Re-order blocks when a block is placed in an occupied snap point

addons/block_code/drag_manager/drag_manager.gd

@@ -9,6 +9,7 @@ signal block_modified
 @export var block_canvas_path: NodePath
 
 const Constants = preload("res://addons/block_code/ui/constants.gd")
+const BLOCK_AUTO_PLACE_MARGIN: Vector2 = Vector2(16, 8)
 
 var drag_offset: Vector2
 var dragging: Block = null
@@ -33,10 +34,6 @@ func _process(_delta):
 
 		var dragging_global_pos: Vector2 = dragging.get_global_rect().position
 
-		# TODO: check if dropped snap point is occupied
-		# if so, replace with this node and attach the previous one
-		# to this node's bottom snap
-
 		# Find closest snap point not child of current node
 		var closest_snap_point: SnapPoint = null
 		var closest_dist: float = INF
@@ -92,6 +89,7 @@ func _update_preview(snap_point: SnapPoint):
 		preview_block.color = Color(1, 1, 1, 0.5)
 		preview_block.custom_minimum_size = dragging.get_global_rect().size
 		preview_block.size_flags_horizontal = Control.SIZE_SHRINK_BEGIN
+		preview_block.size_flags_vertical = Control.SIZE_SHRINK_BEGIN
 
 		previewing_snap_point.add_child(preview_block)
 
@@ -105,7 +103,9 @@ func drag_block(block: Block, copied_from: Block = null):
 		new_pos += block.get_global_rect().position
 
 	var parent = block.get_parent()
-	if parent:
+	if parent is SnapPoint:
+		parent.remove_snapped_block(block)
+	elif parent:
 		parent.remove_child(block)
 
 	block.position = new_pos
@@ -142,7 +142,13 @@ func drag_ended():
 				# Can snap block
 				preview_block.free()
 				preview_block = null
-				previewing_snap_point.add_child(dragging)
+				var orphaned_block = previewing_snap_point.set_snapped_block(dragging)
+				if orphaned_block:
+					# Place the orphan block somewhere outside the snap point
+					orphaned_block.position = (
+						(previewing_snap_point.block.global_position - block_canvas_rect.position) + (previewing_snap_point.block.get_size() * Vector2.RIGHT) + BLOCK_AUTO_PLACE_MARGIN
+					)
+					_block_canvas.add_block(orphaned_block)
 			else:
 				# Block goes on screen somewhere
 				dragging.position = (get_global_mouse_position() - block_canvas_rect.position - drag_offset)

addons/block_code/ui/blocks/utilities/parameter_input/parameter_input.gd

@@ -100,18 +100,7 @@ func _ready():
 	snap_point.block_type = block_type
 	snap_point.variant_type = variant_type
 
-	match variant_type:
-		TYPE_COLOR:
-			switch_input(_color_input)
-		TYPE_VECTOR2:
-			switch_input(_vector2_input)
-		TYPE_BOOL:
-			switch_input(_bool_input)
-		_:
-			switch_input(_text_input)
-
-	if option:
-		switch_input(_option_input)
+	_update_visible_input()
 
 
 func get_snapped_block() -> Block:
@@ -148,11 +137,29 @@ func _on_line_edit_text_changed(new_text):
 	modified.emit()
 
 
-func switch_input(node: Node):
+func _update_visible_input():
+	if snap_point.has_snapped_block():
+		_switch_input(null)
+	elif option:
+		_switch_input(_option_input)
+	else:
+		match variant_type:
+			TYPE_COLOR:
+				_switch_input(_color_input)
+			TYPE_VECTOR2:
+				_switch_input(_vector2_input)
+			TYPE_BOOL:
+				_switch_input(_bool_input)
+			_:
+				_switch_input(_text_input)
+
+
+func _switch_input(node: Node):
 	for c in _input_switcher.get_children():
 		c.visible = false
 
-	node.visible = true
+	if node:
+		node.visible = true
 
 
 func _on_color_input_color_changed(color):
@@ -169,3 +176,7 @@ func _update_panel_bg_color(new_color):
 
 func _on_option_input_item_selected(index):
 	modified.emit()
+
+
+func _on_snap_point_snapped_block_changed(block):
+	_update_visible_input()

addons/block_code/ui/blocks/utilities/parameter_input/parameter_input.tscn

@@ -156,6 +156,7 @@ size_flags_horizontal = 3
 
 [node name="BoolInput" type="MarginContainer" parent="InputSwitcher"]
 unique_name_in_owner = true
+visible = false
 layout_mode = 2
 theme_override_constants/margin_left = 8
 
@@ -187,3 +188,4 @@ variant_type = 4
 [connection signal="text_changed" from="InputSwitcher/Vector2Input/HBoxContainer/XLineEdit" to="." method="_on_line_edit_text_changed"]
 [connection signal="text_changed" from="InputSwitcher/Vector2Input/HBoxContainer/YLineEdit" to="." method="_on_line_edit_text_changed"]
 [connection signal="item_selected" from="InputSwitcher/BoolInput/BoolInputOption" to="." method="_on_option_input_item_selected"]
+[connection signal="snapped_block_changed" from="SnapPoint" to="." method="_on_snap_point_snapped_block_changed"]

addons/block_code/ui/blocks/utilities/snap_point/snap_point.gd

@@ -9,6 +9,8 @@ extends MarginContainer
 ## When block_type is [enum Types.BlockType.VALUE], the type of the value that can be used at this snap point.
 @export var variant_type: Variant.Type
 
+signal snapped_block_changed(block: Block)
+
 var block: Block
 
 
@@ -18,7 +20,48 @@ func _ready():
 
 
 func get_snapped_block() -> Block:
-	if get_child_count() == 0:
-		return null
+	for node in get_children():
+		if node is Block:
+			return node
+	return null
+
+
+func has_snapped_block() -> bool:
+	return get_snapped_block() != null
+
+
+func set_snapped_block(snapped_block: Block) -> Block:
+	var orphaned_block: Block = _pop_snapped_block()
+
+	if snapped_block:
+		add_child(snapped_block)
+
+	if snapped_block and orphaned_block:
+		var last_snap = _get_last_snap(snapped_block)
+		if last_snap:
+			last_snap.set_snapped_block(orphaned_block)
+			orphaned_block = null
+
+	snapped_block_changed.emit(snapped_block)
+
+	return orphaned_block
+
+
+func remove_snapped_block(snapped_block: Block):
+	assert(snapped_block == get_snapped_block())
+	set_snapped_block(null)
+
+
+func _pop_snapped_block() -> Block:
+	var snapped_block = get_snapped_block()
+	if snapped_block:
+		remove_child(snapped_block)
+	return snapped_block
+
 
-	return get_child(0) as Block
+func _get_last_snap(block: Block) -> SnapPoint:
+	var last_snap: SnapPoint
+	while block:
+		last_snap = block.bottom_snap
+		block = last_snap.get_snapped_block() if last_snap else null
+	return last_snap