block_canvas.gd

@@ -168,24 +168,23 @@ func load_tree(parent: Node, node: SerializedBlockTreeNode):
 		load_tree(scene.get_node(c[0]), c[1])
 
 
-func get_canvas_block_trees() -> SerializedBlockTreeNodeArray:
-	var block_trees := SerializedBlockTreeNodeArray.new()
+func rebuild_block_trees():
+	_current_bsd.block_trees.array = []
 	for c in _window.get_children():
-		block_trees.array.append(build_tree(c))
-
-	return block_trees
+		_current_bsd.block_trees.array.append(build_tree(c))
 
 
 func build_tree(block: Block) -> SerializedBlockTreeNode:
-	var n = SerializedBlockTreeNode.new()
-	n.serialized_block = SerializedBlock.new(block.get_block_class(), block.get_serialized_props())
+	block.update_resources()
+	block.resource.path_child_pairs = []
 
 	for snap in find_snaps(block):
-		for c in snap.get_children():
-			if c is Block:  # Make sure to not include preview
-				n.path_child_pairs.append([block.get_path_to(snap), build_tree(c)])
+		for child in snap.get_children():
+			if not child is Block:  # Make sure to not include preview
+				continue
+			block.resource.path_child_pairs.append([block.get_path_to(snap), build_tree(child)])
 
-	return n
+	return block.resource
 
 
 func find_snaps(node: Node) -> Array:

addons/block_code/ui/blocks/block/block.gd

@@ -26,6 +26,9 @@ signal modified
 ## The scope of the block (statement of matching entry block)
 @export var scope: String = ""
 
+## The resource containing the block properties and the snapped blocks
+@export var resource: SerializedBlockTreeNode
+
 var bottom_snap: SnapPoint
 
 
@@ -64,6 +67,16 @@ func get_instruction_node() -> InstructionTree.TreeNode:
 	return node
 
 
+func update_resources() -> bool:
+	if resource == null:
+		resource = SerializedBlockTreeNode.new()
+		resource.serialized_block = SerializedBlock.new(get_block_class(), get_serialized_props())
+	var old_serialized_props = resource.serialized_block.serialized_props  #.duplicate(true)
+	resource.serialized_block.serialized_props = get_serialized_props()
+	var changed = old_serialized_props != resource.serialized_block.serialized_props
+	return changed
+
+
 # Override this method to add more serialized properties
 func get_serialized_props() -> Array:
 	return serialize_props(["block_name", "label", "color", "block_type", "position", "scope"])

addons/block_code/ui/main_panel.gd

@@ -142,14 +142,13 @@ func save_script():
 	undo_redo.add_undo_property(_current_block_code_node.block_script, "block_trees", _current_block_code_node.block_script.block_trees)
 	undo_redo.add_undo_property(_current_block_code_node.block_script, "generated_script", _current_block_code_node.block_script.generated_script)
 
-	var block_trees := _block_canvas.get_canvas_block_trees()
+	_block_canvas.rebuild_block_trees()
 	var generated_script = _block_canvas.generate_script_from_current_window(block_script)
-	block_script.block_trees = block_trees
 	block_script.generated_script = generated_script
 	block_script.version = Constants.CURRENT_DATA_VERSION
 
-	undo_redo.add_do_property(_current_block_code_node.block_script, "block_trees", block_trees)
-	undo_redo.add_do_property(_current_block_code_node.block_script, "generated_script", generated_script)
+	undo_redo.add_do_property(_current_block_code_node.block_script, "block_trees", _current_block_code_node.block_script.block_trees)
+	undo_redo.add_do_property(_current_block_code_node.block_script, "generated_script", _current_block_code_node.block_script.generated_script)
 	undo_redo.commit_action()