Fix drag preview shape

Previously all blocks had a statement shape as drag preview. Now that we
have a good mapping of blocks / shapes, use the corresponding shape.

A especial case is the control block which uses the background twice,
one for the top part and one for the bottom part. For simplicity, use
the statement shape in this case.

Also, move drag colors to constants.

addons/block_code/drag_manager/drag.gd

@@ -179,7 +179,7 @@ func _get_distance_to_snap_point(snap_point: SnapPoint) -> float:
 func _update_action_hint():
 	match action:
 		DragAction.REMOVE:
-			_block.modulate = Color(1.0, 1.0, 1.0, 0.5)
+			_block.modulate = Constants.DRAG_REMOVE_COLOR
 		_:
 			_block.modulate = Color.WHITE
 
@@ -193,7 +193,15 @@ func _update_preview():
 		# Make preview block
 		_preview_block = Background.new()
 
-		_preview_block.color = Color(1, 1, 1, 0.5)
+		_preview_block.color = Constants.DRAG_PREVIEW_COLOR
+		if _block.definition.type == Types.BlockType.CONTROL:
+			# Especial case for control block, use statement shape as preview:
+			_preview_block.block_type = Types.BlockType.STATEMENT
+		else:
+			_preview_block.block_type = _block.definition.type
+			if _block.definition.type == Types.BlockType.VALUE and _block.definition.variant_type == TYPE_BOOL:
+				_preview_block.is_pointy_value = true
+
 		_preview_block.custom_minimum_size = _block.get_global_rect().size / scale
 		_preview_block.size_flags_horizontal = Control.SIZE_SHRINK_BEGIN
 		_preview_block.size_flags_vertical = Control.SIZE_SHRINK_BEGIN

addons/block_code/ui/constants.gd

@@ -13,6 +13,8 @@ const MINIMUM_DRAG_THRESHOLD = 25
 const ROUND_RESOLUTION = 10
 
 const FOCUS_BORDER_COLOR = Color(225, 242, 0)
+const DRAG_REMOVE_COLOR = Color(1, 1, 1, 0.5)
+const DRAG_PREVIEW_COLOR = Color(225, 242, 0, 0.3)
 
 ## Properties for builtin categories. Order starts at 10 for the first
 ## category and then are separated by 10 to allow custom categories to