Drag and drop differences between Godot 3 and 4?

Question

I'd been following Godot tutorials to add Drag & Drop functionality to Control nodes. They've presumably been created for Godot 3.x, but my project is 4.0. And I can't seem to get it to work, thinking something has changed.

To make sure it's due to the difference in Godot versions, I did the exact same steps to reproduce the situation in both Godot 4.0 and 3.5.1:

1. Create new project, all default settings

2. Add Node2D root scene

3. Add a PanelContainer child to that

4. Add a TextureRect child to that, and drag the Godot icon resource on it for testing

5. Attach a new script to PanelContainer with this code:

    extends PanelContainer
   
    func get_drag_data(_position):
        var preview = TextureRect.new()
        preview.texture = $TextureRect.texture
        set_drag_preview(preview)
        return { id = "foobar" }
   

6. Run the game

The results:

• In 3.5.1, as expected, you can drag around the Godot icon;
• In 4.0, nothing happens, dragging the icon around won't work;

What am I missing? How to get dragging of nodes working in version 4.x?

I've tried a few extra things to answer my own question:

• Search the web, but at the time of writing it seems to give results that are 3.x-specific;
• Go through the node's "Inspector" properties, especially Mouse properties

Answer 1

Nearly discarded my question because I found the answer myself, but perhaps just posting it will help others running into the same gotcha...

If you look at the official documentation for both versions, there's a tiny but all-important difference:

• v3.5 docs: Variant get_drag_data ( Vector2 position ) virtual
• v4.0 docs: Variant _get_drag_data ( Vector2 at_position ) virtual const

So in v4.x there is an _ (underscore) prefix to the method that wasn't there in 3.x.

The godot engine source code even have a rename map entry for this change, presumably to help with converting projects? For reference: see the commit that introduced this change.