Dimitrie/cnx 938 did not find a layer in cache (#468)

* fix: adds a converter for displayable objects

* fix: ensures correct layer creation for collections with empty names

Connectors/Rhino/Speckle.Connectors.RhinoShared/HostApp/RhinoLayerBaker.cs

@@ -83,7 +83,7 @@ public int GetLayerIndex(Collection[] collectionPath, string baseLayerName)
       return existingLayerIndex;
     }
 
-    throw new SpeckleException("Did not find a layer in the cache.");
+    throw new SpeckleException($"Did not find a layer in the cache with the name {layerFullName}");
   }
 
   /// <summary>
@@ -99,7 +99,8 @@ private int CreateLayerFromPath(Collection[] collectionPath, string baseLayerNam
     Layer? previousLayer = currentDocument.Layers.FindName(currentLayerName);
     foreach (Collection collection in collectionPath)
     {
-      currentLayerName += s_pathSeparator + collection.name;
+      currentLayerName += s_pathSeparator + (string.IsNullOrWhiteSpace(collection.name) ? "unnamed" : collection.name);
+
       currentLayerName = currentLayerName.Replace("{", "").Replace("}", ""); // Rhino specific cleanup for gh (see RemoveInvalidRhinoChars)
       if (_hostLayerCache.TryGetValue(currentLayerName, out int value))
       {
@@ -133,6 +134,10 @@ out int mIndex
       }
 
       int index = currentDocument.Layers.Add(newLayer);
+      if (index == -1)
+      {
+        throw new SpeckleException($"Could not create layer {currentLayerName}.");
+      }
       _hostLayerCache.Add(currentLayerName, index);
       previousLayer = currentDocument.Layers.FindIndex(index); // note we need to get the correct id out, hence why we're double calling this
     }

Converters/Rhino/Speckle.Converters.RhinoShared/ToHost/TopLevel/DisplayableObjectToHostTopLevelConverter.cs

@@ -0,0 +1,77 @@
+using Speckle.Converters.Common;
+using Speckle.Converters.Common.Objects;
+using Speckle.Sdk.Common;
+using Speckle.Sdk.Common.Exceptions;
+using Speckle.Sdk.Models;
+
+namespace Speckle.Converters.Rhino.ToHost.TopLevel;
+
+[NameAndRankValue(nameof(DisplayableObject), NameAndRankValueAttribute.SPECKLE_DEFAULT_RANK)]
+public class DisplayableObjectConverter
+  : IToHostTopLevelConverter,
+    ITypedConverter<DisplayableObject, List<(RG.GeometryBase a, Base b)>>
+{
+  private readonly ITypedConverter<SOG.Point, RG.Point> _pointConverter;
+  private readonly ITypedConverter<SOG.Line, RG.LineCurve> _lineConverter;
+  private readonly ITypedConverter<SOG.Polyline, RG.PolylineCurve> _polylineConverter;
+  private readonly ITypedConverter<SOG.Arc, RG.ArcCurve> _arcConverter;
+  private readonly ITypedConverter<SOG.Mesh, RG.Mesh> _meshConverter;
+  private readonly IConverterSettingsStore<RhinoConversionSettings> _settingsStore;
+
+  public DisplayableObjectConverter(
+    ITypedConverter<SOG.Point, RG.Point> pointConverter,
+    ITypedConverter<SOG.Line, RG.LineCurve> lineConverter,
+    ITypedConverter<SOG.Polyline, RG.PolylineCurve> polylineConverter,
+    ITypedConverter<SOG.Arc, RG.ArcCurve> arcConverter,
+    ITypedConverter<SOG.Mesh, RG.Mesh> meshConverter,
+    IConverterSettingsStore<RhinoConversionSettings> settingsStore
+  )
+  {
+    _pointConverter = pointConverter;
+    _lineConverter = lineConverter;
+    _polylineConverter = polylineConverter;
+    _arcConverter = arcConverter;
+    _meshConverter = meshConverter;
+    _settingsStore = settingsStore;
+  }
+
+  public object Convert(Base target) => Convert((DisplayableObject)target);
+
+  public List<(RG.GeometryBase a, Base b)> Convert(DisplayableObject target)
+  {
+    var result = new List<RG.GeometryBase>();
+    foreach (var item in target.displayValue)
+    {
+      RG.GeometryBase x = item switch
+      {
+        SOG.Line line => _lineConverter.Convert(line),
+        SOG.Polyline polyline => _polylineConverter.Convert(polyline),
+        SOG.Arc arc => _arcConverter.Convert(arc),
+        SOG.Mesh mesh => _meshConverter.Convert(mesh),
+        SOG.Point point => _pointConverter.Convert(point),
+        _ => throw new ConversionException($"Found unsupported fallback geometry: {item.GetType()}")
+      };
+      x.Transform(GetUnitsTransform(item));
+      result.Add(x);
+    }
+
+    return result.Zip(target.displayValue, (a, b) => (a, b)).ToList();
+  }
+
+  private RG.Transform GetUnitsTransform(Base speckleObject)
+  {
+    /*
+     * POC: CNX-9270 Looking at a simpler, more performant way of doing unit scaling on `ToNative`
+     * by fully relying on the transform capabilities of the HostApp, and only transforming top-level stuff.
+     * This may not hold when adding more complex conversions, but it works for now!
+     */
+    if (speckleObject["units"] is string units)
+    {
+      var scaleFactor = Units.GetConversionFactor(units, _settingsStore.Current.SpeckleUnits);
+      var scale = RG.Transform.Scale(RG.Point3d.Origin, scaleFactor);
+      return scale;
+    }
+
+    return RG.Transform.Identity;
+  }
+}