godot-ldtk-importer/addons/csharp_ldtk_importer/LdtkSceneBuilder.cs

using System.Linq;
using CSharpLdtkImporter.Models;
using Godot;

namespace CSharpLdtkImporter;

public class LdtkSceneBuilder
{
    private readonly LdtkData _ldtkData;
    private readonly string _basePath;
    private readonly Godot.Collections.Dictionary<int, TileSet> _tileSetCache = new();

    public LdtkSceneBuilder(LdtkData ldtkData, string sourceFile)
    {
        _ldtkData = ldtkData;
        _basePath = sourceFile.GetBaseDir();
    }

    public Node2D BuildLdtkProjectRoot()
    {
        var root = new Node2D { Name = "LDTKProject" };

        // Step 1: Build the entire node hierarchy in memory.
        foreach (var level in _ldtkData.Levels)
        {
            var levelNode = BuildLevel(level);
            root.AddChild(levelNode);
        }

        // Step 2: After the tree is built, set the owner for all descendants.
        // This is the crucial step that fixes the "Invalid owner" error.
        SetOwnerRecursive(root, root);

        return root;
    }

    // A helper function to recursively set the owner on all children.
    private void SetOwnerRecursive(Node node, Node owner)
    {
        foreach (var child in node.GetChildren())
        {
            child.Owner = owner;
            SetOwnerRecursive(child, owner);
        }
    }

    private Node2D BuildLevel(LdtkLevel level)
    {
        var levelRoot = new Node2D { Name = level.Identifier };
        
        foreach (var layer in level.LayerInstances.Reverse())
        {
            var layerNode = layer.Type switch
            {
                "Tiles" => BuildTileMapLayer(layer),
                "AutoLayer" => BuildTileMapLayer(layer),
                "Entities" => BuildEntityLayer(layer),
                _ => new Node2D { Name = $"{layer.Identifier}_Unsupported" }
            };
           
            levelRoot.AddChild(layerNode);
        }
        
        return levelRoot;
    }
    
    private TileMapLayer BuildTileMapLayer(LdtkLayerInstance layer)
    {
        var tileMapLayer = new TileMapLayer { Name = layer.Identifier };
        if (!layer.TilesetDefUid.HasValue) return tileMapLayer;

        var tileSet = GetOrCreateTileSet(layer.TilesetDefUid.Value);
        if (tileSet == null) return tileMapLayer;
        tileMapLayer.TileSet = tileSet;

        var allTiles = layer.GridTiles.Concat(layer.AutoLayerTiles);
        if (tileMapLayer.TileSet.GetSource(0) is not TileSetAtlasSource atlasSource) return tileMapLayer;
        
        int atlasWidthInTiles = atlasSource.GetAtlasGridSize().X;
        if (atlasWidthInTiles == 0) return tileMapLayer;

        foreach (var tile in allTiles)
        {
            var gridCoords = new Vector2I(tile.Px[0] / layer.GridSize, tile.Px[1] / layer.GridSize);
            var atlasCoords = new Vector2I(tile.TileId % atlasWidthInTiles, tile.TileId / atlasWidthInTiles);
            long alternativeId = 0;
            if ((tile.FlipBits & 1) == 1) alternativeId |= TileSetAtlasSource.TransformFlipH;
            if ((tile.FlipBits & 2) == 2) alternativeId |= TileSetAtlasSource.TransformFlipV;
            tileMapLayer.SetCell(gridCoords, 0, atlasCoords, (int)alternativeId);
        }
        return tileMapLayer;
    }

    private Node2D BuildEntityLayer(LdtkLayerInstance layer)
    {
        var entityLayerRoot = new Node2D { Name = layer.Identifier };
        foreach (var entity in layer.EntityInstances)
        {
            var marker = new Marker2D
            {
                Name = entity.Identifier,
                Position = new Vector2(entity.Px[0], entity.Px[1])
            };
            entityLayerRoot.AddChild(marker);
        }
        return entityLayerRoot;
    }
    
    private TileSet GetOrCreateTileSet(int tilesetDefUid)
    {
        if (_tileSetCache.TryGetValue(tilesetDefUid, out var cachedTileSet)) return cachedTileSet;

        var tilesetDef = _ldtkData.Defs.Tilesets.FirstOrDefault(t => t.Uid == tilesetDefUid);
        if (tilesetDef?.RelPath == null) return null;

        var texturePath = _basePath.PathJoin(tilesetDef.RelPath);
        var texture = ResourceLoader.Load<Texture2D>(texturePath);
        
        if (texture == null)
        {
            GD.PushError($"LDTK Importer: Could not load texture at path: {texturePath}");
            return null;
        }

        var newTileSet = new TileSet
        {
            TileShape = TileSet.TileShapeEnum.Square,
            TileLayout = TileSet.TileLayoutEnum.Stacked,
            TileSize = new Vector2I(tilesetDef.TileGridSize, tilesetDef.TileGridSize)
        };

        var atlasSource = new TileSetAtlasSource
        {
            Texture = texture,
            TextureRegionSize = new Vector2I(tilesetDef.TileGridSize, tilesetDef.TileGridSize)
        };
        
        newTileSet.AddSource(atlasSource);
        
        var (widthInTiles, heightInTiles) = (texture.GetWidth() / tilesetDef.TileGridSize, texture.GetHeight() / tilesetDef.TileGridSize);
        for (int x = 0; x < widthInTiles; x++)
        {
            for (int y = 0; y < heightInTiles; y++)
            {
                atlasSource.CreateTile(new Vector2I(x, y));
            }
        }

        _tileSetCache[tilesetDefUid] = newTileSet;
        return newTileSet;
    }
}