Add add_item method to Tree Node

[BrodyEller]

Describe the project you are working on:
GUI based app where markers can be added and organized into a tree structure, displayed in a Tree node. Each marker contains some information that gets serialized to a json file on save. Originally I used an ItemList and array to store the markers but now I want the user to be able to organize them into groups using a Tree node.

Describe the problem or limitation you are having in your project:
Tree has the method create_item which creates and returns a TreeItem object. While this works well, I have extra information I want to store in each TreeItem. To do this, I'd like to subclass TreeItem using extends TreeItem, add my properties, and use the custom class almost exactly how I would a normal TreeItem. I cannot add a custom type to my Tree node however since create_item creates a TreeItem node for me, instead of allowing me to use a custom type.

Describe the feature / enhancement and how it helps to overcome the problem or limitation:
Add another method to the Tree class called add_item which works very similar to create_item but has a parameter to pass in an instance of a custom type that extends TreeItem.

Describe how your proposal will work, with code, pseudocode, mockups, and/or diagrams:
Something like this, may or may not work, I just altered the current create_item method real quick:

void Tree::add_item(TreeItem *p_item, TreeItem *p_parent, int p_idx) {

	ERR_FAIL_COND_V(blocked > 0, NULL);

	if (p_parent) {

		// Append or insert a new item to the given parent.
		ERR_FAIL_COND_V(!p_item, NULL);
		p_item->cells.resize(columns.size());

		TreeItem *prev = NULL;
		TreeItem *c = p_parent->children;
		int idx = 0;

		while (c) {
			if (idx++ == p_idx) {
				p_item->next = c;
				break;
			}
			prev = c;
			c = c->next;
		}

		if (prev)
			prev->next = p_item;
		else
			p_parent->children = p_item;
		p_item->parent = p_parent;

	} else {

		if (!root) {
			// No root exists, make the given item the new root.
			ERR_FAIL_COND_V(!p_item, NULL);
			p_item->cells.resize(columns.size());

			root = p_item;
		} else {
			// Root exists, append or insert to root.
			add_item(p_item, root, p_idx);
		}
	}
}

If this enhancement will not be used often, can it be worked around with a few lines of script?:
Those who don't need this functionality can continue to use Tree just as they have before. It doesn't break any current projects.

Is there a reason why this should be core and not an add-on in the asset library?:
I'm not sure there is any workaround in pure GDScript and it is very simple to implement in the engine.

I'm willing to work on this and submit a PR, just wanted to make sure there was no GDScript solution and that this was a good way to go about this.

[BrodyEller]

After trying to implement this, it seems that TreeItem can't be instantiated in GDScript since it is a virtual class. Either way, my issue can be solved using object metadata instead so closing.

[rilpires]

I understand that for your problem it had a workaround, but can we reopen this issue?
An add_item function would be useful and a complement for TreeItem::remove_child. What's the point of removing a TreeItem then?

I would like to move TreeItems and its children around between differente Trees. Without an TreeItem::add_item this is impossible, or am I missing something?

Anyway, TreeItem::remove_child documentation says:

Removes the given child TreeItem and all its children from the Tree. Note that it doesn't free the item from memory, so it can be reused later. To completely remove a TreeItem use Object.free().

so it can be reused later

How can I properly reuse it later then?

[YuriSizov]

As for the new APIs, there is an approved PR that may interest you already: godotengine/godot#46773

[CsloudX]

As for the new APIs, there is an approved PR that may interest you already: godotengine/godot#46773

I think it should be add_child and move_child like node's method.
LOOK:

|-TreeRoot
  |-NodeA
    |-Child
      |-AA
      |-BB
        |-ZZ
      |-CC
  |-NodeB

How can I move Child to as a NodeB's child by move_before and move_after, like this:

|-TreeRoot
  |-NodeA
  |-NodeB
    |-Child
      |-AA
      |-BB
        |-ZZ
      |-CC

[radlotus]

rilpires

The issue is still present. You can't reuse TreeItems after removing them from the Tree. You can't add them back to the Tree.

[Calinou]

The issue is still present. You can't reuse TreeItems after removing them from the Tree. You can't add them back to the Tree.

Please open a new proposal based on the API used in 4.0.beta1, as this proposal refers to the old 3.x API (which won't get significant new features on its own, only backwards-compatible backports).