Bug reproduce:

1. create a code 1 and scope 1 individually on the canvas.
2. drag code 1 into the scope 1. By now, everything works well.
3. create a larger scope 2, drag scope 1 into scope 2

Now, the level of code 1 and scope 1 are the same. To compare that clearly, create a code 2 and drag it into scope 1, see their background colors in the minimap, which are supposed to be the same as their parents are scope 1.

Solution

Therefore, I propose to update node.level in a pre-order DFS way to ensure all involved descendant nodes are in correct levels, or the rendering order and background colors are incorrect.