Implemented Entity and Component Drop-Targets and added Name property for entities

- Also fixed non generic GetComponent
- Use UUID as Drag-Drop value for entities
- Removed unused methods from ComponentEditWindow
- Started a marginally type-safe version of ImGui.Payload

ScriptCore/Editor/EntityEditor.cs

@@ -272,13 +272,11 @@ internal class EntityEditor
         }
         else if (fieldType.IsSubclassOf(typeof(Entity)) || fieldType == typeof(Entity))
         {
-            // TODO: Show entity drop target
-            ImGui.Text($"{fieldName} Entity ({fieldType.Name})");
+            newValue = ShowEntityDropTarget(fieldName, fieldType, reference);
         }
         else if (fieldType.IsSubclassOf(typeof(Component)))
         {
-            // TODO: Show component drop target
-            ImGui.Text($"{fieldName} Component ({fieldType.Name})");
+            newValue = ShowComponentDropTarget(fieldName, fieldType, reference);
         }
         else if (fieldType == typeof(string))
         {
@@ -338,6 +336,171 @@ internal class EntityEditor
         return newValue;
     }
 
+    private static object ShowComponentDropTarget(string fieldName, Type fieldType, object currentValue)
+    {
+        object newValue = DidNotChange;
+        
+        ImGui.Text($"{fieldName}: ");
+        ImGui.SameLine();
+
+        Component component = currentValue as Component;
+
+        string entityName = "None";
+
+        if (component != null)
+        {
+            entityName = component.Entity.Name;
+        }
+        
+        Type actualType = component?.GetType();
+
+        entityName += $" ({(actualType ?? fieldType).Name})";
+        
+        if (ImGui.Button(entityName))
+        {
+            if (component?.Entity != null)
+            {
+                // TODO: Hightlight Entity in hierarchy
+                // TODO: Highlight Component in editor
+            }
+        }
+
+        if (ImGui.BeginDragDropTarget())
+        {
+            ImGuiPayloadPtr peekPayload = ImGui.AcceptDragDropPayload("ENTITY", ImGuiDragDropFlags.AcceptPeekOnly);
+
+            bool allowDrop = false;
+            
+            unsafe
+            {
+                if (peekPayload.NativePtr != null)
+                {
+                    UUID draggedId = *(UUID*)peekPayload.Data;
+
+                    Entity draggedEntity = new Entity(draggedId);
+
+                    allowDrop = draggedEntity.HasComponent(fieldType);
+                }
+
+                if (allowDrop)
+                {
+                    ImGuiPayloadPtr payload = ImGui.AcceptDragDropPayload("ENTITY");
+                    
+                    if (payload.NativePtr != null)
+                    {
+                        UUID droppedId = *(UUID*)payload.Data;
+                        
+                        Entity draggedEntity = new Entity(droppedId);
+
+                        try
+                        {
+                            newValue = draggedEntity.GetComponent(fieldType);
+                        }
+                        catch (Exception e)
+                        {
+                            Log.Error(e);
+                        }
+                    }
+                }
+            }
+
+            ImGui.EndDragDropTarget();
+        }
+
+        return newValue;
+    }
+
+    private static object ShowEntityDropTarget(string fieldName, Type fieldType, object currentValue)
+    {
+        object newValue = DidNotChange;
+
+        ImGui.Text($"{fieldName}: ");
+        ImGui.SameLine();
+
+        string entityName = "None";
+        
+        Entity entity = currentValue as Entity;
+
+        if (entity != null)
+        {
+            entityName = entity.Name;
+        }
+
+        Type actualType = entity?.GetType();
+
+        entityName += $" ({(actualType ?? fieldType).Name})";
+
+        if (ImGui.Button(entityName))
+        {
+            if (entity != null)
+            {
+                // TODO: Hightlight Entity in hierarchy
+            }
+        }
+
+        if (ImGui.BeginDragDropTarget())
+        {
+            ImGuiPayloadPtr peekPayload = ImGui.AcceptDragDropPayload("ENTITY", ImGuiDragDropFlags.AcceptPeekOnly);
+
+            bool allowDrop = false;
+            
+            unsafe
+            {
+                if (peekPayload.NativePtr != null)
+                {
+                    UUID draggedId = *(UUID*)peekPayload.Data;
+
+                    Entity draggedEntity = new Entity(draggedId);
+
+                    // TODO: Check if entity is valid?
+
+                    if (fieldType == typeof(Entity))
+                    {
+                        allowDrop = true;
+                    }
+                    else
+                    {
+                        Entity scriptInstance = Entity.GetScriptReference(draggedId, typeof(Entity));
+
+                        allowDrop = fieldType.IsInstanceOfType(scriptInstance);
+                    }
+                }
+
+                if (allowDrop)
+                {
+                    ImGuiPayloadPtr payload = ImGui.AcceptDragDropPayload("ENTITY");
+                    
+                    if (payload.NativePtr != null)
+                    {
+                        UUID droppedId = *(UUID*)payload.Data;
+                        
+                        if (fieldType == typeof(Entity))
+                        {
+                            newValue = new Entity(droppedId);
+                        }
+                        else
+                        {
+                            newValue = Entity.GetScriptReference(droppedId, typeof(Entity));
+                        }
+                    }
+                }
+            }
+
+            ImGui.EndDragDropTarget();
+        }
+
+        ImGui.SameLine();
+
+        if (ImGui.Button("..."))
+        {
+            // TODO: Show entity selector
+        }
+
+        ImGuiExtension.AttachTooltip("Search entity...");
+
+        return newValue;
+    }
+
     private static object ShowStringEditor(object reference, Type fieldType, string fieldName, IEnumerable<Attribute> attributes)
     {
         object newValue = DidNotChange;

ScriptCore/Entity.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Diagnostics;
+using System.Reflection;
 using System.Runtime.CompilerServices;
 using GlitchyEngine.Core;
 using GlitchyEngine.Extensions;
@@ -11,6 +12,15 @@ namespace GlitchyEngine;
 /// </summary>
 public class Entity : EngineObject
 {
+    /// <summary>
+    /// Gets or sets the name of the entity.
+    /// </summary>
+    public string Name
+    {
+        get => ScriptGlue.Entity_GetName(_uuid);
+        set => ScriptGlue.Entity_SetName(_uuid, value);
+    }
+
     /// <summary>
     /// Only to be called by the engine. Don't call this constructor yourself, it will not result in a valid entity.
     /// If you want to create a new entity use <see cref="Entity(string)"/> or <see cref="Entity(string, Type[])"/>
@@ -102,7 +112,12 @@ public class Entity : EngineObject
         
         if (HasComponent(componentType))
         {
-            return Activator.CreateInstance(componentType, true, _uuid) as Component;
+            Component component = Activator.CreateInstance(componentType, true) as Component;
+
+            if (component != null)
+                component._uuid = _uuid;
+
+            return component;
         }
 
         return null;
@@ -312,13 +327,13 @@ public class Entity : EngineObject
     /// <param name="id">The id of the entity whose script instance shall be returned.</param>
     /// <param name="type">The type of the script.</param>
     /// <returns>The script instance or null.</returns>
-    internal static object GetScriptReference(UUID id, Type type)
+    internal static Entity GetScriptReference(UUID id, Type type)
     {
-        Debug.Assert(type.IsSubclassOf(typeof(Entity)));
+        Debug.Assert(typeof(Entity).IsAssignableFrom(type));
 
         ScriptGlue.Entity_GetScriptInstance(id, out object scriptInstance);
 
-        return scriptInstance;
+        return scriptInstance as Entity;
     }
 
     /// <summary>

ScriptCore/ScriptGlue.cs

@@ -46,6 +46,12 @@ internal static class ScriptGlue
     [MethodImpl(MethodImplOptions.InternalCall)]
     internal static extern void Entity_RemoveScript(UUID entityId);
     
+    [MethodImpl(MethodImplOptions.InternalCall)]
+    public static extern string Entity_GetName(UUID entityId);
+    
+    [MethodImpl(MethodImplOptions.InternalCall)]
+    public static extern string Entity_SetName(UUID entityId, string name);
+    
 #endregion Entity
 
 #region TransformComponent